Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/25/17

Area Forecast Discussion
National Weather Service La Crosse WI
620 PM CDT Tue Oct 24 2017 .SHORT TERM...(This evening through Wednesday) Issued at 248 PM CDT Tue Oct 24 2017 Afternoon satellite and surface observations show a stacked low pressure system drifting eastward across the Northern Great Lakes. This system has brought cloudy skies and strong northwest winds to the local area today, with gusts approaching 40 mph. With the surface pressure gradient weakening and winds no longer reaching advisory criteria, Will canceled the wind advisory for the entire area. The main concern for tonight into Wednesday will be a vorticity/jet streak streaming down from southeast Manitoba/southwest Ontario. Associated low-level frontogenesis under the left exit region of the 300 mb jet streak should provide enough forcing to overcome a lower layer of dry air and produce at least light precipitation east of the Mississippi River from around 25.09Z to 25.15Z Wednesday. Model soundings indicate below freezing thermal profiles with deep lift and saturation through the DGZ and surface temperatures around 32F. Therefore, snow is the expected precipitation type until diurnal heating warms surface temperatures above freezing. Given the time of year with regards to ground temperatures, do not anticipate much in the way of snow accumulation, but recent runs of the RAP are hinting at weak banding potential. The rest Wednesday should remain dry under partly to mostly cloudy skies. Northwest winds will be gusty west of the Mississippi River, but not as strong as today. Temperatures will remain near to slightly below normal. .LONG TERM...(Wednesday night through Tuesday) Issued at 248 PM CDT Tue Oct 24 2017 This looks to be a somewhat active period with the potential for some light precipitation for much of the period. The northwest flow aloft has become established over the region and this does not look like it will be breaking down in the near future. After a bit of short wave ridging Wednesday, this will quickly break down as the next short wave trough drops southeast out of the Canadian Rockies Wednesday night. This system will evolve into a closed upper level low over the Upper Mississippi River Valley Friday that will move slowly northeast across the Great Lakes into early next week. The first chance for precipitation will arrive Thursday afternoon and night in the warm air advection ahead of the system. The 24.12Z GFS suggests up to 4 ubar/s of up glide on the 290K isentropic surface as the system comes. Initially, most of this goes into cloud production trying to saturate the column, but it looks by late Thursday afternoon, this should be overcome for at least a chance of some light precipitation across the northern sections of the area. These chances will continue to drop south Thursday night but may become more confined to areas east of the Mississippi River as the isentropic upglide slides more over that area. This could leave southeast Minnesota and northeast Iowa dry for much of Thursday night. As the upper level low closes off over the region Friday, a deformation band of precipitation will start to form on the northwest side of the surface low. Some differences between the models on where the surface low will be located, but for the most part, they all agree that most of the area will have at least a chance of seeing some of the deformation precipitation, with the highest chances across the northern parts of the area. As the surface low then starts to move slowly northeast away from the area Saturday, it looks like the deformation zone should gradually swing east across the entire area and then start to diminish from west to east Saturday night into Sunday. Temperatures will be cold enough at times for the precipitation to fall as a rain/snow mix or as just some light snow. With the expected light nature of the precipitation and warm ground surface, would not anticipate much if any accumulation to occur. By early next week, another system looks like it will move dropping southeast out of Canada toward the Upper Midwest and Great Lakes. There are some differences between the 24.12Z ECMWF and GFS on just how far south this system will get before turning more to the east. For now, will just a some small chances for precipitation across much of the area for Monday. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 620 PM CDT Tue Oct 24 2017 Clear skies and breezy northwest winds this evening will be short-lived as a band of VFR ceilings currently across ND/northern MN dive southward overnight. Expect cloud bases in the 6000 to 8000 ft agl layer with winds decreasing a bit and shifting to the west-southwest. Some light snow is possible tonight, but expecting it to be mainly north and east of KLSE, so will keep TAFs dry. Periods of VFR clouds will continue through the day on Wednesday with modest northwest wind, gusting at times to around 20 kts at KRST. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...MH LONG TERM...04 AVIATION...Rogers
Area Forecast Discussion
National Weather Service Taunton MA
954 PM EDT Tue Oct 24 2017 .SYNOPSIS... A north-south line of widespread rain with embedded heavier showers and isolated thunderstorms will gradually sweep E across S New England through Wednesday night. With any heavy rain there is a flash flood threat. Another round of showers expected Thursday as a strong disturbance moves across the region. High pressure returns Friday and Saturday with dry and seasonably mild conditions, then more rain and wind is possible late Sunday into Monday as another system approaches from the west. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... 10 pm update... South to north training of heavy rain along a slowly eastward moving occluded front will present a flash flood threat through the overnight hours. Strong low-level-jet deciphered from latest vertical wind profilers ushering sub-tropical air N, squeezed between an occluded front to a bombing low over the Great Lakes region and a high pressure gyre across the NW Atlantic. SPC meso- analysis highlighting precipitable waters up to 1.7 inches that is maintained by strong moisture transport within the low-levels and deep moist convergence along the front. High freezing level heights, seeing the measure of lift along the front contributing to efficient warm-rain processes as well as cloud tops reaching 25-30 kft agl. Conditionally unstable profile as discerned from 0z soundings enabling instability of around 250 J/kg in a region of 0-1 km shear and helicity that promotes bowing segments and storm-cell rotation, several threats continue in the way of strong to damaging winds and flash flooding. Following closely to latest high-res guidance, but believe that both the HRRR and the RAP are moving things a bit too quickly. The frontal boundary is squeezed between airmasses that are slowly juxtaposition per WV satellite, holding their place more or less or getting stretched out. Growing concern that we are in for a long night of flash flooding that will result in dangerous conditions with homes becoming inundated, potential for water rescues. Very anomalous situation that warrants to expect the unexpected. Widespread 1-inch rainfall amounts with locally heavier outcomes with any S to N training with anticipated rain amounts of 2 to 4 inches, some of that occurring in a short period of time far exceeding flash flood guidance which is presently around 2 to 3 inches for the 1-hour and 3-hour timeframes. Forecast wind gusts averaging around 25 to 35 mph, but within the heavier rain cells anticipating gusts to exceed 40 mph possibly up to 50 mph. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Wednesday... As the front lines up parallel with the long wave upper flow from S-N, the cold front continues its very slow trek across eastern areas during the day Wednesday. There is the possibility of the front stalling during the afternoon. This will keep moisture feed working across eastern Mass and RI, while the rains slowly lessen further W. Good instability continues early Wed morning with LIs down to around -1 and TQ values in the upper teens so kept mention of thunderstorms through about mid morning Wed. However, will still see showers falling heavily at times through the day, possibly with some locations seeing up to 1"/hour rainfall rates. Drier air starts to work into western areas as PWATS fall quickly behind the slow moving front. Also, the low level jet also shifts E with the front, so while S-SW winds continue, they will diminish by mid to late morning Wed. Across eastern areas, gusty winds continue as well as threat for heavy rainfall at times. There is the potential of another 1-2 inches of rain to fall, possibly higher in localized heavy downpours. Back edge of best moisture will slowly push off the coast late Wed afternoon as higher PWAT air moves offshore, but scattered showers will linger even into western areas through the day. Temps will be turning cooler across the west with highs in the lower-mid 60s, with readings ranging to the upper 60s across eastern areas. Wednesday night... Big question during this timeframe is whether the front clears the coast or lingers through the night which will keep the potential for at least light rainfall across eastern areas. The outer Cape and Nantucket may see another inch of rain early Wed night. Also some question as to whether another weak low forms along the front, again enhancing the potential of rain across the east. At this point, it looks like that the low may actually push the front along, but will linger across E coastal areas by around daybreak Thursday. Have carried likely to CAT POPs across central and eastern areas and CHC POPs over the west. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Highlights... * Numerous showers and a few T-storms possible Thu * Mainly dry and seasonably mild Fri/Sat * Return to stormy conditions late Sun/Mon with more rain and wind Overview... High amplitude +PNA/-EPO pattern across the CONUS during the extended period with anomalous ridging across the northern Pacific coast and north Atlantic. This allows high amplitude trough to reload across the central CONUS late in the week into next weekend. Prior to this, the start of the extended period will feature numerous showers as neg tilt trough and closed low lifts NE across New Eng during Thu. Ridging becomes re-established off the east coast late in the week into the weekend ahead of amplifying upstream trough resulting in dry and seasonably mild conditions, then a return to stormy weather is likely sometime Sun/Mon timeframe as high amplitude trough lifts NE across New Eng. Timing and details of potential wind and rainfall still uncertain at this time range. Thursday... Cold front will be moving offshore with any lingering showers exiting the Cape/Islands in the morning. Otherwise, rather robust negative tilt trough/closed low and assocd cold pool will lift northward across New Eng. 500 mb temps cooling to -24C and steepening mid level lapse rates combined with deep column moisture and good synoptic forcing will result in numerous convective showers redeveloping across the region and can`t rule out an isold t-storm given the convective instability and marginal MUCAPES. In addition to brief downpours, small hail will also be possible given the low WBZ heights. Seasonable temps expected. Friday and Saturday... High pres returns with building ridge along the east coast will result in sunshine and seasonably mild temps. Sunday into Monday... Next high amplitude trough to the west will become negatively tilted as it lifts across New Eng Monday. The attending cold front will be preceded by a strong low level jet which will transport anomalous moisture north. Ensemble guidance showing PWAT plume +2SD and low level jet +3SD which are impressive anomalies at this time range suggesting potential for another round of heavy rainfall and strong winds sometime late Sun into Mon, although confidence in timing and details remain low. Mild temps expected in southerly flow regime. Tuesday... Looks mainly dry and seasonable behind departing system as high pres builds over the mid atlc coast. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday Night/...Moderate confidence. Tonight into Wednesday... Trending MVFR with -RA/RA, IFR with RA/+RA with respect to both CIGs and VSBYs. Also with RA/+RA a VCTS mention. Impacts through Wednesday, across the W overnight into morning, across the E morning through the day. Slow movement of outcomes and gradual improvement E through the timeframe. Could see flooding at terminals. Gusty S winds around 25 to 35 kts, locally higher with RA/+RA potentially exceeding 40 kts and a LLWS threat with 2 kft agl winds around 50-55 kts overnight, pushing offshore Wednesday. Wednesday night... RA/+RA expected to be along the immediate coast if not mostly offshore with -RA/RA outcomes elsewhere. Low-end VFR / MVFR to the W while IFR towards the E. S winds less, no longer a threat anywhere of gusty winds or LLWS. KBOS Terminal...Moderate confidence in TAF. Gradual trend downward towards the AM push, with impacts developing after midnight (5z). Could be too early in moving outcomes offshore Wednesday morning in terms of +RA, LLWS and gusty winds. KBDL Terminal...Moderate confidence in TAF. Worst conditions ongoing across the terminal. Flash flooding is possible. Trending IFR with RA/+RA and a VCTS mention. Impacts through 6z but that may be too early, potential to last a bit longer. Closely monitoring. Outlook /Thursday through Sunday/... Thursday: High confidence. Mainly MVFR, with areas VFR possible. SHRA likely, slight chance TSRA. Thursday Night: High confidence. Mainly VFR, with local MVFR possible in the evening. Windy with local gusts to 30 kt, mainly SE New Eng. Chance evening SHRA, isolated TSRA. Friday: High confidence. VFR. Breezy. Friday Night through Saturday Night: High confidence. VFR. Sunday: Moderate confidence. Mainly VFR, but MVFR possible in showers Sunday night. Becoming breezy Sunday night. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday Night/...Moderate confidence. Tonight... Expect S winds gusting to 35-40 kt with seas up to 7-11 ft across the open waters, highest across the southern outer waters this evening. Visibility restrictions in developing fog. Showers, heavy at times, with chance for thunderstorms which may produce gusts over 40 kt. Winds start to diminish after midnight across the waters S of Block Island. Wednesday... S winds continue to gust up to around 35 kt with seas up to 7-11 ft early. Winds will diminish during the day from W-E. Showers will continue, heavy at times, along with patchy fog producing visibility restrictions. Showers linger across the eastern waters through the day as the front slows its east progression. Wednesday night... Continued S winds at 15 kt or less, highest across the eastern waters. Seas will remain at 6-9 ft on the open waters, so small crafts will continue. Visibility restrictions in showers and patchy fog. Outlook /Thursday through Sunday/...Moderate confidence. Thursday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 10 ft. Rain showers likely, isolated thunderstorms. Thursday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 11 ft. Friday: Winds less than 25 kt. Areas of rough seas. Friday Night: Winds less than 25 kt. Seas up to 5 ft. Saturday through Saturday Night:Winds less than 25 kt. Sunday: Low risk for Small Craft Advisory winds with local gusts up to 30 kt by late Sunday. Seas locally approaching 5 ft. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Flash Flood Watch through Wednesday morning for CTZ002>004. Wind Advisory until 2 AM EDT Wednesday for CTZ002-003. Wind Advisory until 5 AM EDT Wednesday for CTZ004. MA...Wind Advisory until 8 AM EDT Wednesday for MAZ007-013>021. Flash Flood Watch from 2 AM EDT Wednesday through Wednesday afternoon for MAZ005>007-013>024-026. Flash Flood Watch through Wednesday morning for MAZ002>004- 008>012. Wind Advisory until 2 AM EDT Wednesday for MAZ002-003-008>011. Wind Advisory until 5 AM EDT Wednesday for MAZ004>006-012-026. Wind Advisory until 11 AM EDT Wednesday for MAZ022>024. RI...Wind Advisory until 8 AM EDT Wednesday for RIZ001>008. Flash Flood Watch from 2 AM EDT Wednesday through Wednesday afternoon for RIZ001>008. MARINE...Gale Warning until noon EDT Wednesday for ANZ231>234-250-254. Gale Warning until 6 AM EDT Wednesday for ANZ230-251. Gale Warning until 4 AM EDT Wednesday for ANZ236. Gale Warning until 8 AM EDT Wednesday for ANZ235-237. Gale Warning until 10 AM EDT Wednesday for ANZ255-256. && $$ SYNOPSIS...KJC/EVT NEAR TERM...KJC/Sipprell/EVT SHORT TERM...EVT LONG TERM...KJC AVIATION...KJC/Sipprell/EVT MARINE...KJC/Sipprell/EVT
Area Forecast Discussion
National Weather Service Caribou ME
1053 PM EDT Tue Oct 24 2017 .SYNOPSIS... A warm and humid airmass being drawn in on southerly flow will bring the potential for widespread rain Wednesday and again Thursday. Locally heavy rainfall is expected at times Wednesday and Thursday as low pressure developing just off the Southeast states moves straight north across the region. && .NEAR TERM /THROUGH WEDNESDAY/... 1050 PM Update... Decided to slow down the main rain band based on the latest radar trends showing leading edge of rain moving into sw Maine attm. Some light showers were lifting up out ahead of the main line. The latest RAP and HRRR were matching up well and bring the heavy rainfall into sw areas w/in the next 2 to 3 hrs and then this area will lift to the ne moving into the Central Highlands and Downeast overnight into the early Wednesday morning. The flow coming in from the Gulf of Mexico and the Atlantic will lead to periods of heavy rainfall by early morning. Further n, the steady rain will hold off til around 7-8 AM. QPF was also adjusted collaborating w/GYX and the NERFC. Temps were staying up in the 60s. A slight adjustment to the overnight mins was done to raise the mins a degree or two. It will feel somewhat tropical out there. The other concern as stated earlier will be the potential for convection. The latest lightning display show a line of tstms from MA and CT down into the western Atlc. This activity was lifting n. Flash Flood Warnings have been issued for portions of CT and MA this evening. Some of the high res models including the HRRR and RAP show elevated convection moving into Hancock County and western Washington County. Deep moisture profile up through 700MBS by daybreak and a llvl jet of 50 kts could lead to torrential rainfall and some stronger wind gusts. Will be briefing the midnight crew on this potential. Previous Discussion... Expect the front to make only slow progress east tonight, as the upper flow around a deep upper trough to our west remains parallel to the approaching frontal boundary. Deep layered southerly flow through the atmospheric column will transport abundant moisture northward late tonight into Wednesday. This will result in the potential for periods of locally heavy rainfall late tonight and into Wednesday. The heaviest rainfall tonight through Wednesday will be across down east areas, where 2.0 inches or more of rainfall is possible through Wednesday. Although some localized ponding of water is possible on Wednesday, no significant issues are expected through the day Wednesday. It will remain continued unseasonably mild tonight and again Wednesday with highs on Wednesday reaching the mid to upper 60s. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... Most models have gone back to the idea of having additional banding of hvy rnfl working back into the FA from the SE late Wed ngt into Thu after the initial hvy rn banding crosses the Rgn on Wed. The culprit for this is the potential of a 2nd strong s/wv alf diving SSE from NW Can erly this eve bottoming out ovr the SE states south of the Srn Aplchns by Wed eve. This system then lifts NNE with a negative tilt, taking a sfc low from just off the SE U.S. coast straight N into our Rgn by Thu eve. This in effect, allows the deep PWAT stream to back into the FA late Wed ngt into Thu as s/wv ridging increases briefly ahead of the s/wv trof axis. Subsequently, we now mention hvy rn potential into Thu. Hvy rn banding should then be be pushed E of the FA Thu aftn as sig mid lvl ht falls with the immediate s/wv trof pushes the deep trop atmos rvr stream E into the Can Maritimes. Mid lvl dry slotting should keep rnfl amts lighter Mid to late aftn Thu and Thu ngt across ern ptns of the FA with more rnfl ovr Wrn areas as deformation banding with the upper low just catches this area. All and all total rnfl amts attm look to range from 2 inches ovr the NW to 4+ inches ovr Downeast areas. Given model uncertainties regarding where the best rnfl banding will set up late Wed ngt and Thu, we will hold off on issuing flood watches attm, but reserve the right to issue on later updates. For example, its interesting to note that the NAM/SREF shows heaviest rnfl further W on Thu, particularly ovr the Cntrl highland areas which is somewhat backed up by the latest 12z ECMWF dtmnstc model run which indicate a little more wrly track of the sfc low thru our area. This would also give the Rgn a greater wind potential durg the day Thu, which we do not show attm. So, to say the least, fcst confidence is not hi attm regarding the rnfl outcome with the Thu ptn of the event. Regardless of the absolute outcome, any left ovr shwrs should be exiting NE of the FA Fri morn, with partial clrg working SW to NE across the Rgn ovr the remainder of the day. Temps will cont abv normal even behind the cold front for Fri. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Fair conditions will prevail Fri ngt thru Sun with cooler, but still abv seasonal norm temps. Hi cldnss will begin to increase from W to E across the FA late Sat ngt into Sun ahead of the next sig sfc low and s/wv trof complex from the Midwest. Cldnss will thicken with the apch of this system Sun ngt with rn xpctd beginning very late Sun ngt and contg thru Mon which may be accompanied by strong Srly winds as the sfc low tracks W of our Rgn thru NW New Eng and S Cntrl QB. We bumped max PoPs up to hi likely based on the potential for sig total QPF with this event, but given the speed of the system, much less than xpctd with this current Wed/Thu event. Rn will taper to sct shwrs SW to NE across the Rgn Mon ngt, leaving ptly to mcldy skies with slightly abv normal temps. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... NEAR TERM: VFR conditions this evening will give way to MVFR overnight in lowering ceilings, with IFR expected after midnight in developing rain. The rain may be heavy at times toward day break Wednesday. Gutsy south winds can be expected tonight. Low level wind shear is also expected to be a concern late tonight into Wednesday morning KBGR/KBHB vicinity. Expect continued IFR most of the day Wednesday in rain and low ceilings. SHORT TO LONG TERM: LIFR to IFR conditions will likely be ongoing Wed ngt and Thu across all of the TAF sites as rn, hvy attms, and ngt and morn tm patchy fog conts. Conditions improve from SW to NE to MVFR Thu ngt as rn tapers to sct shwrs and then to VFR from SW to NE across the sites on Fri. VFR conditions will then cont Fri ngt into Sun. && .MARINE... NEAR TERM: A gale warning has been issued starting late tonight through Wednesday afternoon, with gusts as high as 35 kt expected. Visibility will be reduced in rain and patchy fog, mainly late tonight through Wednesday. SHORT TO LONG TERM: At least SCA winds with high wvs will be an issue Wed ngt into Fri morn, with a short pd of gale force wind gusts possible Thu aftn and/or eve. Winds and seas slowly subside Fri aftn and Fri ngt to below SCA thresholds by Sat morn....contg so thru Sun. Went with a blend of WW3 and NWPS wv guidance for fcst wv hts for this update. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...Gale Warning from 4 AM to 4 PM EDT Wednesday for ANZ050>052. && $$ Near Term...Hewitt