Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/17/16


SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NWS ANCHORAGE AK
429 AM AKST MON FEB 15 2016 .ANALYSIS AND UPPER LEVELS... A DECAYING UPPER LEVEL LOW OVER THE SOUTHERN ALASKA PENINSULA/EASTERN ALEUTIANS IS IN THE PROCESS OF TRANSFERRING ITS ENERGY EASTWARD TO A DEVELOPING UPPER LOW AND ATTENDANT SURFACE LOW OVER THE NORTH PACIFIC WELL SOUTH OF THE GULF. THIS EASTWARD SHIFT TO THE UPPER LOW...AND THE PATTERN AS A WHOLE...IS ALSO BEING AIDED BY THE ENCROACHING SUBTROPICAL JET PUSHING EASTWARD ACROSS THE WESTERN AND CENTRAL ALEUTIANS. THIS IS EVIDENCED BY THE RAPIDLY MOVING UPPER LEVEL CLOUD COVER PUSHING EAST ACROSS THE WESTERN BERING AND ALEUTIANS. THE SUBTROPICAL JET IS ALSO ENERGIZING A DEEPENING LOW RACING NORTHEASTWARD OFF THE COAST OF THE KAMCHATKA PENINSULA. THIS LOW AND ITS ASSOCIATED FRONT WILL BE THE PRIMARY DRIVERS OF THE ACTIVE WEATHER ACROSS THE BERING THE NEXT COUPLE DAYS. THE UPPER LEVELS ARE RELATIVELY TRANQUIL ACROSS SOUTHCENTRAL AS THE LARGER AND STRONGER UPPER LEVEL FEATURES TRAVERSE WELL SOUTH OF THE AREA. ANCHORAGE`S 00Z SOUNDING AND MORE RECENT ACARS SOUNDINGS SHOW SLOW COOLING HAS OCCURRED THROUGHOUT THE LOWEST 100 MB. MESONET OBS FROM THE HIGHER ELEVATIONS EAST OF ANCHORAGE HAVE BEEN COOLING THE PAST FEW HOURS AS THOSE OBSERVATIONS COOL THROUGH THE 30S. IR SATELLITE OBSERVATIONS AROUND SOUTHCENTRAL SUGGEST A GENERAL DISSIPATION OF THE CLOUD COVER OVERNIGHT HAS OCCURRED IN RESPONSE TO WEAK UPPER LEVEL RIDGING BUILDING ACROSS SOUTHCENTRAL. NEARLY STATIONARY WEAK UPPER LEVEL AND SURFACE TROUGHINESS ACROSS THE BRISTOL BAY REGION HAS KEPT A NARROW AREA OF RAIN AND SNOW FOR PORTIONS OF BRISTOL BAY THROUGH MOST OF THE OVERNIGHT. THIS FEATURE HAS BEEN SLOWLY DIMINISHING AS IT DRIFTS NORTHWESTWARD. ELSEWHERE...WIDESPREAD CLOUD COVER PERSISTS ALSO DUE TO THE WEAK LIFT ASSOCIATED WITH THE TROUGH. LIGHT OFFSHORE FLOW INTO THE LOW OVER THE SOUTHERN ALASKA PENINSULA ARE KEEPING A SEASONABLE AIR MASS IN PLACE ACROSS THE KUSKOKWIM VALLEY AND DELTA. && .MODEL DISCUSSION... THE MODELS CONTINUE TO COME INTO BETTER AGREEMENT WITH THE TIMING AND INTENSITY OF THE FRONT EXPECTED TO SWEEP ACROSS THE BERING INTO SOUTHWEST ALASKA. THE NAM WAS THE MODEL OF CHOICE THIS MORNING. WITH THE LOCAL AND GLOBAL MODELS LARGELY IN AGREEMENT...THEN NAM WAS CHOSEN TO BETTER HANDLE THE LOCAL EFFECTS AS THE FRONT SWEEPS THROUGH. A FEW DIFFERENCES ARISE VERY LATE IN THE PERIOD WHEN THE FRONT MOVES INTO SOUTHWEST ALASKA AS TO HOW STRONG THE PRECIPITATION WILL BE WITH IT. NONETHELESS FORECAST CONFIDENCE IS HIGHER NOW THAT THE MODELS ARE IN BETTER CONSENSUS. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)... THE LAST OF THE SERIES OF UPPER LEVEL WAVES IS MOVING THROUGH SOUTHCENTRAL ALASKA THIS MORNING. THIS WAVE IS RAPIDLY WEAKENING AS THE UPPER LEVEL LOW MOVES EASTWARD AHEAD OF A RIDGE BUILDING IN FROM THE WEST. THERE ARE SOME RAIN AND SNOW SHOWERS OVER THE KENAI PENINSULA AND PRINCE WILLIAM SOUND REGIONS THIS MORNING BUT THESE SHOWERS SHOULD TAPER OFF THROUGH THE DAY. WITH THE APPROACHING RIDGE THE MIDDLE OF THE WEEK SHOULD SEE SOME CLEARING FOR MOST OF SOUTHCENTRAL. THIS PATTERN WILL ALSO BRING SOME GUSTY NORTHERLY WINDS TO THE NORMAL OUTFLOW AREAS SUCH AS SEWARD AND WHITTIER AS WELL AS THOMPSON PASS AND THE COPPER RIVER DELTA. && .SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)... RAIN AND SNOW SHOWERS OVER THE BRISTOL BAY AREA HAVE STARTED TO TAPER OFF AS A LOW PRESSURE SYSTEM OVER THE ALASKA PENINSULA CONTINUES TO DISSIPATE THIS MORNING. WITH THE LINGERING MOISTURE FROM THE DISSIPATING LOW AND A WEAKENING PRESSURE GRADIENT... PATCHY FOG WILL BECOME THE MAIN CONCERN ACROSS PARTS OF THE SOUTHWEST MAINLAND TODAY. AS HIGH PRESSURE SETTLES IN OVER THE AREA TONIGHT...THE POTENTIAL FOR MORE WIDESPREAD FOG OVER THE SOUTHWEST MAINLAND WILL INCREASE AND PERSIST THROUGH TUESDAY MORNING. A FAST MOVING FRONT MOVING IN FROM THE BERING WILL BEGIN TO OVERSPREAD THE LOWER KUSKOKWIM DELTA AND BRISTOL BAY COAST TUESDAY...SPREADING INCREASINGLY STRONG SOUTHERLY WINDS...RAIN... AND THE POTENTIAL FOR ACCUMULATING SNOW OVER SOME OF THE INTERIOR AREAS THROUGH WEDNESDAY. && .SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)... HIGH PRESSURE CONTINUES TO SETTLE OVER THE CENTRAL AND EASTERN BERING AS A WEAKENING LOW NEAR COLD BAY CONTINUES TO FALL APART. THIS WILL QUICKLY BE REPLACED BY A FAST MOVING GALE-FORCE WARM FRONT WHICH WILL RACE FROM THE WESTERN ALEUTIANS/BERING THIS MORNING AND REACH THE EASTERN ALEUTIANS AND ALASKA PENINSULA BY TUESDAY MORNING. MOST OF THE PRECIPITATION WILL FALL AS RAIN... BUT A MIX WITH SNOW MAY OCCUR FARTHER NORTH ACROSS THE PRIBILOF ISLANDS BEFORE RAPIDLY TURNING TO RAIN. RAIN AND SNOW SHOWERS WILL FOLLOW BEHIND THE FRONT ALONG WITH GUSTY WESTERLY WINDS...AS COLDER AIR FROM EASTERN RUSSIA SWEEPS IN BEHIND THE FRONT. && .LONG TERM FORECAST (DAYS 3 THROUGH 7)... ...FROM PREVIOUS DISCUSSION... THE WEAKENING OF THE NORTH AMERICA RIDGE AND TWO LOWS SWINGING INTO THE FAR SOUTHEASTERN GULF AND EASTERN NORTH PACIFIC WILL HELP SHIFT AN UPPER LEVEL RIDGE OVER MAINLAND ALASKA. THE RIDGE WILL SHARPEN TUESDAY NIGHT AS A FRONT ASSOCIATED WITH A COLD UPPER LEVEL LOW CENTERED OVER EASTERN RUSSIA REACHES THE WEST COAST OF ALASKA AND PUSHES AGAINST IT. THE FRONT SUPPORTED BY A VERY STRONG JET STREAM JUST SOUTH OF THE ALEUTIANS AS WELL AS A LARGE AREA OF COLD AIR OVER THE BERING WILL PROGRESS EAST WEDNESDAY GRADUALLY WEAKENING THE UPPER RIDGE. AS THE FRONT HITS THE UPPER RIDGE THE ENERGY FROM THE FRONT WILL SPLIT...WITH THE JET AND A PORTION COLD AIR ALOFT DIGGING SOUTH OF THE WESTERN GULF WHILE THE NORTHERN PORTION OF THE FRONT IS SHEARED APART BY THE NORTHWESTERLY RETURN FLOW AROUND THE LARGE UPPER LOW OVER RUSSIA. A RESULTING DEFORMATION BAND STRETCHED ACROSS SOUTHWEST ALASKA WEDNESDAY INTO THURSDAY WILL NEED TO BE WATCHED FOR THE POTENTIAL TO BRING A FAIR BIT OF ACCUMULATING SNOW. THE RIDGE ALOFT WILL STRENGTHEN AGAIN AND BECOME ESTABLISHED OVER EASTERN INTERIOR ALASKA AND THE YUKON TERRITORY FRIDAY. GENERAL TROUGHING WILL REMAIN STRETCHED FROM BRISTOL BAY ACROSS THE ALASKA PENINSULA AND INTO THE SOUTHWESTERN GULF WITH SMALLER TROUGHS FALLING APART AS THEY ROTATE FURTHER NORTH INTO THE GULF. THE PATTERN WILL BECOME MORE AMPLIFIED OVER THE WEEKEND WITH THE UPPER RIDGE STRENGTHENING ACROSS WESTERN CANADA AND A CLOSED VERTICALLY STACKED LOW SETTING UP SOUTH OF KODIAK ISLAND AROUND 50N THEN TRACKING NORTH AS IT WEAKENS THROUGH MONDAY. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...NONE. MARINE...GALES...165 170 173 178-181 185 HEAVY FREEZING SPRAY...185. && $$ SYNOPSIS AND MODEL DISCUSSION...ML SOUTHCENTRAL ALASKA...EZ SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...TP LONG TERM...JR
AREA FORECAST DISCUSSION
NWS LAKE CHARLES LA
1142 AM CST MON FEB 15 2016 .AVIATION... THUNDERSTORMS EXTEND FROM AVOYELLES PARISH SOUTHWEST INTO JEFFERSON COUNTY IN SOUTHEAST TEXAS. THIS BROKEN LINE IS MOVING EAST. AIRCRAFT NEAR THESE STORMS WILL EXPERIENCE LIGHTNING ALONG WITH GUSTY WINDS IN AND NEAR AIRPORT TAF LOCATIONS. CONDITIONS ARE EXPECTED TO IMPROVE TOWARDS SUNSET AS A COLD FRONT PUSHES DOWN AND INTO THE REGION. CEILINGS ARE ALSO VARYING FROM 016 TO 045 BUT THIS WILL ALSO IMPROVE BEHIND THE FRONT. && .PREV DISCUSSION... /ISSUED 1020 AM CST MON FEB 15 2016/ UPDATE... TORNADO WATCH 14 HAS BEEN ISSUED UNTIL 6 PM. DISCUSSION... UPDATED TEXT PRODUCTS TO INCLUDE TOR WATCH 14. LATEST RADAR TRENDS INDICATE A BAND OF STRONG TO SVR STORMS EXTENDING FM AVOYELLES PARISH SW TO SABINE LAKE. THESE STORMS WERE DEVELOPING IN AN ENVIRONMENT CONDUCIVE FOR ROTATING STORMS...WITH 0-1 KM SRH NR 215 M2/S2...30 KT LOW LVL SHEAR AND DEEP LAYER SHEAR APPROACHING 50 KT PER 12Z KLCH SOUNDING. IN ADDITION...DECENT INSTABILITY IS IN PLACE WITH MUCAPE VALUES APPROACHING 2000 J/KG AND THIS SHOULD INCREASE ESPECIALLY ACRS ERN PORTIONS OF THE AREA AS THE BAND OF STORMS ENCOUNTERS DAYTIME HEATING. ALL SVR MODES...LARGE HAIL/DAMAGING WINDS/TORNADOES...WILL BE POSSIBLE. RECENT HRRR RUNS SEEM TO HAVE A DECENT HANDLE ON THE CONVECTION AND ITS EVOLUTION THROUGH THE AFTN SO BLENDED WITH INHERITED POPS TO ADJUST. ALSO AMENDED WX GRIDS TO REFLECT SVR POTENTIAL ACRS OUR LA ZONES THROUGH THE REMAINDER OF THE MORNING AND AFTN. FINALLY...TWEAKED HOURLY TEMPERATURES AND DEWPOINTS TO REFLECT RECENT OBS. ALSO ADJUSTED HIGH TEMPERATURES DOWN SLIGHTLY ACRS OUR NERN ZONES WHERE CLOUDS AND SHOWERS/STORMS WILL LIKELY LIMIT HEATING. 24 PREV DISCUSSION... /ISSUED 749 AM CST MON FEB 15 2016/ DISCUSSION... BASED ON LATEST SPC DISCUSSION...AND CURRENT RADAR TRENDS...HAVE ADDED SEVERE STORM WORDING TO THE FORECAST FOR TODAY FOR THE ENTIRE FORECAST AREA. THE THREAT WILL END FROM WEST TO EAST THIS AFTERNOON. PREV DISCUSSION... /ISSUED 542 AM CST MON FEB 15 2016/ DISCUSSION... SCT SHRA WITH ISO TSRA ACROSS THE REGION THIS MORNING. MVFR TO IFR CEILINGS WITH VCSH EXPECTED TO PERSIST THIS MORNING. BEST CHANCE OF TSRA WILL BE LATER THIS MORNING INTO THE EARLY AFTERNOON HOURS...KEEPING TEMPO GROUP FOR THIS FROM 16-20Z. ALSO...S TO SW WINDS EXPECTED TO PICK UP AS WELL DURING THIS TIME ~18-20KTS WITH GUSTS TO NEAR 30 KT. HIGHER GUSTS POSSIBLE WITHIN THE TSRA...AS HIGHLIGHTED WITHIN TEMPO GROUPS. AFTER 20-22Z...FRONTAL SYSTEM PASSING THRU...WITH WINDS SHIFTING TO THE WEST AND THEN NW DURING THE EVENING HOURS...WITH CLEARING SKIES AND VFR TO FOLLOW. DML PREV DISCUSSION... /ISSUED 313 AM CST MON FEB 15 2016/ DISCUSSION... SCATTERED SHOWERS AND A FEW THUNDERSTORMS ARE MOVING NORTHEAST ACROSS THE ENTIRE FORECAST AREA EARLY THIS MORNING...THANKS TO A FAST-MOVING MID-LEVEL SHORTWAVE. A COLD FRONT AND CORRESPONDING MID TO UPPER LEVEL SHORTWAVE WILL MOVE ACROSS THE REGION RATHER QUICKLY THIS AFTERNOON. PER SPC...SOME OF THE STORMS THIS AFTERNOON COULD BE STRONG TO SEVERE...WITH DAMAGING WINDS AND LARGE HAIL THE PRIMARY THREATS...ESPECIALLY IN SOUTH CENTRAL LOUISIANA WHERE A SLIGHT RISK IS NOTED. AFTER THE RAIN ENDS THIS AFTERNOON...THE WEATHER MAPS TURNS QUIET FOR THE REMAINDER OF THE WEEK. A SECOND COLD FRONT DOES MOVE THROUGH THE REGION LATE TUESDAY...BUT IT IS EXPECTED TO BE DRY WITH LIMITED TO NO MOISTURE AVAILABLE. THE NEXT RAIN MAKER WILL BE SUNDAY AND MONDAY...WHEN THE NEXT FRONT COMES THROUGH THE REGION. THIS WEEK WILL SEE TEMPERATURES RUN ABOVE NORMAL WITH HIGHS IN THE 70S. LOWS WILL START OUT IN THE 40S TUESDAY AND WEDNESDAY MORNINGS BEFORE WARMING INTO THE 50S FOR THE REMAINDER OF THE WEEK AND WEEKEND. 15 && .PRELIMINARY POINT TEMPS/POPS... AEX 44 74 45 72 / 10 0 0 0 LCH 48 74 49 73 / 10 0 0 0 LFT 48 72 49 73 / 10 0 0 0 BPT 49 76 49 73 / 10 0 0 0 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...NONE. TX...NONE. GM...NONE. && $$ AVIATION...19
AREA FORECAST DISCUSSION
NWS BUFFALO NY
506 PM EST MON FEB 15 2016 .SYNOPSIS... A DEEP STORM SYSTEM WILL MOVE INTO THE REGION TONIGHT AND TUESDAY WITH HEAVY SNOW DEVELOPING ACROSS WESTERN NEW YORK AND SNOW CHANGING TO RAIN ACROSS CENTRAL NEW YORK. SIGNIFICANT ICE ACCUMULATIONS ARE POSSIBLE ALONG THE SAINT LAWRENCE RIVER VALLEY IN NORTHERN JEFFERSON COUNTY ON TUESDAY. THIS WILL ALL CHANGE BACK TO SNOW SHOWERS TUESDAY EVENING BEFORE ENDING. BEYOND THIS STORM SYSTEM... A FEW LIGHT SNOW SHOWERS ARE POSSIBLE WEDNESDAY WITH COLDER AIR LINGERING THROUGH THE END OF THE WEEK BEFORE MORE MODERATE TEMPERATURES BY THE WEEKEND. && .NEAR TERM /THROUGH TUESDAY NIGHT/... AS OF 21Z...REGIONAL RADARS ARE INDICATING LIGHT PRECIP BEGINNING TO OVERSPREAD WESTERN NY AS WELL AS...TO A LESSER EXTENT...THE NORTH COUNTRY. SFC OBS INDICATE THAT AT LEAST ACROSS WESTERN NY THIS PRECIP IS FALLING AS VERY LIGHT FREEZING DRIZZLE...LIKELY DUE TO AN INVERSION AND SUSPECTED DRY LAYER LOCATED AT 900MB PER AMDAR DATA. THE FREEZING DRIZZLE IS VERY LIGHT AND MIXING WITH VERY LIGHT SNOW AND SHOULD CHANGE OVER ENTIRELY TO SNOW OVER THE NEXT COUPLE OF HOURS AS SYNOPTIC LIFT INCREASES AND THE LOWER LEVELS SATURATE COMPLETELY. OTHERWISE...WV IMAGERY THIS AFTERNOON SHOWS AN IMPRESSIVE WAVE DIGGING INTO THE DEEP SOUTH WITH AN IMPRESSIVE BAROCLINIC LEAF AND WIDESPREAD SYNOPTIC ASCENT AHEAD OF IT. THIS WAVE WILL REACH THE APEX OF THE TROUGH IN THE EAST THIS EVENING BEFORE TRACKING NORTHWARD ALONG A TIGHT BAROCLINIC ZONE ACROSS THE FORECAST AREA TONIGHT INTO TUESDAY. A RAPIDLY DEEPENING SURFACE LOW WILL TRACK ALONG THE APPALACHIAN MOUNTAINS FROM NEAR WESTERN NORTH CAROLINA TONIGHT TO NEAR THE MOHAWK VALLEY BY TUESDAY AFTERNOON. THIS INLAND-TRACKING SURFACE LOW WILL SET UP A MESSY WINTER STORM ACROSS THE FORECAST AREA... FOR WHICH A WINTER STORM WARNING IS NOW IN EFFECT ACROSS ALL OF WESTERN AND NORTH CENTRAL NEW YORK. HOWEVER... IMPACTS ACROSS THE FORECAST AREA WILL BE VERY DIFFERENT RANGING FROM JUST HEAVY SNOW ACROSS WESTERN NY TO A MUCH MORE MESSY SNOW/RAIN/FREEZING RAIN THREAT ACROSS THE NORTH COUNTRY. WESTERN NY (WEST OF THE GENESEE VALLEY)... SNOW WILL DEVELOP OVERNIGHT TONIGHT BECOMING HEAVIEST TUESDAY MORNING BEFORE TAPERING OFF FROM WEST TO EAST BY TUESDAY AFTERNOON. THE EXPECTED TRACK OF THE SURFACE LOW WILL KEEP WESTERN NY ON THE COLD SIDE OF THE STRONG BAROCLINIC ZONE... WITH FORECAST MODELS CONTINUING TO INDICATE AN AXIS OF IMPRESSIVE DEFORMATION ON THE WEST SIDE OF THE SURFACE LOW ACROSS WESTERN NY. THUS EXPECT MUCH OF WESTERN NY TO SEE 6 TO 12 INCHES OF SNOW... WITH A NARROW CORRIDOR OF 12 TO 18 INCHES LIKELY SOMEWHERE BETWEEN BUFFALO AND ROCHESTER WHERE THE BEST DEFORMATION AND BANDED SNOW DEVELOPS. THE BULK OF THE SNOW WILL IMPACT WESTERN NY BETWEEN ABOUT MIDNIGHT AND EARLY AFTERNOON TUESDAY... WITH THE POTENTIAL FOR HEAVY SNOWFALL RATES OF 1 TO 2 INCHES AN HOUR DEVELOPING BETWEEN ABOUT 5AM AND NOON IN THE FAVORED AXIS OF HEAVIEST SNOWFALL BETWEEN BUFFALO AND ROCHESTER. NEAR ROCHESTER AND ALONG THE GENESEE VALLEY... SIMILAR TO WESTERN NY SNOW WILL DEVELOP OVERNIGHT AND BECOME HEAVIEST TOWARD SUNRISE TUESDAY. HOWEVER... THERE WILL BE A SHARP TRANSITION ZONE BETWEEN SNOW TO THE WEST AND RAIN TO THE EAST THAT DEVELOPS NEAR THE GENESEE VALLEY DURING THE DAY TUESDAY. SNOW ACCUMULATIONS FOR LOCATIONS ALONG THIS TRANSITION ZONE WILL BE HEAVILY DEPENDENT ON THE TRACK OF THE SURFACE LOW... WITH LOCATIONS JUST WEST OF THE TRANSITION ZONE LIKELY THE SEE SOME OF THE HEAVIEST SNOWFALL AMOUNTS... WHILE LOCATIONS JUST TO THE EAST WILL SEE MUCH LOWER AMOUNTS WITH A PERIOD OF RAIN DURING THE DAY TUESDAY. PRESENTLY... ROCHESTER LOOKS TO BE JUST ON THE COLD SIDE OF THIS AXIS... BUT WOULD NOT RULE OUT A FEW HOURS WHERE PRECIPITATION CHANGES TO A WINTRY MIX DURING THE DAY. SNOWFALL AMOUNTS WILL RANGE FROM 9 TO 18 INCHES TOWARD THE NORTHWEST CORNERS OF THESE COUNTIES WITH LOWER AMOUNTS OF 5 TO 7 INCHES TOWARD THE SOUTHEAST CORNERS OF THESE COUNTIES. FROM WAYNE COUNTY EAST TO LEWIS COUNTY (EXCLUDING JEFFERSON COUNTY)... A BAND OF MODERATE TO HEAVY SNOW WILL TRACK NORTHWARD ACROSS THIS AREA OVERNIGHT BEFORE MUCH WARMER AIR SURGES INTO THE AREA BY TUESDAY. THIS WILL CAUSE SNOW TO QUICKLY TRANSITION THROUGH A WINTRY MIX TO ALL RAIN THROUGH MUCH OF THE DAY. THESE LOCATIONS CAN EXPECT 4 TO 7 INCHES OF SNOW TONIGHT BEFORE JUST SOME SLUSHY LIGHT ACCUMULATIONS ON TUESDAY BEFORE PRECIPITATION CHANGES TO ALL RAIN. RAIN MAY ACTUALLY BE HEAVY AT TIMES TUESDAY WITH RAINFALL AMOUNTS OF AN INCH OR TWO ON TUESDAY. RAIN WILL THEN CHANGE BACK TO SNOW TUESDAY EVENING WITH A BURST OF MODERATE TO HEAVY SNOW PRODUCING A QUICK 2 TO 5 INCHES AS THE DEFORMATION AXIS ON THE BACK SIDE OF THE SURFACE LOW TRACK ACROSS THE AREA. JEFFERSON COUNTY...JEFFERSON COUNTY WILL EVOLVE SIMILARLY TO LOCATIONS SOUTH OF THERE (SEE SECTION ABOVE)... HOWEVER THE IMPORTANT DIFFERENCE IS THE POTENTIAL FOR SIGNIFICANT ICE ACCUMULATIONS OVER NORTHERN PORTIONS OF THE COUNTY ALONG THE SAINT LAWRENCE RIVER VALLEY. WITH MODELS MORE CONSISTENT ON THE TRACK OF THE SURFACE LOW... IT REMAINS VERY LIKELY THAT NORTHEAST WINDS WILL FUNNEL COLDER AIR AT THE SURFACE DOWN THE VALLEY. THE STRONG SURGE OF WARM ADVECTION AHEAD OF THE SURFACE LOW RIDING OVER THE SUB- FREEZING SURFACE TEMPERATURES WILL PRODUCE SIGNIFICANT FREEZING RAIN ACCUMULATIONS ALONG THE VALLEY. SURFACE TEMPERATURES ARE MOST LIKELY TO REMAIN BELOW FREEZING JUST NORTH OF WATERTOWN ALONG THE RIVER VALLEY... WHICH WILL ALLOW FOR A HALF INCH TO AN INCH OF ICE ACCUMULATION DURING THE DAY TUESDAY. THIS COULD BRING DOWN NUMEROUS TREE LIMBS AND POWER LINES RESULTING IN WIDESPREAD POWER OUTAGES ALONG THE VALLEY. IN ADDITION... THE THREAT OF HEAVY RAINFALL ACROSS CENTRAL AND NORTH CENTRAL NEW YORK HAS PROMPTED A FLOOD WATCH. STORM TOTAL QPF AMOUNTS OF 2 TO 3 INCHES ARE EXPECTED... WITH AROUND AN INCH AND HALF TO TWO INCHES OF THAT FALLING AS RAIN. EXCESSIVE RUNOFF FROM HEAVY RAIN AND SOME SNOW MELT MAY RESULT IN FLOODING IN LOW LYING AND POOR DRAINAGE AREAS. SMALL CREEKS MAY ALSO SEE SIGNIFICANT RISES. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... ON WEDNESDAY A RELATIVELY WEAK MID LEVEL TROUGH AND SURFACE COLD FRONT WILL CROSS THE LOWER LAKES. A PERIOD OF LARGE SCALE ASCENT IN THE DPVA REGIME AHEAD OF THE TROUGH MAY PROVIDE ENOUGH FORCING FOR A FEW SCATTERED SNOW SHOWERS. A MODEST AMOUNT OF LAKE MOISTURE AND ALSO UPSLOPE FLOW WILL BRING A HIGHER LIKELIHOOD OF SOME LIGHT SNOW EAST OF LAKES ERIE AND ONTARIO WHERE SOME VERY MINOR ACCUMULATIONS ARE POSSIBLE WEDNESDAY AND WEDNESDAY EVENING. EXPECT HIGHS NEAR THE MID FEBRUARY AVERAGES WITH LOW 30S ON THE LAKE PLAINS AND UPPER 20S HIGHER TERRAIN. LATER WEDNESDAY NIGHT INTO EARLY THURSDAY BOUNDARY LAYER FLOW WILL BECOME NORTHWEST. THIS MAY PRODUCE A BRIEF PERIOD OF SCATTERED LAKE EFFECT SNOW SHOWERS SOUTHEAST OF THE LAKES...BUT MARGINAL INSTABILITY AND A DRY AIRMASS WILL GREATLY LIMIT INTENSITY AND COVERAGE. EXPECT ANY ACCUMULATION TO BE AN INCH OR LESS FROM ROCHESTER TO OSWEGO COUNTY AND ACROSS THE WESTERN SOUTHERN TIER. A COLDER AIRMASS WILL BUILD INTO THE REGION WEDNESDAY NIGHT WITH LOW TEMPS BY DAYBREAK THURSDAY IN THE LOWER TEENS ON THE LAKE PLAINS AND SINGLE DIGITS INLAND. THURSDAY HIGH PRESSURE BUILDS OVER THE LOWER LAKES. ANY LINGERING LAKE EFFECT SNOW SHOWERS SOUTHEAST OF LAKE ONTARIO WILL END EARLY IN THE DAY. STRONG SUBSIDENCE AND DRYING WILL BRING A GOOD DEAL OF SUNSHINE. TEMPERATURES WILL REMAIN CHILLY WITH HIGHS ONLY IN THE UPPER TEENS TO LOWER 20S IN MOST AREAS. HIGH PRESSURE DRIFTS EAST TO NEW ENGLAND THURSDAY NIGHT WITH SUBSIDENCE AND DRY AIR HOLDING OFF ANY PRECIP FROM THE NEXT SYSTEM UNTIL FRIDAY MORNING. && .LONG TERM /FRIDAY THROUGH MONDAY/... FRIDAY THROUGH SATURDAY A STRONG CLIPPER SYSTEM WILL MOVE FROM LAKE SUPERIOR ACROSS SOUTHERN QUEBEC. DEEP SOUTHWESTERLY FLOW AHEAD OF THIS SYSTEM WILL TRANSPORT WARMER AIR INTO OUR REGION WITH HIGHS IN THE LOWER 40S FRIDAY AND MID 40S SATURDAY FOR MOST OF THE AREA. THIS WILL ALLOW MOST OF THE PRECIP TO FALL AS LIGHT RAIN. THE NORTH COUNTRY WILL STAY COOLER...ESPECIALLY ACROSS THE HIGHER TERRAIN OF THE TUG HILL AND WESTERN ADIRONDACKS. THIS MAY ALLOW PRECIP TYPE TO REMAIN MORE WET SNOW WITH HIGHS IN THE MID TO UPPER 30S INLAND FROM THE LAKE. BY SUNDAY NIGHT AND MONDAY MODEL GUIDANCE BEGINS TO DIVERGE. THE GFS BRINGS A COLD FRONT SOUTH ACROSS THE LAKES WITH A FEW SNOW SHOWERS AND COLDER TEMPERATURES...WHILE THE ECMWF DEVELOPS A WEAK SOUTHERN STREAM WAVE WITH SOME LIGHT SNOW ON MONDAY. EITHER SCENARIO WILL BRING A CHANCE OF SOME LIGHT SNOW WITH TEMPERATURES RETURNING CLOSER TO AVERAGE. && .AVIATION /22Z MONDAY THROUGH SATURDAY/... OVER THE LAST HOUR KBUF/KTYX RADAR HAVE INDICATED INCREASING RETURNS OF VERY LIGHT PRECIP ACROSS WESTERN NY AND THE NORTH COUNTRY. SFC OBS INDICATE THAT MUCH OF THIS PRECIP IS REACHING THE GROUND AS -FZDZ MIXING WITH --SN. THE WINDOW OF -FZDZ SHOULD BE BRIEF AS PRECIP CHANGES ENTIRELY OVER TO SNOW AROUND 01Z WITH INCREASING LIFT AND LOW LEVEL SATURATION. AFTER 01Z...CONDITIONS DETERIORATE TO IFR ACROSS THE REGION AS SNOW DEVELOPS AND INTENSIFIES TOWARD TUESDAY MORNING. IFR/LIFR CIGS/VIS WILL PERSIST IN MODERATE TO HEAVY SNOW THROUGH TUESDAY AFTERNOON IN WESTERN NY LIKELY IMPACTING KIAG/KBUF/KJHW/KROC. KROC WILL BE CLOSE TO THE TRANSITION ZONE TO A WINTRY MIX AND RAIN DURING THE DAY TUESDAY... BUT SHOULD STAY MAINLY SNOW. KART WILL SEE A TRANSITION FROM SNOW TO RAIN AND/OR FREEZING RAIN DURING THE DAY TUESDAY. WHILE THE BEST CHANCE FOR SIGNIFICANT ICE ACCUMULATIONS IS NORTH OF KART...THERE MAY BE PERIODS OF FREEZING RAIN LEADING TO SOME LIGHT ICING THROUGH MID-DAY. OUTLOOK... TONIGHT AND TUESDAY...WIDESPREAD IFR WITH SNOW IN WESTERN NEW YORK AND SNOW CHANGING TO RAIN IN CENTRAL NEW YORK. WEDNESDAY...MVFR WITH A CHANCE OF SNOW SHOWERS. THURSDAY...MAINLY VFR. FRIDAY AND SATURDAY...MVFR WITH A CHANCE OF RAIN AND SNOW. && .MARINE... A STRONG LOW PRESSURE SYSTEM WILL MOVE THROUGH NY STATE ON TUESDAY... WITH NORTHEAST WINDS BECOMING NORTHWEST LATER IN THE DAY AS THE LOW TRACKS TOWARD QUEBEC. HAVE ISSUED SMALL CRAFT ADVISORIES FOR WINDS AND WAVES ALONG THE SOUTHERN LAKE ONTARIO SHORELINE TUESDAY THROUGH TUESDAY NIGHT. && .HYDROLOGY... A VERY COMPLEX HYDRO EVENT WILL UNFOLD ON TUESDAY ACROSS THE NORTHERN FINGER LAKES AND EASTERN LAKE ONTARIO REGION. SNOW WILL OVERSPREAD THE AREA OVERNIGHT...THEN CHANGE TO RAIN EARLY TUESDAY BEFORE GOING BACK TO SNOW BY EARLY EVENING. THE RAIN WILL BE HEAVY DURING THE DAY TUESDAY WITH RAINFALL AMOUNTS OF 1.5 TO 2 INCHES POSSIBLE. THE HEAVIEST RAINFALL IS LIKELY TO FOCUS IN A CORRIDOR ALONG AND JUST WEST OF INTERSTATE 81. EXCESSIVE RUNOFF FROM THE RAINFALL PLUS SOME SNOW MELT MAY RESULT IN FLOODING IN LOW LYING AND POOR DRAINAGE AREAS AND POSSIBLY SMALL CREEKS. THE NEW SNOW ON THE GROUND WILL INITIALLY ABSORB SOME OF THE RAINFALL...BUT SHOULD THEN RELEASE WATER FOR AT LEAST SEVERAL HOURS IN THE MIDDLE OF THE DAY WHEN TEMPERATURES ARE WARMEST. WITH THE ABOVE IN MIND...WE HAVE ISSUED A FLOOD WATCH FOR ONTARIO... WAYNE...NORTHERN CAYUGA...OSWEGO...JEFFERSON...AND LEWIS COUNTIES. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...FLOOD WATCH FROM TUESDAY MORNING THROUGH TUESDAY EVENING FOR NYZ004>008-014. WINTER STORM WARNING FROM 10 PM THIS EVENING TO 1 AM EST WEDNESDAY FOR NYZ007. WINTER STORM WARNING UNTIL 1 AM EST WEDNESDAY FOR NYZ004>006- 008. WINTER STORM WARNING UNTIL 7 PM EST TUESDAY FOR NYZ001>003- 010>014-019>021-085. MARINE...SMALL CRAFT ADVISORY FROM 10 AM TUESDAY TO 7 AM EST WEDNESDAY FOR LOZ042>044. && $$ SYNOPSIS...CHURCH NEAR TERM...CHURCH/WOOD SHORT TERM...HITCHCOCK LONG TERM...HITCHCOCK AVIATION...CHURCH/WOOD MARINE...CHURCH HYDROLOGY...HITCHCOCK
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
318 AM CST WED FEB 17 2016 .SHORT TERM... 316 AM CST TODAY THROUGH FRIDAY NIGHT... 08Z SURFACE ANALYSIS DEPICTS A COLD FRONT SAGGING INTO NORTHERN ILLINOIS...IN THE WAKE OF THE DISTURBANCE WHICH BROUGHT LIGHT SNOW TO THE REGION TUESDAY AFTERNOON AND EVENING. DRIER LOW-LEVEL AIR WAS HELPING TO BREAK UP CLOUD COVER FROM THE NORTH- NORTHWEST...WHICH WILL ALLOW MOST AREAS TO SEE SOME SUNSHINE TODAY. SLIGHTLY COOLER AIR ALOFT BEHIND THE FRONT SHOULD BE OFFSET BY SUN...WITH GUIDANCE TEMPS IN THE 30-35 RANGE TODAY VERY REASONABLE. SURFACE HIGH PRESSURE BUILDING SOUTHEAST ACROSS THE NORTHERN-CENTRAL GREAT LAKES THROUGH THIS EVENING WILL SUPPORT LIGHT NORTH-NORTHEAST WINDS THROUGH THE DAY. ALL IN ALL...NOT TOO BAD A DAY FOR MID-FEBRUARY. BROAD UPPER RIDGE OVER THE WESTERN CONUS WILL DEVELOP EASTWARD TONIGHT AND THURSDAY...DOWNSTREAM OF AN UPPER TROUGH IMPINGING ON THE WEST COAST. THIS WILL SET THE STAGE FOR A SIGNIFICANT WARM-UP TO END THE WEEK AND HEAD INTO THE WEEKEND. SURFACE LOW PRESSURE DEVELOPS IN THE LEE OF THE NORTHERN ROCKIES ON THURSDAY IN RESPONSE TO WESTERN TROUGH...AND MOVES TO THE UPPER MISSISSIPPI VALLEY ON FRIDAY. WINDS ACROSS THE MIDWEST SHIFT TO THE SOUTH-SOUTHEAST LATER TONIGHT AND INCREASE AS SURFACE PRESSURE FALLS DEVELOP ACROSS THE REGION. RESULTING WARM ADVECTION BRING 925 MB TEMPS ABOVE FREEZING ON THURSDAY...AND INCREASE TO +10 TO +12 C FRIDAY BEFORE PACIFIC COLD FRONT PUSHES EAST ACROSS THE CWA DURING THE MID-DAY AND EARLY AFTERNOON HOURS. LOW LEVEL THERMAL PROGS SUPPORT TEMPS WARMING TO AROUND 40 THURSDAY...RISING THURSDAY NIGHT AND REACHING THE MID-5OS TO LOWER 60S FRIDAY. 00Z ECMWF SUGGESTS EVEN WARMER TEMPS POSSIBLE FRIDAY AFTERNOON...LOW- MID 60S SOUTH OF I88. WITH DEEP SURFACE LOW MOVING ACROSS THE UPPER MISSISSIPPI VALLEY AND NORTHERN GREAT LAKES FRIDAY...VERY WINDY CONDITIONS ARE EXPECTED. WEST-SOUTHWEST WINDS MAY GUST 45+ MPH FOR A TIME FRIDAY AFTERNOON AS BOUNDARY LAYER MIXES MORE DEEPLY BEHIND THE COLD FRONT. MAY VERY WELL HAVE TO CONSIDER A WIND ADVISORY IF THIS CONTINUES TO BE THE TREND GOING INTO FRIDAY. DESPITE STRONG ASCENT...PRECIPITATION THREAT APPEARS PRETTY LOW AS DEEP MOISTURE IS LACKING. VARIOUS MODELS SQUEEZE OUT A LITTLE LIGHT QPF OVER THE FAR NORTHERN REACHES OF THE FORECAST AREA THURSDAY NIGHT INTO FRIDAY AND HAVE MAINTAINED SOME SLIGHT CHANCE POPS...THOUGH EXPECT MOST AREAS WILL BE DRY. FORECAST SOUNDINGS INDICATE DECREASING CLOUDS IN DRIER AIR FRIDAY AFTERNOON AND NIGHT. CONTINUED BREEZY WINDS AND ONLY MARGINALLY COOLER AIR BEHIND THE FRONT WILL KEEP TEMPS ABOVE FREEZING FRIDAY NIGHT. RATZER && .LONG TERM... 316 AM CST SATURDAY THROUGH TUESDAY... UPPER TROUGH CONTINUES TO MOVE TO THE EAST OF THE REGION SATURDAY WITH UPPER PATTERN REMAINING FAIRLY ZONAL AND NOT MUCH COLD AIR ADVECTION. ECMWF/GFS/GEM ALL INDICATE A SHORT WAVE TROUGH MOVING THROUGH THE FLOW ACROSS THE NORTHERN PLAINS SATURDAY NIGHT...WHICH DIGS INTO THE REGION SUNDAY. SOME SPREAD EXISTS IN TIMING WITH THIS FEATURE AND HAVE FAVORED THE SLIGHTLY QUICKER ECMWF/GFS SOLUTION THOUGH DIFFERENCES OCCUR WITH THE STRENGTH OF THE SURFACE REFLECTION OF THIS FEATURE AS THE ECMWF IS WEAKER WITH THE SURFACE LOW. GUIDANCE IS SIMILAR IN BUILDING WEST COAST UPPER RIDGE BY MONDAY-TUESDAY HOWEVER...INDUCING AMPLIFICATION OF THE DOWNSTREAM TROUGH ACROSS EASTERN NORTH AMERICA AND SIGNALING A SHIFT BACK TO NEAR NORMAL TEMPERATURES TO START NEXT WEEK. WARMTH DOES LAST WHILE FLOW REMAINS MORE WESTERLY SATURDAY AND SUNDAY...WITH GUIDANCE TEMPS FAIRLY CLOSE FROM THE MID-40S TO MID- 50S. HIGHS TAIL OFF INTO THE MID-30S BY MONDAY AND TUESDAY...JUST A BIT BELOW NORMAL. PRECIP WISE...SLIGHT CHANCE POPS FOR RAIN CARRIED SATURDAY NIGHT INTO SUNDAY WITH MINOR-AMPLITUDE LEAD SHORT WAVE MOVING THROUGH THE FLOW...AND RAIN/SNOW SHOWERS SUNDAY NIGHT INTO MONDAY WITH THE PUSH OF COLDER AIR AS FLOW AMPLIFIES. DRY HIGH PRESSURE THEN SPREADS ACROSS THE AREA TUESDAY. RATZER && .AVIATION... FOR THE 06Z TAFS... LINGERING SNOW FLURRIES HAVE EXITED EAST OF THE AREA...WITH VERY SPOTTY ECHOES UPSTREAM IN SOUTHEAST WISCONSIN. THERE IS A PRETTY STEADY STREAM OF MVFR CIGS IN IOWA INTO NORTHWEST ILLINOIS...BUT IN WISCONSIN AND NORTHERN ILLINOIS CIG CONTINUE TO LIFT THROUGH MVFR TO EVEN LOW END VFR. MPH SOUNDING AND AMDAR SOUNDINGS AROUND KMKX SHOW A SHALLOW MOISTURE LAYER. WITH LOW LEVEL FLOW FROM THE NORTH-NORTHWEST...EXPECT THAT LIFTING AND SCATTERING WILL OCCUR ACROSS MOST OF THE AREA TONIGHT. DEWPOINT DEPRESSIONS ARE INITIALLY SOMEWHAT LOW BEHIND THE COLD FRONT TONIGHT...THUS SOME PATCHY FOG WILL CONTINUE AT LEAST OVERNIGHT UNTIL DRIER AIR FILTERS IN. FOG SHOULD NOT BE A BIG DEAL IN MOST AREAS THOUGH GUIDANCE IS HITTING IT A BIT HARDER WEST TOWARDS KRFD. TUESDAY SHOULD BE FAIRLY BENIGN AS HIGH PRESSURE MOVES OVERHEAD THEN SHIFTS EAST TUESDAY AFTERNOON AND EVENING. LIGHTER NW WINDS BECOME VARIABLE THEN TAKE ON AN EASTERLY AND EVENTUALLY SOUTHEASTERLY DIRECTION LATER IN THE DAY AND EVENING. MOST GUIDANCE KEEPS WINDS UNDER 10 KT IN THE EAST WIND SHIFT. KMD && .MARINE... 221 AM CST NORTHERLY WINDS HAVE STRENGTHENED OVERNIGHT WITH THE PASSAGE OF A SURFACE TROUGH AND FRONTAL BOUNDARY...WITH WINDS GENERALLY STAYING IN THE 15 TO 25 KT RANGE. AS WAS EXPECTED...THERE WERE A FEW GUSTS TO 30 KT. THESE HAVE MAINLY BEEN OBSERVED OVER THE NORTH HALF...AND EXPECT THESE OCCASIONAL HIGHER GUSTS TO BE POSSIBLE OVER THE NEXT COUPLE OF HOURS. HOWEVER...DO EXPECT WINDS TO DIMINISH OVER THE ENTIRE LAKE FOR THE REMAINDER OF THE MORNING WITH THIS TREND THEN CONTINUING INTO THE AFTERNOON. THESE LIGHTER WINDS WILL PERSIST INTO MOST OF TONIGHT BUT DO EXPECT WINDS TO BEGIN INCREASING ONCE AGAIN OUT OF THE SOUTH AS HIGH PRESSURE SHIFTS EAST OF THE REGION...AND WITH LOW PRESSURE DEVELOPING OVER THE NORTHERN PLAINS. CONTINUE THE INCREASING TREND THURSDAY AND PARTICULAR THURSDAY AFTERNOON INTO THURSDAY NIGHT...WHEN GALES WILL BECOME LIKELY OVER THE NEARSHORE AND OPEN WATERS. WITH CONFIDENCE GROWING...DID ISSUE A GALE WATCH FOR THE ENTIRE OPEN WATERS AND NEARSHORE FROM THURSDAY AFTERNOON THROUGH FRIDAY EVENING. AS LOW PRESSURE MOVES THROUGH THE REGION DURING THIS TIME...SOUTHERLY GALES WILL BE LIKELY INTO FRIDAY BEFORE WINDS TURN MORE WESTERLY LATE IN THE DAY FRIDAY. RODRIGUEZ && .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
221 AM CST WED FEB 17 2016 .UPDATE... MADE SOME TWEAKS TO GOING FORECAST. HAVE REFINED HOURLY POPS FOR DEPARTURE OF SNOW SHOWERS AND FLURRIES OFF TO THE SOUTHEAST. BASED OFF RADAR ECHO INTENSITY TRENDS...WOULD NOT EXPECT ANY FURTHER MINOR ACCUMULATIONS IN EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA. BASED ON FORECAST SOUNDINGS AND MONITORING M-PING REPORTS FOR ANY FREEZING DRIZZLE...HAVE NOT SEEN ANY...SO HAVE REMOVED FREEZING DRIZZLE FROM SOUTHEAST CWA OVERNIGHT. OTHER CHANGE WAS TO LOWER OVERNIGHT MINS MAINLY IN NORTHERN ILLINOIS ALONG AND NORTH OF I-88. IR AND FOG SATELLITE SHOWS BACK EDGE OF LOW CLOUDS MOVING THROUGH WISCONSIN. MAY BE SOME HIGH CLOUDS OVERHEAD AS BACK EDGE MOVES IN BUT EXPECTING ENOUGH CLEARING TO SUPPORT LOWS OF MID TEENS TO AROUND 20 AND LOWER 20S IN CHICAGO. ALSO ADDED PATCHY FOG MENTION ALONG AND WEST OF FOX RIVER VALLEY OVERNIGHT GIVEN THAT DEWPOINT SPREADS WILL BE FAIRLY LOW AS SOME CLEARING OCCURS. WILL NEED TO MONITOR FOR SOME SPOTS OF LOCALLY DENSE FOG. RC && .SHORT TERM... 211 PM CST THROUGH WEDNESDAY... A BAND OF SNOW SHOWERS IS SLOWLY MARCHING SOUTHEAST AND CURRENTLY JUST WEST OF I-55. THE SNOW IS ASSOCIATED WITH A WEAK UPPER LEVEL WAVE MOVING OVER NORTHEAST IL AND INDIANA THIS AFTERNOON. WEAKER SNOW SHOWERS EXTEND NORTH THROUGH SOUTHERN WISCONSIN AND WEST THROUGH WESTERN ILLINOIS WITH A COLD FRONT DRAPED ACROSS CENTRAL WISCONSIN AND WESTERN IOWA. THE COLD FRONT AND ASSOCIATED UPPER LEVEL VORTICITY STREAMER WILL SWEEP THROUGH THIS EVENING AND OVERNIGHT BRINGING AND END TO THE SNOW. IN GENERAL...EXPECTING LIGHT SNOW WITH A FEW MODERATE SNOW SHOWERS. VISIBILITY WILL GENERALLY BE AROUND 4 TO 5 MILES IN THE SNOW WITH VISIBILITIES UNDER 1 OR 2 MILES UNDER THE HEAVIER SNOW SHOWERS. WHEN ALL IS SAID AND DONE EXPECTING UNDER A HALF INCH OF SNOW ACROSS THE REGION. MOST AREAS WILL RECEIVE ONLY A COUPLE TENTHS OF AN INCH AT BEST WITH ISOLATED HIGHER AMOUNTS. AFTER MIDNIGHT...PARTS OF NORTHWEST INDIANA MAY SEE FREEZING DRIZZLE MIXED IN WITH FLURRIES/LIGHT SNOW SHOWERS AS THE COLUMN IS NOT LONGER SATURATED UP THROUGH THE DGZ. A LIGHT GLAZE OR LESS IS EXPECTED. HIGH PRESSURE SPREADS OVERHEAD WEDNESDAY LEADING TO DRIER CONDITIONS. THINKING LAKE EFFECT SNOW WILL FALL EAST OF PORTER COUNTY SO NO SNOW IS EXPECTED ACROSS THE WARNING AREA. AREAS NORTH OF I-88 MAY EVEN SEE SUNSHINE AS SKIES ARE EXPECTED TO SCATTER OUT IN THE AFTERNOON. COLDER AIR ALOFT SINKS SOUTH WEDNESDAY LEADING TO SLIGHTLY COLDER TEMPS TOMORROW. HIGHS WILL BE AROUND FREEZING. JEE && .LONG TERM... 257 PM CST WEDNESDAY NIGHT THROUGH TUESDAY... THE MAIN HIGHLIGHTS IN THE EXTENDED PERIOD CONTINUE TO BE THE NICE WARM-UP EXPECTED LATER IN THE WEEK. FOLLOWING THE EASTWARD PROGRESSION OF A SURFACE RIDGE OF HIGH PRESSURE TOWARDS THE EAST COAST ON THURSDAY...THE LOWER LEVEL FLOW WILL TURN SOUTHERLY. THIS SHOULD HELP TEMPERATURES BEGIN TO WARM NICELY INTO THE UPPER 30S TO THE LOWER 40S BY THURSDAY AFTERNOON. TEMPERATURES WILL LIKELY CONTINUE ON AN UPWARD TREND THURSDAY NIGHT AS SURFACE WINDS CONTINUE TO INCREASE IN RESPONSE TO STRONG PRESSURE FALLS SETTING UP OVER THE UPPER MIDWEST AND GREAT LAKES REGION IN RESPONSE TO THE APPROACH OF A POTENT AREA OF LOW PRESSURE OVER THE DAKOTAS. THIS STORM SYSTEM WILL LIKELY INDUCE DOWN SLOPE FLOW...RESULTING IN A DRY AND VERY WARM AIRMASS SETTING UP OVER THE CENTRAL PLAINS ON THURSDAY. THE ASSOCIATED THERMAL RIDGE IS THEN EXPECTED TO ADVECT EASTWARD OVER THE CENTRAL STATES BY FRIDAY. CURRENT INDICATIONS CONTINUE TO SUGGEST THAT SURFACE TEMPERATURES COULD WARM WELL INTO THE 50S...TO POSSIBLY EVEN SOME LOW 60S FRIDAY AFTERNOON AS THIS WARM AND DRIER AIRMASS SETS UP OVER THE AREA. THE ONE CAVEAT TO THIS REALLY WARM WEATHER ON FRIDAY IS THAT IT LOOKS TO ALSO COME DURING A VERY WINDY DAY. AFTER THE SMALL POTENTIAL FOR A FEW SHOWERS EARLY FRIDAY...A FRONTAL BOUNDARY WILL SHIFT ACROSS THE AREA BY AROUND MIDDAY. IN ITS WAKE...IT APPEARS THAT THE WINDS WILL INCREASE OUT OF THE WEST-SOUTHWEST...WITH THE POTENTIAL OF A PERIOD OF WIND ADVISORY CRITERIA WIND GUSTS (45 MPH) FRIDAY AFTERNOON AS SOME STRONG PRESSURE RISES OVERSPREAD THE AREA. ADDITIONALLY...MUCH DRIER AIR IN THE FRONTS WAKE COULD ALSO RESULT IN LOWER RH`S THAN CURRENTLY FORECAST...AS THIS AIRMASS LOOKS TO BE ADVECTING IN OFF THE HIGH PLAINS. IF THIS OCCURS...THE COMBINATION OF THE STRONG WINDS AND DRY MILD AIR COULD INCREASE FIRE WEATHER CONCERNS SOME FRIDAY AFTERNOON. IT APPEARS THE MILD WEATHER WILL CONTINUE INTO THE WEEKEND AS WELL AS A QUASI-ZONAL FLOW PATTERN ALOFT KEEPS THE AIRMASS MILD OVER THE REGION. TEMPERATURES COULD AGAIN GET INTO THE 50S WITH LIGHTER WINDS OVER THE WEEKEND. AFTER A MILD WEEKEND...MODELS AND ENSEMBLES ARE IN DECENT AGREEMENT IN SUGGESTING ANOTHER COLD PUSH WILL SHIFT OVER THE AREA EARLY NEXT WEEK AS UPPER RIDGING BEGINS TO BUILD AGAIN OVER THE WESTERN CONUS. THIS SHOULD ALLOW ANOTHER TROUGH AND SURFACE COLD FRONT TO SHIFT OVER THE AREA BY MONDAY. AS A CONSEQUENCE...COLDER WEATHER AND SOME CHANCES OF LIGHT SNOW LOOKS TO BEGIN NEXT WEEK. KJB && .AVIATION... FOR THE 06Z TAFS... LINGERING SNOW FLURRIES HAVE EXITED EAST OF THE AREA...WITH VERY SPOTTY ECHOES UPSTREAM IN SOUTHEAST WISCONSIN. THERE IS A PRETTY STEADY STREAM OF MVFR CIGS IN IOWA INTO NORTHWEST ILLINOIS...BUT IN WISCONSIN AND NORTHERN ILLINOIS CIG CONTINUE TO LIFT THROUGH MVFR TO EVEN LOW END VFR. MPX SOUNDING AND AMDAR SOUNDINGS AROUND KMKX SHOW A SHALLOW MOISTURE LAYER. WITH LOW LEVEL FLOW FROM THE NORTH-NORTHWEST...EXPECT THAT LIFTING AND SCATTERING WILL OCCUR ACROSS MOST OF THE AREA TONIGHT. DEWPOINT DEPRESSIONS ARE INITIALLY SOMEWHAT LOW BEHIND THE COLD FRONT TONIGHT...THUS SOME PATCHY FOG WILL CONTINUE AT LEAST OVERNIGHT UNTIL DRIER AIR FILTERS IN. FOG SHOULD NOT BE A BIG DEAL IN MOST AREAS THOUGH GUIDANCE IS HITTING IT A BIT HARDER WEST TOWARDS KRFD. TUESDAY SHOULD BE FAIRLY BENIGN AS HIGH PRESSURE MOVES OVERHEAD THEN SHIFTS EAST TUESDAY AFTERNOON AND EVENING. LIGHTER NW WINDS BECOME VARIABLE THEN TAKE ON AN EASTERLY AND EVENTUALLY SOUTHEASTERLY DIRECTION LATER IN THE DAY AND EVENING. MOST GUIDANCE KEEPS WINDS UNDER 10 KT IN THE EAST WIND SHIFT. KMD && .MARINE... 221 AM CST NORTHERLY WINDS HAVE STRENGTHENED OVERNIGHT WITH THE PASSAGE OF A SURFACE TROUGH AND FRONTAL BOUNDARY...WITH WINDS GENERALLY STAYING IN THE 15 TO 25 KT RANGE. AS WAS EXPECTED...THERE WERE A FEW GUSTS TO 30 KT. THESE HAVE MAINLY BEEN OBSERVED OVER THE NORTH HALF...AND EXPECT THESE OCCASIONAL HIGHER GUSTS TO BE POSSIBLE OVER THE NEXT COUPLE OF HOURS. HOWEVER...DO EXPECT WINDS TO DIMINISH OVER THE ENTIRE LAKE FOR THE REMAINDER OF THE MORNING WITH THIS TREND THEN CONTINUING INTO THE AFTERNOON. THESE LIGHTER WINDS WILL PERSIST INTO MOST OF TONIGHT BUT DO EXPECT WINDS TO BEGIN INCREASING ONCE AGAIN OUT OF THE SOUTH AS HIGH PRESSURE SHIFTS EAST OF THE REGION...AND WITH LOW PRESSURE DEVELOPING OVER THE NORTHERN PLAINS. CONTINUE THE INCREASING TREND THURSDAY AND PARTICULAR THURSDAY AFTERNOON INTO THURSDAY NIGHT...WHEN GALES WILL BECOME LIKELY OVER THE NEARSHORE AND OPEN WATERS. WITH CONFIDENCE GROWING...DID ISSUE A GALE WATCH FOR THE ENTIRE OPEN WATERS AND NEARSHORE FROM THURSDAY AFTERNOON THROUGH FRIDAY EVENING. AS LOW PRESSURE MOVES THROUGH THE REGION DURING THIS TIME...SOUTHERLY GALES WILL BE LIKELY INTO FRIDAY BEFORE WINDS TURN MORE WESTERLY LATE IN THE DAY FRIDAY. RODRIGUEZ && .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
1034 PM CST TUE FEB 16 2016 .UPDATE...940 PM CST MADE SOME TWEAKS TO GOING FORECAST. HAVE REFINED HOURLY POPS FOR DEPARTURE OF SNOW SHOWERS AND FLURRIES OFF TO THE SOUTHEAST. BASED OFF RADAR ECHO INTENSITY TRENDS...WOULD NOT EXPECT ANY FURTHER MINOR ACCUMULATIONS IN EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA. BASED ON FORECAST SOUNDINGS AND MONITORING M-PING REPORTS FOR ANY FREEZING DRIZZLE...HAVE NOT SEEN ANY...SO HAVE REMOVED FREEZING DRIZZLE FROM SOUTHEAST CWA OVERNIGHT. OTHER CHANGE WAS TO LOWER OVERNIGHT MINS MAINLY IN NORTHERN ILLINOIS ALONG AND NORTH OF I-88. IR AND FOG SATELLITE SHOWS BACK EDGE OF LOW CLOUDS MOVING THROUGH WISCONSIN. MAY BE SOME HIGH CLOUDS OVERHEAD AS BACK EDGE MOVES IN BUT EXPECTING ENOUGH CLEARING TO SUPPORT LOWS OF MID TEENS TO AROUND 20 AND LOWER 20S IN CHICAGO. ALSO ADDED PATCHY FOG MENTION ALONG AND WEST OF FOX RIVER VALLEY OVERNIGHT GIVEN THAT DEWPOINT SPREADS WILL BE FAIRLY LOW AS SOME CLEARING OCCURS. WILL NEED TO MONITOR FOR SOME SPOTS OF LOCALLY DENSE FOG. RC && .SHORT TERM... 211 PM CST THROUGH WEDNESDAY... A BAND OF SNOW SHOWERS IS SLOWLY MARCHING SOUTHEAST AND CURRENTLY JUST WEST OF I-55. THE SNOW IS ASSOCIATED WITH A WEAK UPPER LEVEL WAVE MOVING OVER NORTHEAST IL AND INDIANA THIS AFTERNOON. WEAKER SNOW SHOWERS EXTEND NORTH THROUGH SOUTHERN WISCONSIN AND WEST THROUGH WESTERN ILLINOIS WITH A COLD FRONT DRAPED ACROSS CENTRAL WISCONSIN AND WESTERN IOWA. THE COLD FRONT AND ASSOCIATED UPPER LEVEL VORTICITY STREAMER WILL SWEEP THROUGH THIS EVENING AND OVERNIGHT BRINGING AND END TO THE SNOW. IN GENERAL...EXPECTING LIGHT SNOW WITH A FEW MODERATE SNOW SHOWERS. VISIBILITY WILL GENERALLY BE AROUND 4 TO 5 MILES IN THE SNOW WITH VISIBILITIES UNDER 1 OR 2 MILES UNDER THE HEAVIER SNOW SHOWERS. WHEN ALL IS SAID AND DONE EXPECTING UNDER A HALF INCH OF SNOW ACROSS THE REGION. MOST AREAS WILL RECEIVE ONLY A COUPLE TENTHS OF AN INCH AT BEST WITH ISOLATED HIGHER AMOUNTS. AFTER MIDNIGHT...PARTS OF NORTHWEST INDIANA MAY SEE FREEZING DRIZZLE MIXED IN WITH FLURRIES/LIGHT SNOW SHOWERS AS THE COLUMN IS NOT LONGER SATURATED UP THROUGH THE DGZ. A LIGHT GLAZE OR LESS IS EXPECTED. HIGH PRESSURE SPREADS OVERHEAD WEDNESDAY LEADING TO DRIER CONDITIONS. THINKING LAKE EFFECT SNOW WILL FALL EAST OF PORTER COUNTY SO NO SNOW IS EXPECTED ACROSS THE WARNING AREA. AREAS NORTH OF I-88 MAY EVEN SEE SUNSHINE AS SKIES ARE EXPECTED TO SCATTER OUT IN THE AFTERNOON. COLDER AIR ALOFT SINKS SOUTH WEDNESDAY LEADING TO SLIGHTLY COLDER TEMPS TOMORROW. HIGHS WILL BE AROUND FREEZING. JEE && .LONG TERM... 257 PM CST WEDNESDAY NIGHT THROUGH TUESDAY... THE MAIN HIGHLIGHTS IN THE EXTENDED PERIOD CONTINUE TO BE THE NICE WARM-UP EXPECTED LATER IN THE WEEK. FOLLOWING THE EASTWARD PROGRESSION OF A SURFACE RIDGE OF HIGH PRESSURE TOWARDS THE EAST COAST ON THURSDAY...THE LOWER LEVEL FLOW WILL TURN SOUTHERLY. THIS SHOULD HELP TEMPERATURES BEGIN TO WARM NICELY INTO THE UPPER 30S TO THE LOWER 40S BY THURSDAY AFTERNOON. TEMPERATURES WILL LIKELY CONTINUE ON AN UPWARD TREND THURSDAY NIGHT AS SURFACE WINDS CONTINUE TO INCREASE IN RESPONSE TO STRONG PRESSURE FALLS SETTING UP OVER THE UPPER MIDWEST AND GREAT LAKES REGION IN RESPONSE TO THE APPROACH OF A POTENT AREA OF LOW PRESSURE OVER THE DAKOTAS. THIS STORM SYSTEM WILL LIKELY INDUCE DOWN SLOPE FLOW...RESULTING IN A DRY AND VERY WARM AIRMASS SETTING UP OVER THE CENTRAL PLAINS ON THURSDAY. THE ASSOCIATED THERMAL RIDGE IS THEN EXPECTED TO ADVECT EASTWARD OVER THE CENTRAL STATES BY FRIDAY. CURRENT INDICATIONS CONTINUE TO SUGGEST THAT SURFACE TEMPERATURES COULD WARM WELL INTO THE 50S...TO POSSIBLY EVEN SOME LOW 60S FRIDAY AFTERNOON AS THIS WARM AND DRIER AIRMASS SETS UP OVER THE AREA. THE ONE CAVEAT TO THIS REALLY WARM WEATHER ON FRIDAY IS THAT IT LOOKS TO ALSO COME DURING A VERY WINDY DAY. AFTER THE SMALL POTENTIAL FOR A FEW SHOWERS EARLY FRIDAY...A FRONTAL BOUNDARY WILL SHIFT ACROSS THE AREA BY AROUND MIDDAY. IN ITS WAKE...IT APPEARS THAT THE WINDS WILL INCREASE OUT OF THE WEST-SOUTHWEST...WITH THE POTENTIAL OF A PERIOD OF WIND ADVISORY CRITERIA WIND GUSTS (45 MPH) FRIDAY AFTERNOON AS SOME STRONG PRESSURE RISES OVERSPREAD THE AREA. ADDITIONALLY...MUCH DRIER AIR IN THE FRONTS WAKE COULD ALSO RESULT IN LOWER RH`S THAN CURRENTLY FORECAST...AS THIS AIRMASS LOOKS TO BE ADVECTING IN OFF THE HIGH PLAINS. IF THIS OCCURS...THE COMBINATION OF THE STRONG WINDS AND DRY MILD AIR COULD INCREASE FIRE WEATHER CONCERNS SOME FRIDAY AFTERNOON. IT APPEARS THE MILD WEATHER WILL CONTINUE INTO THE WEEKEND AS WELL AS A QUASI-ZONAL FLOW PATTERN ALOFT KEEPS THE AIRMASS MILD OVER THE REGION. TEMPERATURES COULD AGAIN GET INTO THE 50S WITH LIGHTER WINDS OVER THE WEEKEND. AFTER A MILD WEEKEND...MODELS AND ENSEMBLES ARE IN DECENT AGREEMENT IN SUGGESTING ANOTHER COLD PUSH WILL SHIFT OVER THE AREA EARLY NEXT WEEK AS UPPER RIDGING BEGINS TO BUILD AGAIN OVER THE WESTERN CONUS. THIS SHOULD ALLOW ANOTHER TROUGH AND SURFACE COLD FRONT TO SHIFT OVER THE AREA BY MONDAY. AS A CONSEQUENCE...COLDER WEATHER AND SOME CHANCES OF LIGHT SNOW LOOKS TO BEGIN NEXT WEEK. KJB && .AVIATION... FOR THE 06Z TAFS... LINGERING SNOW FLURRIES HAVE EXITED EAST OF THE AREA...WITH VERY SPOTTY ECHOES UPSTREAM IN SOUTHEAST WISCONSIN. THERE IS A PRETTY STEADY STREAM OF MVFR CIGS IN IOWA INTO NORTHWEST ILLINOIS...BUT IN WISCONSIN AND NORTHERN ILLINOIS CIG CONTINUE TO LIFT THROUGH MVFR TO EVEN LOW END VFR. MPX SOUNDING AND AMDAR SOUNDINGS AROUND KMKX SHOW A SHALLOW MOISTURE LAYER. WITH LOW LEVEL FLOW FROM THE NORTH-NORTHWEST...EXPECT THAT LIFTING AND SCATTERING WILL OCCUR ACROSS MOST OF THE AREA TONIGHT. DEWPOINT DEPRESSIONS ARE INITIALLY SOMEWHAT LOW BEHIND THE COLD FRONT TONIGHT...THUS SOME PATCHY FOG WILL CONTINUE AT LEAST OVERNIGHT UNTIL DRIER AIR FILTERS IN. FOG SHOULD NOT BE A BIG DEAL IN MOST AREAS THOUGH GUIDANCE IS HITTING IT A BIT HARDER WEST TOWARDS KRFD. TUESDAY SHOULD BE FAIRLY BENIGN AS HIGH PRESSURE MOVES OVERHEAD THEN SHIFTS EAST TUESDAY AFTERNOON AND EVENING. LIGHTER NW WINDS BECOME VARIABLE THEN TAKE ON AN EASTERLY AND EVENTUALLY SOUTHEASTERLY DIRECTION LATER IN THE DAY AND EVENING. MOST GUIDANCE KEEPS WINDS UNDER 10 KT IN THE EAST WIND SHIFT. KMD && .MARINE... 309 PM CST A VERY ACTIVE PERIOD OF WEATHER EXPECTED OVER THE LAKES FOR THURSDAY THROUGH FRIDAY. A COLD FRONT WILL SHIFT DOWN THE LAKE EARLY THIS EVENING...WITH NORTHWESTERLY WINDS OF 25 TO 30 KT EXPECTED TONIGHT IN ITS WAKE. SURFACE HIGH PRESSURE WILL THEN SHIFT OVER THE LAKE ON WEDNESDAY AFTERNOON...RESULTING IN A PERIOD OF LIGHT AND VARIABLE WINDS. HOWEVER...ONCE THIS HIGH SHIFTS EAST OF THE LAKE BY THURSDAY...EXPECT SOUTHERLY WINDS TO INCREASE. A STRONG STORM SYSTEM IS EXPECTED TO SHIFT OVER THE DAKOTAS BY THURSDAY EVENING. THIS WILL SET UP A FAVORABLE PRESSURE GRADIENT FOR LAKE MICHIGAN TO SUPPORT SOUTHERLY GALES THURSDAY NIGHT INTO FRIDAY MORNING. THEREAFTER...THE STORM SYSTEM IS EXPECTED TO APPROACH THE NORTHERN LAKES REGION BY FRIDAY AFTERNOON. AS IT DOES SO...IT WILL LIKELY DRIVE A STRONG FRONT OVER THE LAKE...WITH A PERIOD OF WEST-SOUTHWESTERLY GALES LIKELY THROUGH FRIDAY EVENING. CURRENTLY FELT IT WAS A BIT TOO EARLY TO GO WITH A GALE WATCH...BUT ONE MAY BE NEEDED TONIGHT IF CONDITIONS CONTINUE TO SUPPORT SUCH. KJB && .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