Area Forecast Discussion
Issued by NWS Burlington, VT

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431 FXUS61 KBTV 221938 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 238 PM EST Sun Jan 22 2017 .SYNOPSIS... A weak backdoor front will continue to produce clouds and slightly cooler temperatures through Monday. A complex storm system will spread a wintry mix of snow...sleet...and freezing rain across the North Country on Monday Night into Tuesday. A plowable snow and sleet accumulation is expected...with still some uncertainty on exact amounts. Also...some ice accumulation is likely...especially central and eastern Vermont. && .NEAR TERM /THROUGH MONDAY/... As of 212 PM EST Sunday...Backdoor cold front is now south of our forecast area with modest 925mb to 850mb cold air advection occurring. The cold air advection will continue to strengthen overnight as 975mb to 850mb east/northeast winds develop at 15 to 25 knots. Sounding profiles show this layer cooling between -2c and -5c by 12z Monday...along with better mixing to help lift some of the low clouds and fog. Have continued to mention chc to low likely pops across the high peaks into southern VT zones this evening...associated with weak 5h vort in the flow aloft and upslope flow on easterly winds. Any qpf/ice accumulation will be very minor and mainly confined above 2000 feet. Spotty areas of freezing drizzle/drizzle are possible given the lack of deep moisture. An sps maybe issued later to highlight this potential if temps cool fast enough with lingering moisture. Temps will be tricky tonight as drier air moves into the Northeast Kingdom...some clearing may occur allowing temps to drop back into the mid 20s...elsewhere thinking mainly upper 20s to lower 30s. Little change is anticipated on Monday with highs mainly in the upper 20s to mid 30s most locations. Expect northeast winds at 10 to 20 knots across the Saint Lawrence Valley with some higher gusts possible near kmss. Models have trended slower with precip arrival time associated with our next complex system...so have chance pops central/southern cwa after 21z. Any precip will be light and under 0.05 through 00z Tuesday. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
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As of 212 PM EST Sunday...Short term period looking at a significant sleet storm with light icing in eastern Vermont and mixing with snow in northern New York. Low pressure moving off the mid Atlantic states at the start of the short term period, with ridge of high pressure over northern New England. Cool surface flow around the high will bring surface temperatures in the 20s Tuesday night. As the low moves northeast up the Atlantic coast, easterly low level flow will bring a nose of +2 to +4C air between 700 & 800 mb to the region. Forecasting predominantly sleet with this weather event as the warm layer prevents snow from reaching the ground in appreciable amounts. As surface low moves northeast impressive 60 knot 850 mb jet noses into southern Vermont at 06z and moves across eastern Vermont through 12z. Expect 40-50 mph wind gusts mainly across the ridgetops Tuesday night, with some downslope enhancement on the west side of the southern Green Mountains. Will also see terrain enhancement to precipitation with these winds, increasing precip amounts on the eastern slopes of the Green and Adirondack mountains, with some shadowing in the northern Connecticut and Champlain valleys. Looking for precipitation to spread south to north across the region, beginning 03-06z while surface low is centered off the delmarva and overspread entire area by 12z. Usually a sharp cutoff with precipitation as these move northeast somewhere over northern NY. While far western part of our area in the St. Lawrence Valley will be in the colder air, that is where there will be less QPF thus lower snowfall amounts. Any snow will be heavy and dense with low ratios. Even any areas that have primarily snow in northern New York will have an 8:1 ratio at best. Winter Weather Advisory will be issued with this afternoon package for the entire area, based more on sleet and some light icing in Vermont, becoming more sleet and snow in northern New York. Good confidence in the sleet forecast in Vermont, but my confidence decreases with western extent. Bulk of precipitation lifts north of the forecast area during the day Tuesday, however as winds shift northwesterly with the passage of the surface low will see some lingering upslope snowshowers. With that in mind will have Winter Weather Advisory go through Tuesday evening to encompass any lingering winter weather impacts.
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&& .LONG TERM /WEDNESDAY THROUGH SATURDAY/...
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As of 237 PM EST Sunday...While things will remain active, the extended period looks to be mainly just an enhanced period of snow shower activity as the region remains under the influence of 500mb through through the end of the period. Wednesday morning starts with a quick break in showers before the next system moves through Wednesday afternoon into Thursday bringing snow/rain showers, though most of the stronger activity should remain in the higher elevation`s with the valleys seeing marginal activity at best. The week closes out with minimal chances of snow showers, again mainly in the higher elevations into the weekend as temps look to remain mild with highs in the mid 30`s to 40`s and lows upper 20`s to lower 30`s until the weekend when temps trend closer to Jan normals.
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&& .AVIATION /20Z Sunday THROUGH Friday/... Through 18Z Monday...Aviation focus continues to be on low cigs and associated ifr/lifr conditions at slk/rut/btv. Thinking mvfr cigs will develop at btv by 20z...and 22z or so at rut...but prevail most of the time at slk. Soundings at kmss show low level moisture advecting back into the Saint Lawrence Valley this evening so have lowered cigs back toward ifr conditions by 00z. Otherwise...used a persistent forecast overnight with cigs ranging from vfr to ifr depending upon location. Not expecting widespread fog...due to increasing 975mb to 925mb winds of 15 to 25 knots...especially after 06z. Outlook 18Z Monday through Thursday... Expecting a wintry mix of precip to develop on Monday evening and continue into Tuesday with the potential for moderate icing and major impacts to the aviation community. A mix of snow...sleet...and freezing rain is expected...with the heaviest precip occurring between 03z-15z Tuesday. Expect mvfr to ifr cigs/vis with periods of lifr vis in the heavier bursts of snow/sleet. Also...gusty southeast/east winds are likely at Rutland during this time period...with areas of wind shear and turbulence areawide associated with 925mb to 800mb winds of 50 to 60 knots. Improving conditions with lingering rain/snow showers on Weds into Thursday. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...Winter Weather Advisory from 7 PM Monday to 10 PM EST Tuesday for VTZ001>012-016>019. NY...Winter Weather Advisory from 7 PM Monday to 10 PM EST Tuesday for NYZ026>031-034-035-087. && $$ SYNOPSIS...Taber NEAR TERM...Taber SHORT TERM...Hanson LONG TERM...MV AVIATION...Taber

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