Area Forecast Discussion
Issued by NWS Burlington, VT

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499 FXUS61 KBTV 191758 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 1258 PM EST Thu Jan 19 2017 .SYNOPSIS... As surface high pressure and an a ridge aloft build into the region today, areas of morning drizzle should dissipate through the day, but a developing low level inversion will keep skies cloudy right through Friday and into the weekend along with above normal temperatures. A storm system shifting out of the southeastern states Monday will bring the potential for a wintry mix Monday night, changing to all rain for Tuesday. && .NEAR TERM /THROUGH FRIDAY/...
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As of 1245 PM EST Thursday...Clouds and more clouds continue across our region this afternoon...with the plenty for a few breaks across the southern CPV and parts of the lower CT river valley. Otherwise...clouds will prevail with areas of light drizzle/snow depending upon elevation/temps. Have noted SLK down to 3/4sm in light snow and mist past hour and latest web cams from the dacks confirm some light snow is falling. Have bumped pops up across the mountains and mention the combination of drizzle/freezing drizzle and snow showers through the mid afternoon hours. Soundings continue to show very limited moisture in the favorable snow growth region. Otherwise...temps hold steady for the rest of the day with light west/northwest winds. Mid/upper level shortwave trough shifting through the Northeast this morning continues to provide areas of low clouds and drizzle to the North Country through mid-day before surface high pressure and an upper ridge building east from the Ohio Valley brings an end to precipitation this afternoon. Moving forward into tonight and Friday, despite strong subsidence building in aloft, a developing low level inversion will trap abundant moisture below 925mb with very light winds in the boundary layer. This combination isn`t good for any clearing, except at the mountain top level, so will continue to highlight cloudy skies through Friday morning before the inversion possibly breaks Friday afternoon with some peaks of sun possible towards sunset. Should be interesting to see what the summits look like Friday morning as I suspect they`ll be above the clouds. With so much cloud cover through the period, temps will have a hard time warming much today and falling off tonight so think highs will mainly run in the mid/upper 30s and lows only in the mid 20s to low 30s. Light wind fields and warm air moving over fresh snowpack will also enhance the potential for fog to develop tonight, and feel it will be fairly widespread after sunset reducing visibility below a mile at times. Not much airmass change for Friday either so temps should be similar to Thursday, but with the hope of a little afternoon sun could see some low 40s out there, mainly in the Champlain Valley.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY/... As of 311 AM EST Thursday...Relatively quiet weather continues into the Friday night/Saturday time frame. A quick perusal of this morning`s data suggests a fairly consistent theme showing blocking upper ridging across New England will act to dampen an approaching shortwave trough advancing northeast from the Ohio Valley/Mid-Atlantic during this period. With light warm thermal advection rippling in aloft expect a return to mainly cloudy skies with perhaps some spotty very light rain and/or snow arriving from the southwest over time and weakening in coverage as we progress into Saturday. Any snow accumulations will be negligible and generally less than an inch - mainly across elevated terrain. Temperatures will continue very mild with lows Friday night from the mid 20s to lower 30s and Saturday maxes from the upper 30s to lower 40s. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... As of 311 AM EST Thursday...As we progress into the extended portion of the forecast the one certainty is a continuation of unseasonably mild weather with daily mean departures averaging from +10 to +20 degrees. This has been a very consistent signal among varying ensemble output over the past 10 days or so. Our most notable weather will occur during the Monday/Tuesday time frame as a rather potent southern stream system phases with northern stream energy across the northeast before exiting into the maritimes by mid-week. Examination of model thermal profiles suggests at least a threat of some light sleet or freezing rain in customary areas of northern New York and eastern VT into Monday evening before boundary layer warming transitions p-type to rain in all areas by Tuesday. For the Champlain Valley this will primarily be a light rain event. Any icing threat appears rather marginal at this time given such mild boundary layer temperatures but a light glaze can`t be ruled out, at least at this point. Other minor concern will be the potential for gusty southeasterly downsloping winds, especially along the western slopes of the Green Mountains later Monday afternoon into Monday night as mean 925-850 mb flow may exceed 40 knots. This will eventually predicate some adjustment of model qpf fields as valley/terrain shadowing/enhancement effects will be magnified. Higher-res guidance will certainly provide more detail as we draw closer in time. Behind this system mean lower to mid level flow remains southwesterly, so little cooldown/airmass change is expected through Thursday at this point. With several additional shortwave impulses crossing the area the idea of a daily threat of scattered rain/snow shower activity also appears reasonable as progress into Wed/Thu. Afternoon highs should from the mid 30s to lower 40s with overnight lows averaging in the upper 20s to lower 30s - more typical of March than January. && .AVIATION /18Z Thursday THROUGH Tuesday/...
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Through 18Z Friday...Challenging aviation forecast with regards to ifr potential this evening into the overnight hours...with models struggling with boundary layer moisture profiles. Current obs show a mix of ifr at slk to mvfr at rut/btv/mpv/mss and vfr at pbg. Expecting mvfr cigs to prevail at most sites thru 00z this evening...with occasional ifr vis/cigs continuing at slk. Tonight...expecting additional ifr cigs with areas of fog/freezing fog to develop associated with light winds and plenty of boundary layer moisture. Difficult to determine areal coverage of fog...but thinking most likely ifr/lifr conditions will be at slk/mss with ifr possible at pbg/btv/rut/mpv. Conditions will slowly improve to mvfr cigs by 16z Friday with light winds. Outlook 18Z Friday through Tuesday... Areal coverage and cigs heights associated with plenty of low level moisture continues to be the aviation focus for Friday into Saturday. Expecting mainly mvfr from 18z Friday to 00z Saturday...with trends toward ifr/lifr in low cigs and areas of fog/br. A few sprinkles or flurries possible Saturday with general mvfr mountains to vfr valleys. Next system spreads a wintry mix across our taf sites late Monday into Tuesday with widespread mvfr to ifr conditions likely...along with breezy southeast downslope winds possible at rutland.
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&& .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Lahiff NEAR TERM...Lahiff/Taber SHORT TERM...JMG LONG TERM...JMG AVIATION...Taber

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