Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 171624 RRA AFDBTV Area Forecast Discussion...DELAYED National Weather Service Burlington VT 1124 AM EST Wed Jan 17 2018 .SYNOPSIS...
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Light snow will continue today with additional snow amounts generally up to 2 inches expected, with up to 4 inches expected in southern and eastern Vermont. As a developing coastal low retreats further up the New England Coast this evening, expect widespread snow to taper off later today. Some light snow showers will develop through the end of the week along with a general warming trend going into the weekend.
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As of 1124 AM EST Wednesday...Winter Weather Advisory remains in effect for Rutland, Windsor, and Orange counties of Vermont until 100 PM today. Radar shows an area of light snow moving northeastward across the area this morning and expect that to continue through mid to late afternoon until the upper level trof axis passes east of the region. Locally low visibilities and clouds in the Champlain Valley are caught up in a low level inversion but that should improve this afternoon. Previous Discussion...Light warm air advection snow continues over southern/eastern Vermont in the pre dawn hours, with areas further north seeing more sporadic localized snow showers. Expect snow to become more widespread once again within the next few hours as heights fall aloft in advance of an upper level open wave and a developing coastal surface low tracks inside of benchmark (40N 70W). Southern and eastern Vermont will see some influx of Atlantic moisture this morning as southwesterly flow briefly takes on more of a southerly/southeasterly component ahead of the approaching low. This will result in slightly higher snow fall accumulations in the southern and eastern part of the state. Overall, expect to receive generally 3 to 5 inches of snowfall out of the system through this evening in southern and eastern Vermont. Northern New York and northern Vermont will pick up lighter amounts (generally up to 3 inches) as the best moisture transport and lift associated with the surface cyclone will stay further south and east. As the surface low tracks further northeast up the New England coast, flow will quickly switch back to westerly and the stratiform snow will taper off from west to east this afternoon through early evening. Low level lapse rates will steepen in response to cold air advection behind the departing low this evening, supporting the development of some light lake effect snow east and northeast of Lake Ontario tonight through tomorrow. Southern Saint Lawrence and Franklin counties in New York could pick up a dusting to 2 inches out of the band by Thursday night. Temperatures will remain fairly seasonal through Thursday night with highs generally in the 20s and lows in the high single digits to teens tonight under partly clear skies.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 417 AM EST Wednesday...The short-term forecast period will maintain a moderating temperature trend, which will last through the weekend and early next week. Still appears that sfc anticyclone across the Tennessee River Valley will be associated with low-level ridge axis extending newd into PA and the srn tier of NY Thursday night into Friday. Combination of WSWLY low- level flow from Lake Ontario (on nrn periphery of ridge axis), and modest mid-level shortwave trough crossing NY/northern New England Thursday night into Friday, will bring about sufficient moisture and ascent for light snow shower activity, mainly for the nrn Adironacks into the nrn Green Mtns. PoPs peak at 40-50% during the pre-dawn hrs on Friday, with snowfall amts of a dusting to 1" generally possible for the nrn Adirondacks and northern Green Mtns (little or no snow accumulation expected in the valleys). Will see partial clearing in the wake of this shortwave trough by Friday afternoon, and developing S-SW flow will result in continued warming trend. Looking for overnight low generally in the teens - except lower 20s in the St. Lawrence Valley - for Thursday night. Temperatures warm into the lower 30s for Friday, and then generally falling back to the low-mid 20s for Friday night, under variably cloudy skies. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 417 AM EST Wednesday...Will see the development of weakly anticyclonic flow in the mid-levels over the weekend with gradual height rises as deep-layer ridge builds across the sern CONUS. Not expecting much in the way of precipitation during the weekend as a result, though the GFS shows a developing frontal zone just north of the intl border, especially during the day Sunday. Can`t rule out some light precipitation, but overall activity along the developing quasi-stationary front should mainly occur across srn Quebec. Carried just 20 PoPs across nrn sections. Should see temperatures rising into the upr 30s to lower 40s on Saturday and Sunday, again with expectation that frontal zone sets up just to our north. Differences between the ECMWF and GFS are greater thereafter into early next week, and have increased for the 00Z model cycle. Frontal system is still expected to pass to our west across the Great Lakes and Ontario, with the GFS a bit faster in the overall synoptic evolution. The ECMWF is slower and a bit further east, with potentially secondary low development during the day Tuesday across central New England. The 00Z ECMWF suggests the bulk of precipitation would occur during the day Tuesday, whereas the GFS suggests moderate precipitation (mainly rain) for Monday night. ECMWF-MOS also suggests less of a warmup with this potential evolution than does the GFS MEX-MOS. With both timing/vertical temperature profile uncertainty larger than normal, have limited precipitation types to rain or snow attm. Certainly, with overall low-lvl warm advection regime, some threat of freezing rain and/or sleet also exists, but a skillful forecast of those p-types is difficult given current model spread. Would generally expected mixed wintry precipitation changing to plain rain in advance of cold front, with precipitation ending as rain/snow showers later Tuesday night into Wednesday. Official temperature forecast is closer to GFS scenario, with highs in the upr 30s to lower 40s for Monday into Tuesday, potentially falling late with cold frontal passage. Will need to continue to monitor this system, as moderate precipitation and above freezing temperatures may affect existing ice jams across the region. That said, extent of thawing degree hours and overall precipitation/moisture not nearly as significant as what occurred last Thursday/Friday. Thus, hydro impacts should be comparatively minor and exist mainly as a function of existing ice jams and modest increases in river levels into those local areas. && .AVIATION /16Z WEDNESDAY THROUGH SUNDAY/... Through 12Z Wednesday...Currently experiencing mixed MVFR to LIFR conditions this morning with some in response to light snow moving through the North Country. Steadiest snow remains over southern/eastern Vermont with IFR to MVFR conditions expected to continue at RUT/MPV through 22Z, with gradual improvement to VFR expected after. More sporadic snow showers and lingering low clouds will make conditions more variable at MSS/SLK/PBG/BTV through the morning and early afternoon, however expect general improvement to VFR conditions at all sites by 00Z. Winds will generally be under 10 knots through the period. Outlook... Thursday: Mainly VFR, with local MVFR possible. Slight chance SHSN. Thursday Night: Mainly VFR, with areas MVFR possible. Slight chance SHSN. Friday: Mainly MVFR, with areas VFR possible. NO SIG WX. Friday Night: VFR. Slight chance SHSN. Saturday: Mainly VFR, with areas MVFR possible. Slight chance SHRA. Saturday Night: Mainly VFR, with local IFR possible. Slight chance SHSN. Sunday: Mainly MVFR, with local IFR possible. Slight chance SHRA, Slight chance SHSN. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...Winter Weather Advisory until 1 PM EST this afternoon for VTZ010>012-019. NY...None. && $$ SYNOPSIS...RSD NEAR TERM...RSD SHORT TERM...Banacos LONG TERM...Banacos AVIATION...RSD is the U.S. government's official web portal to all federal, state and local government web resources and services.