KALY issues Area Forecast Discussion (AFD) valid 2019-12-06T21:16:00Z 608 FXUS61 KALY 062116 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 416 PM EST Fri Dec 6 2019 .SYNOPSIS... Light snow ends early this evening with high pressure returning for the weekend leading to dry and cooler conditions. Then, our next system moves into the Northeast early in the work week bringing in milder temperatures and widespread rainfall. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Winter Weather Advisory in effect until 10 PM for Bennington County, Eastern Rensselaer County and Northern Berkshire County... Updated at 3:30 PM...Our clipper is progressing into New England with its cold front pushing into the southern Adirondacks and western Mohawk Valley. There are a few bands of steadier snow moving into the Capital District so we issued a Special Weather Statement to alert motorists to use caution while traveling during the evening commute. As the best lift continues exiting to our east, expect snow to taper off from west to east early this evening. The back end of the snow is already moving through the Tug Hill Plateau. Based on spotter reports and the latest trends, still expecting total snow amounts to finish between 1 to 3 inches with up 5 inches in the higher terrain of the Adirondacks and Greens. Our advisory is still in effect until 10PM but we may expire it earlier if needed. Winds shift northwest as the cold front crosses through the region this evening. With high pressure building into the Great Lakes, the tightening pressure gradient of eastern NY will lead to breezy winds. Gusts up to 15-20mph are possible. Cold air advection increases overnight with 850mb isotherms between -13C to -15C moving over the warm Lake Ontario waters. The strung out upper level shortwave trough will also remain over the Great Lakes as well providing some additional lift. The northwest mixed layer flow and high res guidance supports some lake effect snow showers reaching into extreme southern Herkimer County and perhaps western Schoharie County tonight but it's possible some of the bands miss our area given the 320 degree mixed layer flow direction. We limited POPs to slight chance and low end chance in these areas with just coating to less than an inch of snow accumulations. Otherwise, some partial clearing is expected tonight and with a fresh snow pack in place, temperatures should drop into the teens and low 20s tonight. We show lows a few degrees above the blended guidance due to breezy conditions overnight that could impede cooling. && .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 /21Z FRIDAY THROUGH WEDNESDAY/... Steady snow associated with a clipper storm will impact KGFL/KALB/KPSF through the early evening hours. Within snowfall, visibility will be reduced to 1SM with IFR conditions. Cannot rule out a few moderate bursts, so will include a TEMPO for LIFR conditions with visibility of 1/2SM to 3/4SM. Further south, KPOU will miss most of the precip, but a stray rain/snow shower will be possible, so will address with a VCSH. Winds will be out of the south, mainly at light speeds of 5 kts or less. The storm's cold front will move through around 23z-00z and winds will switch to the northwest. Winds may briefly pick up this evening to around 10 kts with a few higher gusts, especially at KALB/KPSF. Although precip will have ended, lingering clouds around 2-3 kft will continue for a few hours, especially at KPSF, where MVFR conditions may linger for a little while. Clouds should clear out by midnight for the valley sites with winds becoming lighter from a northwest direction. However, clouds look to increase once again after daybreak Saturday thanks to northwesterly flow moving across the eastern Great lakes. Some MVFR cigs may return for Saturday, especially at KALB/KPSF. Outlook... Saturday Night: No Operational Impact. NO SIG WX. Sunday: Low Operational Impact. Breezy NO SIG WX. Sunday Night: Moderate Operational Impact. Breezy Chance of RA. Monday: High Operational Impact. Definite RA. Monday Night: High Operational Impact. Definite RA. Tuesday: High Operational Impact. Likely RA. Tuesday Night: Moderate Operational Impact. Scattered SHRA...SHSN. Wednesday: Moderate Operational Impact. Scattered 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...Winter Weather Advisory until 10 PM EST this evening for NYZ054. MA...Winter Weather Advisory until 10 PM EST this evening for MAZ001. VT...Winter Weather Advisory until 10 PM EST this evening for VTZ013. && $$ SYNOPSIS...Speciale NEAR TERM...Speciale SHORT TERM...Speciale LONG TERM...Thompson AVIATION...Frugis HYDROLOGY...Thompson