Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 151154 AFDALY Area Forecast Discussion National Weather Service Albany NY 654 AM EST Fri Dec 15 2017 .SYNOPSIS... Seasonably cold temperatures will continue through the weekend. Moderate accumulations of lake effect snow are likely in the Western Adirondacks tonight into Saturday. Elsewhere, mainly light snow showers will be possible Saturday as a cold front passes through the region. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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As of 640 AM EST, A few light snow showers this morning are extending from lake Ontario into the Mohawk Valley region. Cannot rule out a few flakes reaching Albany this morning as well. Otherwise, very chilly temperatures around eastern New York and western New England, with values below zero at Glens Falls ranging up to the low teens. Further details regarding todays forecast follow... Prev Disc...The area remains under mainly flat upper level flow as the next upper impulse digs into the longwave trough. At the surface, weak high pressure will nose into the area this morning and quickly exit by the afternoon as the next wave of low pressure shifts eastward across the Great Lakes and as a coastal low develops off of the Carolinas. This coastal low is expected to stay far enough offshore such that it will limit the impacts to just some snow showers south and east of the Greater Capital District (mainly in Litchfield and Berkshire counties). As these weather makers shift towards the region today, low level moisture and cloud cover will increase, leading to another chilly and cloudy day with highs in the upper teens and lower 20s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
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A Winter Weather Advisory has been issued for northern Herkimer county and northern Hamilton county, mainly along Route 20 and west of Route 30 from 10 PM this evening through 1 PM Saturday... The next upper level shortwave will approach and pivot through the region tonight with an attendant surface low tracking eastward north of the St. Lawrence Valley.This should allow winds to back such that they align with the long axis of Lake Ontario for a time late tonight into early Saturday. Surface to 850 mb delta-Ts will range from 20-25 C, and deeper moisture associated with the upper level wave will enhance lake effect processes, resulting in a period of moderate to heavy lake effect snow for portions of the western Adirondacks. Therefore, have issued a winter weather advisory for northern Herkimer and Hamilton counties from 10 PM this evening through 1 PM Saturday. It looks like the lake effect band will shift south as the low level winds veer northwesterly late Saturday morning. This should allow for the dominant lake effect band to break up and shift southward. Current forecast accumulations of 3 to 6 inches, with locally higher amounts possible support an advisory for now but will monitor conditions to see if a warning is needed. Upslope snow showers may begin to occur across the higher terrain of western New England tonight as well. Elsewhere, clouds and a moderate wind will keep temps from falling as much tonight compared to early this morning, although lows will likely be below normal. Some lingering snow showers will possibly spread toward the I-90 corridor and into the valleys Saturday as the lake effect band shifts southward, but minimal accumulation is expected as there is no midlevel forcing with the height rises. A cold and dry night is expected Saturday night with diminishing winds as high pressure builds into the region.
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&& .LONG TERM /SUNDAY THROUGH THURSDAY/... Many differences between the various operational deterministic model guidance and ensemble solutions, the extended period remains a rather low confidence forecast at this time. We begin this long term period with a cut-off low across the four corners region with a short wave ejecting out of this system across the Plains and through the Ohio Valley then into the northeast corridor Sunday night. The upper flow will be rather confluent as broad isentropic lift and overrunning evolves through the evening hours. A period of light snow is expected overnight which could make a tricky morning commute Monday morning. This aforementioned wave departs off the New England coastline Monday morning with perhaps a narrow ridge of high pressure tracking across the region before the next upstream disturbance approaches. This is when models diverge a bit as waves across Canada will eventually dictate the synoptic pattern through most of next week. All global models suggest a deepening surface low across central Canada but differ significantly on placement and intensity. Its downstream impacts will be the approach of a cold front for tuesday into Tuesday night. The GFS is quite aggressive with the GGEM the least aggressive but all suggest frontal passage to occur by Tuesday evening. So the chance of rain/snow showers as H850 temperatures moderate to near or above 0C before returning below freezing Tuesday night. This system and its cyclonic flow regime will quickly depart through Wednesday before the next warm front and overrunning situation sets up for the second half of the week with light precipitation chances on the increase Thursday. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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VFR conditions are in place this morning with light and variable winds. Per GOES 16 data, seems some of the Lake Effect clouds were making into the KALB-KPSF with sct-bkn VFR decks. As this band lifts northward, we will keep some of these restrictions into the TAFs at this time. For KPOU and KGFL, should remain VFR due to upstream higher terrain blocking some of these CIGS from progressing eastward. Winds will become S-SW around 5 kts. Mid level clouds will increase during the afternoon hours, with all sites seeing bkn cigs around 7-12 kft by late in the day. Some lake effect snow may brush into the KALB-KPSF this evening with upslope areas of KPSF the higher chance where we will place a TEMPO group at this time. Outlook... Friday Night: Low Operational Impact. Slight Chance of SHSN. Saturday: Moderate Operational Impact. Breezy Chance of SHSN. Saturday Night: No Operational Impact. NO SIG WX. Sunday: No Operational Impact. NO SIG WX. Sunday Night: Moderate Operational Impact. Chance of SHSN. Monday: Low Operational Impact. Slight Chance of SHRA...SHSN. Monday Night: Moderate Operational Impact. Chance of SHRA...SHSN. Tuesday: Moderate Operational Impact. Chance of RA...SN.
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&& .HYDROLOGY... No hydrologic problems are expected through the weekend. Temperatures will largely remain below freezing into the weekend, promoting ice formation on areas lakes and streams. Any snowfall is mainly expected to be light, although moderate accumulation of lake effect snow is expected over the western Adirondacks tonight into Saturday morning, and light to moderate accumulation is possible over the higher terrain of western New England 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...Winter Weather Advisory from 10 PM this evening to 1 PM EST Saturday for NYZ032-033. MA...None. VT...None. && $$ SYNOPSIS...Thompson/JVM NEAR TERM...JVM SHORT TERM...Thompson/JVM LONG TERM...BGM AVIATION...Frugis/BGM HYDROLOGY...Thompson/JVM

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