Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 202140 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 540 PM EDT Tue Oct 20 2020 .SYNOPSIS... Low pressure will pass to the north on Wednesday. This will lift a warm front northward across the area early Wednesday morning, which will quickly be followed by a cold front. This will produce showers and possibly a few thunderstorms late tonight and Wednesday. High pressure will then build across New England which will provide a southerly flow with warm and dry weather for the end of the work week. && .NEAR TERM /THROUGH WEDNESDAY/... Conditions through the evening will be mainly dry as frontal boundary has moved into eastern NY and south into Pennsylvania. The frontal zone will remain stalled through this evening, with nothing more than a few spotty light showers or patchy drizzle through the first half of the night, especially toward the Finger Lakes and Southern Tier. Late tonight through Wednesday morning the frontal zone will move back quickly northward as a warm front, forced by rapidly increasing southerly flow ahead of a trough moving through the Upper Midwest. A 50+ knot low level jet will support strong moisture transport and isentropic upglide along the warm front, with showers blossoming late tonight through Wednesday morning. 12Z model guidance supports the best coverage of showers across the lakes and into the North Country. Elevated instability of up to 500J/kg for parcels rooted above the surface may also support a few scattered thunderstorms as well. Weak low pressure will pass by to the north of the region Wednesday. The frontal zone will quickly return southeast as a cold front in the afternoon, supporting another round of showers and possibly a few scattered thunderstorms. Rain will begin to taper off from northwest to southeast late afternoon and early evening following the passage of the cold front. Wind gusts may reach 30 knots northeast of Lake Erie and 20-25 knots elsewhere Wednesday. Temperatures will briefly surge into the upper 60s across Western NY and lower 70s from the Genesee Valley to Central NY by midday to early afternoon, only to fall again late in the day following the cold front. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... A bubble of high pressure will pass across Ontario and Quebec Wednesday night. The region will remain on the southern periphery of the surface high which will rapidly diminish any of the residual showers from the eastward progressing front from earlier in the day. The front that moved through the region on Wednesday will make its reprise Thursday though this time as a warm front. Strong warm air advection will increase temperatures at 850mb to near +12C across portions of Western New York Thursday afternoon, while reaching the North Country Thursday night. Mostly dry conditions are expected through Thursday night as the better forcing associated with the warm front will be confined to a deepening area of low pressure over the Mid-West. In regards to temperatures on Thursday, clouds will limit the full heating potential, therefore highs are expected to peak in the low to mid 60s across the North Country and Lake Plains, whereas mid to upper 60s are expected across the Southern Tier. Warm conditions will persist into Friday since southerly flow will continue as the warm front continues to progress further northeast into Quebec. Highs on Friday will climb up into the low to mid 70s. The aforementioned surface low pressure will continue to track northeast Friday. As such, its associated cold front will approach the region from the west on Friday, therefore chances for showers will increase across the western border of New York by Friday afternoon. The cold front will then track across the region Friday night into Saturday. Showers will likely enter western New York Friday night before diminishing as the front tracks east. A couple of rumbles of thunder can`t be ruled out across the Niagara Frontier Friday evening, though these chances are low due to the timing of the frontal passage. It should be noted that if the front were to pass earlier Friday evening, the chances for thunder will be better. && .LONG TERM /SATURDAY THROUGH TUESDAY/... The cold front from Friday night, will weaken into Saturday as the surface low tracks further north into Canada. In its wake, high pressure will build across the Great Lakes late Saturday and Sunday, resulting in dry conditions Saturday night into Sunday. An unsettled pattern for the remainder of this period as a deepening upper level trough over Western CONUS propagates eastward and looks to push a warm front through the area Monday morning. A cold front then follows in its wake, crossing the area Tuesday morning. Model guidance differs on the exact position and timing, but precipitation looks to overspread the area with the passage of these fronts, hence the widespread chance for rain showers through the start of the work week. && .AVIATION /22Z TUESDAY THROUGH SUNDAY/... Widespread MVFR/lower VFR CIGS will prevail through the evening as winds shift to the southeast and downsloping results in drier low level air and lifting cloud bases. The exception will be KJHW, which is expected to remain IFR most of the night since downsloping will not be a factor there. Late tonight the frontal zone that settled south of our area earlier today will return northward as a warm front, with showers increasing late tonight along with a few rumbles of thunder possible. A strengthening low level jet will bring several hours of low level wind shear late tonight. Showers will continue on Wednesday, both with the warm front and then with a cold front which will move through mid-day. Expect mainly MVFR flight conditions through 18Z, with areas of IFR possible in heavier rain and lower cigs. Conditions will gradually improve Wednesday afternoon when drier air builds in behind the cold front. Outlook... Wednesday night...Mainly VFR. Patchy IFR valley fog possible. Thursday and Friday...VFR. Friday night and Saturday...MVFR with showers likely, improving to VFR Saturday afternoon. Sunday...VFR. && .MARINE... North to northeast winds will continue through this evening on Lakes Erie and Ontario, producing choppy conditions at times. East winds may briefly increase on Lake Ontario later tonight as a warm front moves north. This will be followed by a period of gusty southwest winds Wednesday as another cold front crosses the eastern Great Lakes. Issued a Small Craft advisory for Lake Erie for Wednesday and Wednesday evening. Small craft headlines are also likely to be needed for portions of Lake Ontario Wednesday into Wednesday night. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...Small Craft Advisory from 8 AM to 8 PM EDT Wednesday for LEZ040-041. && $$ SYNOPSIS...Apffel NEAR TERM...Apffel/Hitchcock/JLA SHORT TERM...EAJ LONG TERM...EAJ/PP AVIATION...Apffel/JLA MARINE...Apffel/Hitchcock is the U.S. government's official web portal to all federal, state and local government web resources and services.