Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 172341 AFDALY Area Forecast Discussion National Weather Service Albany NY 641 PM EST Wed Jan 17 2018 .SYNOPSIS... A low pressure system will move into the Canadian Maritimes this evening, with snow ending across our area. Seasonably cold and mainly dry weather is expected tonight through Thursday, except for some lake effect snow showers across the western Adirondacks. An upper level disturbance may trigger additional snow showers for Thursday night into early Friday. Fair weather, with a gradual warming trend is expected for this upcoming weekend. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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As of 640 PM EST...The Winter Weather Advisories have been canceled. Some upslope snow showers continue over the the northern and central Taconics into western New England, and some lake effect snow showers and flurries continue over the western Adirondacks based on the KENX and Mosaic radar and observations. Some adjustments to POPs and Wx. Please see our latest PNS with snowfall totals. We will continue to update over the next few hours. Previous near term... As of 415 PM EST, still areas of mainly light snow across the upper Hudson Valley extending south through southern VT, the Berkshires, and portions of the Capital Region. Another band of light snow was edging eastward through the central Mohawk Valley into Schoharie CO and heading east. This second band appears to be tied close to the actual upper level trough, and is expected to continue to move eastward over the next 2-3 hours. This band could tend to flare up in intensity as it tracks into the higher terrain of the Taconics, southern Greens and at least northern Berkshires. Since this band will continue moving east during the main evening commute, we decided to extend the previous Winter Weather Advisory until 8 PM this evening. Also, we have downgraded the previous Winter Storm Warning to an Advisory, also ending at 8 PM, for western New England (outside of Litchfield CO CT). If trends continue with snow tapering off, existing advisories may be cancelled earlier than the 8 PM EST expiration time. For southern areas, the threat of any additional snow showers appears much more limited, thus no Warnings/Advisories at this time. So, snow tapering to snow showers this evening, with additional localized accumulations of up to 2 inches across portions of southern VT, and only a coating to an inch elsewhere within the advisory area. Lake enhanced/Effect snow showers may also lead to a quick 1-3 inches across portions of the western Adirondacks, esp north of Route 28. Eventually, subsidence in the wake of the upper level trough should allow for some clearing to occur, especially in valley areas. Some additional high clouds ahead of the next shortwave may spill into the region toward daybreak. With a fresh snowpack in place, it will not take much for the boundary layer to at least briefly decouple, allowing temps to drop off quickly into the single digits in most areas, if not colder. However, if clouds and/or wind persist longer, slightly warmer overnight lows could result.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/... Thursday, a mix of sun and clouds, with chilly temperatures, mainly in the 20s for lower elevations, and teens across higher terrain. Some additional Lake Effect snow showers could lead to an inch or two across far northern Herkimer CO. For Thursday night, a potent upper level shortwave, currently noted on WV satellite imagery across south central Canada, is expected to track across the region. With some added lake moisture, and mid level warm advection combined with strengthening cyclonic vorticity advection, a burst of snow showers may occur, especially for areas near and north of the I-90 corridor. Minor accumulations of up to an inch could occur, except locally higher across portions of the western Adirondacks, and perhaps higher elevations of southern VT. Lows should mainly be in the teens. Friday-Saturday, after any residual snow showers Friday morning, expect a clearing trend for later Friday into Saturday, although snow showers could linger across the western Adirondacks. Friday highs should mainly reach the 20s to lower 30s, with Friday night lows in the teens/20s. Milder for Saturday, with highs reaching the lower/mid 30s across higher terrain, to near or over 40 in valley areas, warmest across the mid Hudson Valley region. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... Temperatures will close the weekend above normal, as high pressure will be ridging in from the Southeast and lower Mid Atlantic States. The mid and upper level flow will be zonal closing the weekend, as a cold front will be near the St Lawrence River Valley, and northern New England. Lows temps Sat night fall back into mid and upper 20s, and highs on Sunday will be about 10 degrees above normal with upper 30s to mid 40s in the valley areas and hills, and 30s over the mtns. A few rain or snow showers may graze the western Adirondacks with the front nearby and weak disturbances in the fast flow through Sunday. Sunday night through Monday...An upper level trough moves in the central Plains, and closes off. Diffluent flow sets-up upstream over the Midwest and Great Lakes Region. A warm front moves towards NY and PA with a slight to very low chance of snow showers Sunday night, though there are timing difference with the latest 12Z GFS/ECMWF/CAN GGEM and GEFS, and much of the night time period may be dry. A lead mid-level short-wave coupled with the warm front may produce spotty light pcpn into Monday, as the synoptic forcing looks rather weak, but some light rain or snow showers looks possible. The H500 low cuts off over the Midwest and western Great Lakes Region on Monday. Lows Sunday night should fall back into the mid 20s to around 30F before the clouds increase with the spotty light pcpn, and highs in the warm advection regime will be in the mid 30s to lower 40s. Monday night through Tuesday...The low to mid-level southerly flow increases ahead of the cutoff cyclone and its cold front, as the latest 12Z GEFS has +v-component wind anomalies /southerlies/ increase +2 to +3 standard deviations /STD DEVs/ above normal with PWATS increasing to 1 to 2 STD DEVS above normal. Some snow melt, and ice break is possible, as low temps will likely be above normal with mid and upper 30s in the valleys, and upper 20s to mid 30s over the higher terrain. The cutoff cyclone moves northeast into southeast Ontario with some Gulf and Atlantic moisture moving into the forecast area ahead of the cold or occluded front with a potential weak wave moving along it. The ptype could be messy with rain mixed with sleet, then rain, and finally transitioning to snow late in the day depending on the frontal passage. We will have to monitor for any hydro issues especially with the present ice jams, as highs will be in the mid and upper 30s north and west of the Capital Region, and lower to mid 40s south and east. Total QPF may be in the half an inch to inch plus range Mon night into Tuesday. Tuesday night into Wednesday...The cold or occluded front moves through with the pcpn ending as snow showers, as colder air filter in. In the strong cold advection, lows fall back into the teens to mid 20s. The threat for isolated to scattered snow showers continues in the cyclonic flow, especially along the favored westerly upslope areas of the western Adirondacks/southern Greens. High temps will be near normal for the mid week. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... Snow continues to taper in intensity from southwest to northeast across the Terminals. However, still some areas of IFR continuing. After sunset, snow should begin to diminish but leave behind MVFR CIGS for most areas. West-northwest winds 10kts or less should continue through the afternoon hours, then become light and variable for the Hudson Valley locations but remain westerly at KPSF. SCT-BKN CIGS within MVFR thresholds should return on Thursday with a weak frontal passage and some lake effect clouds. Outlook... Thursday Night: Moderate Operational Impact. Chance of SHSN. Friday: No Operational Impact. NO SIG WX. Friday Night: No Operational Impact. NO SIG WX. Saturday: No Operational Impact. NO SIG WX. Saturday Night: No Operational Impact. NO SIG WX. Sunday: No Operational Impact. NO SIG WX. Sunday Night: Low Operational Impact. Slight Chance of SHRA...SHSN. Monday: Moderate Operational Impact. Chance of SHRA...SHSN...RA. && .HYDROLOGY... Ongoing flooding due to ice jams will continue to be addressed with areal flood warnings, as some lingering issues continue due to existing ice jams which have become frozen in place. A gradual warming trend is expected to occur beginning this weekend. In terms of precipitation, only some snow showers are expected through Friday, with generally dry conditions expected over the upcoming weekend. 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...
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CT...None. NY...None. MA...None. VT...None.
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