FXUS61 KBUF 221916 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 304 PM EDT Sat Aug 22 2026 .WHAT HAS CHANGED... A Severe Thunderstorm Watch is in effect until 9 PM EDT this evening for Orleans, Genesee, Wyoming, Allegany Counties and farther west in WNY. Damaging straight-line wind gusts are expected to be the main hazard with any severe storm. Only minor changes with this forecast update. && .KEY MESSAGES... 1.) Isolated to scattered showers and thunderstorms, some severe, are expected through tonight. 2.) Unsettled weather continues Sunday through Tuesday. Monday is expected to be the coolest day of the upcoming week. && .DISCUSSION... Key Message 1...Isolated to scattered showers and thunderstorms, some severe, are expected into tonight. Cyclonic S'erly to SW'erly flow aloft and embedded shortwave troughs impact our region through tonight as a deepening mid/upper-level low wobbles SSE'ward from northern ON to the northern Great Lakes. At the surface, a consolidating and deepening low should wobble E'ward from the northern Great Lakes toward southeastern ON amidst mid/upper-level divergence and MSLP falls downstream of the low aloft. This low track should allow a warm front to continue drifting NE'ward through the Finger Lakes and the Eastern Lake Ontario Region through this evening and usher- in a moister air mass at the surface and aloft, while a cold front will continue sweeping E'ward from Lower MI and should reach far- western NY by daybreak Sunday. Intervals of sunshine and low- level WAA ahead of and behind the surface warm front will allow highs to reach mainly the mid 70's to lower 80's late this afternoon. Lows tonight should reach the mid 50's to mid 60's around daybreak Sunday. Isolated to scattered showers and thunderstorms are expected, especially late this afternoon through tonight as weak to moderate CAPE, including elevated CAPE is released by the following: moist isentropic ascent ahead of shortwave trough axes, low-level convergence/moist ascent along the cold front, and downshear gust fronts interacting favorably with ambient low-level vertical wind shear in the warm sector. Note: the warm front passage will likely continue to be accompanied by dry weather as pockets of dry air at the surface and especially aloft precede the surface warm front. Deep-layer bulk shear is expected to remain moderate and diurnal convective mixing of the boundary layer is expected to yield steep low-level lapse rates and moderate DCAPE through this early evening, west of roughly the Genesee Valley. Thus, severe thunderstorms capable of producing damaging straight-line wind gusts are a concern in and especially west of the Genesee Valley. Steepening mid-level lapse rates associated with mid/upper-level cooling associated with the deepening low/trough aloft and resulting increase in MUCAPE in the hail growth zone may allow a severe storm or two to produce damaging hail the size of quarters. The severe storm threat should end by late evening, following the onset of boundary layer stabilization via nocturnal cooling. Note: lake- effect rain showers and thunderstorms are possible east and especially southeast of Lake Erie toward and especially by daybreak, as 850 mb temperatures cool to near 10C over the ~24C lake amidst rich (i.e abundant/deep) synoptic-scale low-level moisture, sizable lake-induced CAPE/lake-induced EL's as high as 15kft to 25kft above lake level develop, and W'erly mean low- level flow veers quickly to NW'erly behind the cold front. Key Message 2...Unsettled weather continues Sunday through Tuesday. Monday is expected to be the coolest day of the upcoming week. Cyclonic flow aloft, mainly SW'erly on Sunday, should become W'erly to NW'erly Sunday night through Tuesday as the aforementionedmid/upper-level low wobbles E'ward from the northern Great Lakes toward southern QC through Monday and then NE'ward toward the Gulf of St. Lawrence on Tuesday. At the surface, the aforementioned low will weaken gradually as it wobbles NE'ward toward the Gulf of St. Lawrence and becomes vertically-stacked with the low aloft. The cold front should sweep E'ward through the rest of our CWA by early evening. Behind the front, a lake-aggregate surface trough should linger over/near the eastern Great Lakes through Monday before a surface ridge begins to build from the western Great Lakes by Tuesday. This weather pattern evolution at the surface and aloft will allow a cooler air mass to overspread our region behind the cold front and then linger through Tuesday. Daytime highs should reach mainly the mid 60's to mid 70's on Sunday. The coolest highs are expected in the higher terrain of Western NY. Daytime highs should reach only the 60's to lower 70's on Monday, when the core of the cooler air mass is expected to reside over our region. Slightly warmer highs, mainly in the mid 60's to mid 70's, are expected on Tuesday. Overnight lows should reach mainly the upper 40's to mid 50's Sunday night and Monday night. Isolated to scattered showers and thunderstorms are expected along and ahead of Sunday's cold front. A few of these storms may become severe roughly along and east of the Genesee Valley, where peeks of sunshine and daytime warming may yield weak to moderate boundary layer CAPE, steep low-level lapse rates, and moderate DCAPE amidst moderate deep-layer bulk shear in the warm sector. Behind the cold front, periods of lake-effect rain showers and thunderstorms are expected primarily east and southeast of Lakes Erie and Ontario on Sunday through Tuesday as a sufficiently-cold/moist low-level air mass crosses the ~23C to ~24C lakes and sizable lake-induced CAPE continues to develop through Monday, but then begins to wane on Tuesday as a lowering/stabilizing subsidence inversion accompanies the building surface ridge. Shortwave trough passages preceded by SW'erly mean low-level flow should allow lake-effect showers/thunderstorms to impact locations generally northeast of the lakes, especially Lake Ontario, at times on Sunday and Monday, behind the cold front. Outside lake-effect showers and thunderstorms, additional rain showers are expected on Sunday through Tuesday as shortwave trough passages and attendant surface trough axes coincide with at least weak potential instability in the lowest ~1 km AGL. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... Surface low pressure overhead of the central Great Lakes this afternoon will slide east into the eastern Great Lakes, pushing a pair of fronts across the region this evening and overnight. These surface features are what are driving the line of scattered convection across the Ohio Valley and the center of Lake Erie as of 17Z. This line is expected to progress eastward this afternoon (18Z to 00Z), spreading convection inland. With the better instability across far WNY, a few of the thunderstorms may become severe, producing gusty winds in excess of 50kts. Overall flight conditions will remain VFR, with the exception of the aforementioned thunderstorms where conditions may drop down to brief and localized MVFR/IFR from ceilings and visibility. With the cold frontal passage this evening (after 00Z/Sun), widespread showers and embedded thunderstorms will pass east across the area, causing ceilings to drop to widespread MVFR with a swath of IFR conditions across the western Southern Tier (impacting KJHW) and the higher elevations east of Lake Ontario. Wrap around moisture and cooler temperatures aloft in the wake of the front Sunday morning will support lake enhanced showers east of Lakes Erie and Ontario Sunday, which will maintain widespread low end VFR ceilings with MVFR ceilings within any lake effect showers and clouds east of the Lakes. Outlook... Monday...Periodic showers and isolated to scattered thunderstorms with associated MVFR/IFR, with mainly VFR expected outside of any precipitation. Monday night through Tuesday night...Lake effect rain, mainly east and southeast of the Lakes with associated restrictions diminishing off Lake Erie Monday night and Tuesday and off Lake Ontario Tuesday and Tuesday night. Otherwise mainly VFR. Wednesday...Mainly VFR. Thursday...Mainly VFR, except MVFR/IFR conditions possible from scattered showers and thunderstorms in the afternoon. && .MARINE... Behind a departing area of surface high pressure, a modest southeasterly to southerly flow will continue through the day today. A deepening area of low pressure passing just north of the Lakes will push first a warm front (today) and later a cold front (Sunday) across the lakes...with showers and a few thunderstorms along each frontal boundary. Behind the cold front Sunday, an upper level low will bring an early taste of autumn with a brisk west wind developing within a decently strong pressure gradient and moderate instability over the Lakes. While initial southerly flow Sunday should bring Small Craft Advisory (SCA) conditions to the lakes Sunday, the southwest flow under the upper level low Sunday night through Monday night, and then westerly flow Tuesday, will likely continue the choppy waters on the Lakes with SCA likely. In addition to the brisk winds, there will be the potential for waterspouts with the development of sizable lake-induced instability as cool air associated with cyclonic flow around the upper-level low crosses the warm lakes. Greater waterspout potential will materialize as early as tonight over Lake Erie and Sunday over Lake Ontario. The waterspout threat should continue through Tuesday. However, expected thunderstorms over Lake Erie this afternoon into evening may produce waterspouts as well, especially if storms organize into a line. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ DISCUSSION...Jaszka AVIATION...EAL MARINE...Jaszka/Thomas