Area Forecast Discussion
Issued by NWS Albany, NY

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946 FXUS61 KALY 182322 AFDALY Area Forecast Discussion National Weather Service Albany NY 622 PM EST Sat Nov 18 2017 .SYNOPSIS... Periods of wet weather will overspread the region tonight as a warm front lifts northward across the region. A strong cold front will sweep across the area Sunday morning, resulting in windy conditions and falling temperatures. Precipitation will become less widespread and begin to mix with snow over the higher terrain. Lake effect snow will occur in favored regions Sunday night into Monday. && .NEAR TERM /THROUGH SUNDAY/... As of 600 PM EST...Mesonet observations reveal wet bulb freezing temperatures remain in place across portions of the Mohawk Valley which has been addressed with the SPS and updated hourly grids/forecast. Otherwise, strong band of precipitation was fast approaching from the southwest as initial shot of isentropic lift and theta-e advection was underway. PoPs/Wx was updated slightly per observations and latest mesoscale model runs of the NAM3Km and HRRR. Prev Disc...The magnitude of warm advection increases through the evening hours as low level jet increases toward 50kts this evening upstream as temperatures should steady off and beginning climbing overnight. The initial shot of isentropic lift should allow for break out of showers south of I90 to advance northward before the second and stronger surge of higher theta-e air arrives late this evening. This is when periods of rain will occur. As the region becomes well embedded in the warm sector late tonight, periods of rain should begin to transition toward showers as temperatures continue to climb through the 40s for many locations. Toward 10-12Z timeframe, per the latest RAP/HRRR, cold front will be crossing the western Mohawk Valley, Dacks and Schoharie Valley. Thermal profiles per west-east cross sections suggest the cold advection should be delayed a bit so we will hold onto the liquid portion of the forecast at this time. Strong cold frontal passage occurs through the early morning hours on Sunday. Surface low is progged to deepen toward 978mb across the St Lawrence Valley as deformation axis moves across the Dacks, Mohawk Valley. A period of rain/snow transitioning to all snow should commence through the morning hours Sunday. In addition, winds will quickly shift to the west-northwest and increase rather quickly in magnitudes. Mixing layer heights appear to be a little lower than yesterdays solutions as per close coordination with neighboring offices, we will issue a wind advisory for the southern 2/3rds of the region. Combination of downsloping, funneling potential down the Mohawk, into the higher terrain of the Taconics, Berks and NW CT should observed wind gusts over 45 mph. Precipitation should taper off toward noon as the low tracks well north of the region and deformation weakens. Then as the cold advection moves across the warm waters of the Great Lakes (GLERL analysis of Lake Ontario temperatures were near 10C), lake effect snow showers should develop as delta T/s climb toward 20C. Per 3kmNAM wind trajectories seems 280-290 degree trajectories set up but overall lake band structures and organization may be delayed a bit as weak mid level short wave ridge may suppress convective updrafts a bit. That changes toward Sunday night, however. Temperatures will be falling through the day as H850 temperatures fall back toward -6C to -8C with -10C isotherm just upstream. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... Winds should subside below advisory levels Sunday evening but still remain gusty. Another upstream short wave approaches Sunday night as this will be best opportunity for lake effect snow to develop and impact the region. Trajectories are expected to remain around the 290 degrees which favors the western Mohawk Valley and Schoharie Valley. Its possible overnight that some of these bands may migrate into the Capital District and favorable upslope conditions of the Taconics and Berks. At this time, seems accumulations up to 4 inches are possible for the western portions of the region with around 1 inch or less expected elsewhere. Additional adjustments are expected as we watch where the bands of snow develop and remain persistent. The band(s) of snow should lift northward toward Monday morning as the aforementioned short wave lifts east and north of the region and boundary layer flow backs a bit. So portions of Herkimer and Hamilton county get some snow Monday morning then as inversion heights lower, bands should weaken along with warming H850 temperatures toward Monday evening. A period of warm advection begins to unfold Monday night where additional cloud coverage is expected. Some upslope light precipitation may occur into the Dacks and southern Greens before much drier air arrives late at night. As for temperatures, we will blend with the latest ensemble superblend approach with lows mainly into the 20s and highs mainly into the 30s. && .LONG TERM /TUESDAY THROUGH SATURDAY/... A progressive, northern stream-dominant pattern with fast moving disturbances looks to continue through much of the long term. One such disturbance will track from north of the Great Lakes into northern Quebec Tuesday-Wednesday. Warm advection ahead of this system should allow for a surge of relatively mild air and above normal temps for Tuesday, with highs mainly in the 40s to lower 50s, along with a gusty south/southwest wind. A cold front associated with this system should track across the region Tuesday night into Wednesday morning, accompanied by scattered rain showers in valleys, and rain changing to snow showers across higher terrain late Tuesday night, with some possible brief Lake Effect/Enhanced snow showers during Wednesday across portions of the southern Adirondacks/Mohawk Valley. Mild temps initially Tue night should fall into the 30s by daybreak Wed, except for some 20s across the western Adirondacks. Cold advection kicks in Wednesday, although temps may briefly reach the lower/mid 40s in valley areas in the morning before falling in the afternoon; with higher terrain areas in the 30s in the morning, then possibly 20s by late afternoon. A ridge of high pressure should bring fair and seasonably cool conditions for Thanksgiving, with highs mostly in the 30s. Then, the next impulse approaches for Thursday night-Fri AM, although it looks farther north then its predecessor, with weaker overall forcing/moisture. Perhaps some snow showers across the western Adirondacks. Lows Thursday night in the 20s in valleys, and teens for higher terrain; highs Friday in the 30s to lower 40s. Yet another northern stream system may approach from the Great Lakes for Saturday, with perhaps some late day and nighttime rain showers in valleys, and rain/snow showers across higher terrain. Highs Sat in the 30s and 40s, with lows Sat nt mainly in the 30s. Could be quite windy again late Saturday into Saturday night, depending on the ultimate strength of the approaching system. && .AVIATION /23Z SATURDAY THROUGH THURSDAY/... Strengthening low pressure will track across the eastern Great Lakes into southern Quebec overnight into Sunday. A cold front associated with this system will cross the area Sunday morning. Periods of light to moderate rain will overspread the region this evening, and continue overnight. Moistening of the lower levels of the atmosphere will allow Cigs to drop to MVFR with occasional IFR overnight. Vsbys should also dip into the MVFR ranges, although can not rule out lower Vsbys at times, esp at KGFL and KPSF. The cold front should cross the TAF sites between roughly 12Z- 14Z/Sun. A line of gusty rain showers may accompany or immediately precede this front, and can not even rule out an isolated thunderstorm. In the wake of the front, conditions should improve to VFR, although can not rule out areas of MVFR Cigs at KPSF into the afternoon. A few passing rain/snow showers could occur at the TAF sites during Sunday afternoon. Winds will be mainly south to southeast tonight at 5-10 KT, although will be stronger at times at KALB, mainly 10-15 KT, with occasional gusts up to 20-25 KT possible. Winds will shift into the west, then northwest in the wake of the cold front Sunday morning, with speeds increasing to 10-20 KT, and gusts of 30-40 KT, strongest and most persistent at KALB and KPSF. Low level wind shear is likely overnight at KGFL/KPSF and KPOU, as surface winds remain from the southeast to south at less than 8 KT, while winds around 2000 FT AGL increase from the south to 35-40 KT. Outlook... Sunday Night: Moderate Operational Impact. Windy With Gusts To 33.0 Scattered SHRA...SHSN. Monday: Moderate Operational Impact. Windy With Gusts To 33.0 Scattered SHRA...SHSN. Monday Night: No Operational Impact. NO SIG WX. Tuesday: Low Operational Impact. Breezy NO SIG WX. Tuesday Night: Low Operational Impact. Isolated SHRA. Wednesday: Moderate Operational Impact. Scattered SHRA...SHSN. Wednesday Night: No Operational Impact. NO SIG WX. Thanksgiving Day: No Operational Impact. NO SIG WX. && .FIRE WEATHER... Periods of wet weather will overspread the region tonight as a warm front lifts northward across the region. A strong cold front will sweep across the area Sunday morning, resulting in windy conditions and falling temperatures. Precipitation will become less widespread and begin to mix with snow over the higher terrain. Lake effect snow will occur in favored regions Sunday night into Monday. && .HYDROLOGY... No hydrologic problems are expected on the main stem rivers through next week. A strong low pressure system will approach from the Great Lakes Region tonight. Widespread wet weather will occur throughout the forecast area into tonight. A cold front will sweep through Sunday morning with additional rain changing to snow over the higher terrain. At this time, total QPF from this system looks to range from a half inch to near an inch, with isolated higher amounts over portions of the Green Mountains. A colder air mass will then build in Sunday night through early next week, with some lake effect snow downwind of Lake Ontario affecting the western Adirondacks and Mohawk/Schoharie Valleys. 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...Wind Advisory from 6 AM to 6 PM EST Sunday for CTZ001-013. NY...Wind Advisory from 6 AM to 6 PM EST Sunday for NYZ038>040- 047>054-058>061-063>066-082. MA...Wind Advisory from 6 AM to 6 PM EST Sunday for MAZ001-025. VT...None. && $$ SYNOPSIS...BGM NEAR TERM...BGM SHORT TERM...BGM LONG TERM...KL AVIATION...Frugis/KL FIRE WEATHER...BGM/Thompson HYDROLOGY...BGM/Thompson

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