Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 151801 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 101 PM EST Wed Nov 15 2017 .SYNOPSIS... High pressure moves east of the region today which allows for southerly winds to develop. This combined with some sunshine will allow for temperatures to climb into the upper 30s to middle 40s. Dry weather is expected today but an upper level trough of low pressure will gradually move into the region late tonight and especially on Thursday. Some rain and snow is expected late tonight before changing over to rain on Thursday. Colder air moves back in Thursday night and the rain will change back to snow...but only minor accumulations are possible over the higher terrain. Dry weather returns for Friday before another trough of low pressure moves in for the weekend and brings more rain and snow. && .NEAR TERM /THROUGH THURSDAY/... As of 935 AM EST Wednesday...Just a small area of pesky low clouds/fog around Montpelier at this time, but even that will be dissipating shortly. Going forecast is on track, and all I did for the late morning refresh was to incorporate the latest surface observations and interpolate that out for the next few hours. Previous Discussion... Satellite trends continue to show the erosion of clouds across the area early this morning...mainly over the Saint Lawrence Valley of New York and northeast Vermont. Unfortunately its still going to take awhile to get the remainder of the area cleared out and it looks like later this morning it should as southerly flow develops along with sufficient mixing. Highs today should reach the upper 30s to middle 40s with no precipitation expected. Upper trough moving across the Upper Midwest this morning will eventually move into the region late tonight and especially on Thursday. Feel precipitation will not get into the area until after midnight tonight...but clouds and southerly flow will keep temperatures up in the larger valleys to support precipitation in the form of rain with snow in the mountains. Eventually warmer air moves in on Thursday at all levels to change most of the area over to rain showers as highs reach into the upper 30s to middle 40s. Downslope wind component to the flow pattern suggests Champlain Valley will see the least amount of precipitation tonight into Thursday...generally under a tenth of an inch...and a tenth to a quarter inch over the remainder of the area. In terms of snow the mountains will see a dusting to 2 inches tonight into Thursday. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 420 AM EST Wednesday...The short term will feature developing northwesterly low-level upslope flow of 25 to 30 knots as the main forcing for lift transitions from the thermodynamics with the upper trof to orographic. Cold air advection will commence as 925mb temps around 0C fall to -12C by Fri morn so any rain showers will change to snow showers as freezing levels lower from around 3000 ft to the surface area wide by around 06z. Upslope forcing will peak out 06-09z with Froude numbers just below 1 suggesting precip/snowfall mainly at and just west of the summits with little in the valleys. Snow showers will gradually dry up by mid morning with moisture decreasing and rising heights aloft. Not expecting a whole lot of QPF Thursday night into Friday, mainly 0.10 or less to as much as 0.40 at some of the summits. Could be a inch or less of snow on the higher terrain mainly on the western slopes but increasing as you go up in elevation 4 or 5 inches at the summits above 3000 ft. Low temps by Friday morning will be in the 20s. Highs on Friday mainly in the upper 20s to lower 30s as skies clear out. Clouds will be on the increase again Friday night as a ridge of high pressure moves in but warm advection starts aloft. Lows will be in the mid teens to lower 20s. In addition, winds will become increasing brisk as they shift from the south to west northwest Thursday night post cold frontal passage at 20-30 mph. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 420 AM EST Wednesday...The long term feature of interest will be the development of a closed low in southeastern Canada over the weekend with our area under its influence with lots of clouds, rain and snow showers and cooling temperatures. Another more vigorous system will approach Saturday as a rather strong low pressure system moving up through the Great Lakes then north and west of region Saturday night into Sunday. It still looks like Sat will be the wettest of the week with warm advection front and warm air advection followed by a sharp cold/occluded front Sat night. Timing has slowed a bit from yesterday`s forecast as precip looks to reach BTV midday Saturday. Precip type could still start as a mix or change from snow to rain Sat followed by mainly rain showers by Sat eve. Saturday could be pretty windy with some gusty winds possible both ahead and behind the cold front with cold advection on Sunday. Any rain showers will be changing to snow showers behind the cold front Saturday night with Lake Ontario and upslope snow showers continuing Sunday. Monday into Tuesday now look mainly dry as the trof lifts out quickly with warm advection on the back side with high pressure over the Southeast US. Models in OK agreement through the weekend but timing differences creep into the forecast early next week for lower confidence. Temperatures will be on the cool side of average with highs mainly in the lower 30s to lower 40s with lows in 20s. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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Through 18Z Thursday...VFR area wide early this afternoon, and this will remain the case through this evening. After about 06z, ceilings will begin to lower into MVFR from west to east. Precipitation will also develop at the same time. From the Champlain Valley across northern NY, although it may start as a very brief period of light snow, especially at higher elevations (eg: SLK) expecting it to be primarily rain. Across eastern VT, precipitation will take longer to transition from snow to rain. In fact, there may be several hours between roughly 11z-14z where snow, rain and even a little sleet is expected to be mixed together. This will primarily affect the MPV TAF site. MVFR ceilings will persist area wide Thursday. Surface winds will become southerly and gust to around 20 knots in many locations from the Champlain Valley westward from this evening into Thursday morning. Outlook... Thursday Night: Mainly VFR, with areas MVFR possible. Chance SHRA, Chance SHSN. Friday: VFR. NO SIG WX. Friday Night: VFR. NO SIG WX. Saturday: Mainly VFR, with areas MVFR possible. Definite RA, Chance SN. Saturday Night: Mainly MVFR, with local IFR possible. Definite RA, Definite SN, Definite SHSN. Sunday: Mainly MVFR, with areas VFR possible. Chance SHRA, Chance SHSN. Sunday Night: Mainly MVFR, with areas VFR possible. Chance SHSN.
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&& .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Evenson NEAR TERM...Evenson/Nash SHORT TERM...Sisson LONG TERM...Sisson AVIATION...Nash is the U.S. government's official web portal to all federal, state and local government web resources and services.