Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 140239 AFDALY Area Forecast Discussion National Weather Service Albany NY 939 PM EST Wed Dec 13 2017 .SYNOPSIS... Cold and blustery conditions will continue through the end of the week. Lake effect snow will diminish this evening, but a clipper system is expected to bring some light snow to areas from the Capital District southward late tonight. Another system will bring the chance for mainly light snow Friday and Friday night, with some heavier lake effect snow possible. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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Mid and high clouds on the leading edge of the approaching upper system will cloud up the region through the evening. Snow is still spreading east and north. Winds are in the process of diminishing as well. Just a few minor adjustments to the sky cover, temperatures and timing of snow through tonight. The previous AFD has a few more details and is below... Current water vapor imagery shows the deep upper trough pivoting out of the local forecast area, while upper level moisture was streaming into the southern Great Lakes ahead of a digging wave. Tonight, the digging wave across the central Plains will dampen out a bit as it rotates into the northeastern US, while a reinforcing wave will be on its heels. The attendant surface low will track west to east across PA and emerge into the New York Bight by 12Z Thursday. The approach of this system will disrupt the wind pattern over Lake Ontario, bringing an end to the lake effect regime after 00Z. Forcing for ascent in the form of isentropic lift and midlevel frontogenesis will spread into southern portions of the forecast area after 06Z tonight. Model cross sections and BUFKIT time/height sections indicate rather weak ascent and paltry moisture. However, the ascent does overlap the dendritic growth zone for a fairly deep layer, so the snow that does manage to fall will likely see good ratios. This forecast package has bumped up PoPs and snowfall accumulations somewhat, mainly from the Mohawk Valley/Capital District/Berkshires and points south. Model QPF fields still support amounts generally an inch or less for most of this area, with 1 to 2 inches possible for southern portions of our Catskills/Mid-Hudson Valley/Northwest Connecticut zones, which falls within WPC-generated ensemble guidance. Although temperatures will bottom out from the negative single digits to the upper teens, the apparent temperature may actually come up a bit from current values in the negative single digits to teens as winds diminish.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... The progressive nature of the clipper system should allow most of the snowfall to end by or shortly after 12Z. Cold and dry air advection will ensue for much of the day Thursday, although with decreasing cloud cover we may actually see temps a couple degrees warmer than Wednesday. It will be another blustery day, although not quite as much as Wednesday, with westerly winds gusting to 25 to 35 mph. Wind chills look to remain in the negative single digits to upper teens for much of the region. A west-northwesterly low-level flow would favor a lake effect response, although there is a ton of dry air and inversion heights are quite low, so do not have PoPs extending inland much from the westernmost Mohawk Valley. Moisture and inversion depths increase a bit overnight, so could see some light accumulations over the Mohawk Valley. Another chilly night with lows in the single digits and teens. Friday and Friday night, additional midlevel energy will slide across the forecast area downstream of a closed upper low. Some weak isentropic lift ahead of this wave may result in some light snow showers during the day for the Mohawk Valley/western Adirondacks. Another chilly day with highs in the teens and 20s. At night, a front will cross the region and allow for lake effect activity to begin over favored areas of the Adirondacks/Mohawk Valley, with a few snow showers possibly spreading into the Schoharie Valley/Capital District/western New England. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Upper energy departs through the day Saturday as upper troughing lifts north and flat upper ridging begins to build east from the midwest and Great Lakes. There could be a few leftover lake effect snow showers but more sun than clouds likely with slowly moderating temperatures. Highs Saturday in the upper 20s to lower 30s but lower 20s northern areas. Sunday through Wednesday there are considerable differences in sources of guidance and ensembles in the timing and track of upper impulses within the chaotic northern stream upper flow. Some guidance has a strong system tracking through our region Monday and Monday night with secondary weaker upper energy affecting our region Tuesday and Wednesday. Other guidance shows more moderation through the beginning of next week before a potential significant system could affect our region more toward Tuesday and Wednesday. Because of the fast chaotic upper flow and the high level of uncertainty, not going to try to get too specific with timing of enhanced chances of snow showers Sunday through Tuesday with some possible mixed rain showers in southern areas Monday and Tuesday. Wednesday is the most uncertain and confining any scattered snow shower activity to western and northern areas if there is any lake effect. We will know more about next week as we get closer. Highs Sunday in the lower to mid 30s but mid 20s higher terrain. Highs Monday and Tuesday in the upper 30s to lower 40s but lower 30s higher terrain. Highs Wednesday in the lower to mid 30s but upper 20s higher terrain. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... Mainly VFR conditions expected through this evening. The only exception will be at KPSF where lingering cloudiness will extend the MVFR ceilings this evening. Clouds will start to increase again this evening with ceilings starting above 3000 feet and lowering overnight, as a clipper low tracks eastward across OH/PA tonight. Some light snow on the northern periphery of this system will likely reach KPOU/KPSF/KALB between 06Z-09Z, with mainly MVFR conditions. Will mention IFR at KPOU since this terminal will be closer to the track of the low pressure center. The light snow will end between 13Z-15Z, with conditions improving to VFR thereafter. Westerly winds will continue to be gusty this evening up to 25 to 30 Kt but will diminish. Winds will shift to the southwest after dark, with wind speeds steadily decreasing through the night to less than 10 kt. Winds become northwest by around 14Z Thursday at around 10 Kt with gusts around 20 Kt continuing through Thursday afternoon. Outlook... Thursday Night: No Operational Impact. NO SIG WX. Friday: No Operational Impact. NO SIG WX. Friday Night: Moderate Operational Impact. Chance of SHSN. Saturday: Low Operational Impact. Isolated SHSN. Saturday Night: No Operational Impact. NO SIG WX. Sunday: Low Operational Impact. Isolated SHSN. Sunday Night: Moderate Operational Impact. Scattered SHSN. Monday: Low Operational Impact. Scattered SHRA...SHSN. && .HYDROLOGY... No hydrologic problems are expected through the weekend. Temperatures will largely remain below freezing through the end of the week and into the weekend, promoting ice formation on areas lakes and streams. Periodic chances for light snow will occur as well. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...Thompson NEAR TERM...NAS/Thompson SHORT TERM...Thompson LONG TERM...NAS AVIATION...NAS HYDROLOGY...Thompson

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