Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 052245 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 545 PM EST Thu Dec 5 2019 .SYNOPSIS... Snow showers early this evening will diminish tonight. Then, an Alberta Clipper will bring a widespread light snow event during the daytime tomorrow with some impacts to the evening commute expected. High pressure returns for the weekend leading to dry and cooler conditions. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... As of 4PM, bands of light snow showers and flurries are moving across the eastern Catskills, Schoharie County, the southern Berkshires and Litchfield County, CT. Some flakes are also being observed in the Hudson Valley but they are not accumulating. Temperatures are generally in the upper 20s in the eastern Catskills and Schoharie County and with additional snow showers upstream in Central NY, we added some minor snow accumulations to these higher terrain areas through 00z Friday. Otherwise, snow showers should diminish in coverage tonight as subsidence builds aloft. Partial clearing tonight combined with a deep snow pack should help temperatures cool down into the upper teens to low 20s. Clouds increase in coverage from west to east after 06z tonight ahead of our approaching Alberta Clipper. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... A potent shortwave progresses towards Lake Erie and Lake Ontario by 12z Friday with warm air advection increasing over New York as the surface low`s warm front advances into the region. Isentropic lift intensifies quickly over eastern NY after 12z which should allow snow to overspread the region from west to east by mid-late morning Friday. An area of enhanced 850-700mb FGEN looks to develop midday into the early afternoon hours along and north of I-90 and the latest HREF guidance shows increased probabilities for greater than one inch per hour snowfall rates for the Mohawk/Schoharie Valley into the Upper Hudson Valley and southern VT and the northern Berkshires. BUFKIT sounding from GFL also shows good lift through the dendritic snow growth zone during this period suggesting the potential for moderate to heavy snowfall rates. The BUFKIT sounding from ALB shows the the dendritic snow growth zone higher up in the atmosphere and may be higher than the layer with the best lift. Areas south of I-90 should see snow at the onset of the event Friday morning but snow should mix with rain towards midday/early PM as the warm nose impinges up the Hudson Valley and into NW CT. Some areas could even turn dry. While initial snow ratios for areas along and north of I-90 should be high (15-17:1) leading to a lighter/fluffy snow at the start of the event, snow rates could decrease (11-13:1) heading into the afternoon as warm air increases aloft. Surface temperatures during the event should struggle to warm given the fact that snow begins in the morning and wet-bulbing diabatic cooling processes should limit the diurnal spread. Generally expecting highs along and north of I-90 to only reach into the upper 20s to near 32. However, areas south of I-90 which get into the warm sector should rise into the mid-30s. The best warm air advection exits western New England by mid- afternoon which should end the chances for moderate/heavy snowfall rates. The cold front associated with our Alberta Clipper quickly pushes through the region towards sunset with snow ending from west to east early evening. Winds could also turn breezy with gusts 15-20mph in the wake of the front. Impacts to the evening commute are possible from this event especially in areas where roads and/or sidewalks are untreated. Total snowfall amounts expected to range 1 to 3 inches with up to 4-5 inches possible in southern Vermont, northern Berkshires and northern Taconics. We have issued a Winter Weather Advisory for these areas. Heading south of I-90, we could see a tight gradient set-up south of Capital District as snow totals decrease quickly where the warm nose impinges into the ALY CWA. Generally expecting snow amounts south of I-90 to range from coatings up to an inch. Higher amounts of 1 to 2 inches in the eastern Catskills and southern Berkshire County. After some scattered lake enhanced snow shower activity Friday evening, expecting gradual clearing and drying Friday night as high pressure builds into the Northeast. Dry and cooler weather returns Saturday and Saturday night. High temperatures Saturday in the upper 20s to low 30s with overnight lows turning much colder. Clear skies and a deep snow pack should facilitate radiational cooling with lows falling into the single digits and teens. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Mild temperatures and rain early next week. We are expecting to end the weekend with fair weather and continued below normal temperatures as ridging dominates at the surface and aloft. Aloft the ridge is expected to crest over the region Sunday while at the surface the high is expected to shift off the coast. A southerly flow about the departing high will begin a moderation of our temperatures. After a very cold night temperatures are expected to rebound into the 30s with only 20s limited to mainly above 1500 feet. Guidance continues to develop a low pressure system over the Southern Plains from southern stream energy then and tracks it northeastward across the Great Lakes region and Saint Lawrence Valley through early next week with interaction with northern stream energy. There are timing and strengthen differs however there is consistency our region will be in the warm side of the system. At this time, looking at temperatures warming above freezing on Monday and remaining above freezing into Tuesday night until colder air is ushered back in with the passage of the system`s cold front. Based on the current forecast expecting precipitation to overspread the region Monday morning with some now initially as it should be cold enough then rain through Tuesday. 12Z GEFS guidance indicates 850 mb temperatures of +1-2 SD, 850 mb winds +2-3 SD and PWATS +2-3 SD in the warm sector just ahead the system`s cold front. Forecasting highs in the 40s Monday with 30s limited to across portions of the southern Adirondacks, lows in the upper 30s to lower 40s Monday night and highs Tuesday lower 40s to lower 50s. Expecting ripening of the deep snowpack due to the mild temperatures and rainfall with at least some runoff and rises on area waterways. However it is too early to determine if there will be a flooding threat during this period. Seasonable temperatures will be ushered back into the region Tuesday night and Wednesday in the wake of the cold front, however a secondary front is expected to cross the region ushering in even colder air in. Highs Wednesday in the 20s and lower 30s with lows mainly between 10 and 20 degrees with single digits above 1500 feet and highs Thursday only in 20s with teens above 1500 feet. In addition to the cold, low level flow is expected to become favorable of lake effect snows across the Tug Hill Plateau into portions of the western Adirondacks. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... Upper level trough will remain over the region into early this evening. Scattered lake enhanced snow showers are expected from around KALB to KPSF later this afternoon into early evening. Occasional/brief deterioration to MVFR/IFR conditions will be possible within any snow showers. Best chance for IFR will be at KPSF. Snow showers expected to remain far enough away from KPOU/KGFL to omit mention in TAFs. Snow showers will end by around 00Z, with VFR conditions prevailing overnight. Mid level clouds will increase late tonight ahead of a clipper type system approaching from the Great Lakes. This system will bring widespread mainly light snow to the KALB/KPSF/KGFL terminals starting late Friday morning. Steadier snow should set up north of KPOU, so will only mention VCSH there. Vsbys will quickly lower to IFR levels once snow commenced between 15Z-16Z. Surface winds will be west-northwest around 10-20 kt, with gusts around 25-30 kt at KALB/KPSF. Winds will become west-southwest overnight, gradually decreasing to around 3-5 kt late. Winds will become southerly around 4-6 kt Friday morning. Outlook... Friday Night: Low Operational Impact. Slight Chance of SHSN. Saturday: No Operational Impact. NO SIG WX. Saturday Night: No Operational Impact. NO SIG WX. Sunday: No Operational Impact. NO SIG WX. Sunday Night: Moderate Operational Impact. Chance of RA. Monday: High Operational Impact. Likely RA. Monday Night: High Operational Impact. Likely RA. Tuesday: High Operational Impact. Likely RA. && .HYDROLOGY... Temperatures will remain below normal through Sunday, so little melting and/or runoff is expected through the next several days. A period of light snow is expected on Friday. This will allow the snow pack to be maintained and for some ice to build on shallow waterways, especially during the overnight hours. Temperatures will likely rise to above normal values by Monday into Tuesday, with periods of rain likely. This will likely lead to at least some ripening and melting of the snowpack and runoff, although it is too early to determine if there will be a flooding threat during this period. Rises on area waterways are likely during this timeframe. For details on specific area rivers and lakes, including latest 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 AM to 10 PM EST Friday for NYZ054. MA...Winter Weather Advisory from 10 AM to 10 PM EST Friday for MAZ001. VT...Winter Weather Advisory from 10 AM to 10 PM EST Friday for VTZ013. && $$ SYNOPSIS...Speciale NEAR TERM...Speciale SHORT TERM...Speciale LONG TERM...IAA AVIATION...JPV HYDROLOGY...Thompson is the U.S. government's official web portal to all federal, state and local government web resources and services.