Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/31/16


Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
349 AM CDT Mon Oct 31 2016 .SHORT TERM... 318 AM CDT Through Tuesday... Fairly benign conditions in place early this morning with high pressure overhead. Earlier holes in cloud cover and weak winds have brought dewpoint depressions down to support some patchy, and infrequently locally somewhat dense fog, but high clouds continue to stream overhead with active westerly flow aloft. With low level warm advection on the back side of the high, some lower clouds may also develop though guidance is not filling it all in. It will be a cool start to the day for many areas with readings bottoming out near daybreak in the mid 30s to lower 40s outside of the main urban core. With the progressive flow in place, high pressure will quickly shift eastward today. A series of disturbances aloft across the northern Rockies will consolidate into a more organize shortwave across the upper Midwest this evening. This will drive a modest 992 mb surface low across northern Lake Superior late tonight and to James Bay later Tuesday. This pattern will allow warm southwest flow to advect a mild airmass to the region today and Tuesday. The warming will be tempered initially with SE surface flow. Upper soundings at ILX and DVN show a strong temperature inversion at 850 mb, locally from AMDAR soundings a bit lower around 900 mb, thus weak mixing in spite of increasing southeast winds today will hold temps in the lower 60s or so, still above normal. Let`s call it partly cloudy with some patchy lower clouds but a continued stream of higher clouds. Warm moist advection tonight will support temperatures only dipping slightly or possibly rising later tonight as dewpoints climb through the 50s. This pattern does support the development of low stratus, which is occurring upstream in Oklahoma, eastern KS/NE and western MO/IA. In spite of the steep lapse rates aloft advecting overhead tonight, most guidance keeps precip with the isentropic lift to the north and if any stratus develops maybe some sprinkles/drizzle later tonight into early Tuesday. The warm advection continues tonight into Tuesday which should allow for a bit more mixing on Tuesday. 925 mb temperature climatology supports highs of 71-79, a touch higher than our model blender. Some of this may be initially delayed by any status development which at this point is favored for I-80 northward. The warm advection should be strong enough on Tuesday such that clouds may have little effect on highs except maybe north. KMD && .LONG TERM... 318 AM CDT Tuesday night through Sunday... As the wave passes by to our north Tuesday night, it will send a frontal boundary south to the IL/WI border to start Tuesday evening, then looks to hang out across northern Illinois into Wednesday as southwest low level flow holds the boundary in place. Forcing appears benign initially, but shortwave energy will continue to ride along the boundary overnight. Models are mixed as to the strength of these waves and keep height falls to a minimum, so have maintained a chance of showers and small chance of storms given weak instability Tuesday night. North central IL/far northeast IL would be the favored locations where better potential lower level fgen may exist coupled with some weak surface reflections. The front gets a bit of a shove southward on Wednesday and becomes a bit more active as height falls commence ahead of the approaching western U.S. trough axis. Combined forcing from a strengthening jet to our north and the lower level frontal zone will support an uptick in shower coverage during morning. Additional shortwave energy will ride northeast along the frontal zone as the trough continues to nudge the front southward providing another round of showers and a few storms focused from Chicago southward. 1.5 inch PWATs suggest the potential for some decent rainfall with these waves of precipitation, possibly in excess of an inch. The current axis favored for the heavy precipitation is generally Chicago metro southward. An while instability is not great, dewpoints in the upper 50s to low 60s suggest maintaining the t-storm mention. High pressure will be in control Thursday through Saturday. After a brief cool down back to normal Thursday, mostly sunny conditions with warming temperatures seem to be supported by the model suite and ensembles to bring another period of mild and dry weather, about as good as it gets for early November. Flow will be more westerly so dewpoints remain in the 40s, and highs look to remain locked in the 60s/lows in the 40s through the weekend. The high will shift eastward Sunday but moisture advection will be to our west. KMD && .AVIATION... For the 06Z TAFs... The main concerns for the forecast period will be the potential for the return of MVFR cigs overnight, and then southeast winds becoming gusty by early afternoon. The center of high pressure is moving across the upper Great Lakes with a ridge axis extending southwest to the middle Mississippi valley. With the ridge axis across the terminals, winds should generally be lgt/vrbl through the remainder of the overnight hours. As the high moves to the eastern Great Lakes by late morning and low pressure deepens over the northern plains, winds will becm sely and increase through the day. Gusts are likely by afternoon, but with increasing coverage of mid and high level cloudiness, gusts may not be quite as high as would be the case with full mixing. Confidence in a south-southeast direction is high. Confidence in gust magnitude is moderate, with some gusts higher than 20 kt possible in the afternoon. Expect the gustiness will actually increase after sunset with winds gradually veering to southwesterly. With 50+ kt southwest flow around 2,000 ft developing by 03Z Tuesday, a ocnl gusts higher than 25 kt are possible. There will also be some potential for LLWS as well. Some mvfr clouds are are moving inland from Lake Michigan, with GYY firmly mvfr and a few other sites invof the lake also reporting mvfr cigs. ORD/MDW are indicating sct025-030 at issuance time and there is the potential for some expansion of the mvfr cigs to ORD/MDW, but do not anticipate cigs below 2000 ft. Given the expansion of the lower cloud noted at IGQ and what can be seen in satellite imagery, have gone with a tempo MVFR in the ORD and MDW TAFs. With diurnal warming, expect that cigs should improve to vfr shortly after dawn and the remainder of the forecast period should be vfr and dry. && .MARINE... 345 AM CDT Headlines...Have made no changes to current headlines as latest forecast guidance is similar to previous runs. Will maintain the Gale Watch over the southern portion of Lake Michigan as there is still some uncertainty at the the duration and extend of gale force winds. Confidence in gales is much higher for the northern portion of the lake where the pressure gradient will be stronger between exiting high pressure and low pressure tracking through the nrn plains today and into swrn Ontario tonight. The low is expected to quickly track to James Bay by mid day Tuesday while dragging a weak cold front across the lake. Winds should diminish quickly overnight tonight following the passage of the front and weak high pressure builds across the lake. Will also maintain the small craft advisory as is currently in place. The chances for gales over the nearshore waters are low. A trough of low pressure and an associated quasi-stationary front will set up across the srn tip of the lake on Wednesday. High pressure building across the middle and upper Mississippi Valley will force the front swd to the Ohio Valley Thursday. The high should spread across the lake Thursday night. && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742...1 PM Monday TO 4 AM Tuesday. Small Craft Advisory...LMZ743-LMZ744-LMZ745...4 PM Monday TO 4 AM Tuesday. Gale Watch...LMZ777-LMZ779...4 PM Monday TO 4 AM Tuesday. && $$ 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
National Weather Service Chicago/Romeoville, IL
643 AM CDT Mon Oct 31 2016 .SHORT TERM... 318 AM CDT Through Tuesday... Fairly benign conditions in place early this morning with high pressure overhead. Earlier holes in cloud cover and weak winds have brought dewpoint depressions down to support some patchy, and infrequently locally somewhat dense fog, but high clouds continue to stream overhead with active westerly flow aloft. With low level warm advection on the back side of the high, some lower clouds may also develop though guidance is not filling it all in. It will be a cool start to the day for many areas with readings bottoming out near daybreak in the mid 30s to lower 40s outside of the main urban core. With the progressive flow in place, high pressure will quickly shift eastward today. A series of disturbances aloft across the northern Rockies will consolidate into a more organize shortwave across the upper Midwest this evening. This will drive a modest 992 mb surface low across northern Lake Superior late tonight and to James Bay later Tuesday. This pattern will allow warm southwest flow to advect a mild airmass to the region today and Tuesday. The warming will be tempered initially with SE surface flow. Upper soundings at ILX and DVN show a strong temperature inversion at 850 mb, locally from AMDAR soundings a bit lower around 900 mb, thus weak mixing in spite of increasing southeast winds today will hold temps in the lower 60s or so, still above normal. Let`s call it partly cloudy with some patchy lower clouds but a continued stream of higher clouds. Warm moist advection tonight will support temperatures only dipping slightly or possibly rising later tonight as dewpoints climb through the 50s. This pattern does support the development of low stratus, which is occurring upstream in Oklahoma, eastern KS/NE and western MO/IA. In spite of the steep lapse rates aloft advecting overhead tonight, most guidance keeps precip with the isentropic lift to the north and if any stratus develops maybe some sprinkles/drizzle later tonight into early Tuesday. The warm advection continues tonight into Tuesday which should allow for a bit more mixing on Tuesday. 925 mb temperature climatology supports highs of 71-79, a touch higher than our model blender. Some of this may be initially delayed by any status development which at this point is favored for I-80 northward. The warm advection should be strong enough on Tuesday such that clouds may have little effect on highs except maybe north. KMD && .LONG TERM... 318 AM CDT Tuesday night through Sunday... As the wave passes by to our north Tuesday night, it will send a frontal boundary south to the IL/WI border to start Tuesday evening, then looks to hang out across northern Illinois into Wednesday as southwest low level flow holds the boundary in place. Forcing appears benign initially, but shortwave energy will continue to ride along the boundary overnight. Models are mixed as to the strength of these waves and keep height falls to a minimum, so have maintained a chance of showers and small chance of storms given weak instability Tuesday night. North central IL/far northeast IL would be the favored locations where better potential lower level fgen may exist coupled with some weak surface reflections. The front gets a bit of a shove southward on Wednesday and becomes a bit more active as height falls commence ahead of the approaching western U.S. trough axis. Combined forcing from a strengthening jet to our north and the lower level frontal zone will support an uptick in shower coverage during morning. Additional shortwave energy will ride northeast along the frontal zone as the trough continues to nudge the front southward providing another round of showers and a few storms focused from Chicago southward. 1.5 inch PWATs suggest the potential for some decent rainfall with these waves of precipitation, possibly in excess of an inch. The current axis favored for the heavy precipitation is generally Chicago metro southward. An while instability is not great, dewpoints in the upper 50s to low 60s suggest maintaining the t-storm mention. High pressure will be in control Thursday through Saturday. After a brief cool down back to normal Thursday, mostly sunny conditions with warming temperatures seem to be supported by the model suite and ensembles to bring another period of mild and dry weather, about as good as it gets for early November. Flow will be more westerly so dewpoints remain in the 40s, and highs look to remain locked in the 60s/lows in the 40s through the weekend. The high will shift eastward Sunday but moisture advection will be to our west. KMD && .AVIATION... For the 12Z TAFs... The main concerns for the forecast period will be southeast winds becoming gusty by early afternoon. The center of high pressure is moving across the upper Great Lakes with a ridge axis extending southwest to the middle Mississippi valley. With the ridge axis across the terminals, winds should generally be lgt/vrbl early this morning. As the high moves to the eastern Great Lakes by late morning and low pressure deepens over the northern plains, winds will becm sely and increase through the day. Gusts are likely by afternoon, but with increasing coverage of mid and high level cloudiness, gusts may not be quite as high as would be the case with full mixing. Confidence in a ssely direction is high. Confidence in gust magnitude is moderate, with some gusts higher than 20 kt possible in the afternoon. Expect the gustiness should increase after sunset with winds gradually veering to southwesterly. With 50+ kt southwest flow around 2,000 ft developing this evening, ocnl gusts higher than 25 kt are possible. There will also be some potential for LLWS as well. The mvfr clouds have scattered out and expect increasing mid and high level cloud cover to increase through the day and into tonight. Otherwise, the forecast period should be vfr and dry. && .MARINE... 345 AM CDT Headlines...Have made no changes to current headlines as latest forecast guidance is similar to previous runs. Will maintain the Gale Watch over the southern portion of Lake Michigan as there is still some uncertainty at the the duration and extend of gale force winds. Confidence in gales is much higher for the northern portion of the lake where the pressure gradient will be stronger between exiting high pressure and low pressure tracking through the nrn plains today and into swrn Ontario tonight. The low is expected to quickly track to James Bay by mid day Tuesday while dragging a weak cold front across the lake. Winds should diminish quickly overnight tonight following the passage of the front and weak high pressure builds across the lake. Will also maintain the small craft advisory as is currently in place. The chances for gales over the nearshore waters are low. A trough of low pressure and an associated quasi-stationary front will set up across the srn tip of the lake on Wednesday. High pressure building across the middle and upper Mississippi Valley will force the front swd to the Ohio Valley Thursday. The high should spread across the lake Thursday night. && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742...1 PM Monday TO 4 AM Tuesday. Small Craft Advisory...LMZ743-LMZ744-LMZ745...4 PM Monday TO 4 AM Tuesday. Gale Watch...LMZ777-LMZ779...4 PM Monday TO 4 AM Tuesday. && $$ 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
National Weather Service Honolulu HI
952 AM HST Mon Oct 31 2016 .SYNOPSIS... Breezy and gusty trade winds will persist into Tuesday as surface high pressure remains north of the state. Wet and slightly unstable conditions will linger on the Big Island today as drier air spreads across the rest of the island chain. A drier and more stable air mass will produce modest windward rainfall through the rest of the week, with trade winds easing slightly Wednesday through the weekend. && .DISCUSSION... Breezy as gusty trade winds will persist today. A strong north Pacific jet stream has pushed a relatively strong subtropical ridge to about 500 miles north of the state along 29N. The local pressure gradient remains tight as an active portion of the ITCZ is passing a few hundred miles south of the islands. As this area moves westward today, the ECMWF and GFS show the low level pressure gradient relaxing slightly, with 850 mb winds declining about 5 kt from the current 25 to 30 kt. During this time, a mid level ridge will begin to gradually build over the islands, causing the weak inversion, currently around 7000 to 9000 ft according to the overnight soundings and recent aircraft data, to strengthen and lower. The net result should be little change to the breezy and gusty trade winds, and areas over and downwind of terrain on the Big Island and portions of Maui County will see wind gusts near wind advisory strength. Relatively wet conditions will linger on the Big Island today, while a drier air mass spreads over the rest of the state. Satellite-derived precipitable water (PW) estimates show values below one inch already over Kauai with a field of stable stratocumulus to the east and northeast. As this air mass moves over the smaller islands today, shower activity will diminish greatly, confining modest rainfall to windward slopes. PW values over the Big Island remain near normal this morning, and a sharp upper level trough overhead continues to produce slight instability. As a result, expect active, but diminishing, shower activity on windward Big Island through the day with spotty showers developing along interior and leeward slopes. Breezy trade winds will decrease a notch late Tuesday and Wednesday. A strong jet stream running across the north Pacific will keep the subtropical ridge slightly weakened and displaced a bit south of normal over the central Pacific. This will cause trades to back off slightly into the moderate to locally breezy range through much of the week. Drier trade wind weather is due for much of the upcoming week. The ECMWF and GFS show PW values hovering around an inch, roughly 25 percent below normal, and mid level ridging will build overhead, creating stable conditions. This should result in decreased shower activity, with modest rainfall limited to windward slopes and mainly dry conditions leeward. && .AVIATION... A drier airmass will continue to fill in today, with conditions improving along windward and mountain areas. AIRMET SIERRA for mountain obscuration remains posted over Oahu, Maui, and the Big Island, as clouds and showers linger over the north and east slopes. These will likely be cancelled in the next few hours, and from then on passing scattered showers should be expected. Breezy trade winds will continue through the period. AIRMET TANGO for low level turb over and immediately south through west of the mountains remains posted. Additionally, some of the windier channels will experience surface winds 30 KT or greater and AIRMET TANGO for strong surface winds is posted for the Alenuihaha and Pailolo Channels and coastal waters south of the Big Island. An upper level jet over the islands may introduce light upper level turb between FL250/410 today, with model guidance suggesting the chance for turb increasing tonight. AIRMET TANGO for upper level turb may need to be issued as conditions develop. && .MARINE... A Small Craft Advisory (SCA) remains posted for all waters today, with trade winds holding at near gale strength over the typically windy waters around the Big Island and Maui. The SCA will remain in place for most waters through Tuesday and will likely be trimmed back to the typical windier locations by mid to late week as the trades ease a notch. A High Surf Advisory remains posted for most east facing shores today, as rough, trade wind driven seas of around 8 to 9 ft at 8 seconds continue. A gradual decline will occur during the next couple of days, with trade wind energy holding at 5 to 7 ft at 8 seconds from Tuesday through the weekend. A very active weather pattern across the northern Pacific will translate to a large north-northwest swell late Wednesday through Thursday. The latest ensemble wave guidance has been trending up over the past several model cycles with the mean consistently coming in above the operational WAVEWATCH III. A blend of these two solutions has been included in the forecast and supports near warning-level surf for Wednesday night and Thursday. This swell will become reinforced by another, slightly smaller, north- northwest swell Thursday night and Friday before trending down over the upcoming weekend. As a result of these back-to-back sources, north and west shore surf well above the advisory level will begin as early as sunset Wednesday and continue through as late as Friday night. && .HFO WATCHES/WARNINGS/ADVISORIES... High Surf Advisory until 6 PM HST Monday for East facing shores of Kauai, Oahu, Molokai, Maui, and the Big Island. Small Craft Advisory until 6 PM HST Tuesday for Oahu Leeward Waters-Kaiwi Channel-Maui County Windward Waters-Maui County Leeward Waters-Maalaea Bay-Pailolo Channel-Alenuihaha Channel- Big Island Windward Waters-Big Island Leeward Waters-Big Island Southeast Waters. Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters- Kauai Channel-Oahu Windward Waters. && $$ Public...Wroe Aviation...Eaton Marine...Wroe/Gibbs