Area Forecast Discussion
Issued by NWS Buffalo, NY
Issued by NWS Buffalo, NY
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749 FXUS61 KBUF 210241 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 1041 PM EDT Sat Jul 20 2024 .SYNOPSIS... A moisture starved cold front will drop southward into the area tonight through Sunday, bringing a band of clouds and possibly a few isolated showers, but most areas will stay dry. The next chance for widespread showers and thunderstorms will arrive Monday afternoon through Tuesday, along with an increase in humidity. && .NEAR TERM /UNTIL 6 PM SUNDAY EVENING/... Satellite imagery shows broken high clouds across the forecast area this evening. A weak frontal zone sits north of the region and is just getting into the Saint Lawrence River/northern NY. Tonight through Sunday, a mid level trough will dig southeast across Quebec, forcing an associated weak backdoor cold front south across NY and New England. DPVA ahead of the trough and low level convergence along the frontal zone, along with a narrow axis of moisture will support scattered showers tonight across the Saint Lawrence Valley, although the best chance of rain will stay mainly north of Jefferson and Lewis counties most of the night. The best chance of rain for our portion of the North Country will be late tonight through Sunday morning. Otherwise the rest of the area will stay dry tonight. Expect some patchy valley fog across the western Southern Tier. The weak backdoor cold front will continue to drift south Sunday, crossing the remainder of the area before stalling and washing out across northern PA Sunday night. The majority of the large scale forcing for ascent will move east across northern New England later Sunday, leaving the weak low level front orphaned from synoptic scale forcing. The weak zone of low level convergence will support a band of cloud cover and perhaps in isolated shower. The best chance of a few showers will likely be found along a line from near or just northeast of Buffalo down through the western Finger Lakes where the advancing weak cold front will interact with the Lake Erie lake breeze, resulting in a WNW to ESE oriented zone of low level convergence. Any showers that do materialize will taper off and end Sunday evening, leaving mainly dry weather to prevail Sunday night. Clouds may linger for a portion of the night across Western NY as the frontal zone stalls just south of the region, and a weak mid level shortwave begins to move northeast out of the Ohio Valley. Expect patchy valley fog once again across the western Southern Tier. && .SHORT TERM /6 PM SUNDAY EVENING THROUGH TUESDAY NIGHT/... The persistent surface ridge which has kept our weather dry will gradually break down early next week. The weakening ridge will keep most area rain-free Monday, but a weak mid-level shortwave will approach the region bringing small chances for showers and thunderstorms inland of northeasterly lake breezes. This includes the Western Southern Tier, western Finger Lakes, and the upper Genesee Valley. Showers and a few thunderstorms may linger into Monday night at these locations. 12Z model consensus is a bit faster with this shortwave, with some models having the shortwave exit into New England by Tuesday afternoon. As a result, will scale back PoPs some on Tuesday, although a broad cyclonic flow and diurnal instability have the potential to generate some showers and thunderstorms. Weak flow aloft will lead to slow moving storms, but PWAT values will be modest at around 1.4 inches so the flood potential will be limited by non-zero. WPC has southern portions of the forecast area in a marginal risk for excessive rainfall. Temperatures will be slightly above normal with daytime highs in the upper 70s to mid 80s. With dew points in the lower to mid 60s it will not feel as muggy as it could be in July. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... An upper level trough will dig across the Great Lakes region Wednesday and Thursday before sliding east across New England on Friday. This will tap into some GOMEX moisture, with dew points increasing into the upper 60s and PWAT values increasing to about 1.7 inches. The approaching trough will result in persistent chances of showers and thunderstorms Wednesday and Thursday, especially during the afternoon and evening hours when diurnal instability will peak. A few strong thunderstorms can`t be ruled out, but forecast wind profiles show modest winds aloft which suggest locally heavy rain is the greater risk. Typical long range model discrepancies on how the trough will evolve limits certainty in timing, placement, and amounts. There will be some lingering cloud cover and possibly a few showers Friday as the trough exits into New England. Then fair weather returns just in time for the weekend, with high pressure building across the region Saturday. Temperatures will depend on convection and cloud cover, but in general will average near to slightly above normal during the period. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... VFR conditions will prevail in most areas through the rest of the weekend. A weak cold front located north of the region will move south tonight through Sunday. This will produce a few showers tonight across the Saint Lawrence Valley mainly well north and east of KART, with dry weather prevailing elsewhere. Some patchy valley fog will develop across the Southern Tier overnight through early Sunday morning with local IFR. There is a chance this may impact the KJHW terminal for a few hours around or just before daybreak, but the better chance of fog will be found in the deeper river valleys east of KJHW, such as KOLE. The weak front will continue south on Sunday, and may produce a few isolated showers across Western NY and the western Finger Lakes with VFR still prevailing. Winds will increase out of the north behind the cold front. Outlook... Monday...Mainly VFR. A chance of showers and thunderstorms in the afternoon, mainly across the Southern Tier and Finger Lakes. Tuesday and Wednesday...VFR/MVFR with showers and thunderstorms likely at times, especially inland from the lakes. Thursday...Areas of MVFR with showers and thunderstorms likely. && .MARINE... A weak backdoor cold front will drift south across Lake Ontario overnight through early Sunday with little fanfare other than forcing winds to veer from the west-southwest this afternoon to the north overnight, and then northeast on Sunday. Winds will generally remain 10 knots or less with little wave action through the rest of the weekend. Monday, east to northeast winds will increase into the 10-15 knot range on Lake Ontario and Lake Erie, producing some chop on both lakes. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...Hitchcock NEAR TERM...Hitchcock SHORT TERM...Apffel LONG TERM...Apffel AVIATION...Hitchcock MARINE...Hitchcock