Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/13/16


AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
532 PM CST SAT MAR 12 2016 .SHORT TERM... 231 PM CST TONIGHT THROUGH SUNDAY... MAIN FOCUS IN THE NEAR TERM OF THE FORECAST IS ON PRECIPITATION TRENDS AS RAIN EVENTUALLY OVERSPREADS THE AREA THROUGH SUNDAY MORNING. 18Z SURFACE ANALYSIS DEPICTS WEAKENING HIGH PRESSURE CENTERED JUST EAST OF THE CWA OVER THE CENTRAL GREAT LAKES. FARTHER SOUTH...AN AREA OF LOW PRESSURE WAS DEVELOPING ALONG THE LOUISIANA COAST...AND IS PROGGED TO DEVELOP NORTHWARD THIS EVENING INTO REGION OF WEAK PRESSURE FALLS OVER THE ARKLATEX AND LOWER MISSISSIPPI VALLEY. THIS IS IN RESPONSE TO MID-LEVEL SHORT WAVE/OLD CLOSED UPPER LOW OVER TEXAS WHICH IS BEING KICKED OUT TO THE NORTHEAST BY ANOTHER STRONG MID-LEVEL CIRCULATION SEEN IN AFTERNOON WATER VAPOR IMAGERY OVER THE FOUR CORNERS REGION. THIS LEAD SHORT WAVE LIFTS NORTHEAST ACROSS IL/IN SUNDAY...WITH PRECIP POTENTIAL RAMPING UP ESPECIALLY LATE TONIGHT AND EARLY SUNDAY AS WAVE APPROACHES AND INCREASES MOIST ASCENT ACROSS LOW LEVEL WARM FRONTAL BAROCLINIC ZONE CURRENTLY ANALYZED ACROSS THE LOWER MISSOURI/TENNESSEE RIVER VALLEYS. IN FACT A WEAKER LEAD SHORT WAVE WAS ALREADY PRODUCING SOME LIGHT RAIN ACROSS PARTS OF NORTHEAST MO/EASTERN IA/NORTHWEST AND NORTH CENTRAL IL THIS AFTERNOON IN A REGION OF ELEVATED MOISTURE TRANSPORT AND ISENTROPIC ASCENT ON THE 300-305 K THETA SURFACES. AMDAR AND RAP ANALYSIS SOUNDINGS DEPICT LOW LEVELS BELOW 500-600 MB ARE FAIRLY DRY ACROSS FAR NORTHERN IL...AND WILL LIKELY TAKE SOME TIME TO MOISTEN AND SATURATE MORE FULLY. HOWEVER...SCATTERED LIGHT SHOWERS ARE LIKELY ESPECIALLY ACROSS NORTHWEST AND NORTH CENTRAL IL INTO THIS EVENING. POPS WILL GRADUALLY INCREASE FROM SOUTH-NORTH OVERNIGHT AS LOW LEVEL WARM/MOIST ADVECTION STRENGTHENS AND AFOREMENTIONED SHORT WAVE APPROACHES. MID-LEVEL SHORT WAVE CONTINUES TO PROPAGATE A LITTLE MORE SLOWLY TO THE NORTHEAST ACROSS THE AREA SUNDAY...WITH SURFACE LOW PRESSURE WAVE TRACKING ACROSS THE SOUTHEAST PART OF THE CWA DURING THE AFTERNOON. SHOWERS/RAIN ARE EXPECTED TO BE FAIRLY PERSISTENT ACROSS THE CWA GIVEN THE PROXIMITY OF MID-LEVEL FORCING AND THE LOW LEVEL BAROCLINIC ZONE. GUIDANCE GENERALLY DEPICTS THE GREATEST RAINFALL ACROSS THE SOUTHEAST THIRD TO HALF OF THE CWA BY SUNDAY EVENING WITH AMOUNTS GENERALLY IN THE 0.75 TO 1.00 INCH RANGE. THIS APPEARS REASONABLE AGAIN GIVEN ALIGNMENT OF FORCING FEATURES AND PWATS OF 1+ INCHES WHICH IS WELL ABOVE THE 90 PERCENTILE BASED ON ILX SOUNDING CLIMATOLOGY FOR MID-MARCH. DEEP MOIST-ADIABATIC LAPSE RATES ALSO APPEAR TO YIELD SOME WEAK ELEVATED CAPE ACROSS THE SOUTHEAST PORTION OF THE CWA AND HAVE INCLUDED SLIGHT CHANCE FOR THUNDER ACROSS ABOUT THE SOUTHERN TIER OR SO OF CWA COUNTIES FROM AFTER MIDNIGHT TONIGHT INTO SUNDAY. TEMPS REACHED THE UPPER 50S/LOW 60S AWAY FROM LAKE MICHGAN THIS AFTERNOON THOUGH CLOUD COVER HAS LIMITED THE CLIMB SOMEWHAT. CLOUD COVER AND INCREASING LOW LEVEL DEW POINT TEMPS SHOULD KEEP MIN TEMPS TONIGHT IN THE 40S MOST AREAS AND AROUND 50 FAR SOUTH...AND DESPITE EXTENSIVE CLOUD COVER AND RAIN ON SUNDAY...PURE ADVECTION OF WARMER AIR MASS SHOULD RESULT IN TEMP AGAIN IN THE UPPER 50S/LOW 60S SOUTH. INCREASING EAST WINDS (10-20 MPH) WILL COMBINE WITH THE CLOUDS AND RAIN TO KEEP THINGS COOLER NORTH OF THE LOW LEVEL SURFACE WAVE AND BAROCLINIC REGION...WITH TEMPS FROM THE MID 40S ALONG THE LAKE TO THE LOWER 50S FARTHER INLAND IN LINE GUIDANCE TRENDS. RATZER && .LONG TERM... 303 PM CST SUNDAY NIGHT THROUGH SATURDAY... MAIN FORECAST CONCERNS/CHALLENGES ARE WITH LINGERING PRECIP CHANCES SUNDAY NIGHT INTO MONDAY MORNING AND THEN WITH RETURNING CHANCES FOR SHOWERS AND THUNDERSTORMS LATE MONDAY NIGHT INTO TUESDAY AFTERNOON/EVENING...WITH THE POSSIBILITY OF ISOLATED STRONG TO SEVERE THUNDERSTORMS DURING THAT TIME. A WET START TO THE PERIOD IS STILL APPEARING LIKELY SUNDAY NIGHT. CYCLONIC FLOW IN PLACE WITH MID LEVEL ENERGY TRAVERSING THIS FLOW ALONG WITH SLOWLY MOVING SURFACE REFLECTION LOOK TO STILL PROVIDE PERIODIC RAIN SHOWERS SUNDAY NIGHT. DID MAINTAIN LIKELY POPS FOR THE AREA IN THE EVENING BUT SLOWLY DECREASE FROM WEST TO EAST OVERNIGHT INTO EARLY MONDAY MORNING AS THIS SYSTEM BEGINS TO DEPART TO THE EAST/NORTHEAST. FORECAST SOUNDINGS DO INDICATE SOME WEAK INSTABILITY IN PLACE FOR THE FAR SOUTHERN CWA IN THE EVENING AND THIS SEEMS REASONABLE GIVEN THAT LOCATION WILL STILL LIKELY BE IN AN AXIS OF HIGHER MOISTURE CONTENT AIR. SO HAVE INCLUDED MENTION OF SLIGHT CHANCE THUNDER MAINLY FOR THE INDIANA COUNTIES SOUTH OF THE KANKAKEE RIVER. ANY THUNDER CHANCES QUICKLY DIMINISH LATER IN THE NIGHT WITH THE ARRIVAL OF DRIER AIR AND WEAKENING FORCING. CONTINUE THE LOWERING TREND WITH POPS ON MONDAY AS THIS SYSTEM FURTHER DEPARTS. HOWEVER...THERE DOES APPEAR TO BE A POSSIBILITY FOR SOME ISOLATED TO SCATTERED SHOWER DEVELOPMENT ALONG THE BACK SIDE OF THIS SYSTEM WITH SOME WEAK LARGE SCALE ASCENT AND FORCING ALONG DEPARTING BOUNDARY. DO LEAVE SOME CHANCE POPS IN THE MORNING BUT GO MAINLY DRY IN THE AFTERNOON. AFTER LIKELY DRY CONDITIONS IN THE AFTERNOON AND A PORTION OF THE EVENING ON MONDAY...DO BRING BACK SLIGHT CHANCE POPS ACROSS NORTH CENTRAL ILLINOIS AND THEN CHANCE POPS AFTER MIDNIGHT. APPROACHING SYSTEM TAKING SHAPE OVER THE PLAINS WILL ALLOW BACKING LOW/MID LEVEL FLOW TO INCREASE DURING THIS NIGHT. AS THIS OCCURS...WAA LOOKS TO RAMP UP WITH AT LEAST SOME ISOLATED SHOWER DEVELOPMENT ALONG THIS WAA AXIS. GUIDANCE PRETTY CONSISTENT WITH INCREASING INSTABILITY ALSO DURING THIS PERIOD...AND SO HAVE INCLUDED SLIGHT CHANCE THUNDER GIVEN THIS SIGNAL AND PATTERN. MORNING GUIDANCE COMING IN FAIRLY CONSISTENT WITH ONE ANOTHER ON THE NEXT SYSTEM TO LIKELY IMPACT THE REGION ON TUESDAY. FORECAST GUIDANCE STILL ADVERTISING AN UPPER LEVEL TROUGH BECOMING HIGHLY AMPLIFIED OVER THE PLAINS DURING THE DAY TUESDAY...WHILE UPPER LEVEL JET STREAK OF AT LEAST 120KT SWINGS THROUGH THE REGION. MID LEVEL FLOW/ENERGY IS ALSO APPEARING RATHER ROBUST WITH MID LEVEL FLOW OF AROUND 100KT BECOMING POSSIBLE...AND WITH GUIDANCE INDICATING A STOUT VORT MAX TO PUSH THROUGH THE REGION IN THE LATE AFTERNOON AND EARLY EVENING. GROWING MORE CONCERNED FOR THUNDERSTORM CHANCES ACROSS MUCH OF THE CWA DURING THIS TIME ESPECIALLY AS A WARM/MOIST ENVIRONMENT ADVECTS NORTH OUT AHEAD OF THIS SYSTEM. IN REGARDS TO MOISTURE RETURN...MODEL CONSENSUS IS STILL INDICATING MODEST MOISTURE RETURN DURING THE DAY TUESDAY BUT WITH SOME PIECES OF GUIDANCE INDICATING A LITTLE MORE AGGRESSIVE RETURN OF MOISTURE TO THE AREA. IN THIS SCENARIO...INSTABILITY INCREASES SIGNIFICANTLY WITH THE THREAT OF THUNDERSTORMS AND EVEN STRONG TO SEVERE THUNDERSTORM DEVELOPMENT LIKELY INCREASING. HOWEVER...NOT COMPLETELY SOLD ON THIS SOLUTION QUITE YET AND HAVE GONE WITH MORE OF A CONSERVATIVE APPROACH. EVEN IN THIS CONSERVATIVE APPROACH...THIS MODEST MOISTURE RETURN COULD STILL YIELD WEAK INSTABILITY IN UPWARDS OF 500-1000 J/KG. GIVEN THIS HIGHLY DYNAMIC SYSTEM AND EXPECTED STRONG KINEMATIC FIELD...EVEN THIS POSSIBLE INSTABILITY IN THE PRESENCE OF THESE FEATURES COULD ALLOW FOR AT LEAST SOME ISOLATED STRONG TO SEVERE THUNDERSTORMS. STILL A LITTLE EARLY TO GATHER ANY STRONG CONFIDENCE ON EXACTLY HOW TUESDAY WILL UNFOLD. HOWEVER...THIS PERIOD WARRANTS CLOSE MONITORING FOR THIS THUNDERSTORM POTENTIAL. RODRIGUEZ && .AVIATION... FOR THE 00Z TAFS... VFR CIGS EXPECTED THROUGH TONIGHT GRADUALLY BUILDING DOWNWARD THROUGH THE NIGHT WITH WDLY SCTD -SHRA WEST OF CHICAGO AND BRIEF SPRINKLES/POSSIBLE -SHRA IN THE CHICAGO METRO AREA TONIGHT. CONDITIONS EXPECTED TO DETERIORATE MORE QUICKLY SUNDAY MORNING WITH CIGS LIKELY DROPPING FROM VFR TO IFR WITHIN A FEW HOURS WITH STEADY -RA/DZ. EAST WINDS OFF THE CHILLY LAKE SHOULD RE-ENFORCE THE LOW LEVEL INVERSION AND ANTICIPATE CIGS TO FALL TO LIFR BY EARLY AFTERNOON WITH IFR OR POSSIBLY LIFR VSBY ALSO EXPECTED WITH DZ/RA/FG. NO IMPROVEMENT IN CONDITIONS IS LIKELY SUNDAY NIGHT. IZZI && .MARINE... 252 PM CST FEW CONCERNS IN THE NEAR TERM AS SURFACE HIGH PRESSURE CONTINUES TO WEAKEN AND DRIFT EAST OVER THE CENTRAL/LOWER GREAT LAKES. MODEST EAST WINDS WERE DEVELOPING ACROSS THE SOUTH END OF THE LAKE IN RESPONSE TO A WEAK AREA OF LOW PRESSURE WHICH WAS DEVELOPING ACROSS THE LOWER MISSISSIPPI AND MISSOURI VALLEYS...AND EAST WINDS WILL CONTINUE TO INCREASE A BIT INTO SUNDAY ACROSS THE LAKE AS THIS LOW LIFTS NORTHEAST INTO IL/IN BY EVENING. IT APPEARS AT THIS TIME THAT THIS LOW WILL PASS JUST SOUTH OF THE LAKE SUNDAY NIGHT. THE SURFACE PRESSURE PATTERN WILL THEN SLACKEN AGAIN INTO MONDAY WITH LIGHT NORTH WINDS DEVELOPING BEHIND THE DEPARTING WEAK LOW. A MORE POTENT LOW PRESSURE SYSTEM IS STILL BEING WATCHED FOR THE MIDDLE OF NEXT WEEK...WITH FORECAST MODELS STILL DEVELOPING A DEEP SURFACE LOW OVER THE WESTERN LAKES OR UPPER MISSISSIPPI VALLEY BY LATE TUESDAY AND MOVING THE LOW ACROSS THE LAKES THROUGH THURSDAY. THIS WOULD STILL SUPPORT THE POTENTIAL FOR STRONG WEST-SOUTHWEST WINDS/GALES BY WEDNESDAY AS COOLER AIR WRAPS AROUND THE SYSTEM. THERE IS STILL AMPLE SPREAD BETWEEN MODEL SOLUTIONS AT THIS TIME HOWEVER... MAKING CONFIDENCE IN THE DETAILS OF THE WIND FIELD FAIRLY LOW. RATZER && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
130 AM CST SUN MAR 13 2016 .SHORT TERM... 231 PM CST TONIGHT THROUGH SUNDAY... MAIN FOCUS IN THE NEAR TERM OF THE FORECAST IS ON PRECIPITATION TRENDS AS RAIN EVENTUALLY OVERSPREADS THE AREA THROUGH SUNDAY MORNING. 18Z SURFACE ANALYSIS DEPICTS WEAKENING HIGH PRESSURE CENTERED JUST EAST OF THE CWA OVER THE CENTRAL GREAT LAKES. FARTHER SOUTH...AN AREA OF LOW PRESSURE WAS DEVELOPING ALONG THE LOUISIANACOAST...AND IS PROGGED TO DEVELOP NORTHWARD THIS EVENING INTO REGION OF WEAK PRESSURE FALLS OVER THE ARKLATEX AND LOWER MISSISSIPPI VALLEY. THIS IS IN RESPONSE TO MID-LEVEL SHORT WAVE/OLD CLOSED UPPER LOW OVER TEXAS WHICH IS BEING KICKED OUT TO THE NORTHEAST BY ANOTHER STRONG MID-LEVEL CIRCULATION SEEN IN AFTERNOON WATER VAPOR IMAGERY OVER THE FOUR CORNERS REGION. THIS LEAD SHORT WAVE LIFTS NORTHEAST ACROSS IL/IN SUNDAY...WITH PRECIP POTENTIAL RAMPING UP ESPECIALLY LATE TONIGHT AND EARLY SUNDAY AS WAVE APPROACHES AND INCREASES MOIST ASCENT ACROSS LOW LEVEL WARM FRONTAL BAROCLINIC ZONE CURRENTLY ANALYZED ACROSS THE LOWER MISSOURI/TENNESSEE RIVER VALLEYS. IN FACT A WEAKER LEAD SHORT WAVE WAS ALREADY PRODUCING SOME LIGHT RAIN ACROSS PARTS OF NORTHEAST MO/EASTERN IA/NORTHWEST AND NORTH CENTRAL IL THIS AFTERNOON IN A REGION OF ELEVATED MOISTURE TRANSPORT AND ISENTROPIC ASCENT ON THE 300-305 K THETA SURFACES. AMDAR AND RAP ANALYSIS SOUNDINGS DEPICT LOW LEVELS BELOW 500-600 MB ARE FAIRLY DRY ACROSS FAR NORTHERN IL...AND WILL LIKELY TAKE SOME TIME TO MOISTEN AND SATURATE MORE FULLY. HOWEVER...SCATTERED LIGHT SHOWERS ARE LIKELY ESPECIALLY ACROSS NORTHWEST AND NORTH CENTRAL IL INTO THIS EVENING. POPS WILL GRADUALLY INCREASE FROM SOUTH-NORTH OVERNIGHT AS LOW LEVEL WARM/MOIST ADVECTION STRENGTHENS AND AFOREMENTIONED SHORT WAVE APPROACHES. MID-LEVEL SHORT WAVE CONTINUES TO PROPAGATE A LITTLE MORE SLOWLY TO THE NORTHEAST ACROSS THE AREA SUNDAY...WITH SURFACE LOW PRESSURE WAVE TRACKING ACROSS THE SOUTHEAST PART OF THE CWA DURING THE AFTERNOON. SHOWERS/RAIN ARE EXPECTED TO BE FAIRLY PERSISTENT ACROSS THE CWA GIVEN THE PROXIMITY OF MID-LEVEL FORCING AND THE LOW LEVEL BAROCLINIC ZONE. GUIDANCE GENERALLY DEPICTS THE GREATEST RAINFALL ACROSS THE SOUTHEAST THIRD TO HALF OF THE CWA BY SUNDAY EVENING WITH AMOUNTS GENERALLY IN THE 0.75 TO 1.00 INCH RANGE. THIS APPEARS REASONABLE AGAIN GIVEN ALIGNMENT OF FORCING FEATURES AND PWATS OF 1+ INCHES WHICH IS WELL ABOVE THE 90 PERCENTILE BASED ON ILX SOUNDING CLIMATOLOGY FOR MID-MARCH. DEEP MOIST-ADIABATIC LAPSE RATES ALSO APPEAR TO YIELD SOME WEAK ELEVATED CAPE ACROSS THE SOUTHEAST PORTION OF THE CWA AND HAVE INCLUDED SLIGHT CHANCE FOR THUNDER ACROSS ABOUT THE SOUTHERN TIER OR SO OF CWA COUNTIES FROM AFTER MIDNIGHT TONIGHT INTO SUNDAY. TEMPS REACHED THE UPPER 50S/LOW 60S AWAY FROM LAKE MICHGAN THIS AFTERNOON THOUGH CLOUD COVER HAS LIMITED THE CLIMB SOMEWHAT. CLOUD COVER AND INCREASING LOW LEVEL DEW POINT TEMPS SHOULD KEEP MIN TEMPS TONIGHT IN THE 40S MOST AREAS AND AROUND 50 FAR SOUTH...AND DESPITE EXTENSIVE CLOUD COVER AND RAIN ON SUNDAY...PURE ADVECTION OF WARMER AIR MASS SHOULD RESULT IN TEMP AGAIN IN THE UPPER 50S/LOW 60S SOUTH. INCREASING EAST WINDS (10-20 MPH) WILL COMBINE WITH THE CLOUDS AND RAIN TO KEEP THINGS COOLER NORTH OF THE LOW LEVEL SURFACE WAVE AND BAROCLINIC REGION...WITH TEMPS FROM THE MID 40S ALONG THE LAKE TO THE LOWER 50S FARTHER INLAND IN LINE GUIDANCE TRENDS. RATZER && .LONG TERM... 303 PM CST SUNDAY NIGHT THROUGH SATURDAY... MAIN FORECAST CONCERNS/CHALLENGES ARE WITH LINGERING PRECIP CHANCES SUNDAY NIGHT INTO MONDAY MORNING AND THEN WITH RETURNING CHANCES FOR SHOWERS AND THUNDERSTORMS LATE MONDAY NIGHT INTO TUESDAY AFTERNOON/EVENING...WITH THE POSSIBILITY OF ISOLATED STRONG TO SEVERE THUNDERSTORMS DURING THAT TIME. A WET START TO THE PERIOD IS STILL APPEARING LIKELY SUNDAY NIGHT. CYCLONIC FLOW IN PLACE WITH MID LEVEL ENERGY TRAVERSING THIS FLOW ALONG WITH SLOWLY MOVING SURFACE REFLECTION LOOK TO STILL PROVIDE PERIODIC RAIN SHOWERS SUNDAY NIGHT. DID MAINTAIN LIKELY POPS FOR THE AREA IN THE EVENING BUT SLOWLY DECREASE FROM WEST TO EAST OVERNIGHT INTO EARLY MONDAY MORNING AS THIS SYSTEM BEGINS TO DEPART TO THE EAST/NORTHEAST. FORECAST SOUNDINGS DO INDICATE SOME WEAK INSTABILITY IN PLACE FOR THE FAR SOUTHERN CWA IN THE EVENING AND THIS SEEMS REASONABLE GIVEN THAT LOCATION WILL STILL LIKELY BE IN AN AXIS OF HIGHER MOISTURE CONTENT AIR. SO HAVE INCLUDED MENTION OF SLIGHT CHANCE THUNDER MAINLY FOR THE INDIANA COUNTIES SOUTH OF THE KANKAKEE RIVER. ANY THUNDER CHANCES QUICKLY DIMINISH LATER IN THE NIGHT WITH THE ARRIVAL OF DRIER AIR AND WEAKENING FORCING. CONTINUE THE LOWERING TREND WITH POPS ON MONDAY AS THIS SYSTEM FURTHER DEPARTS. HOWEVER...THERE DOES APPEAR TO BE A POSSIBILITY FOR SOME ISOLATED TO SCATTERED SHOWER DEVELOPMENT ALONG THE BACK SIDE OF THIS SYSTEM WITH SOME WEAK LARGE SCALE ASCENT AND FORCING ALONG DEPARTING BOUNDARY. DO LEAVE SOME CHANCE POPS IN THE MORNING BUT GO MAINLY DRY IN THE AFTERNOON. AFTER LIKELY DRY CONDITIONS IN THE AFTERNOON AND A PORTION OF THE EVENING ON MONDAY...DO BRING BACK SLIGHT CHANCE POPS ACROSS NORTH CENTRAL ILLINOIS AND THEN CHANCE POPS AFTER MIDNIGHT. APPROACHING SYSTEM TAKING SHAPE OVER THE PLAINS WILL ALLOW BACKING LOW/MID LEVEL FLOW TO INCREASE DURING THIS NIGHT. AS THIS OCCURS...WAA LOOKS TO RAMP UP WITH AT LEAST SOME ISOLATED SHOWER DEVELOPMENT ALONG THIS WAA AXIS. GUIDANCE PRETTY CONSISTENT WITH INCREASING INSTABILITY ALSO DURING THIS PERIOD...AND SO HAVE INCLUDED SLIGHT CHANCE THUNDER GIVEN THIS SIGNAL AND PATTERN. MORNING GUIDANCE COMING IN FAIRLY CONSISTENT WITH ONE ANOTHER ON THE NEXT SYSTEM TO LIKELY IMPACT THE REGION ON TUESDAY. FORECAST GUIDANCE STILL ADVERTISING AN UPPER LEVEL TROUGH BECOMING HIGHLY AMPLIFIED OVER THE PLAINS DURING THE DAY TUESDAY...WHILE UPPER LEVEL JET STREAK OF AT LEAST 120KT SWINGS THROUGH THE REGION. MID LEVEL FLOW/ENERGY IS ALSO APPEARING RATHER ROBUST WITH MID LEVEL FLOW OF AROUND 100KT BECOMING POSSIBLE...AND WITH GUIDANCE INDICATING A STOUT VORT MAX TO PUSH THROUGH THE REGION IN THE LATE AFTERNOON AND EARLY EVENING. GROWING MORE CONCERNED FOR THUNDERSTORM CHANCES ACROSS MUCH OF THE CWA DURING THIS TIME ESPECIALLY AS A WARM/MOIST ENVIRONMENT ADVECTS NORTH OUT AHEAD OF THIS SYSTEM. IN REGARDS TO MOISTURE RETURN...MODEL CONSENSUS IS STILL INDICATING MODEST MOISTURE RETURN DURING THE DAY TUESDAY BUT WITH SOME PIECES OF GUIDANCE INDICATING A LITTLE MORE AGGRESSIVE RETURN OF MOISTURE TO THE AREA. IN THIS SCENARIO...INSTABILITY INCREASES SIGNIFICANTLY WITH THE THREAT OF THUNDERSTORMS AND EVEN STRONG TO SEVERE THUNDERSTORM DEVELOPMENT LIKELY INCREASING. HOWEVER...NOT COMPLETELY SOLD ON THIS SOLUTION QUITE YET AND HAVE GONE WITH MORE OF A CONSERVATIVE APPROACH. EVEN IN THIS CONSERVATIVE APPROACH...THIS MODEST MOISTURE RETURN COULD STILL YIELD WEAK INSTABILITY IN UPWARDS OF 500-1000 J/KG. GIVEN THIS HIGHLY DYNAMIC SYSTEM AND EXPECTED STRONG KINEMATIC FIELD...EVEN THIS POSSIBLE INSTABILITY IN THE PRESENCE OF THESE FEATURES COULD ALLOW FOR AT LEAST SOME ISOLATED STRONG TO SEVERE THUNDERSTORMS. STILL A LITTLE EARLY TO GATHER ANY STRONG CONFIDENCE ON EXACTLY HOW TUESDAY WILL UNFOLD. HOWEVER...THIS PERIOD WARRANTS CLOSE MONITORING FOR THIS THUNDERSTORM POTENTIAL. RODRIGUEZ && .AVIATION... FOR THE 06Z TAFS... WDLY SCATTERED -SHRA STILL EXPECTED THROUGH THE OVERNIGHT HOURS WITH MORE OF AN UPTICK IN COVERAGE OF SHOWERS EXPECTED SUNDAY MORNING...LIKELY BUILDING INTO MORE OF A STEADY RAIN BY MID-LATE MORNING SUNDAY. RAIN SHOULD BEGIN TO TAPER OFF TO MORE OF A LIGHT RAIN OR MORE LIKELY DRIZZLE BY LATE AFTERNOON INTO SUNDAY EVENING. VFR CIGS WILL CONTINUE TO STEADILY LOWER OVERNIGHT...LIKELY TO MVFR EARLY SUNDAY MORNING THEN QUICKLY DETERIORATING TO IFR SUNDAY MORNING. CONTINUED RAIN/MOISTENING OF THE LOW LEVELS COMBINED WITH WINDS OFF THE STILL COLD LAKE SHOULD RESULT IN A LOW AND SHARP INVERSION WITH CIGS LIKELY BUILDING DOWN TO LIFR IN THE AFTERNOON. GUIDANCE AND SYNOPTIC CLIMO BOTH SUGGEST POTENTIAL FOR VLIFR CIGS/VSBY SUNDAY EVENING WITH DRIZZLE AND FOG CONTINUING. GENERALLY STUCK CLOSE TO MAV/MET GUIDANCE FOR CIGS/VSBY SUNDAY AFTERNOON AND NIGHT WHICH DOES BRING CONDITIONS CLOSE TO THE DECK. GUIDANCE WAS A BIT MORE OPTIMISTIC AT MDW...SO KEPT THEM A BIT HIGHER FOR NOW...BUT CONFIDENCE IS LOW AND WILL NEED TO BE WATCHED. AT ORD...THE TOWER ENDS UP IN THE CIGS AT 200FT WHICH TYPICALLY LEADS TO TOWER VSBY OF 1/2SM TO 1/4SM SO FELT MORE COMFORTABLE BRINGING ORD TO NEAR THE DECK SUNDAY EVENING. CONFIDENCE IN LOW CIGS/VSBY IS MEDIUM-HIGH SUNDAY EVENING THOUGH CONFIDENCE IS LOWER IN PRECISELY HOW LOW IT GETS. IZZI && .MARINE... 125 AM CST EASTERLY WINDS WILL BE ON THE INCREASE TODAY ACROSS THE LAKE AS LOW PRESSURE DEVELOPS ACROSS CENTRAL ILLINOIS BY THIS AFTERNOON. LOW-LEVEL MOISTURE WILL ALSO BE STEADILY INCREASING AND IS LIKELY TO DEVELOP FOG...ESPECIALLY ACROSS THE SOUTH AS SHOWERS EASE IN COVERAGE THROUGH THE AFTERNOON. THE FOG WILL PROBABLY BE DENSE IN PARTS BY TONIGHT...AND MAYBE EVEN DURING THE AFTERNOON...AND AN ADVISORY MAY BE NEEDED. THIS INCLUDES THE ILLINOIS AND INDIANA NEARSHORES. THE DEEP LOW PRESSURE FOR MIDWEEK IS STILL FORECAST TO MOVE EASTWARD INTO THE MINNESOTA/WISCONSIN REGION BY TUESDAY NIGHT AND PERSIST INTO WEDNESDAY EVENING. THE TREND WITH THE STRENGTH OF THIS LOW HAS BEEN SLIGHTLY DOWNWARD THE PAST 12-24 HOURS IN FORECAST MODELS...WHICH WOULD LIKELY KEEP GUSTS BELOW GALE FORCE OVER THE LAKE DURING THAT TIME. WITH SUCH A DEEP LOW THE PATTERN STILL BEARS WATCHING FOR POTENTIAL GALES AND AT LEAST SMALL CRAFT ADVISORY CRITERIA IS ANTICIPATED FOR A PERIOD OR TWO DURING MIDWEEK. MTF && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1123 PM CST SAT MAR 12 2016 .SHORT TERM... 231 PM CST TONIGHT THROUGH SUNDAY... MAIN FOCUS IN THE NEAR TERM OF THE FORECAST IS ON PRECIPITATION TRENDS AS RAIN EVENTUALLY OVERSPREADS THE AREA THROUGH SUNDAY MORNING. 18Z SURFACE ANALYSIS DEPICTS WEAKENING HIGH PRESSURE CENTERED JUST EAST OF THE CWA OVER THE CENTRAL GREAT LAKES. FARTHER SOUTH...AN AREA OF LOW PRESSURE WAS DEVELOPING ALONG THE LOUISIANA COAST...AND IS PROGGED TO DEVELOP NORTHWARD THIS EVENING INTO REGION OF WEAK PRESSURE FALLS OVER THE ARKLATEX AND LOWER MISSISSIPPI VALLEY. THIS IS IN RESPONSE TO MID-LEVEL SHORT WAVE/OLD CLOSED UPPER LOW OVER TEXAS WHICH IS BEING KICKED OUT TO THE NORTHEAST BY ANOTHER STRONG MID-LEVEL CIRCULATION SEEN IN AFTERNOON WATER VAPOR IMAGERY OVER THE FOUR CORNERS REGION. THIS LEAD SHORT WAVE LIFTS NORTHEAST ACROSS IL/IN SUNDAY...WITH PRECIP POTENTIAL RAMPING UP ESPECIALLY LATE TONIGHT AND EARLY SUNDAY AS WAVE APPROACHES AND INCREASES MOIST ASCENT ACROSS LOW LEVEL WARM FRONTAL BAROCLINIC ZONE CURRENTLY ANALYZED ACROSS THE LOWER MISSOURI/TENNESSEE RIVER VALLEYS. IN FACT A WEAKER LEAD SHORT WAVE WAS ALREADY PRODUCING SOME LIGHT RAIN ACROSS PARTS OF NORTHEAST MO/EASTERN IA/NORTHWEST AND NORTH CENTRAL IL THIS AFTERNOON IN A REGION OF ELEVATED MOISTURE TRANSPORT AND ISENTROPIC ASCENT ON THE 300-305 K THETA SURFACES. AMDAR AND RAP ANALYSIS SOUNDINGS DEPICT LOW LEVELS BELOW 500-600 MB ARE FAIRLY DRY ACROSS FAR NORTHERN IL...AND WILL LIKELY TAKE SOME TIME TO MOISTEN AND SATURATE MORE FULLY. HOWEVER...SCATTERED LIGHT SHOWERS ARE LIKELY ESPECIALLY ACROSS NORTHWEST AND NORTH CENTRAL IL INTO THIS EVENING. POPS WILL GRADUALLY INCREASE FROM SOUTH-NORTH OVERNIGHT AS LOW LEVEL WARM/MOIST ADVECTION STRENGTHENS AND AFOREMENTIONED SHORT WAVE APPROACHES. MID-LEVEL SHORT WAVE CONTINUES TO PROPAGATE A LITTLE MORE SLOWLY TO THE NORTHEAST ACROSS THE AREA SUNDAY...WITH SURFACE LOW PRESSURE WAVE TRACKING ACROSS THE SOUTHEAST PART OF THE CWA DURING THE AFTERNOON. SHOWERS/RAIN ARE EXPECTED TO BE FAIRLY PERSISTENT ACROSS THE CWA GIVEN THE PROXIMITY OF MID-LEVEL FORCING AND THE LOW LEVEL BAROCLINIC ZONE. GUIDANCE GENERALLY DEPICTS THE GREATEST RAINFALL ACROSS THE SOUTHEAST THIRD TO HALF OF THE CWA BY SUNDAY EVENING WITH AMOUNTS GENERALLY IN THE 0.75 TO 1.00 INCH RANGE. THIS APPEARS REASONABLE AGAIN GIVEN ALIGNMENT OF FORCING FEATURES AND PWATS OF 1+ INCHES WHICH IS WELL ABOVE THE 90 PERCENTILE BASED ON ILX SOUNDING CLIMATOLOGY FOR MID-MARCH. DEEP MOIST-ADIABATIC LAPSE RATES ALSO APPEAR TO YIELD SOME WEAK ELEVATED CAPE ACROSS THE SOUTHEAST PORTION OF THE CWA AND HAVE INCLUDED SLIGHT CHANCE FOR THUNDER ACROSS ABOUT THE SOUTHERN TIER OR SO OF CWA COUNTIES FROM AFTER MIDNIGHT TONIGHT INTO SUNDAY. TEMPS REACHED THE UPPER 50S/LOW 60S AWAY FROM LAKE MICHGAN THIS AFTERNOON THOUGH CLOUD COVER HAS LIMITED THE CLIMB SOMEWHAT. CLOUD COVER AND INCREASING LOW LEVEL DEW POINT TEMPS SHOULD KEEP MIN TEMPS TONIGHT IN THE 40S MOST AREAS AND AROUND 50 FAR SOUTH...AND DESPITE EXTENSIVE CLOUD COVER AND RAIN ON SUNDAY...PURE ADVECTION OF WARMER AIR MASS SHOULD RESULT IN TEMP AGAIN IN THE UPPER 50S/LOW 60S SOUTH. INCREASING EAST WINDS (10-20 MPH) WILL COMBINE WITH THE CLOUDS AND RAIN TO KEEP THINGS COOLER NORTH OF THE LOW LEVEL SURFACE WAVE AND BAROCLINIC REGION...WITH TEMPS FROM THE MID 40S ALONG THE LAKE TO THE LOWER 50S FARTHER INLAND IN LINE GUIDANCE TRENDS. RATZER && .LONG TERM... 303 PM CST SUNDAY NIGHT THROUGH SATURDAY... MAIN FORECAST CONCERNS/CHALLENGES ARE WITH LINGERING PRECIP CHANCES SUNDAY NIGHT INTO MONDAY MORNING AND THEN WITH RETURNING CHANCES FOR SHOWERS AND THUNDERSTORMS LATE MONDAY NIGHT INTO TUESDAY AFTERNOON/EVENING...WITH THE POSSIBILITY OF ISOLATED STRONG TO SEVERE THUNDERSTORMS DURING THAT TIME. A WET START TO THE PERIOD IS STILL APPEARING LIKELY SUNDAY NIGHT. CYCLONIC FLOW IN PLACE WITH MID LEVEL ENERGY TRAVERSING THIS FLOW ALONG WITH SLOWLY MOVING SURFACE REFLECTION LOOK TO STILL PROVIDE PERIODIC RAIN SHOWERS SUNDAY NIGHT. DID MAINTAIN LIKELY POPS FOR THE AREA IN THE EVENING BUT SLOWLY DECREASE FROM WEST TO EAST OVERNIGHT INTO EARLY MONDAY MORNING AS THIS SYSTEM BEGINS TO DEPART TO THE EAST/NORTHEAST. FORECAST SOUNDINGS DO INDICATE SOME WEAK INSTABILITY IN PLACE FOR THE FAR SOUTHERN CWA IN THE EVENING AND THIS SEEMS REASONABLE GIVEN THAT LOCATION WILL STILL LIKELY BE IN AN AXIS OF HIGHER MOISTURE CONTENT AIR. SO HAVE INCLUDED MENTION OF SLIGHT CHANCE THUNDER MAINLY FOR THE INDIANA COUNTIES SOUTH OF THE KANKAKEE RIVER. ANY THUNDER CHANCES QUICKLY DIMINISH LATER IN THE NIGHT WITH THE ARRIVAL OF DRIER AIR AND WEAKENING FORCING. CONTINUE THE LOWERING TREND WITH POPS ON MONDAY AS THIS SYSTEM FURTHER DEPARTS. HOWEVER...THERE DOES APPEAR TO BE A POSSIBILITY FOR SOME ISOLATED TO SCATTERED SHOWER DEVELOPMENT ALONG THE BACK SIDE OF THIS SYSTEM WITH SOME WEAK LARGE SCALE ASCENT AND FORCING ALONG DEPARTING BOUNDARY. DO LEAVE SOME CHANCE POPS IN THE MORNING BUT GO MAINLY DRY IN THE AFTERNOON. AFTER LIKELY DRY CONDITIONS IN THE AFTERNOON AND A PORTION OF THE EVENING ON MONDAY...DO BRING BACK SLIGHT CHANCE POPS ACROSS NORTH CENTRAL ILLINOIS AND THEN CHANCE POPS AFTER MIDNIGHT. APPROACHING SYSTEM TAKING SHAPE OVER THE PLAINS WILL ALLOW BACKING LOW/MID LEVEL FLOW TO INCREASE DURING THIS NIGHT. AS THIS OCCURS...WAA LOOKS TO RAMP UP WITH AT LEAST SOME ISOLATED SHOWER DEVELOPMENT ALONG THIS WAA AXIS. GUIDANCE PRETTY CONSISTENT WITH INCREASING INSTABILITY ALSO DURING THIS PERIOD...AND SO HAVE INCLUDED SLIGHT CHANCE THUNDER GIVEN THIS SIGNAL AND PATTERN. MORNING GUIDANCE COMING IN FAIRLY CONSISTENT WITH ONE ANOTHER ON THE NEXT SYSTEM TO LIKELY IMPACT THE REGION ON TUESDAY. FORECAST GUIDANCE STILL ADVERTISING AN UPPER LEVEL TROUGH BECOMING HIGHLY AMPLIFIED OVER THE PLAINS DURING THE DAY TUESDAY...WHILE UPPER LEVEL JET STREAK OF AT LEAST 120KT SWINGS THROUGH THE REGION. MID LEVEL FLOW/ENERGY IS ALSO APPEARING RATHER ROBUST WITH MID LEVEL FLOW OF AROUND 100KT BECOMING POSSIBLE...AND WITH GUIDANCE INDICATING A STOUT VORT MAX TO PUSH THROUGH THE REGION IN THE LATE AFTERNOON AND EARLY EVENING. GROWING MORE CONCERNED FOR THUNDERSTORM CHANCES ACROSS MUCH OF THE CWA DURING THIS TIME ESPECIALLY AS A WARM/MOIST ENVIRONMENT ADVECTS NORTH OUT AHEAD OF THIS SYSTEM. IN REGARDS TO MOISTURE RETURN...MODEL CONSENSUS IS STILL INDICATING MODEST MOISTURE RETURN DURING THE DAY TUESDAY BUT WITH SOME PIECES OF GUIDANCE INDICATING A LITTLE MORE AGGRESSIVE RETURN OF MOISTURE TO THE AREA. IN THIS SCENARIO...INSTABILITY INCREASES SIGNIFICANTLY WITH THE THREAT OF THUNDERSTORMS AND EVEN STRONG TO SEVERE THUNDERSTORM DEVELOPMENT LIKELY INCREASING. HOWEVER...NOT COMPLETELY SOLD ON THIS SOLUTION QUITE YET AND HAVE GONE WITH MORE OF A CONSERVATIVE APPROACH. EVEN IN THIS CONSERVATIVE APPROACH...THIS MODEST MOISTURE RETURN COULD STILL YIELD WEAK INSTABILITY IN UPWARDS OF 500-1000 J/KG. GIVEN THIS HIGHLY DYNAMIC SYSTEM AND EXPECTED STRONG KINEMATIC FIELD...EVEN THIS POSSIBLE INSTABILITY IN THE PRESENCE OF THESE FEATURES COULD ALLOW FOR AT LEAST SOME ISOLATED STRONG TO SEVERE THUNDERSTORMS. STILL A LITTLE EARLY TO GATHER ANY STRONG CONFIDENCE ON EXACTLY HOW TUESDAY WILL UNFOLD. HOWEVER...THIS PERIOD WARRANTS CLOSE MONITORING FOR THIS THUNDERSTORM POTENTIAL. RODRIGUEZ && .AVIATION... FOR THE 06Z TAFS... WDLY SCATTERED -SHRA STILL EXPECTED THROUGH THE OVERNIGHT HOURS WITH MORE OF AN UPTICK IN COVERAGE OF SHOWERS EXPECTED SUNDAY MORNING...LIKELY BUILDING INTO MORE OF A STEADY RAIN BY MID-LATE MORNING SUNDAY. RAIN SHOULD BEGIN TO TAPER OFF TO MORE OF A LIGHT RAIN OR MORE LIKELY DRIZZLE BY LATE AFTERNOON INTO SUNDAY EVENING. VFR CIGS WILL CONTINUE TO STEADILY LOWER OVERNIGHT...LIKELY TO MVFR EARLY SUNDAY MORNING THEN QUICKLY DETERIORATING TO IFR SUNDAY MORNING. CONTINUED RAIN/MOISTENING OF THE LOW LEVELS COMBINED WITH WINDS OFF THE STILL COLD LAKE SHOULD RESULT IN A LOW AND SHARP INVERSION WITH CIGS LIKELY BUILDING DOWN TO LIFR IN THE AFTERNOON. GUIDANCE AND SYNOPTIC CLIMO BOTH SUGGEST POTENTIAL FOR VLIFR CIGS/VSBY SUNDAY EVENING WITH DRIZZLE AND FOG CONTINUING. GENERALLY STUCK CLOSE TO MAV/MET GUIDANCE FOR CIGS/VSBY SUNDAY AFTERNOON AND NIGHT WHICH DOES BRING CONDITIONS CLOSE TO THE DECK. GUIDANCE WAS A BIT MORE OPTIMISTIC AT MDW...SO KEPT THEM A BIT HIGHER FOR NOW...BUT CONFIDENCE IS LOW AND WILL NEED TO BE WATCHED. AT ORD...THE TOWER ENDS UP IN THE CIGS AT 200FT WHICH TYPICALLY LEADS TO TOWER VSBY OF 1/2SM TO 1/4SM SO FELT MORE COMFORTABLE BRINGING ORD TO NEAR THE DECK SUNDAY EVENING. CONFIDENCE IN LOW CIGS/VSBY IS MEDIUM-HIGH SUNDAY EVENING THOUGH CONFIDENCE IS LOWER IN PRECISELY HOW LOW IT GETS. IZZI && .MARINE... 252 PM CST FEW CONCERNS IN THE NEAR TERM AS SURFACE HIGH PRESSURE CONTINUES TO WEAKEN AND DRIFT EAST OVER THE CENTRAL/LOWER GREAT LAKES. MODEST EAST WINDS WERE DEVELOPING ACROSS THE SOUTH END OF THE LAKE IN RESPONSE TO A WEAK AREA OF LOW PRESSURE WHICH WAS DEVELOPING ACROSS THE LOWER MISSISSIPPI AND MISSOURI VALLEYS...AND EAST WINDS WILL CONTINUE TO INCREASE A BIT INTO SUNDAY ACROSS THE LAKE AS THIS LOW LIFTS NORTHEAST INTO IL/IN BY EVENING. IT APPEARS AT THIS TIME THAT THIS LOW WILL PASS JUST SOUTH OF THE LAKE SUNDAY NIGHT. THE SURFACE PRESSURE PATTERN WILL THEN SLACKEN AGAIN INTO MONDAY WITH LIGHT NORTH WINDS DEVELOPING BEHIND THE DEPARTING WEAK LOW. A MORE POTENT LOW PRESSURE SYSTEM IS STILL BEING WATCHED FOR THE MIDDLE OF NEXT WEEK...WITH FORECAST MODELS STILL DEVELOPING A DEEP SURFACE LOW OVER THE WESTERN LAKES OR UPPER MISSISSIPPI VALLEY BY LATE TUESDAY AND MOVING THE LOW ACROSS THE LAKES THROUGH THURSDAY. THIS WOULD STILL SUPPORT THE POTENTIAL FOR STRONG WEST-SOUTHWEST WINDS/GALES BY WEDNESDAY AS COOLER AIR WRAPS AROUND THE SYSTEM. THERE IS STILL AMPLE SPREAD BETWEEN MODEL SOLUTIONS AT THIS TIME HOWEVER... MAKING CONFIDENCE IN THE DETAILS OF THE WIND FIELD FAIRLY LOW. RATZER && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO
AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
1106 AM PDT SUN MAR 13 2016 .SYNOPSIS... BROAD WEST NORTHWEST FLOW ALOFT WILL PUSH A WEAK FRONT INTO THE REGION...BRING SOME RAIN TO NORTHERN AREAS TODAY THROUGH EARLY MONDAY...WITH A CHANCE OF RAIN ACROSS THE REMAINDER OF THE REGION TONIGHT AND EARLY MONDAY. THEN...DRY WEATHER IS EXPECTED INTO NEXT WEEKEND. BUILDING HIGH PRESSURE WILL BRING A SIGNIFICANT WARMING TREND MONDAY THROUGH WEDNESDAY...WITH A SLOW COOLING TREND THURSDAY THROUGH SATURDAY AS HIGH PRESSURE WEAKENS. && .SHORT TERM...(TDY-TUE) SKIES WERE CLOUDY NORTH OF VENTURA COUNTY THIS MORNING...BUT WILL QUICKLY BECOME MOSTLY CLOUDY ACROSS VENTURA THEN L.A. COUNTY IN THE NEXT COUPLE OF HOURS. SKIES WERE MOSTLY CLEAR ACROSS L.A. COUNTY EXCEPT FOR A FEW BANDS OF LOW CLOUDS AROUND THE WEST SAN FERNANDO VALLEY AND IN THE FOOTHILLS NEAR SIMI VALLEY AND THOUSAND OAKS. SKIES WILL CONTINUE TO BE MOSTLY CLOUDY THIS AFTERNOON AND TONIGHT AS BROAD W TO NW FLOW ALOFT WILL CONTINUE TO USHER IN PLENTY OF CLOUDS OVER THE FORECASTE AREA. A WEAK UPPER DISTURBANCE IN THE BROAD NW FLOW WILL BRING SOME LIGHT BUT STEADY RAIN ACROSS THE NW PORTION OF SLO COUNTY TODAY...AND PERIODS OF ON AND OFF RAIN FOR INTERIOR LOCATIONS OF AREAS N OF POINT CONCEPTION AS MENTIONED IN PREVIOUS DISCUSSION. NOT ANTICIPATING ANY CHANGES TO THE SHORT TERM FORECAST THIS MORNING. A WEAKENING ASSOCIATED COLD FRONT WILL CONTINUE TO MOVE INTO SLO/SBA COUNTIES LATER TODAY. AS THE FRONT CONTINUES TO MOVE SOUTH OVER THE SOCAL BIGHT AND INTO VENTURA AND LOS ANGELES COUNTIES...THE FRONT WILL DISSAPATE. THE NW FLOW OVER VENTURA COUNTY WILL MAKE IT DIFFICULT FOR ANY APPRECIABLE PRECIP TO OCCUR. MORE LIKELY SOME DRIZZLE OR VERY LIGHT RAIN THIS EVENING. THE LOWER TO MID LEVEL FLOW BECOMES MORE CYCLONIC OVER L.A COUNTY THIS EVENING...ESPECIALLY EASTERN L.A. COUNTY WHERE A BETTER CHANCE OF LOCALLY HIGHER AMOUNTS OF PRECIP SHOULD OCCUR IN THE SAN GABRIEL VALLEY...ADJACENT FOOTHILLS AND SAN GABRIEL MOUNTAINS. STILL PRECIP TOTALS S OF POINT CONCEPTION SHOULD REMAIN UNDER A TENTH OF AN INCH. MAYBE SLIGHTLY HIGHER IN THE SAN GABRIEL VALLEY FOOTHILLS AND MOUNTAINS. THE HIGHEST RAINFALL TOTALS SHOULD BE IN THE NW CORNER OF SLO COUNTY TO AROUND TWO THIRDS OF AN INCH...TO LESS THAN A QUARTER INCH FOR MOST OTHER LOCATIONS IN SLO/SBA COUNTIES. ***FROM PREVIOUS DISCUSSION*** MAX TEMPS SHOULD BE DOWN A FEW DEGREES IN MOST AREAS. GUSTY WEST WINDS IN THE ANTELOPE VALLEY THIS AFTERNOON AND EVENING COULD APPROACH ADVISORY LEVELS. A FRONTAL SYSTEM MOVING ACROSS CENTRAL CA WILL WEAKEN AS IT DROPS INTO SLO AND NRN SBA COUNTIES TODAY. THERE WILL BE AN INCREASING CHANCE OF RAIN NORTH OF PT CONCEPTION TODAY...WITH RAIN BECOMING LIKELY IN THE AFTERNOON. RAIN...MOSTLY ON THE LIGHT SIDE...WILL CONTINUE ACROSS SLO AND NRN SBA COUNTIES TONIGHT...AND WHILE RATES WILL NOT BE PARTICULARLY HIGH...RAINFALL TOTALS MAY ADD UP TO REASONABLY RESPECTABLE VALUES...ESPECIALLY ACROSS NRN SLO COUNTY. DO NOT EXPECT THE FRONTAL SYSTEM TO HOLD TOGETHER AS AN ACTUAL FRONT S OF PT CONCEPTION...BUT ABUNDANT LOW LEVEL MOISTURE IN WESTERLY FLOW ALONG WITH SOME LIFT THROUGH THE MOIST LAYER COULD BRING RAIN TO THE REMAINDER OF THE REGION TONIGHT. THIS WILL BE ESPECIALLY TRUE ACROSS L.A. COUNTY WHERE THE FLOW DIRECTION WILL BE MOST FAVORABLE AND CYCLONIC. THERE COULD BE SOME LINGERING SHOWERS IN ALL AREAS MON MORNING...AND POSSIBLY ON NORTHERN SLOPES INTO THE AFTERNOON AS THE FLOW TURNS NW TO N. OTHERWISE...CLOUDS SHOULD BE ON THE DECREASE MON AFTERNOON. EXPECT SEVERAL DEGREES OF WARMING IN MOST AREAS ON MON...WITH MAX TEMPS BACK TO NEAR NORMAL LEVELS IN MOST AREAS. RAINFALL TOTALS SHOULD BE ONE TENTH OF AN INCH OR LESS ACROSS VTU AND LOS ANGELES COUNTIES...EXCEPT POSSIBLY A BIT HIGHER ACROSS THE ERN SAN GABRIEL MTNS AND FOOTHILLS. ACROSS SBA AND SLO COUNTIES... EXPECT RAINFALL TOTALS OF ONE TENTH TO ONE THIRD OF AN INCH...EXCEPT POSSIBLY UP TO THREE QUARTERS OF AN INCH ACROSS NWRN SLO COUNTY...MAINLY IN THE HIGHER ELEVATIONS. SNOW LEVELS ARE EXPECTED TO BE ABOVE 7500 FEET THROUGH EARLY MON...WITH LITTLE IN THE WAY OF SNOW ACCUMULATION EXPECTED. AN UPPER RIDGE WILL AMPLIFY IN THE ERN PAC MON NIGHT AND TUE...CAUSING HEIGHTS ACROSS THE REGION TO RISE. INCREASING N-S GRADIENTS MON NIGHT AND EARLY TUE WILL LIKELY BRING SOME GUSTY WINDS TO THE SANTA YNEZ RANGE...THE ADJACENT SOUTH COAST OF SBA COUNTY BELOW PASSES AND CANYONS...THE MTNS OF L.A. AND VTU COUNTIES (PARTICULARLY THROUGH THE INTERSTATE 5 CORRIDOR)... AND POSSIBLY TO THE VALLEYS OF WRN L.A. AND ERN VTU COUNTIES...THE SANTA MONICA RANGE...AND THE L.A. COUNTY COAST BELOW PASSES AND CANYONS FROM MALIBU TO THE HOLLYWOOD HILLS. SKIES WILL BE MOSTLY CLEAR MON NIGHT AND TUE. THERE WILL BE A SIGNIFICANT JUMP IN MAX TEMPS ON TUE...WITH HIGHS LIKELY REACHING OR SLIGHTLY EXCEEDING 80 DEGREES IN THE WARMER LOCATIONS IN THE VALLEYS. .LONG TERM...(WED-SAT) LOW LEVEL FLOW WILL TURN NELY WED...AND HEIGHTS WILL CONTINUE TO RISE ACROSS THE REGION. SOME GUSTY WINDS ARE EXPECTED ACROSS MUCH OF L.A. AND VTU COUNTIES...BUT PROBABLY JUST BELOW ADVISORY LEVELS. MAX TEMPS WED WILL RISE WELL INTO THE 80S ACROSS MANY VALLEY LOCATIONS AND POSSIBLY INTERIOR SECTIONS OF THE COASTAL PLAIN. ANOTHER ROUND OF GUSTY WINDS EXPECTED ACROSS PORTIONS OF L.A. AND VTU COUNTIES WED NIGHT INTO THU MORNING. SLIGHT COOLING IS EXPECTED ON THU ACROSS THE COASTAL PLAIN AS WEAK OFFSHORE FLOW TURNS WEAKLY ONSHORE. HOWEVER...MAX TEMPS ON THU WILL REMAIN WELL ABOVE NORMAL EVEN ACROSS THE COASTAL PLAIN. ADDITIONAL AND MORE WIDESPREAD COOLING IS EXPECTED FRI AND SAT AS AN UPPER TROUGH APPROACHES THE WEST COAST...BUT EVEN THEN...MAX TEMPS WILL BE ABOVE NORMAL. && .AVIATION...13/1800Z MID/UPPER LEVEL RIDGE UPSTREAM WILL APPROACH THE AREA. UPPER LEVEL MODERATE WEST-NORTHWEST WINDS WILL PREVAIL WHILE MID LEVEL LIGHT TO MODERATE WEST WINDS BECOME LIGHT TO MODERATE NORTH-NORTHWEST AFTER 14/20Z. A SURFACE TROUGH OF LOW PRESSURE ALONG THE CENTRAL COAST WILL WEAKEN WHILE SHIFTING SOUTH THROUGH TONIGHT. WEAK ONSHORE PRESSURE GRADIENT THROUGH 14/22Z THEN MIXED WEAK NORTHERLY AND ONSHORE GRADIENT. FREEZING LEVEL WAS APPROXIMATELY 8KFT OVER THE NORTH HALF OF THE AREA AND 10KFT IN THE SOUTH HALF THIS MORNING DIFFER BY PLUS 2KFT MONDAY MORNING. MARINE LAYER AT LAX AT 1600Z IS NONE. KLAX...CHANCE CIGS 027 BETWEEN 14/03-14/11Z WITH LIGHT DRIZZLE AT TIMES BETWEEN 14/07-14/11Z. CHANCE CIGS 015 VSBY 5SM WITH LIGHT DRIZZLE BETWEEN 14/11-14/16Z. CHANCE CIGS 030 BETWEEN 14/16-14/19Z. KBUR...CHANCE CIGS 040 14/03-14/07Z THEN CHANCE CIGS 023 AFTER 14/07Z. VIRTUALLY CERTAIN - 95-100% VERY LIKELY - 80-95% LIKELY - 60-80% CHANCE - 30-60% VERY UNLIKELY - 20% OR LESS && .MARINE...13/900 AM. WEST WINDS WILL LIKELY INCREASE FROM SANTA BARBARA TO SAN MATEO POINT AND THERE IS A CHANCE SMALL CRAFT ADVISORY CONDITIONS WILL EXIST LATE THIS AFTERNOON THROUGH MID EVENING. OTHERWISE WEST WINDS WILL PREVAIL FROM SAN MIGUEL ISLAND TO SAN CLEMENTE ISLAND TODAY WITH SCA CONDITIONS. THE WINDS WILL LIKELY BECOME NORTHWEST AND NORTH AND INCREASE MONDAY THROUGH TUESDAY AND SCA CONDITIONS WILL LIKELY EXIST MONDAY AFTERNOON THROUGH MONDAY EVENING OVER THE ENTIRE AREA. THE WINDS WILL THEN DIMINISH OVER THE SANTA BARBARA, SANTA MONICA AND SAN PEDRO BASINS MONDAY NIGHT BUT PERSIST AND INCREASE FROM PIEDRAS BLANCAS TO SAN CLEMENTE ISLAND TUESDAY. SEAS WILL LIKELY PERSIST AROUND 10 FEET FROM PIEDRAS BLANCAS TO POINT SAL AND FROM POINT SAL TO SAN CLEMENTE ISLAND THIS MORNING. SWELLS FROM 300-310 DEGREES WILL BUILD TO AROUND 15 FEET THIS AFTERNOON THROUGH TONIGHT AND SCA FOR HAZARDOUS SEA CONDITIONS WILL LIKELY PERSIST AS LOCALLY GENERATED SEAS COMBINE WITH THE SWELL THROUGH WEDNESDAY. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...HIGH SURF ADVISORY IN EFFECT UNTIL MIDNIGHT PDT TUESDAY NIGHT FOR ZONES 34-35. (SEE LAXCFWLOX). BEACH HAZARDS STATEMENT IN EFFECT THROUGH THIS EVENING FOR ZONE 39. (SEE LAXCFWLOX). HIGH SURF ADVISORY IN EFFECT UNTIL MIDNIGHT PDT TONIGHT FOR ZONES 40-41-87. (SEE LAXCFWLOX). PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS IN EFFECT UNTIL 6 AM PDT TUESDAY FOR ZONES 645-670-673. (SEE LAXMWWLOX). SMALL CRAFT ADVISORY IN EFFECT UNTIL 10 PM PDT THIS EVENING FOR ZONES 650-655. (SEE LAXMWWLOX). SMALL CRAFT ADVISORY IN EFFECT UNTIL 4 AM PDT TUESDAY FOR ZONE 676. (SEE LAXMWWLOX). && $$ PUBLIC...CK AVIATION...30 MARINE...30 SYNOPSIS...DB WEATHER.GOV/LOSANGELES
Area Forecast Discussion...UPDATED National Weather Service Reno NV 1026 AM PDT SUN MAR 13 2016 .UPDATE... Only minor adjustments to the ongoing forecast this morning. Latest radar imagery showed heaviest snow along the Sierra Crest from Donner Summit through Echo Pass and down to about Ebbetts Pass. Latest webcams from Caltrans indicate snow covered roads along major routes over the crest. Farther north, snow has temporarily eased and allowed roads to improve across Fredonyer Summit and near Bogard. Slide Mt temperatures had risen to mid 20s with surface temperatures in the low-mid 30s suggest snow will occasionally mix with or briefly change over to rain through the afternoon at lake level with only minor accumulations during the day. However, next wave was moving into northern CA and snow intensity will increase late this afternoon with snow levels dropping back below 6000 feet this evening. As far as wind, the 12z KREV sounding indicated a warm stable layer near ridge level. There have been a few reports of LLWS and light-mod turbulence for AIRCRAFT arrivals/departures at KRNO. Gradients continue to increase this morning and the 12z model soundings still indicate increasing winds and potential for damaging winds along the Hwy 395 corridor as the stable layer sharpens and winds decrease above this layer. Hohmann && .PREVIOUS DISCUSSION... /Issued 330 AM PDT SUN MAR 13 2016/ SYNOPSIS... A strong winter storm will impact the region through early Monday with strong winds and periods of heavy mountain snow. Snow amounts will be significant across the northern Sierra and higher terrain of northeast California with significant impacts to travel. Drier and warmer conditions will return for the upcoming week. SHORT TERM... A strong winter storm remains on track early today with snow falling from western Lassen County south into the Tahoe region. Not much is currently falling along the crest in Mono County...but that should change through the day. This winter storm is composed of a series of impulses moving through a very fast mid/upper level flow that is also tapping into substantial moisture. This will bring periods of heavy snow to parts of the Sierra and northeast California but lesser amounts to the east of the Sierra where shadowing will be much more common along with very strong winds. All of this activity winds down late Monday with mainly tranquil weather for Tuesday. Snow levels could be a little tricky in the Sierra today. A substantial push of moisture this morning should keep precipitation intensity high enough to maintain lower snow levels through about noon...but then the intensity may ease a bit. This would allow snow levels to rise briefly in the Sierra and northeast California...possibly above 6000 feet. That would limit the amount of accumulations in the lower valleys of the Sierra... central Plumas County and western Lassen County. Snow levels should fall again tonight as the core of the colder air moves into the region...but the amount of precipitation will be winding down after midnight tonight. East of the Sierra...a substantial stable layer aloft...noted by the warming in the forecast soundings and cross sections...will limit any spillover into far western Nevada to later tonight when the cold air aloft moves in and causes some instability. To the north in northwest Nevada and far northeast California, the chances for precipitation look to be increased today as this area generally benefits from these stronger pushes of moisture. Winds will again increase through the day. While the low level gradient will increase due to the pressure/temperature differential between the Sierra and western Nevada...the aforementioned stable layer aloft with its attendant warming is a tell-tale sign of potential downslope enhancement of the wind today. The strongest winds east of the Sierra should occur between about 8 am and roughly 2 pm today when gusts could reach up to 70 mph in wind prone areas. These gusty winds will abate slightly...but still continue strong into the evening hours and even into the morning hours Monday for areas south of Highway 50 and east of Highway 395. The storm exits to the east Monday afternoon/evening with cool northwest flow developing over the region. A few lingering showers are possible Monday night along with gusty winds to near 35 mph in the northwest flow. Ridging starts to develop well to the west by late Tuesday. We will see some warming aloft but limited warming at the surface as east to northeast flow in the low levels locks some below average high temperatures into much of the area for Monday and Tuesday. 20 LONG TERM...Wednesday through Saturday... Highlights: - Dry with daytime temps near average Wed-Fri, generally light NE-E winds. - Ridge weakens next weekend with showers possible (mainly Sunday). Latest guidance favors a weak and fast moving shortwave with limited precip totals and snow levels rather high (probably above 7000 feet). Medium range guidance continues to keep all areas dry through at least Friday with generally light NE-E winds. With shortwave energy diving south across the eastern Great Basin late Thursday-Thurs night, it now appears more likely that temperatures on Friday will not warm up much from Thursday. Winds may increase a bit Thursday evening mainly in northwest and west central NV. For Saturday, ridge is projected to move east across CA-NV. This should allow a few more degrees of warming with some increase in high clouds. Precipitation chances appear rather slim through Saturday, before moisture increases later in the weekend. While the latest guidance trended weaker, there is still some uncertainty in the strength of this possible weather system, so keep posted on the latest forecasts if you have travel or outdoor plans next weekend. MJD AVIATION... Widespread and significant weather impacts to aviation will continue today and tonight, with conditions improving later Monday. -Winds- The strongest winds are expected from late this morning through early evening with potential for surface gusts above 50 kt and Sierra ridge gusts above 80 kt. Some of these strongest winds will continue through tonight south of Highway 50, while elsewhere winds will drop slightly. Severe and widespread turbulence with periods of LLWS and possible lee side rotors, which could lead to flight delays, cancellations or diverted landings. Windy conditions with gusts 30-40 kt will persist though much of Monday before diminishing by early evening. -Precipitation- Snowfall will be heaviest in the northern Sierra from the Tahoe terminals northward today through tonight, with long periods of poor visibility and low ceilings along with significant snow accumulations on paved surfaces. Snow will arrive later this afternoon and continue through tonight for the Sierra south of Tahoe including KMMH, with lesser accumulations. For western NV including KRNO/KCXP, the best chance for rain is this evening, otherwise most valleys will likely be shadowed with the strong winds being the main impact. MJD && .REV Watches/Warnings/Advisories... NV...High Wind Warning until 3 AM PDT Monday NVZ003-005. Winter Storm Warning until 11 AM PDT Monday NVZ002. Wind Advisory until 11 AM PDT Monday NVZ001-004. CA...High Wind Warning until 3 AM PDT Monday CAZ070-071. Winter Storm Warning until 11 AM PDT Monday CAZ071. High Wind Warning from 3 PM this afternoon to 11 AM PDT Monday CAZ073. Winter Weather Advisory until 11 AM PDT Monday CAZ073. Winter Storm Warning until 11 AM PDT Monday CAZ072. && $$ For more information from the National Weather Service visit... http://weather.gov/reno
AREA FORECAST DISCUSSION
NWS LAS VEGAS NV
245 PM PST SUN MAR 13 2016 .SYNOPSIS...A PACIFIC STORM SYSTEM WILL MOVE THROUGH THE GREAT BASIN TONIGHT INTO MONDAY BRINGING A CHANCE OF PRECIPITATION TO THE SIERRA AND LOCALLY BREEZY TO WINDY CONDITIONS TO THE SOUTHERN GREAT BASIN AND MOJAVE DESERT. DRY AND WARM CONDITIONS ARE EXPECTED TUESDAY THROUGH FRIDAY AS HIGH PRESSURE BUILDS ALONG THE WEST COAST. && .DISCUSSION...TONIGHT THROUGH SUNDAY A LOW AMPLITUDE SHORTWAVE TROUGH WILL MOVE ACROSS NORTHERN CALIFORNIA INTO NEVADA TONIGHT AND THEN INTO UTAH BY MONDAY AFTERNOON. MOST OF THE MOISTURE WITH THIS SYSTEM WILL REMAIN NORTH OF THE AREA BUT AN INCH OR TWO OF SNOW WILL BE POSSIBLE IN THE HIGHER ELEVATIONS OF THE SIERRA TONIGHT WITH JUST A SLIGHT CHANCE OF SHOWERS BRUSHING NORTHERN LINCOLN COUNTY MONDAY. ANY PRECIPITATION OVER LINCOLN COUNTY WILL BE VERY LIGHT. THERE WILL ALSO BE SLIGHT COOLING MONDAY DUE TO THIS TROUGH ALONG WITH CONSIDERABLE HIGH CLOUDS AT TIME TONIGHT AND MONDAY. THE MAIN IMPACT WILL BE WIND WHICH HAS BEEN INCREASING THIS AFTERNOON...ESPECIALLY ACROSS WESTERN SAN BERNARDINO COUNTY WHERE GUSTS OVER 40 MPH HAVE BEEN RECORDED. THE HIGH WIND WARNING FOR THE SIERRA AND ADVISORIES FOR THE OWENS VALLEY AND MUCH OF SAN BERNARDINO COUNTY STILL LOOK GOOD. SOME HIRES MODEL OUTPUT SUGGEST WINDS IN THE LAS VEGAS VALLEY WILL REACH ADVISORY LEVELS. I FEEL THAT THERE COULD BE A COUPLE OF HOURS THIS EVENING IN A SMALL PART OF THE VALLEY...ESPECIALLY FAR WEST AND SOUTH...WHERE THAT IS THE CASE BUT OVERALL NOT WORTH AN ADVISORY. WHILE GUSTY SOUTHWEST WINDS DIMINISH MONDAY AFTERNOON ACROSS THE CENTRAL AND SOUTHERN CWA...BREEZY NORTHWEST WINDS WILL DEVELOP ACROSS ESMERALDA...CENTRAL NYE AND LINCOLN COUNTIES BEHIND THE EXITING TROUGH. A RIDGE OF HIGH PRESSURE WILL GRADUALLY AMPLIFY ALONG THE WEST COAST TUESDAY THROUGH FRIDAY LEADING TO DRY AND MILD TEMPERATURES. THERE WILL ALSO BE LOCALLY BREEZY NORTH WINDS AT TIMES DOWN THE COLORADO RIVER VALLEY. THE UPPER RIDGE WILL SLOWLY TRAVERSE THE CWA SATURDAY AND SUNDAY WITH WARMING TEMPERATURES AND DRY CONDITIONS. IF THE RIDGE AXIS MOVES A LITTLE TO OUR EAST SUNDAY...WE WILL PROBABLY START TO SEE AN INCREASE IN HIGH CLOUD COVER AND POSSIBLY SOME LOCALLY BREEZY SOUTHWEST WINDS. && .AVIATION....FOR MCCARRAN..SOUTH-SOUTHWEST WINDS WILL CONTINUE TO INCREASE THIS AFTERNOON...GUSTING TO 25-30 KTS BY 01Z. THESE GUSTY WINDS WILL PERSIST INTO THIS EVENING...THEN GRADUALLY DIMINISH DURING THE EARLY MORNING HOURS. WIND MAY TURN TO A WEST TO NORTHWEST DIRECTION AROUND 12Z MONDAY...THEN BECOME LIGHT AND VARIABLE FOR MUCH OF MONDAY. FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST CALIFORNIA...GUSTY WEST AND SOUTHWEST WINDS ACROSS MUCH OF THE REGION THROUGH THIS AFTERNOON AND TONIGHT...WITH SUSTAINED SPEEDS GENERALLY 10-20 KTS AND GUSTS 25-30 KTS. STRONGER WINDS WILL OCCUR OVER THE SOUTHERN SIERRA AND THE WESTERN MOJAVE DESERT TODAY (NEAR KDAG/KBYS). MODERATE TO SEVERE TURBULENCE WILL BE POSSIBLE OVER THE OWENS VALLEY AS WELL AS AREAS OF BLOWING DUST FROM LAS VEGAS WEST. GUSTY WINDS WILL CONTINUE MONDAY ACROSS SAN BERNARDINO COUNTY...AS WELL AS CENTRAL NEVADA. AREAS AROUND LAS VEGAS AND NORTHWEST ARIZONA WILL SEE MUCH LIGHTER WINDS MONDAY. MORE NORTHERLY WINDS ARE EXPECTED TUESDAY. && .SPOTTER INFORMATION STATEMENT...SPOTTER ACTIVATION NOT EXPECTED. HOWEVER STRONG WINDS ARE EXPECTED ACROSS PORTIONS OF THE AREA AND SPOTTERS SHOULD REPORT ANY SIGNIFICANT WEATHER OR WEATHER-RELATED DAMAGE ACCORDING TO STANDARD OPERATING PROCEDURES. && $$ DISCUSSION...HARRISON AVIATION...WOLCOTT FOR MORE FORECAST INFORMATION...SEE US ON OUR WEBPAGE: HTTP://WEATHER.GOV/LASVEGAS OR FOLLOW US ON FACEBOOK AND TWITTER
Area Forecast Discussion...UPDATED National Weather Service Reno NV 1026 AM PDT SUN MAR 13 2016 .UPDATE... Only minor adjustments to the ongoing forecast this morning. Latest radar imagery showed heaviest snow along the Sierra Crest from Donner Summit through Echo Pass and down to about Ebbetts Pass. Latest webcams from Caltrans indicate snow covered roads along major routes over the crest. Farther north, snow has temporarily eased and allowed roads to improve across Fredonyer Summit and near Bogard. Slide Mt temperatures had risen to mid 20s with surface temperatures in the low-mid 30s suggest snow will occasionally mix with or briefly change over to rain through the afternoon at lake level with only minor accumulations during the day. However, next wave was moving into northern CA and snow intensity will increase late this afternoon with snow levels dropping back below 6000 feet this evening. As far as wind, the 12z KREV sounding indicated a warm stable layer near ridge level. There have been a few reports of LLWS and light-mod turbulence for AIRCRAFT arrivals/departures at KRNO. Gradients continue to increase this morning and the 12z model soundings still indicate increasing winds and potential for damaging winds along the Hwy 395 corridor as the stable layer sharpens and winds decrease above this layer. Hohmann && .PREVIOUS DISCUSSION... /Issued 330 AM PDT SUN MAR 13 2016/ SYNOPSIS... A strong winter storm will impact the region through early Monday with strong winds and periods of heavy mountain snow. Snow amounts will be significant across the northern Sierra and higher terrain of northeast California with significant impacts to travel. Drier and warmer conditions will return for the upcoming week. SHORT TERM... A strong winter storm remains on track early today with snow falling from western Lassen County south into the Tahoe region. Not much is currently falling along the crest in Mono County...but that should change through the day. This winter storm is composed of a series of impulses moving through a very fast mid/upper level flow that is also tapping into substantial moisture. This will bring periods of heavy snow to parts of the Sierra and northeast California but lesser amounts to the east of the Sierra where shadowing will be much more common along with very strong winds. All of this activity winds down late Monday with mainly tranquil weather for Tuesday. Snow levels could be a little tricky in the Sierra today. A substantial push of moisture this morning should keep precipitation intensity high enough to maintain lower snow levels through about noon...but then the intensity may ease a bit. This would allow snow levels to rise briefly in the Sierra and northeast California...possibly above 6000 feet. That would limit the amount of accumulations in the lower valleys of the Sierra... central Plumas County and western Lassen County. Snow levels should fall again tonight as the core of the colder air moves into the region...but the amount of precipitation will be winding down after midnight tonight. East of the Sierra...a substantial stable layer aloft...noted by the warming in the forecast soundings and cross sections...will limit any spillover into far western Nevada to later tonight when the cold air aloft moves in and causes some instability. To the north in northwest Nevada and far northeast California, the chances for precipitation look to be increased today as this area generally benefits from these stronger pushes of moisture. Winds will again increase through the day. While the low level gradient will increase due to the pressure/temperature differential between the Sierra and western Nevada...the aforementioned stable layer aloft with its attendant warming is a tell-tale sign of potential downslope enhancement of the wind today. The strongest winds east of the Sierra should occur between about 8 am and roughly 2 pm today when gusts could reach up to 70 mph in wind prone areas. These gusty winds will abate slightly...but still continue strong into the evening hours and even into the morning hours Monday for areas south of Highway 50 and east of Highway 395. The storm exits to the east Monday afternoon/evening with cool northwest flow developing over the region. A few lingering showers are possible Monday night along with gusty winds to near 35 mph in the northwest flow. Ridging starts to develop well to the west by late Tuesday. We will see some warming aloft but limited warming at the surface as east to northeast flow in the low levels locks some below average high temperatures into much of the area for Monday and Tuesday. 20 LONG TERM...Wednesday through Saturday... Highlights: - Dry with daytime temps near average Wed-Fri, generally light NE-E winds. - Ridge weakens next weekend with showers possible (mainly Sunday). Latest guidance favors a weak and fast moving shortwave with limited precip totals and snow levels rather high (probably above 7000 feet). Medium range guidance continues to keep all areas dry through at least Friday with generally light NE-E winds. With shortwave energy diving south across the eastern Great Basin late Thursday-Thurs night, it now appears more likely that temperatures on Friday will not warm up much from Thursday. Winds may increase a bit Thursday evening mainly in northwest and west central NV. For Saturday, ridge is projected to move east across CA-NV. This should allow a few more degrees of warming with some increase in high clouds. Precipitation chances appear rather slim through Saturday, before moisture increases later in the weekend. While the latest guidance trended weaker, there is still some uncertainty in the strength of this possible weather system, so keep posted on the latest forecasts if you have travel or outdoor plans next weekend. MJD AVIATION... Widespread and significant weather impacts to aviation will continue today and tonight, with conditions improving later Monday. -Winds- The strongest winds are expected from late this morning through early evening with potential for surface gusts above 50 kt and Sierra ridge gusts above 80 kt. Some of these strongest winds will continue through tonight south of Highway 50, while elsewhere winds will drop slightly. Severe and widespread turbulence with periods of LLWS and possible lee side rotors, which could lead to flight delays, cancellations or diverted landings. Windy conditions with gusts 30-40 kt will persist though much of Monday before diminishing by early evening. -Precipitation- Snowfall will be heaviest in the northern Sierra from the Tahoe terminals northward today through tonight, with long periods of poor visibility and low ceilings along with significant snow accumulations on paved surfaces. Snow will arrive later this afternoon and continue through tonight for the Sierra south of Tahoe including KMMH, with lesser accumulations. For western NV including KRNO/KCXP, the best chance for rain is this evening, otherwise most valleys will likely be shadowed with the strong winds being the main impact. MJD && .REV Watches/Warnings/Advisories... NV...High Wind Warning until 3 AM PDT Monday NVZ003-005. Winter Storm Warning until 11 AM PDT Monday NVZ002. Wind Advisory until 11 AM PDT Monday NVZ001-004. CA...High Wind Warning until 3 AM PDT Monday CAZ070-071. Winter Storm Warning until 11 AM PDT Monday CAZ071. High Wind Warning from 3 PM this afternoon to 11 AM PDT Monday CAZ073. Winter Weather Advisory until 11 AM PDT Monday CAZ073. Winter Storm Warning until 11 AM PDT Monday CAZ072. && $$ For more information from the National Weather Service visit... http://weather.gov/reno
AREA FORECAST DISCUSSION
NWS SEATTLE WA
910 AM PDT SUN MAR 13 2016 .SYNOPSIS...A VIGOROUS STORM WILL BRING VERY WINDY CONDITIONS TO WESTERN WASHINGTON THROUGH THIS EVENING...ALONG WITH RAIN IN THE LOWLANDS AND SNOW IN THE MOUNTAINS. COOL MOIST WESTERLY FLOW WILL MAINTAIN SHOWERS MONDAY THOUGH WEDNESDAY WITH MORE MOUNTAIN SNOW. AN UPPER LEVEL RIDGE IS WILL BRING DRY MILD WEATHER THURSDAY THROUGH SATURDAY. && .SHORT TERM...THE STORM IS MOVING FASTER THAT PREVIOUSLY EXPECTED. BUOY 89 WEST OF THE N OREGON COAST WAS DOWN TO 983 MB AT 15Z...A LITTLE DEEPER THAN FORECAST. HOWEVER THE MOST IMPORTANT CHANGE IS THAT THE LOW IS MOVING FASTER THAN EXPECTED AND THE STRONGEST WINDS ARE NOW EXPECTED 2-3 HOURS SOONER. THE HIGH WIND WARNING STATEMENT HAS BEEN UPDATED WITH THIS CHANGE. RECENT HOURLY HRRR RUNS AS WELL SOME OF THE EARLIER 00Z AND 06Z MODELS ALSO TRACK THE LOW SLIGHTLY FARTHER TO THE NW...MORE OVER THE NW OLYMPICS. THE MODELS ARE ALSO RUNNING SLIGHTLY WEAKER ON THE WINDS. 925 MB WINDS ARE CLOSER TO 50 KT WHICH WOULD TRANSLATE TO SURFACE GUSTS IN THE 50-60 MPH RANGE. SUSTAINED SURFACE WINDS WILL STILL BE IN THE 25-40 MPH RANGE. WINDS WILL DIMINISH SOONER AS WELL WITH WINDS EASING SLOWLY FROM LATE AFTERNOON THROUGH MID EVENING. OTHERWISE THERE IS NO CHANGE TO THE FORECAST. SIGNIFICANT...WARNING LEVEL...SNOW IS STILL EXPECTED OVER MOUNT BAKER AND MOUNT RAINIER THIS AFTERNOON THROUGH MONDAY MORNING...WITH LOWER ADVISORY LEVEL AMOUNTS EXPECTED OVER SNOQUALMIE AND STEVENS PASS. KAM REMAINDER OF THE DISCUSSION FROM THE 301 AM AFD...AN UPPER TROUGH WILL FOLLOW THE FRONTAL SYSTEM TONIGHT...WITH MOIST WESTERLY FLOW AT LOWER LEVELS. FORECAST PRECIPITATION AMOUNTS HAVE NOT CHANGED MUCH. RAINFALL IN THE INTERIOR LOWLANDS FOR TODAY AND TONIGHT SHOULD BE MAINLY 0.25 TO 0.75 INCH...WITH 0.50 TO 1.25 INCH AT THE COAST. THE SNOW LEVEL WILL BE 2500 TO 3500 FT TODAY AND TONIGHT...AND FALL TO 2000 FT MONDAY AS ANOTHER SHORTWAVE IN THE WESTERLY FLOW MOVES THROUGH THE AREA. UP TO 2.5 INCHES LIQUID EQUIVALENT PRECIPITATION WILL FALL IN THE MOUNTAINS TODAY THROUGH MONDAY...WITH THE HEAVIEST AMOUNTS AROUND MOUNT BAKER AND MOUNT RAINIER. A WINTER STORM WARNING WILL REMAIN IN EFFECT FROM NOON TODAY THROUGH NOON MONDAY FOR THE CASCADES OF WHATCOM AND SKAGIT COUNTIES AND THE CASCADES OF PIERCE AND LEWIS COUNTIES. A WINTER WEATHER ADVISORY WILL REMAIN IN EFFECT FOR THE CASCADES OF SNOHOMISH AND KING COUNTIES. AN UPPER RIDGE WILL START BUILDING WELL OFFSHORE ON TUESDAY...BUT MOIST ONSHORE FLOW WILL CONTINUE ACROSS WESTERN WASHINGTON WITH MAYBE ANOTHER WEAK SHORTWAVE MOVING THROUGH. IT STILL LOOKS LIKE A RATHER SHOWERY DAY ESPECIALLY FOR THE COAST AND MOUNTAINS. THE SNOW LEVEL WILL STILL BE 2000 TO 2500 FT. MCDONNAL .LONG TERM...THE UPPER RIDGE WILL BUILD OFFSHORE ALONG 135W ON WEDNESDAY...WITH THE FLOW ALOFT VEERING TO NORTHWEST OVER WESTERN WASHINGTON AND THE AIR MASS GRADUALLY DRYING. THE UPPER RIDGE WILL MOVE SLOWLY TOWARD THE REGION THURSDAY AND FRIDAY...THEN WEAKEN AS IT MOVES INLAND ON SATURDAY. THIS SHOULD BE A DRY PERIOD WITH SOME SUNSHINE. MCDONNAL && .AVIATION...A BROAD UPPER TROUGH OFFSHORE WITH STRONG SW FLOW ALOFT OVER WA. THE FLOW ALOFT WILL TURN MORE WESTERLY TONIGHT. AN INTENSE LOW PRESSURE CENTER JUST OFF THE NORTHERN OREGON COAST THIS MORNING IS EXPECTED TO TRACK NE ACROSS NW WA THIS AFTERNOON WITH ASSOCIATED STRONG WIND OF GUSTS 40-70 KT THROUGH THIS EVENING. AIR MASS STABLE WITH INCREASING MOISTURE THIS MORNING. AIR MASS BECOMING UNSTABLE AFTER 20Z. RAIN SPREADING INLAND THIS MORNING WITH CEILINGS DROPPING TO MVFR MOST AREAS. RAIN TURNING TO SHOWERS THIS AFTERNOON WITH CEILINGS IN THE VICINITY OF SHOWERS REMAINING MVFR...LIKELY BREAKS IN CLOUD COVER BEYOND SHOWERS. EXPECT A LOT OF MECHANICAL TURBC ASSOCIATED WITH THE STRONG WINDS. NOT A GOOD DAY FOR FLYING...TIE AIRCRAFT DOWN OR SHELTER IN A HANGER IF POSSIBLE. KSEA...VFR CEILINGS WILL LIKELY FALL TO MVFR BEFORE 18Z IN RAIN. SE WIND 8-14 KT THIS MORNING PICKING UP MIDDAY AND BECOMING SOUTHERLY WITH GUSTS AS HIGH AS 50 KT OR SO. BUEHNER && .MARINE...A 985 MB SURFACE LOW AT 15Z THIS MORNING 150 NM OFF CASCADE HEAD IS EXPECTED TO TRACK NE AND CROSS THE OLYMPIC PENINSULA AS A 978 MB LOW LATE THIS AFTERNOON. THIS SYSTEM WILL BRING STORM FORCE WINDS TO MOST COASTAL WATERS...IF NOT WITH THE PRE-LOW SOUTHEASTERLIES...THEN WITH THE POST-LOW WEST AND SOUTHWESTERLIES. A GOOD DAY TO STAY IN PORT AND SECURELY TIE YOUR BOAT DOWN. SEAS WILL BUILD TO 20 TO 24 FT TONIGHT WITH THE HIGHEST SEAS AROUND GRAYS HARBOR. SOME BEACH EROSION IS LIKELY. ONSHORE FLOW WILL DIMINISH MONDAY AND TUESDAY. HIGHER PRES IS FORECAST TO BUILD OVER THE REGION WEDNESDAY WITH OFFSHORE FLOW THURSDAY. BUEHNER && .HYDROLOGY...THE SKOKOMISH RIVER WILL PROBABLY FLOOD AGAIN TONIGHT. A FLOOD WATCH IS IN EFFECT FOR MASON COUNTY. OTHERWISE FLOODING IS NOT EXPECTED ON AREA RIVERS FOR THE NEXT WEEK. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...HIGH WIND WARNING TODAY TO 11 PM PDT THIS EVENING FOR BELLEVUE AND VICINITY-BREMERTON AND VICINITY-CENTRAL COAST- EAST PUGET SOUND LOWLANDS-EVERETT AND VICINITY-HOOD CANAL AREA-LOWER CHEHALIS VALLEY AREA-NORTH COAST-SEATTLE AND VICINITY-SOUTHWEST INTERIOR-TACOMA AREA. COASTAL FLOOD ADVISORY UNTIL 11 AM PDT THIS MORNING FOR ADMIRALTY INLET AREA-BREMERTON AND VICINITY-EVERETT AND VICINITY-HOOD CANAL AREA-SEATTLE AND VICINITY-SOUTHWEST INTERIOR-TACOMA AREA. WINTER WEATHER ADVISORY UNTIL NOON PDT TODAY FOR CASCADES OF PIERCE AND LEWIS COUNTIES. WINTER STORM WARNING FROM NOON TODAY TO NOON PDT MONDAY FOR CASCADES OF PIERCE AND LEWIS COUNTIES-CASCADES OF WHATCOM AND SKAGIT COUNTIES. WINTER WEATHER ADVISORY FROM NOON TODAY TO NOON PDT MONDAY FOR CASCADES OF SNOHOMISH AND KING COUNTIES. FLOOD WATCH FROM NOON PDT TODAY THROUGH MONDAY MORNING FOR HOOD CANAL AREA-LOWER CHEHALIS VALLEY AREA-OLYMPICS. HIGH WIND WARNING TO 11 PM PDT THIS EVENING FOR ADMIRALTY INLET AREA-SAN JUAN COUNTY-WESTERN SKAGIT COUNTY-WESTERN WHATCOM COUNTY. COASTAL FLOOD ADVISORY UNTIL 9 AM PDT THIS MORNING FOR CENTRAL COAST. HIGH WIND WARNING TODAY FOR THE EASTERN STRAIT OF JUAN DE FUCA. PZ...SMALL CRAFT ADVISORY FOR ROUGH BAR UNTIL 11 AM PDT MONDAY FOR GRAYS HARBOR BAR. STORM WARNING COAST AND NORTHERN INLAND WATERS. STORM WARNING CENTRAL AND EAST STRAIT OF JUAN DE FUCA. GALE WARNING WEST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA ...ADMIRALTY INLET-PUGET SOUND AND HOOD CANAL. && $$ WWW.WEATHER.GOV/SEATTLE YOU CAN SEE AN ILLUSTRATED VERSION OF THIS DISCUSSION AT WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML