Area Forecast Discussion
Issued by NWS Burlington, VT

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418 FXUS61 KBTV 241311 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 911 AM EDT Thu May 24 2018 .SYNOPSIS... High pressure will provide dry weather today, then warm and summery conditions on Friday with partial to full sunshine. A cold front approaching from the north later Friday may spark a late day shower across the far north. This front will sag into the area for the upcoming weekend with cooler temperatures and a more widespread threat of showers. && .NEAR TERM /THROUGH FRIDAY/...
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As of 911 AM EDT Thursday...Overall forecast in good shape. Other than some mid level clouds associated with stronger flow aloft...most of the area should eventually see a good deal of sunshine. Satellite trends are showing the mid level clouds eroding a bit and with upper trough moving east...that should limit additional thicker cloud cover coming down from Canada. Have tweaked sky grids to match this scenario with rest of forecast remaining untouched. Prior discussion... An outstanding, chamber of commerce day is on tap for our area as surface high pressure builds eastward and lingering upper troughing aloft lifts out to the northeast. Other than some scattered high clouds plenty of sunshine is expected as temperatures top out in the upper 60s to mid 70s. Light northwesterly winds this morning will back to south/southwesterly over time by this afternoon. Pops nil. Mainly clear skies continue tonight with winds light southerly to near calm. Flow atop the nocturnal boundary layer holds in the 10 to 20 kt range so no fog is expected given expected mixing processes. Indeed, quite a nice surge of westerly flow (30-40 kts) in the 925- 850 mb layer does push into the region overnight heralding the arrival of a much warmer airmass from the Central and Northern Plains for Friday. Low temperatures to range mainly through the 50s though some Northeast Kingdom sites may drop into the upper 40s while mildest spots in the St. Lawrence and Champlain Valleys will hold around 60F. For Friday a warm, summerlike day is still in the cards as aforementioned continental airmass advects atop the region on gusty west/southwest flow of 20 to 30 mph and partly to mostly sunny skies. Have leaned toward a blend of MOS and bias- corrected GEM/SREF/downscaled NAM output for high temperatures showing values ranging from the upper 70s to mid 80s, warmest in the Champlain Valley where the westerly flow will aid in downsloping/compressional effects. Plattsburgh, NY tends to outperform most sites under this type of regime, and as such I`ve offered a spot high of 87F for KPBG. The only fly in the ointment will be an outside shot of a stray shower across the far northern tier later in the afternoon as a backdoor cold front begins to encroach from the north/northeast and a push of higher moisture aloft sweeps eastward. With such dry air in the boundary layer (Td values to 30F), rather marginal mid level lapse rates and only lower-end instability I feel anything that does occur will be scattered at best through sunset. As such only lower-end chance pops will be offered in this area and mainly after 300 pm. Areas south of a KSLK-KBTV-K1V4 line look to remain largely dry.
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&& .SHORT TERM /FRIDAY NIGHT/... As of 350 AM EDT Thursday...A cold front will be sagging south along the international border and will bring showers to parts of northern New York and northern Vermont. Timing and how far the front sags south is still yet to be determined. The EC/GFS bring the front to the international border while the NAM sags the front all the south into central NY. The best forcing should remain near the international border and so I`ve largely kept the best chances for precip north with only a slight chance for rainfall across southern Vermont Friday night into Saturday morning. By mid day Saturday I do anticipate showers moving south and covering most of the North Country. Even with PWATs relatively high, I dont anticipate significant precip on Saturday. Currently the thinking is that we`ll see between a quarter to a third of an inch of rainfall north with around a tenth across central and southern Vermont. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 350 AM EDT Thursday...The backdoor front will continue to be a challenge on Sunday as models are still struggling with the placement of where the boundary stalls. The growing consensus as noted by the previous forecaster is that its going to be wetter over Northern New York rather than Vermont on Sunday. A marine airmass will push in from the east but the wedge doesn`t look like it will make it past the Adirondacks. So there`s going to be a pretty strong baroclinic zone across the Saint Lawrence Valley on Sunday. That combined with a surge in PWATs will lead to the potential for some fairly heavy rainfall. While flooding is not an immediate concern we`ll need to continue to monitor for any potential hazards. The upper level trough finally swings through on Monday and Monday night so our period of unsettled weather should come to an end on Tuesday. Temperatures moderate as high pressure starts to build in and we see slightly above normal temps with highs in the upper 70s and lows in the 50s. && .AVIATION /13Z THURSDAY THROUGH MONDAY/...
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Through 12Z Friday...VFR as occasional scattered to broken mid level cigs in the 100-150 AGL range trend SKC by later this afternoon. No precipitation is expected. Winds gradually back from 5-10 kts west/northwesterly to south/southwesterly in the 14-20Z time frame today. After 00Z winds generally light south/southwesterly from 5 to 10 kts, though LLWS from 35-40 kts becoming likely at many terminals from 03-06Z onward with surge of westerly flow aloft. Exception will be at KBTV where developing channeled low level southerly flow will likely keep lower levels more well mixed. Outlook... Friday: VFR. Slight chance SHRA. Friday Night: VFR. Chance SHRA, Slight chance TSRA. Saturday: Mainly VFR, with areas MVFR possible. Chance SHRA. Saturday Night: Mainly VFR, with local MVFR possible. Chance SHRA. Sunday: Mainly VFR, with local MVFR possible. Chance SHRA, Slight chance TSRA. Sunday Night: Mainly VFR, with local MVFR possible. Chance SHRA, Slight chance TSRA. Memorial Day: MVFR. Chance SHRA, Slight chance TSRA.
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&& .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...JMG NEAR TERM...Evenson/JMG SHORT TERM...Deal LONG TERM...Deal AVIATION...JMG

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