Area Forecast Discussion
Issued by NWS Burlington, VT

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504 FXUS61 KBTV 221439 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 939 AM EST Sun Jan 22 2017 .SYNOPSIS... Skies will remain cloudy over the north country for most of this week, with a prolonged period of unsettled weather expected. A low pressure area will develop along the mid Atlantic coast on Monday and will move slowly northeast to around Cape Cod by early Tuesday night. This low pressure area will bring mixed precipitation types to the north country Monday night and Tuesday, with rain, sleet, snow and freezing rain possible Monday night and Tuesday. This low pressure area will then move northeast into the Canadian maritimes by Wednesday morning. Another low pressure area over the Great Lakes will move east and bring a chance of rain and snow showers to the north country from Wednesday through Saturday. && .NEAR TERM /THROUGH MONDAY/... As of 931 AM EST Sunday...Backdoor cold front is currently located over southern VT into central NY with north/northeast surface winds across most of our forecast area. Plenty of low level moisture remains with areas of dense fog...especially cpv and parts of central/eastern vt. Expect vis to slowly increase by late this morning...as slightly drier air with cooler dewpoints advect into our region behind boundary. Also...rap soundings show 975 to 925mb winds increasing between 10 and 15 knots by this afternoon...helping to promote better mixing and decreasing the areal coverage of the fog. Still anticipating plenty of low level clouds with areas of light drizzle or spotty freezing drizzle...especially southern/central Green Mountains. The developing thermal gradient along with enhanced easterly flow this evening...will help in the development of this light precip. Temps under low level cold air advection and plenty of clouds probably remain in the 30s...with a few values near 40f. Have lowered temps by 3 to 5 degrees to account for this thinking. Rest of forecast in good shape. Previous discussion from 427 AM EST Sunday...Models continue to show plenty of low level moisture trapped beneath a low level temperature inversion. Expect this to continue today through Monday. Surface observations showing temperatures at or near the dew point across the region at this time, resulting in quite a bit of fog across the north country early this morning. Expecting this fog to burn off by late this morning. Have gone with slight chance pops for light rain or periods of drizzle today. Temperatures will climb to the upper 30s to lower 40s today. Tonight, models continue to hint at some colder air working into the region today as winds shift to the north. Could see a slight chance of some more drizzle or very light mixed precipitation tonight. Have gone with colder min temperatures today, but still a few degrees warmer than mos guidance, given expected cloud cover. On Monday, models continue to show upper ridge over the region, with a ridge of surface high pressure over the Canadian maritimes. This surface ridge will result in some cold air east of the Green Mountains. ECMWF and GFS models continue trend of slowing down the arrival of precipitation into the region from the low pressure area along the mid Atlantic coast until Monday night. Thus, have kept most of the day on Monday dry, with just cloudy skies expected. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 350 AM EST Sunday...High pressure retreating far to our north and east and mild air over the North Country will set up for complex thermal profiles as low pressure system approaches from the DelMarVa coast Monday night. Precip north of the low will spread from south to north accompanied by a tight pressure gradient and strong easterly 850mb jet. As precip spreads across the North Country, NAM and GFS BUFKIT soundings show warm layer mainly between 800-700mb resulting in widespread wintry mix into Tuesday morning. Models currently suggest sleet/snow mix being the predominant PType for most of the area. With initial surge of moisture expect most areas to see 1-4 inches of snow sleet mix through Tuesday morning. As low continues to track near the coast, reaching SE Long Island midday Tuesday PWATS increase to around three quarters of an inch Monday night and Tuesday. Associated 500mb trough becomes more negatively tilted resulting in warmer air aloft moving into eastern VT and transitioning precip to rain for the latter half of Tuesday. The surface low continues NEwd toward the coast of Maine into Tuesday night with colder air eventually moving into the North Country and ending the precip at snow as it begins to taper off Tuesday night into early Wednesday. Storm total snow/sleet accumulations through 12Z Wednesday will generally range from 2 to 5 inches, with higher amounts possible depending on how long the warm layer remains in place, how quickly the colder air moves in as the surface low moves NE. The strong 850mb jet Monday night into early Tuesday will lead to downsloping winds, easterly slope enhanced precip and westerly slope/valley shadowing. With steady precip and cloudy skies, do not think low level jet will be able to fully mix down, resulting in gusts of 20 to 30 mph in most valleys with stronger gusts for south central Vermont of 30 to 40 mph and higher at the summits of Vermont and northern NY. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 350 AM EST Sunday...Lingering snow showers expected but overall active period continues as we remain under 500mb troughiness. Quick moving low forms in the lee of the Rockies and arrives for the latter half of Wednesday with rain/snow showers expected to be light. Low chances for rain/snow showers continue into the weekend. Above normal temperatures close out the work week with a cooling trend. Saturday temperatures strive to be within 5 degrees of normal for late January. && .AVIATION /15Z Sunday THROUGH Thursday/... Through 12Z Monday...Low level moisture trapped beneath inversion layer will maintain MVFR/IFR ceilings through the next 24hrs with HIR TRRN OBSCD. The inversion doesn`t look likely to break so the low level stratus will persist through the TAF period with patchy fog across the TAF sites. Expect MVFR ceilings at all sites except IFR at SLK. Outlook 12Z Monday through Thursday... 12Z Monday - 18Z Monday...MVFR to IFR ceilings and visibility will slowly improve to MVFR for a short time Monday. 18z Monday through Thursday...Conditions deteriorate to IFR with widespread wintry mix of precipitation moving in late Monday into Tuesday, then temperatures cooling to support snow through Thursday. Strong southeast downslope winds on Monday...especially at KRUT, with gusts in excess of 25kts possible. Brief period of improving conditions possible early Wednesday, before occasional SW renews. Thursday area coverage of showers becomes more patchy through Thursday. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...WGH NEAR TERM...WGH/Taber SHORT TERM...KGM LONG TERM...KGM AVIATION...Deal

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