Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 242339 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 739 PM EDT Sat Sep 24 2016 .SYNOPSIS... High pressure building southward from James Bay will continue to bring dry weather to the area through Monday, along with unseasonably cool temperatures. Tonight will be the coldest night of the young fall season thus far, cold enough for frost to develop over a good portion of the area. Sunday will feature full sunshine and lighter winds, although temperatures will be slightly cooler than Saturday. && .NEAR TERM /THROUGH SUNDAY/...
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As of 735 PM EDT Saturday...Skies are trending clear with onset of diurnal cooling cycle and dissipation of daytime fair wx cumulus, setting the stage for the coldest night of the young fall season. Clearing skies, abating winds and H85 temps falling to 0C (s-central VT) to -3C (nern VT) will combine to produce low temperatures tonight into early Sunday morning ranging through the 30s to locally lower 40s along the immediate Lake Champlain shoreline and Grand Isle County. For most areas outside of the Champlain Valley, this setup will support the idea of patchy to areas of frost forming, enough to continue the previously issued frost advisory, but also hoist a frost advisory for the St. Lawrence Valley and all of southern Vermont. Additionally, temperatures will drop to right around freezing for portions of Essex County of Vermont, so I`ve gone ahead and upgraded to a freeze warning there. Those with agricultural interests in the warned area are advised to harvest or protect tender vegetation left outdoors. Fog will also be a good bet in the climo favored river valleys tonight as well, which could affect the potential for frost in some areas. Really tricky to forecast whether the fog or colder temperatures will win out, or if both will occur. I`ve seen all three scenarios happen, so for now will just go with both! For Sunday, the aforementioned area high pressure continues to build right over the North Country. This should result in lighter winds than today, along with sunnier skies after any morning fog burns off. Unfortunately, 925-850mb temps cool slightly, only supporting highs in the mid 50s to low 60s, a couple degrees cooler than today. With more sunshine though, it shouldn`t feel that bad so get out and enjoy those harvest festivals!
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&& .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... As of 324 PM EDT Saturday...Ridge of high pressure at the surface with building ridge aloft will lead to clear skies, light to calm winds and good radiational cooling conditions. 925mb temps of 3-5C will result in morning low temps at the surface in the mid/upper 20s to low 30s in the high terrain and low to upper 30s in the broad valleys. Tricky part of where lowest temps will occur will be somewhat dependent on fog formation. Expect some areas to see freezing fog, mainly in portions of the Adirondacks and Northeast Kingdom. Otherwise, widespread frost/freeze possible. Large closed mid-level low over the Great Lakes region will approach, with clouds moving into the North Country ahead of it during the day Monday. At the same time, 500mb ridge will crest over the forecast area, keeping conditions dry before the large mid-level low arrives. Winds will shift out of the south with max temps in the 60s. Precip arrives from west to east Monday night with PWATs increasing to over 1 inch and SSW low level jet of 30-40 kts at 850mb. This will likely result in enhancement of showery activity on SW facing slopes and some shadowing on leeward side. Also gusty winds esp in the high terrain will result. Temperatures will be noticeably warmer Monday night with clouds and winds...expect lows in the 40s to low 50s. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 324 PM EDT Saturday...On Tuesday the 500mb closed low traverses across the central to southern Great Lakes as it digs southward with a dry slot moving into the North Country ahead of this low, behind the cold front which brings showers Monday night into Tuesday. This will result in bulk of rain showers exiting east during Tuesday afternoon. Low level jet will also exit east and PWATs look to decrease late in the day. As the mid level low digs southward into the Ohio River Valley Tuesday night into Wednesday, 500mb vort will break off into northern stream and southern stream. High pressure at the surface and bulk of energy either far to the south or north, expect mostly dry conditions Wednesday through Friday night, possibly into Saturday. ECMWF and GFS differ on the evolution and track of the southern stream energy. ECMWF has it become a closed low and meanders over the southern Appalachians late in the period. && .AVIATION /00Z Sunday THROUGH Thursday/... Through 00Z Monday...Expect overall VFR conditions continuing through the next 24 hours. Exceptions will be the potential for VLIFR fog at KMPV/KSLK from 05-14z, where I`m more confident at KMPV whereas at KSLK sub-freezing temperatures may mitigate fog development. To an even lesser degree, there is potential for KRUT to see a period of fog during that same timeframe but with confidence being low have opted to just have a FEW001 deck for now. Winds will remain light overnight, and pick up from the northwest around 10-18 knots after 14z Sunday. Outlook 00z Monday through Thursday... 00z Mon - 00z Tue: Mainly VFR. Overnight IFR with patchy fog possible. 00z Tue - 00z Wed: VFR trending to a mix of VFR/MVFR in scattered showers. 00z Wed - 00z Fri: Mainly VFR with isolated MVFR cigs. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...Freeze Warning from 2 AM to 8 AM EDT Sunday for VTZ004. Frost Advisory from 2 AM to 8 AM EDT Sunday for VTZ003-006>008- 010>012-016>019. NY...Frost Advisory from 2 AM to 8 AM EDT Sunday for NYZ026-027- 029>031-034-087. && $$ SYNOPSIS...Lahiff NEAR TERM...Banacos/Lahiff SHORT TERM...KGM LONG TERM...KGM AVIATION...Lahiff/MV

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