Area Forecast Discussion
Issued by NWS Burlington, VT

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221 FXUS61 KBTV 241132 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 632 AM EST Fri Nov 24 2017 .SYNOPSIS... High pressure over the mid-Atlantic states this morning will briefly build northward into the Northeast today allowing skies to clear and temperatures to rise into the low to mid 40s on increasing southerly flow. A low pressure system passing to our north on Saturday will bring a trailing cold front across the North Country accompanied by scattered rain and snow showers through Saturday night. Cloudy and dry conditions are expected for Sunday. && .NEAR TERM /THROUGH SATURDAY/... As of 257 AM EST Friday...A quiet end to the work week is expected today as high pressure over the mid-Atlantic states builds northward into the Northeast eventually scouring out low clouds across the region this morning to partly/mostly sunny skies this afternoon. Outside of a few scattered snow showers and/or flurries across northern areas early this morning, it`ll be a dry, mild and increasingly windy day as a strengthening pressure gradient between the high and an approaching low to our west will develop southerly winds of 10-20 mph, with a few gusts to 30 mph in vicinity of Lake Champlain. Highs will touch 40 across the Adirondacks and Northeast Kingdom, while warming into the mid-40s elsewhere. Dry conditions continue through tonight as well as the North Country will be entrenched in a warm sector with a warm front to our north and a cold front to our west associated with low pressure passing well north of the border. South winds will remain brisk as the pressure gradient remains tight between the departing high and approaching low. This will keep overnight mins on the mild side in the mid/upper 30s across the deeper valleys, while the mid-slopes of the Adirondacks and eastern Vermont should drop off into the upper 20s to around 30. Aforementioned cold front approaches Saturday but really doesn`t swing through the forecast area until after sunset with a little pre- frontal trough and associated deep layer moisture producing some scattered showers through the day, mainly in the form of rain but a few snow showers are possible across the higher elevations during the morning hours. Overall QPF is very light, generally less than a tenth of an inch, so expect little to no snow accumulation and minor impacts to outdoor activities. Temps remain mild through the day, warming a couple degrees from Friday`s maxes in the low/mid 40s. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 326 AM EST Friday...00Z guidance all still indicating a shortwave moving across the region Saturday night, but have backed off a bit on its intensity. Still looking at a period where scattered snow showers will increase in coverage, especially across the higher terrain of northern NY and northern Vermont. The primary tweak to the going forecast is to decrease the PoPs a few hours quicker on Sunday. Could still have a few high terrain snow showers Sunday morning, but think by noon those will be all gone. Still only expect minor accumulations, perhaps 1-2" at the higher elevations, and a dusting at low elevations. Once the snow showers across the north diminish, it will be a dry but rather cloudy afternoon with northwest winds occasionally gusting to 20 mph. Highs will be slightly below normal, generally low-mid 30s. Sunday night we should see another round of scattered snow showers or periods of light snow across the region as a weak Alberta Clipper and it`s associated upper level trough zips by just to our north. This system will also not have a lot of moisture to work with, basically what it can tap from the Great Lakes. So it looks like another situation where we have 1-2" at higher elevations, with a dusting at lower elevations. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 326 AM EST Friday...00Z guidance still pointing at a rather progressive synoptic pattern next week. We`ll start off with a brief shot of cooler northwest flow for Monday, but quickly transition to a westerly flow pattern that turns more southwest by mid/late week. So it looks like from Tuesday onward, temperatures will be above normal. 00Z GFS and ECMWF are in decent agreement with the overall pattern. The main "weather" features will be a weak front late Tuesday/early Wednesday, and then the next low pressure approaching late Thursday. A few notes on each day follow... Monday: Looks to be the coldest day of the week. Perhaps a few morning mountain snow showers, but some prospects for some sun by afternoon. 925mb temperatures drop to -8 to -10C, so expecting highs only in the upper 20s to lower 30s, with mid 30s in southern valley locations. Tuesday: Looks dry. Flow turns southwest ahead of an approaching front, with warmer air advecting in. 925mb temperatures should warm to about +5C by late in the day. This will support temperatures well into the 40s for most areas - perhaps a few places nearing 50F. Reasonably tight pressure gradient will support 40-50kts of wind around 850mb. So it will likely be a bit breezy (20-30 mph gusts) especially in the St Lawrence and Champlain Valleys. Did try to enhance the winds some in the gridded forecast as base model data that far in the future typically underestimates wind speeds. Weakening front comes through Tuesday night. Temperatures should be warm enough aloft and in the boundary layer that we are looking at light rain as the dominant precipitation type. Wednesday: 00z guidance is a little faster with previous model runs and suggests that it will be mostly dry for the day. However, given uncertainty in timing, maintained some PoPs in the event the front comes through during the morning. Temperature profiles would suggest rain showers ending as a little bit of higher elevation snow showers. Not a very robust front, so we aren`t talking about a lot of rain or snow. Also not a lot of cold air behind the front, so temperatures will still be above normal with highs in the lower 40s. Thursday: Uncertainty in the forecast increases as GFS and ECMWF have more significant timing differences. Both indicate high pressure moves off the coast with flow turning southwest ahead of the next low pressure system. However GFS is faster with bringing in moisture and precipitation by later in the day. ECMWF is about 12 hours slower. Do have some 15-25% PoPs in for Thursday and at the very least increasing clouds. In any event, highs will again be slightly above normal. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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Through 12Z Saturday...Widespread OVC VFR ceilings with a few areas of MVFR will lift from south to north and scatter out to FEW200/SKC this afternoon and remain VFR through the rest of the period. Winds will be mainly south/southeast at 6-10kts from KPBG eastward with some gusts this afternoon and evening up to 20kts at KBTV. Westward at KSLK and KMSS southwesterlies will prevail at 08-12kts with gusts to 20kts and likely some LLWS and turbulence after 23Z as a low level jet streaks in. Approaches over Lake Champlain will also be quite bumpy this afternoon and overnight with low level winds in excess of 30kts likely over the open waters. Outlook... Saturday: Mainly VFR, with local MVFR possible. Scattered SHRA. Saturday Night: Mainly MVFR, with areas VFR possible. Chance SHRA, Slight chance SHSN. Sunday: Mainly VFR, with local MVFR possible. Slight chance SHSN. Sunday Night: Mainly MVFR, with local VFR possible. Chance SHSN. Monday: Mainly MVFR, with areas VFR possible. Slight chance SHSN. Monday Night: Mainly VFR, with local MVFR possible. NO SIG WX. Tuesday: VFR. Slight chance SHRA.
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&& .MARINE... As of 257 AM EST Friday...A LAKE WIND ADVISORY is in effect for increasingly strong winds over the open waters of Lake Champlain this afternoon through Saturday morning. South winds of 10 to 20 knots over the lake this morning will increase markedly this afternoon and especially overnight, where winds will likely top 30 knots with some gusts to 40 knots possible. This will produce very hazardous conditions with wave heights building to peak heights of 5 to 7 feet for a period tonight. Behind a cold front passage, winds will shift to the west and decrease Saturday afternoon. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Lahiff NEAR TERM...Lahiff SHORT TERM...Nash LONG TERM...Nash AVIATION...Lahiff MARINE...Lahiff is the U.S. government's official web portal to all federal, state and local government web resources and services.