Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 211750 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 150 PM EDT Fri Oct 21 2016 .SYNOPSIS... Rain event persists over the North Country as a mid-level longwave trough continues to dig south and east from Canada. This trough will become negatively tilted late Friday into early Saturday, keeping frontal boundary, associated surface low pressure system and rain over the region through Saturday night/early Sunday. Colder air will filter in behind this system along with northwest flow producing upslope rain and snow showers Sunday through Tuesday. Another surface low pressure system looks to affect the Northeast Thursday. && .NEAR TERM /THROUGH SATURDAY/...
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As of 1024 AM EDT Friday...Precip continues to shift more westward with more widespread breaks across the Adirondacks this morning, before eastward momentum and additional moisture shift eastward later this afternoon. Previous discussion...Bulk of precip over Nrn NY and NW VT this morning. With mid-level trough expected to become negatively tilted this afternoon, precip shield looks to pivot NW providing break in rain to VT and portions of Champlain Valley late morning to early afternoon. At the same time, NAM and GFS indicate strong low level deformation producing moderate to heavy rain at times over Nrn NY, before weakening as we head into the evening hours. For this afternoon, the most uncertainty lies with exact positioning of surface low pressure and, therefore, wind direction as there will be a markedly sharp wind shift over the region. Models continue to indicate moisture from coastal system will feed into the NE low pressure system latter half of today into tonight. This combined with diffluent mid-level flow will result in possible periods of moderate rain over VT, especially during the overnight. Saturday morning, models find more consensus on surface low positioning along the southern New England coast, traversing northward during the day. This means deep NW flow over the North Country will bring in colder air and terrain enhanced rain showers.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 400 AM EDT Friday...Rain will gradually change to snow over the higher elevations of the Adirondacks and Green Mountains Saturday night as a closed upper low moves over the region which will provide dynamical cooling aloft with a change to snow over the higher elevations. Have leaned toward the warmer GFS MOS guidance for min temperatures Saturday night, as the NAM MOS guidance looks too cold. Also, combination of cloud cover and gusty west winds will help to keep air well mixed and will help to keep temperatures up. Thus, have lowered snowfall amounts a bit from the previous forecast given a slower changeover to snow in the higher elevations. Models showing precipitation winding down across the region Sunday morning, with most of the activity done by midday on Sunday. Models show the region will still be under cyclonic flow Sunday night from the departing surface low pressure area over Quebec Sunday night. Have kept in some slight chance pops for rain or snow showers Sunday night. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 400 AM EDT Friday...The north country remains under cyclonic flow from the departing surface low pressure area over eastern Quebec Monday and Tuesday. Thus, have kept in slight or low chance pops for rain or snow showers for Monday and Tuesday. High pressure will build slowly east from the Great Lakes Tuesday night, with mainly fair and dry weather from Tuesday night through early Thursday. On Thursday, a warm front will approach the region from the Great lakes and the Ohio valley. Have put in a chance of rain showers into the forecast for mainly Thursday afternoon. && .AVIATION /18Z Friday THROUGH Wednesday/...
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Through 18z Saturday...Varying flight conditions across the North Country with persistent low clouds/IFR/MVFR in NY and rains at KMSS with VFR/MVFR in VT. However...surface cold front moving south across Champlain Valley has brought IFR/LIFR cigs and this trend will continue elsewhere. Precipitation will be in rounds...except at KMSS where it will be peristent through period. Showers moving North into Taf sites this afternoon and exiting by evening then just some isold/sct showers til 15z Sat when more persistent showers/rain returns. Primarily IFR/LIFR tonight with clouds/drizzle and IFR Saturday with clouds and showers/rain. North winds in NY and Champlain Valley will move into rest of VT and eventually shift to NW for Saturday with 10 knots or less tonight but increasing and gusty by late Saturday. The end result...deteriorating conditions with little no changes through period. Outlook 18z Saturday through Tuesday... 18z Saturday through 00z Monday: A prolonged period of unsettled conditions is expected with widespread MVFR/IFR in periods of rain. 00z Monday through 00z Wednesday: A mix of VFR/MVFR with upslope showers in NW flow.
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&& .HYDROLOGY... As of 425 AM EDT Friday...Rainfall amounts ranging from 1-1.5 inches have already fallen across the St Lawrence Valley, northeastward across the northern Champlain Valley this morning. Rain will continue today through Sunday, being most persistent over the St Lawrence Valley and Adirondacks. An additional 1 to 3 inches is expected. Given most of the region is in moderate to severe drought...we are not anticipating any widespread hydro issues. However...some minor urban and street flooding is possible associated with the heavier rainfall rates on Friday with leaves clogging storm drains. Otherwise...some modest rises in local rivers and streams are likely this weekend...but no widespread flooding is anticipated. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...KGM/MV NEAR TERM...KGM SHORT TERM...WGH LONG TERM...WGH AVIATION...KGM/SLW HYDROLOGY...KGM is the U.S. government's official web portal to all federal, state and local government web resources and services.