Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 190917 AFDALY Area Forecast Discussion National Weather Service Albany NY 417 AM EST Sun Nov 19 2017 .SYNOPSIS...
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A strong cold front will sweep across the area this morning. Conditions will become blustery with a colder air mass being ushered in during the day. Precipitation will become less widespread with a mix and changeover to snow across the the higher terrain. Lake effect snow will develop by this evening impacting the western and central Mohawk Valley and Schoharie Valley tonight then shifting northward into the western and southern Adirondacks on Monday. While isolated to scattered showers are expected elsewhere.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 330 am, shortwave trough now crossing central PA/central Appalachians with well-defined dry slot noted on water vapor imagery. This dry slot is coincident with a sharp surface cold front which extends from roughly Wolcott, NY to State College, PA and points south. The surface low is analyzed roughly at the eastern end of Lake Ontario at 983 mb. Good model agreement in tracking this low up the St. Lawrence Valley through 00Z Monday, deepening to roughly 977 mb. While the synoptic-scale warm front is north of the area, the shallow cold airmass is still in place over portions of the Mohawk Valley and Adirondacks. Temps have edged up just enough that the freezing rain threat has likely abated in the Adirondacks. Recent calls to Hamilton/Warren Counties indicated no icing issues to report. Numerous showers continue in the prefrontal airmass over the local forecast area early this morning, the heaviest of which are over the southwestern Adirondacks where a 50+ kt LLJ is intersecting the terrain. The impinging dry slot will allow for lessening coverage of showers as we get toward sunrise. The cold front is still on track to reach western Mohawk Valley/Adirondacks around 11Z, the Hudson Valley around 13Z, and western New England around 14Z. The front will be accompanied by a wind shift to westerly over most areas. Strong cold advection and downward momentum transport will result in winds quickly becoming gusty in the wake of the front. Post-frontal wind gusts across western/central NY/PA have largely ranged in the 25-35 kt range. Cross sections across the front at 12-15Z on the 06Z NAM reveal a deepening boundary layer tapping into 30-40 kt of cross-frontal winds at 925 mb which could represent common gusts within the wind advisory area, roughly along and south of the Mohawk Valley, Capital District, and Berkshires. 850 mb winds are 45-50 kt at the top of the boundary layer, which represents a high-end/isolated gust potential. However, some question with how deep we actually do mix given that there is likely to be sct-bkn coverage of clouds. So, at this time do not anticipate upgrading to a high wind warning and the current hazards look good as they are. As the front passes and rapid cold-air advection ensues (e.g., H850 temps falling roughly 15C from 09-18Z), rain will turn to snow across the western Adirondacks which are likely to get brushed by a progressive deformation zone. This could result in a dusting up to an inch or two of snow in spots today. Another spot which could see an inch or two of accumulation today is the southern Green Mountains with moist upslope flow. Elsewhere, the coverage of showers should diminish today. Tonight, concern turns toward lake effect snow potential. H850 temps fall to near -12C over Lake Ontario, representing a Delta-T of around 22C. A secondary shortwave, seen crossing the Upper Midwest early this morning, will result in a return to cyclonic flow tonight after very brief midlevel ridging this afternoon. Per local research, good setup for inland extent of LES band, given multi-lake (Superior/Georgian Bay) connection, moderate instability, fairly unidirectional low-level flow, good speed shear in the sfc-1 km layer, low speed shear in the 1-3 km layer, and inversion depths approaching 3 km agl per forecast soundings at KUCA. The band looks to target southern parts of the Mohawk Valley into the Schoharie Valley initially (around 00-03Z). Thereafter, the band has the potential to extend eastward toward the Capital District, Taconics, Berkshires, and possibly even NW CT. Roughly 1 to 4 inches is forecast overnight where the band will be the most long-lived (Mohawk/Schoharie Valleys), with a few tenths up to an inch over the remainder of the aforementioned areas depending on where exactly the band sets up. Since it is lake effect, there is potential for sharp snowfall gradients and isolated higher totals if the band remains stationary. Hi-res models show potential for large inland extent, e.g., the 4km NAM extending a snow band clear into northeastern CT.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY/...
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Lake effect snows will continue on Monday. However the low level flow will back as ridging builds in and the band will shift northward out of the Schoharie and western/central Mohawk Valleys into the western and southern Adirondacks. An additional inch or so of snow is expected Monday in the western Mohawk Valley with 1 to 3 inches in the western Adirondacks. Isolated to scattered snow showers are expected across much of the forecast area during the day with upslope snow showers across the Taconics, Berkshires and southern Green Mountains with the brisk westerly flow. It will be another blustery day as the region is squeezed between the departing system and an advancing highs. Will have westerly flow again however not be as strong as today (Sunday). Expecting gusts up to 30 to 35 mph down the Mohawk Valley across the Capital District, Taconics and Berkshires as well as across the eastern Catskills, Litchfield Hills and southern Green Mountains. Temperatures will run 5 to 10 degrees below normal mainly in the 30s. Lower 40s are forecast for the mid Hudson Valley with mid/upper 20s for the terrain 2000 feet and above.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
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Coming soon.
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&& .AVIATION /09Z SUNDAY THROUGH FRIDAY/...
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Numerous showers will continue through around 09Z before activity tapers to showers. Flight conditions vary widely with KGFL socked in with LIFR stratus, while the remaining sites are VFR. Expect the very low cigs to persist at KGFL with possibly some improvement toward daybreak. At the remaining sites, MVFR/VFR should prevail, but a period of IFR could occur at KPSF. A strong cold front is on track to cross through after sunrise, resulting in a sharp wind shift and strong winds around 14Z for KALB/KPSF/KGFL and around 15Z for KPSF. Flight conditions will continue to improve to VFR in the wake of the frontal passage, although a few upslope rain or snow showers could occur at KPSF along and shortly after the frontal passage. Winds from 06Z-12Z will range from nearly calm at KGFL/KPOU to southerly gusting to near 25 kt at KALB/KPSF. Low-level wind shear continues at KGFL/KPOU with 40-50 kt winds at 2kft. Toward 12Z, winds will shift to southwesterly immediately in advance of the front, gusting to 20-25 kt. As the front passes through KALB/KPOU/KGFL around 14Z and KPSF around 15Z, winds will shift to westerly and become quite strong through much of the day, gusting to 30-45 kt, strongest at KALB/KPSF. Winds will remain elevated but gradually decrease Sunday evening. Outlook... Monday Night: No Operational Impact. NO SIG WX. Tuesday: No Operational Impact. NO SIG WX. Tuesday Night: Low Operational Impact. Slight Chance of SHRA...SHSN. Wednesday: Low Operational Impact. Slight Chance of SHRA...SHSN. Wednesday Night: No Operational Impact. NO SIG WX. Thanksgiving Day: No Operational Impact. NO SIG WX. Thursday Night: No Operational Impact. NO SIG WX. Friday: No Operational Impact. NO SIG WX.
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&& .FIRE WEATHER...
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A strong cold front will sweep across the area this morning. Conditions will become blustery with a colder air mass being ushered in during the day. Precipitation will become less widespread with a mix and changeover to snow across the the higher terrain. Lake effect snow will develop by this evening impacting the western and central Mohawk Valley and Schoharie Valley tonight then shifting northward into the western and southern Adirondacks on Monday. While isolated to scattered showers are expected elsewhere.
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&& .HYDROLOGY...
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No hydrologic problems are expected on the main stem rivers for the next several days. A strong cold front will sweep across the area this morning and precipitation will become less widespread with a mix and changeover to snow across the the higher terrain as colder air is ushered in. Lake effect snow will develop by this evening impacting the western and central Mohawk Valley and Schoharie Valley tonight then shifting northward into the western and southern Adirondacks on Monday. While isolated to scattered showers are expected elsewhere. Mainly fair weather is then expected the rest of the week with unsettled weather expected for next weekend. 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.
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&& .ALY WATCHES/WARNINGS/ADVISORIES...
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CT...Wind Advisory until 6 PM EST this evening for CTZ001-013. NY...Wind Advisory until 6 PM EST this evening for NYZ038>040- 047>054-058>061-063>066-082. MA...Wind Advisory until 6 PM EST this evening for MAZ001-025. VT...None.
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&& $$ SYNOPSIS...IAA NEAR TERM...Thompson SHORT TERM...IAA LONG TERM...IAA AVIATION...Thompson FIRE WEATHER...IAA HYDROLOGY...IAA

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