Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 220243 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 1043 PM EDT SAT MAY 21 2016 .SYNOPSIS... Low pressure will settle into the mid-Atlantic states over the next 24 hours, then weaken as it drifts slowly northeast along the New England coast by next Tuesday. As a result, scattered showers will be possible on Sunday, then again by next Tuesday with Monday being primarily dry. Temperatures will remain seasonably mild through Monday, then trend warmer by the middle and later portions of next week. && .NEAR TERM /UNTIL 6 PM SUNDAY EVENING/...
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As of 1043 PM EDT Saturday...Current forecast in good shape, so no changes have been made. Previous discussion from 300 PM EDT Saturday...A generally quiet night remains on tap for the area as surface ridging is bridged aloft by lingering upper troughing at mid and upper levels. Models remain consistent in digging the upper energy southward and over time as it becomes a closed center in the vicinity of the northern mid- Atlantic states by Sunday morning. Broad southwesterly flow aloft will allow thickening mid and upper level clouds to filter into our area overnight with only a minimal/outside shot at a stray shower or sprinkle across our southern counties. Believe the output from most recent runs of the HRRR and assorted CAMs are overdone in their depiction of blossoming showers in this area this evening due to erroneously high surface dewpoints and resultant instability. Based off current radar trends, the thickening upper clouds and a quite dry boundary layer have downplayed this idea accordingly, opting instead for just a very low end threat in the 15-20 percent range this evening into tonight. Low temperatures should run a bit milder than last night given the clouds, generally mid 40s to lower 50s. Winds light. By Sunday the upper closed energy will pivot across the mid-Atlantic region as background flow trends more north to northeasterly. Low to mid-level convergence along the old trough line combined with slightly higher moisture should spell continued mostly cloudy skies along with scattered to numerous showers, especially across the central and eastern portions of Vermont and the Adirondacks where added input from terrain-induced flows will occur. Drier conditions more likely in the northern Champlain Valley west into the St. Lawrence River Valley where higher probabilities of partial sunshine will exist. Also continued an outside shot of a few non-severe thunderstorms per most recent SREF calibrated t-progs of approximately 20 percent and some low-end mixed-layer CAPE to perhaps 500 j/kg. With the higher abundance of clouds high temperatures will be slightly cooler than today, mainly mid 60s to lower 70s, perhaps mid-70s out across the St. Lawrence Valley.
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&& .SHORT TERM /6 PM SUNDAY EVENING THROUGH MONDAY NIGHT/... As of 340 PM EDT Saturday...Any showers or thunderstorms will be ending early sunday night as mid-level trof axis gradually shifts to the southeast leaving a drying NE flow in place. Little change in air mass, and with surface dewpoints expected in the upper 40s/lower 50s, areas seeing rainfall during Sunday will be prone to some fog formation Sunday night. low temperatures will generally in the lower 40s to lower 50s. A closed upper low forms east of the Delmarva peninsula during the day Monday, with an elongated trough axis still in place along the New England coast. precipitation from this system should stay to the south and east of the forecast area, as GFS depicts 1000- 500mb and some precipitable water drying across northern NY and northern VT with continued N-NE flow. with 850 temps around 10c expecting High temperatures on Monday generally 74-78F degrees with North winds 5-10 mph. Models in good agreement that the closed low moves slowly northward monday night east of NJ by tuesday morning, so the deeper moisture begins to return with precipitable water values increasing to near an inch in southern vermont. this is enough to bring a low chance of showers back to southern vermont. again little change in overnight lows with readings in the mid 40s to mid 50s. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 340 PM EDT Saturday...reasonable model agreement in the long term with a gradual pattern shift toward a more summery warm and more humid airmass with chances of showers and thunderstorms. Of course the daily details vary and we may have to contend with a backdoor front next weekend, but it`s just too soon to tell for sure. Models are generally consistent in tracking the closed upper low from east of NJ Tue morning through eastern MA by 06z Wednesday before bumping east of New England Brunswick by Wednesday afternoon followed by a general WSW flow aloft with rising heights by saturday. The North Country will reside on western periphery of the cyclonic flow regime on Tuesday, with axis of instability (Best BL CAPE values of 500-1000 J/kg) across the region from n-central VT SW into portions of the northern Adirondacks during the peak heating hrs. Expectation is for scattered showers and possible thunderstorms to develop with slow westward or southwestward storm motions. PW values continue around 1" may result in some locally heavy downpours, and with WBZ heights around 9kft, can`t rule out some small hail with any stronger cores. PoPs on Tuesday generally 30-50%, highest southeast where east of the green mountains it will be cloudier and cooler with highs in upper 60s to near 70 while it will be more unstable further north and west where temps get into the 70s resulting in scattered showers and thunder. On Wednesday flow becomes more NW behind departing upper low but enough convergence and terrain-induced lift enough for a low chance of showers or isolated thunderstorm, but should see high temps in the upper 70s to around 80 as 850 temps rise to 10 to 12C. Thursday into Saturday low-level flow becomes SW and a more moist and unstable air mass advects into the region for with showers and possible thunderstorms possible. GFS/ECMWF differ on the near surface details with the location of a warm/backdoor front but PoPs Generally 30-40% each day. Should see higher humidity values (dewpoints in the upper 50s to lower 60s possible) Thursday and Friday with high temperatures in the upper 70s to lower 80s but could be slightly warmer or cooler depending upon the status of the front. && .AVIATION /03Z Sunday THROUGH Thursday/... Through 00Z Monday...VFR through the forecast period with broken mid to high cloud cover in place and remaining. Winds generally light south to southwesterly with slight variation per terrain/lake breeze influences, trending light overnight. After 12Z Sunday broken to overcast mid level VFR ceilings in the 050-090 AGL range continue as winds trend light north to northeasterly 5-10 kts. Increasing confidence that scattered showers/isolated thunderstorms will develop across eastern/southern VT and portions of the Adirondacks after 15Z and drift southwesterly over time. Have gone ahead and mentioned a prevailing group at MPV and RUT where best chance to see showers...vcsh mentioned at BTV, PBG, and SLK. Outlook 00Z Monday through Thursday... 00z Mon - 06z Mon: Mainly VFR with periods of brief MVFR visibility possible in rain showers/isolated thunder at all terminals except MSS. 06z Mon - 12z Tue: VFR/high pressure 12z Tue through 00z Thu: Mainly VFR with chance of showers and brief MVFR visibility with coastal low pressure system passing by to the east. Highest confidence of showers at eastern terminals. 00z Thursday onward: VFR/high pressure. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...JMG NEAR TERM...JMG/WGH SHORT TERM...Sisson LONG TERM...Sisson AVIATION...JMG/Neiles

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