Area Forecast Discussion
Issued by NWS Buffalo, NY

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151 FXUS61 KBUF 202205 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 505 PM EST Mon Nov 20 2017 .SYNOPSIS... High pressure over the Tennessee River Valley will move off the mid Atlantic Coast tonight. Warmer air will move into the region Tuesday before the next cold front plows across the area Tuesday night bringing rain showers. Colder air moving in behind the front could bring some light mixed precipitation later Tuesday night with some minor lake effect snow showers Wednesday and Thursday. && .NEAR TERM /THROUGH TUESDAY/... Lake effect snow showers have tapered off considerably late this afternoon with only light activity remaining east of Lake Ontario. Expect little if any additional snow accumulation this evening. Southwest flow of drier and milder air will continue to lift this cloud area northward tonight, as the surface high centered over the Tennessee River Valley shifts east to the Mid Atlantic coast. The mainly clear skies over the western counties this evening will make it into the north country by midnight or shortly thereafter after. The strength of the warm advection will support a non-diurnal temperature trend tonight, as our lows should occur by midnight or so with gradually rising temperatures through daybreak. The high pressure situated off to our southeast will allow for a much milder day with brisk southwest winds ahead of an approaching cold front. Precipitation associated with the front will likely hold off until early evening leaving nearly the entire daylight hours rainfree with a decent amount of sunshine. Trajectories bring our air in from the Ohio/Tennessee Valleys which would support guidance high temperatures in the upper 40s to lower 50s. && .SHORT TERM /TUESDAY NIGHT THROUGH FRIDAY/... Tuesday night a cold front will cross the region forced by a shortwave moving through the lower Great Lakes. Rain showers will spread across the region along and ahead of the cold front, eventually switch to and ending as snow late Tuesday night. Any snow accumulations will be limited to the higher elevation of the Southern Tier and east of Lake Ontario, and will likely be on the order of a half inch with a few isolated spots up to a inch. Precipitation will shut down fairly quickly in the cold air advection behind the cold front, however some minor lake response will linger east of Lake Erie and Lake Ontario in Wednesday morning. High pressure will build across the region Wednesday, which will help suppress any lingering lake effect Wednesday morning, causing it to diminish through the day. This will produce a mainly dry day on Wednesday for Thanksgiving travel, along with near normal temperatures. Expect seasonable conditions for Thanksgiving as surface high pressure to our south shifts eastward. Another shortwave passing well to our north will drag a weak cold front near the North County by Thanksgiving evening, and may help elicit a weak lake effect enhancement off Lake Ontario Thanksgiving night. This will likely produce some scattered snow showers and light accumulations there. Otherwise, expect a mainly dry Thanksgiving day across the region. On Friday...mainly dry and uneventful weather will return as another narrow ridge of high pressure quickly traverses the region in the wake of Thursday night`s cold front. As the axis of this ridge departs to our east...developing warm air advection will help afternoon highs to largely climb back into the lower 40s south of Lake Ontario...and into the mid to upper 30s across the North Country. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... 12Z global models are in agreement with tracking a deep storm system north of the Great Lakes Friday night and into Central Quebec Saturday. Southerly flow ahead of this system should result in a non- diurnal temperature trend Friday night with surface temps rising ahead of an approaching cold front. Expect that temperature profiles by the time the cold front arrives will support mainly plain rain on Saturday with some gusty winds. A strong low level jet and cold front will combine with a deepening mid-level trough to force this period of rain showers Saturday as the system passes to our north. Synoptic moisture is not expected to be anomalously high which does not support a significant amount of rainfall while the jet trailing the front would likely keep wind gust sub-advisory level. Surface highs on Saturday will be pre-frontal with a model consensus pointing toward mid to upper 40s. A trailing blast of arctic air behind the cold front should support a good chance of some upslope and lake effect snow showers Sunday into Monday. 850mb temps are forecast at this time to dip close to -15C on Sunday which would support some extreme lake induced instability and lake induced equilibrium levels rising above 10kft. Northwest flow would steer lake effect snow bands and lighter upslope snow showers to the southeast of the lakes with what appears to be enough synoptic moisture to support a decent lake effect event. With this still being 6-7 days away have limited POPs to chance range but this will be something to watch closely especially for those traveling back home after Thanksgiving. Surface temperatures will run well below normal with the forecasted blast of arctic air. Highs Sunday and Monday will likely remain below or just at freezing. && .AVIATION /22Z MONDAY THROUGH SATURDAY/... VFR conditions will be found across the majority of the region through this evening, as a large area of high pressure will nose north across our region from the southern states. The only issue will be continued lake effect snow that will be found east of Lake Ontario. Tonight, skies will clear so that VFR conditions can be anticipated. Surface winds may still gust to near 25 knots especially downwind of the lakes, but there will be the potential for low level wind shear with a strong southwest low level jet at 45 knots. This may become more impactful if surface winds drop off a bit more than guidance suggests. Outlook... Tuesday...Mainly VFR. Wednesday...Rain and snow showers with a chance of MVFR/IFR. Thursday...VFR, but MVFR in lake effect -SHSN E of the lakes. Friday and Saturday...Mainly VFR. && .MARINE... Fresh to strong southwesterlies will continue across the lower Great Lakes through Tuesday, before a cold front moves through Tuesday night, turning the winds out of the northwest. Moderate to fresh northwesterlies then will continue through the mid week period. While the small craft advisories will continue through Tuesday on the Niagara River and Buffalo harbor, the headiness will be extended through Wednesday for the Lake Erie and Lake Ontario nearshores. Conditions may briefly improves Thursday as the graident relaxes, but winds and waves will again increase toward the weekend ahead of the next approaching low from central Canada. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...Small Craft Advisory until 6 PM EST Tuesday for LEZ020. Small Craft Advisory until 1 PM EST Wednesday for LEZ040- 041. Small Craft Advisory until 6 PM EST Tuesday for LOZ030. Small Craft Advisory until 7 PM EST Wednesday for LOZ042>045. && $$ SYNOPSIS...TMA NEAR TERM...APFFEL/TMA SHORT TERM...CHURCH LONG TERM...SMITH AVIATION...TMA MARINE...TMA

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