Area Forecast Discussion
Issued by NWS Albany, NY

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310 FXUS61 KALY 070352 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 1052 PM EST Fri Dec 6 2019 .SYNOPSIS... High pressure will build in overnight then will move eastward across the region this weekend resulting in fair but cold weather. Our next weather system moves into the Northeast early in the work week bringing in milder temperatures and a widespread rainfall. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Clipper system moves eastward out to sea overnight as high pressure quickly builds in from the west. Please refer to our Public Information Statement for total snowfall reports from Friday`s snowfall. Thanks to those we have sent in reports. Much appreciated and helps the forecast process. Winds will become light overnight as surface high pressure takes control. Any lingering upslope snow showers across the higher terrain to the east of the Hudson River Valley are expected to taper off. The northwesterly low level flow is focusing the lake effect across central New York with low chances for snow showers in the western Mohawk Valley and Schoharie Valley. With some clearing, cold air advection and the snow pack in place expecting temperatures to bottom out in the teens and lower 20s with single digits across the southern Adirondacks. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... Any lake effect effect snow should diminish by Saturday morning as the subsidence inversion lowers. High pressure builds into the Northeast on Saturday with breezy northwest flow continuing to advect in a chilly air mass. Generally expecting mostly to partly cloudy skies with clearing downstream of the higher terrain possible due to downsloping. High temperatures should be below normal due to breezy northwest winds and the chilly air mass moving into the area. Expect high temperatures to reach into the mid to upper 20s with near freezing the mid-Hudson Valley. Skies clear Saturday night as high pressure moves overhead and radiational cooling allows temperatures to decrease quickly. The deep snow pack and calming winds should lead to cold low temperatures reaching into the single digits to low teens by Sunday morning. High pressure heads east into New England on Sunday with warm air advection ensuing. Clouds should gradually increase through the day with high temperatures warming into the low to mid 30s. The stronger temperature and moisture advection holds off until overnight as broad southwest flow intensifies ahead of our next disturbance brewing the Mississippi Valley. Tempertures should actually warm Sunday night but depending on the timing of the thicker cloud coverage, initial overrunning precipitation may fall as a wintry mix including potential for sleet. We gradually increase POPs after 06z with chance POPs overspreading the region from southwest to northeast towards 12z Sunday. && .LONG TERM /MONDAY THROUGH FRIDAY/... In the long term, we are looking for a period of above normal temperatures with rainfall Monday and Tuesday, followed by sharply colder air and mainly dry conditions (aside from lake effect snow in the usual snow belt) Wednesday into Friday. For Monday into Tuesday, a deep trough will dig into the upper Midwest and western Great Lakes, with a warm sector and increasing low level jet forcing spreading into the Northeast corridor. The 850 mb V component increases to around 30 kt, which is +1 to +3 standard deviations per the NAEFS (highest south and east of Albany). As a result, precipitable water values look to increase to 0.75-1.00 inches Monday into Monday night, which are +2 to +3 standard deviations, per the NAEFS. The poleward exit region of a strong upper jet looks to become favorably placed over our region to enhance lift Monday into Monday night, as well. These factors support a high likelihood of precipitation Monday into Monday night. There is a little bit more uncertainty for Tuesday, with the GFS/GEFS being a little more progressive with the trough/cold front compared with the ECMWF, which depicts a slower passage and wetter solution for Tuesday. As a result, the QPF projections between the two camps are different, with the GFS/GEFS Mean showing generally 0.50-1.50 inches, with the ECMWF more in the 1-3" range (highest south/east of Albany). The combination of warm temperatures generally in the 40s to lower 50s, dewpoints in the 40s, and rainfall will lead to ripening of the snow pack and some melting and runoff, although how much is still questionable. Tuesday night into Wednesday night, sharp cold advection will occur with 850 mb temps possibly falling to -15 to -20C. 12Z ECMWF run shows the cold air cutting in while deeper moisture is still in place Tuesday night, which could lead to some accumulating snow before the precip ends. This is the first recent run to depict this scenario, so we will continue to monitor this potential. Otherwise, a drying trend will occur, aside from areas downwind of Lake Ontario, where lake effect snow will be possible. High pressure is likely to build in for Thursday and Friday, keeping temperatures cold but with dry weather expected. && .AVIATION /04Z SATURDAY THROUGH WEDNESDAY/... Clipper system moves off to our east as high pressure quickly builds in from the west tonight. Widespread steady snow has ended however lingering upslope snow showers are possible through the evening across the higher terrain to the east of the Hudson River Valley. Lingering MVFR at will improve to VFR shortly after midnight. Overall cloud cover decreases however will be back on the increase as short wave trough moves over the region with VFR ceilings expected. Cloud cover will decrease once again with the passage of the short wave. Winds became northwesterly and with the pressure rises a brief period of gusty winds is occurring is some areas. Winds will become light overnight as surface high pressure quickly builds in and takes control. Westerly flow expected Saturday at 10 knots of less. Outlook... Saturday Night: No Operational Impact. NO SIG WX. Sunday: No Operational Impact. NO SIG WX. Sunday Night: Moderate Operational Impact. Chance of RA...SN. Monday: High Operational Impact. Definite SHRA. Monday Night: High Operational Impact. Definite SHRA. Tuesday: High Operational Impact. Likely SHRA. Tuesday Night: Moderate Operational Impact. Chance of SHRA...SHSN. Wednesday: Low Operational Impact. Slight Chance of SHSN. && .HYDROLOGY... Temperatures will remain below normal through Sunday, so little melting and/or runoff is expected through the weekend. 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. There is uncertainty with the amount and placement of QPF, with some models indicating potential for 0.50-1.50 inches, and others 1-3 inches. Either way, at least some ripening and melting of the snowpack and runoff is expected, 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. It will turn sharply colder from Wednesday through the end of the week, which should put a stop to any melting/runoff, and allow river levels to recede. 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...None. MA...None. VT...None. && $$ SYNOPSIS...IAA/Speciale NEAR TERM...IAA/Speciale SHORT TERM...Speciale LONG TERM...Thompson AVIATION...IAA/Frugis HYDROLOGY...Thompson

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