Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 190812 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 312 AM EST Thu Jan 19 2017 .SYNOPSIS...
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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.
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&& .NEAR TERM /THROUGH FRIDAY/...
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As of 311 AM EST Thursday...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/...
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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.
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&& .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
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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.
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&& .AVIATION /08Z Thursday THROUGH Monday/... Through 06Z Friday...OVC skies will generally prevail through the period with HIR TRRN OBSCD due to stratus layer. Ceiling heights will be variable between the TAF sites, generally IFR this morning at MSS/SLK, but alternating between MVFR-VFR (generally 2-4kft AGL ceilings) at the remaining TAF locations. There is a weak upper level disturbance passing thru the area during the pre-dawn hours. This feature will bring a chance of snow showers with briefly lowered vsby. Also, the stratus deck alone may result in some patchy drizzle and localized freezing drizzle possible for SLK/MPV thru the pre-dawn hours. Surface winds generally S to SW 5-9kt, trending W-NW for the daylight hours on Thursday. Should see ceilings improve back to at least the MVFR category at MSS/SLK during the daylight hours on Thursday. High pressure builds into the area Thursday, but strengthening inversion around 3kft AGL will tend to trap low- level moisture and hold MVFR stratus in place across most of the region. 06z Friday - 00Z Sunday - High pressure in place with light winds, but inversion layer will trap stratus layer and could continue to see prolonged stretches of MVFR ceilings, and perhaps IFR at times for SLK/MPV. In addition to low clouds, patchy BR/FG also possible. 00Z Sunday through 00Z Tuesday - Generally VFR Sunday. Moisture laden low pressure approaching from the south brings potential for widespread precipitation (mostly rain) for Monday with MVFR and intervals of IFR conditions. SE gusts in excess of 25kts possible at KRUT late Monday. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Lahiff NEAR TERM...Lahiff SHORT TERM...JMG LONG TERM...JMG AVIATION...Banacos

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