Area Forecast Discussion
Issued by NWS Burlington, VT

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580 FXUS61 KBTV 261841 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 241 PM EDT Mon Sep 26 2016 .SYNOPSIS... Nearly stationary upper level low pressure just north of Lake Superior this afternoon will push and occluded front through the North Country tonight, accompanied by some light rain showers. Tuesday and Wednesday will be mainly dry behind the front with temperatures warming to above seasonal normals. Greater chances for rain return Thursday and into the weekend as the upper low moves into the Ohio River Valley and Northeast. && .NEAR TERM /THROUGH TUESDAY/... As of 224 PM EDT Monday...It`s a fantastic early fall day across the North Country as we remain under the influence of high pressure anchored just off the New England coast. Temperatures have rebounded nicely from this mornings chilly start, and are on track to top out in the low 60s east to near 70 west under partial sunshine from an increasing high deck. Moving on into this evening and the overnight hours, mid/high clouds will continue to increase as an occluded front associated with a deep vertically stacked and nearly stationary upper low just north of Lake Superior approaches. Associated rain showers are already moving into far western New York and should shift into the BTV CWA shortly after 00z, and east of the Connecticut River by sunrise Tuesday. Currently showers are very scattered in nature along the boundary, and expect much of the same as it moves through the North Country. Some local enhancement is expected on southern and southwestern facing slopes due to a developing 40kt jet at 925mb, while this feature will in turn limit QPF in the St. Lawrence and Champlain Valleys. Overall not a big QPF event though, with only a tenth to perhaps 2 tenths of rain expected. With increasing winds and southerly flow, lows tonight will be much milder than the past 2 nights, and generally range from the mid/upper 40s across eastern Vermont and the Northern Adirondacks, to low/mid 50s in the deeper Champlain and St. Lawrence Valleys. Behind the front, a strong mid-level dry slot builds over the area for Tuesday so after showers exit during the morning hours across eastern Vermont, we should be looking at a generally dry day. South/southwesterly flow persists behind the boundary, keeping temperatures above seasonal normals and with 925mb temps averaging around +13-15C we should see highs in the mid 60s to low 70s under partly sunny skies. There remains though the outside chance for some lake effect rain showers downwind from Lakes Ontario/Erie tomorrow afternoon, but confidence is fairly low at this time and latest hi-res guidance isn`t all that bullish either so I`ve painted in just some low chance PoP`s during the afternoon up the St. Lawrence River. && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 406 AM EDT Monday...The current suite of medium range guidance leaves a bit to be desired for Tuesday based on timing. All models show a cold front with decent moisture passing through the region and a dry slot developing over the North Country however there is about 12 hours difference in the timing between the GFS and the NAM/GEM/EC with the GFS as the more progressive system. Given the GFS as a slight outlier I trended towards a blend of the NAM/EC with about 50% previous forecast. With moderate southwesterly winds expect the lee sides of the mountains to be shadowed especially in Champlain valley. Given the timing differences I offered chance to slight chance pops for Tuesday morning trending clear towards the afternoon with the lone exception of the Northeast Kingdom where showers may hold on into the evening hours. Then as the dry slot moves in over the North Country the parent upper level low gets sheared off and is broken up with the front sagging offshore into the Atlantic. The closed circulation of the upper level low then pivots down from central Ontario into the Ohio Valley region by mid week. With that low still off to the west and little moisture around expect the mid week from Tues night through Thursday morning to be relatively dry. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 406 AM EDT Monday...An upper level parent low over the Ohio Valley will track towards the North Country by the end of the week and bring surface frontal system with it. Based on current guidance there is quite a bit of spread in the location of that surface low however both the GFS and EC are trending towards a wetter forecast by Thursday afternoon/evening. At the moment it`s more of a wait and see pattern based on how the evolution of the upper level low over the Ohio Valley begins to interact with the surface low that ends up developing. Expect temps to moderate back towards slightly above normal through the week with upper 60s to low 70s during the daytime and lows overnight in the mid to upper 40s. && .AVIATION /19Z Monday THROUGH Saturday/... Through 18Z Tuesday...VFR conditions this afternoon and evening will trend towards MVFR in rain showers as an occluded front traverses the area after 00z. Mid/high cirrus deck will gradually lower through time, remaining VFR through about midnight across northern New York, and 2-4AM across Vermont before lowering to MVFR. Vsby remains largely VFR in the showers, with periods of lowering to MVFR. After 12z, front exits the region to our east with conditions gradually improving back to VFR by 18z. Winds generally not an issue, less than 10kts, but a few gusts towards 18-22kts from the south will persist at KBTV and KPBG this afternoon and evening. Outlook 18z Tuesday through Saturday... 18z Tue - 00z Thu: Generally VFR, though an MVFR marine layer may intrude from the east late Tuesday night through mid-day Wednesday. 00z Thu - 00z Sun: Mainly VFR with MVFR in rain showers possible, especially on Saturday. && .MARINE...
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Funneling south winds ahead of approaching front will bring 15 to 25 knots and possibly higher gusts to Lake Champlain tonight...already 20 knots at times this afternoon. After front passes Tuesday morning, winds should begin to diminish.
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&& .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Lahiff NEAR TERM...Lahiff SHORT TERM...Deal LONG TERM...Deal AVIATION...Lahiff MARINE...slw

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