National Weather Service (2024)

Area Forecast Discussion
Issued by NWS Albany, NY

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-- Discussion containing changed information from previous version are highlighted. --428FXUS61 KALY 261124AFDALYAREA FORECAST DISCUSSIONNational Weather Service Albany NY724 AM EDT Mon Aug 26 2024.SYNOPSIS...Following morning valley fog, showers and thunderstorms, someof which may be strong to severe, are expected from mid-morninginto the evening. Dry weather returns tonight through Tuesday,before additional chances for showers and thunderstorms resumeduring warm and humid conditions on Wednesday.&&.NEAR TERM /THROUGH TONIGHT/....UPDATE...As of 0635 AM EDT, areas of dense fog are ongoingalong the major river valleys as well as smaller valleys in theeastern Catskills, Berkshires, and Litchfield Hills. A SpecialWeather Statement has been issued through 9AM to alert commutersto the risk of reduced visibility on area roadways. Fog willdissipate over the next hour or two following sunrise.Otherwise, the upper-level low and upper shortwave responsiblefor active weather later today are currently located over Maineand southern Quebec per latest vapor channel imagery. Thesefeatures will continue to move south and southeastward throughthis evening and tonight, bringing showers and potentiallystrong to severe thunderstorms to the local area. The forecasttherefore remains on track; see previous discussion below....PREV DISCUSSION [0350 AM EDT]...An initial shortwave rotatingabout an upper-level low centered over southern Quebec hasexited to the south and east, with dry weather expected throughmid-morning. Beneath largely clear skies, efficient cooling willsee temperatures fall to morning lows in the 50s to near 60degrees across the region. Areas of fog are expected within theHudson, Mohawk, and Connecticut River Valleys, as well as withinother smaller valleys in the southern Adirondacks, easternCatskills, and across western New England. Any fog willdissipate in the hours following sunrise.A second, more vigorous upper-level shortwave and associatedupper-level jet streak will dive southward over the region asthe upper low tracks over eastern New England through the daytoday. Areas within the favored left-exit region of the jet willsee synoptic ascent supporting more widespread occurrence ofrain showers, however that region looks to set up generally eastof the Hudson River and more likely into New England while morescattered coverage is expected locally. The passage of theshortwave during peak afternoon heating will yield modestlysteep mid-level lapse rates of 6.5-7.5 C/km, which could inturn support deep buoyant motions given instability of 1000-1500J/kg. Deep-layer shear of 30-35 kt may support some stormsbecoming strong to severe as they track to the south andsoutheast, with the primary hazards remaining damaging windsand large hail. Nearly the entire region remains within aMarginal Risk for severe weather as assessed by the StormPrediction Center.Conditions will rapidly improve through the evening as the uppershortwave exits south and east and heights rise aloft as upperridging builds from the west. Clearing skies will again allowfor areas of valley fog to develop, especially in areas whichsaw accumulating rainfall earlier in the day. Temperatures willremain near seasonal norms today and tonight, reachingafternoon highs in the upper 60s to mid 70s in high terrain andupper 70s to low 80s at lower elevations, and falling toovernight lows in the 50s to near 60 degrees across the region.&&.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...Brief upper ridging passing overhead on Tuesday will see heightsrise aloft and general subsidence develop over the region,yielding dry and tranquil weather with mostly sunny skiesthrough the day. 850-hPa temperatures of 12-15C will allowsurface temperatures to rise above normal, reaching afternoonhighs in the mid to upper 70s in high terrain and low to mid 80sat lower elevations.Another potent upper-level shortwave and associated surfacefrontal low will approach the region Tuesday night, resultingin increasing clouds overnight. Temperatures will remain verymild, only dropping to lows in the 60s for most of the regionand upper 50s in areas above 2000-2500 ft in elevation. Rainshowers will spread from northwest to southeast throughWednesday morning, with thunderstorms developing and rainreaching its maximum coverage during peak diurnal heating inthe afternoon. There remains substantial uncertainty in thetiming and speed of the frontal passage, and some strong tosevere storms cannot be ruled out at this lead time. Givensupportive shear expected near the frontal boundary andsufficient instability to its south, the highest chances for anysevere weather will be south of I-90 and especially closer tothe I-84 corridor, generally corresponding to the Marginal andSlight Risk areas assessed by the Storm Prediction Center.Temperatures will peak earlier generally to the north of I-90where the frontal passage should occur earlier, yielding highsin the upper 60s to mid 70s. To the south, additional daytimeheating ahead of the cold front and 850-hPa temperatures risingto 16-18C will see surface temperatures rise well above normal,reaching the mid 80s to low 90s. Dewpoints in the mid 60s, whilenot extreme, may result in a few hours of heat indices above 95degrees in portions of the Mid-Hudson Valley and northwesternConnecticut. Heat Advisories will be needed in those areas ifthis forecast persists. Cooler air arrives behind the coldfront, allowing overnight temperatures to drop to lows in theupper 40s to mid 50s in high terrain and mid 50s to low 60s atlower elevations on Wednesday night.&&.LONG TERM /THURSDAY THROUGH SUNDAY/...Upper energy exits through the day Thursday with just anisolated shower or thunderstorm in the eastern Catskills andmid Hudson Valley. Otherwise, decreasing clouds Thursday withhighs in the lower to mid 70s with around 70 higher terrain.Flat upper ridging builds into the region from the west Fridayand large scale upper troughing trails behind the flat upperridging. The flat upper ridging will exit east and the uppertroughing will gradually build east toward our region throughthe weekend. As the upper troughing approaches, increasing warmadvection and moisture will support increasing chances forshowers and scattered thunderstorms.Low level wind shift boundary tracks through in the Saturdayafternoon or evening time frame with a potentially drying trendthrough Sunday but only weak cold advection at best. So, theshowers and scattered thunderstorms extend through Saturday andend Saturday night. Then, the upper trough axis and cold fronttracks through later Sunday into Monday, with mainly dry weatherSunday until the cold front tracks through the region withanother period of isolated showers and storms Sunday night. Ofcourse, this far out in time, timing and coverage of showers andstorms and the passage of the cold front may be adjusted as weget closer and more details are known.Highs Friday and Saturday with the showers and storms, in themid to upper 70s and around 70 higher terrain. Highs Sunday,with the potential break in the rain and clouds, in the mid 70sto around 80 with some lower 80s mid Hudson Valley and lower 70shigher terrain. Then potentially cooler by Monday.&&.AVIATION /12Z MONDAY THROUGH FRIDAY/...
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Some fog through about 13Z at KGFL, KPSF and KGFL, with intervals ofIFR visibilities and possible ceilings at 200 feet. Once fog liftsby 13Z, VFR conditions expected.Scattered showers and isolated thunderstorms are expected thisafternoon around KGFL, KALB and KPSF. So, including PROB30 thisafternoon for thunderstorms with MVFR conditions duringthunderstorms, while VCSH at KPOU where there is a lower chance.Chances for showers and thunderstorms should end by 22Z-23Z. Then,VFR conditions continue through this evening at all TAF sites. Byaround or after midnight, light winds and a mostly clear sky shouldpromote some radiation fog with MVFR/IFR visibilities between about06Z-12Z.Winds will be near calm through mid morning, then north tonorthwest at less than 10 Kt late this morning through thisafternoon. Winds become light and variable this evening and continuethrough the rest of the night.Outlook...Tuesday: No Operational Impact. NO SIG WX.Tuesday Night: Low Operational Impact. Slight Chance of SHRA...TSRA.Wednesday: High Operational Impact. Likely SHRA...TSRA.Wednesday Night: Moderate Operational Impact. Chance of SHRA...TSRA.Thursday: Low Operational Impact. NO SIG WX.Thursday Night: No Operational Impact. NO SIG WX.Friday: No Operational Impact. NO SIG WX.Friday Night: Moderate Operational Impact. Chance of SHRA...TSRA.
-- End Changed Discussion --&&.ALY WATCHES/WARNINGS/ADVISORIES...CT...None.NY...None.MA...None.VT...None.&&$$SYNOPSIS...PicardNEAR TERM...PicardSHORT TERM...PicardLONG TERM...NASAVIATION...NAS