Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 210728 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 328 AM EDT Sun May 21 2017 .SYNOPSIS... Strong high pressure across Quebec and northern New England will result in a chilly and mostly clear night, and continued fair weather for much of the day Sunday. Some areas of frost expected this morning across the Northern Adirondack region, as well as portions of north-central and northeastern Vermont. Will see a gradual increase in clouds later Sunday as a warm front approaches from the southwest. This warm front will bring overcast skies and periods of rain during Sunday night into Monday morning. Rainfall amounts between one-third and one-half inch are generally expected across the North Country. Tuesday will see a brief return of surface high pressure. && .NEAR TERM /THROUGH MONDAY/... As of 127 AM EDT Sunday...Mostly clear skies under high pressure and light to calm winds have allowed temperatures to fall into the upper 30s to mid 40s so far. Looking for lows early Sunday morning ranging from the upr 30s to lower 40s in the St. Lawrence and Champlain Valleys, and generally low-mid 30s east of the Green Mtns and in the northern Adirondacks. Will see temperatures rise quickly on Sunday, as winds turn into the south around 10 mph. Afternoon highs will be warmer than the past couple of days, generally ranging from the upr 60s to lower 70s. Anticipate filtered sunshine as upr- mid level clouds spread ewd from the Great Lakes with increasing mid- level WAA regime moving in. That said, there is good amplification of a shortwave ridge across NY/New England 700-500mb layer during the daylight hrs...and a lack of low- level convergence. Thus, kept conditions dry Sunday, with just a slight chance of a rain shower moving into St. Lawrence/Franklin Co toward 23Z (7pm) Sunday. Will see an unsettled period of weather, with well-defined region of 850-700mb WAA and isentropic lift moving enewd across our region during Sunday night thru Monday morning. Rain showers should overspread the region from W-E during Sunday night, per consensus of mesoscale and global model suite. We have increased PoPs to near 80 percent for the pre- dawn hrs Monday based on latest trends in NWP guidance. Should see shower activity gradually move out from west to east Monday morning with decreased forcing for ascent and drier deep-layer RH values into Monday aftn. All in all, looking for 0.33-0.50" precipitation, likely highest in the nrn Adirondacks with S-SW flow regime setting up. Lows on Sunday night generally 45-52F, with Monday`s highs in the low- mid 60s from the Champlain Valley wwd, and in the low-mid 50s with lingering low overcast expected for ern VT. Winds will increase from the south during Sunday night, generally 10-15 mph. We may briefly see Lake Wind Advisory criteria on Lake Champlain from 07Z-14Z Monday, with south winds across the broad lake of 15-25 kt. && .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 /07Z SUNDAY THROUGH THURSDAY/... Through 06z Monday...VFR conditions will persist Sunday into early Sunday evening. Mostly clear skies will see increasing clouds becoming SCT-BKN 150-250 this morning and mid-day, then gradually increasing and lowering through afternoon but still VFR. Any showers will largely be confined to Northern NY after 22Z. MVFR conditions possible in showers after 02Z/Mon at KMSS and KSLK. Light to calm winds this morning will become SE 5-10kts during the daytime hours. 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. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...Frost Advisory until 7 AM EDT this morning for VTZ003-004- 006>008-010. NY...Frost Advisory until 7 AM EDT this morning for NYZ029>031-034. && $$ SYNOPSIS...Banacos NEAR TERM...Banacos/KGM SHORT TERM...Hanson LONG TERM...Hanson AVIATION...KGM is the U.S. government's official web portal to all federal, state and local government web resources and services.