Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 211055 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 655 AM EDT Sun May 21 2017 .SYNOPSIS... Ridge of high pressure aloft will crest over the North Country today providing dry conditions for most of the day. Clouds will increase throughout the day ahead of a warm front approaching from the southwest. This warm front will bring overcast skies and periods of rain tonight into Monday morning. Rainfall amounts between one-quarter and one-half inch are generally expected across the North Country. Dry conditions return on Tuesday with a brief period of surface high pressure, before a deepening longwave trough aloft approaches for the mid-week. && .NEAR TERM /THROUGH MONDAY/...
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As of 655 AM EDT Sunday...Warm air advection evident in hourly temperature trends across the St Lawrence Valley and western Adirondacks. This WAA will spread east, quickly warming temperatures across the North Country. Mid and high level clouds continue to spread across the region in prevalent southerly flow ahead of approaching low pressure and associated front. 500mb ridge will crest over the North Country this afternoon, keeping the region dry outside of a couple sprinkles. With 925mb temperatures reaching the 11C-13C range and persistent southerly flow, expect max temperatures to reach the 60s to low 70s today. Also channeling up the St Lawrence and Champlain valleys will likely lead to some mildly gusty wind. Tonight into early Monday will have bulk of precip as we expect rain showers to move eastward in the St Lawrence Valley around 00Z, reaching the Champlain Valley before 06Z. Mild min temperatures Monday morning with overcast skies and southerly flow, ranging from 40s to mid 50s. As surface ridge slides into the Atlantic and low pressure over Ontario approaches, pressure gradient will increase with increasing winds and gusts, especially early Monday. Showers continue Monday as vorticity grazes NW portions of the forecast area. Clouds persist with Monday high temperatures ranging from the 50s to mid 60s. Storm total QPF continue to be between 0.25-0.5 inch.
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&& .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... As of 325 AM EDT Sunday...Broad southwesterly upper level flow across the region during the short term period with high pressure giving way to a coastal low on Wednesday. Monday night lingering chance pops in Vermont will trend downward to nil by midnight as weak front departs the region. Little airmass change behind the boundary, and low level winds return to southerly by mid day Tuesday. Tuesday weak surface high pressure will keep precipitation at bay, however periodic vort maxes eject out of base of 500 mb trough to west will traverse the area keeping scattered to broken sky cover. One shortwave trough moving up in the southwest flow will spin up a surface low Wednesday morning along the Delmarva coast and move it northeast to southern New England coast Wednesday evening. Chance pops across the region...ECMWF spreads precip shield further west than GFS, and expect to further refine this part of the forecast in coming days. Southwesterly flow will also keep seasonable temperature in place with highs in the 70s and lows in the 40s to lower 50s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... As of 325 AM EDT Sunday...Long term period becomes more active as the upper trough to the west shifts east, spreading precipitation into the area. Model differences seen last night are starting to coalesce into a common solution. Mean upper level trough over eastern US will move east in two phases. First is southern low moving out of Gulf states will swing northeast Thursday, spreading more showers up the east coast. The northern portion of the trough will hang back over the Great Lakes, then move east and merge with the southern low remnants over the gulf of Maine on Friday. The result is a prolonged period of likely pops for rain Thursday and Friday. With all the pieces in motion there should be some breaks at some point in there, but difficult to tease out those details this far out. For Saturday the low finally kicks out with building high pressure. Some lingering showers especially in Vermont in the mountains, but trend will be to salvage at least part of the Memorial Day weekend. Plenty of cloud cover and rain cooled air to keep temperatures a few degrees below normal but still seasonable. Overall flow through this period is southwesterly as well, and no real temperature changes. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/...
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Through 12z Monday...VFR conditions will persist today into early this evening. SCT to BKN clouds at 150-250 continues to spread across the region. Expect increasing and lowering cigs through afternoon but remaining VFR at all sites through 02Z/Mon. Any showers will largely be confined to Northern NY after 22Z. MVFR conditions possible in showers after 02Z/Mon at KMSS and KSLK. Expect rain showers to spread east into the Champlain Valley and the rest of Vermont between 04Z-07Z/Mon. Rain showers continue into Monday morning. South to southeast winds at 5-10kts expected today, with some gusts possible overnight. Outlook... Monday: VFR/MVFR. Breezy. Chance SHRA. Monday Night: VFR. Slight Chance SHRA. Tuesday: VFR. NO SIG WX. Tuesday Night: VFR. Slight Chance SHRA. Wednesday: VFR. Chance SHRA. Wednesday Night: VFR. Chance SHRA. Thursday: VFR. Chance SHRA.
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&& .BTV WATCHES/WARNINGS/ADVISORIES...
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VT...None. NY...None.
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&& $$ SYNOPSIS...KGM NEAR TERM...KGM SHORT TERM...Hanson LONG TERM...Hanson AVIATION...KGM

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