FXUS61 KBUF 221234 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 834 AM EDT Sat Aug 22 2026 .WHAT HAS CHANGED... Made slight adjustments to POP's and QPF through midday today based on latest trends in observations and model guidance, including our 12Z/Sat sounding, which shows rather dry air in the surface to roughly 600 mb layer of the atmospheric column. As of 8:30 AM EDT, a cyclonic MCV was centered over northeastern Lake Erie, near Long Point, ON, and should continue to move generally NE'ward amidst SW'erly mean flow in the 925 to 500 mb layer. Mesoscale and moistening isentropic ascent associated with the vortex may generate isolated to scattered rain showers and a thunderstorm or two through midday, especially west of the longitude of Buffalo, as synoptic-scale flow at the surface and aloft transports moister air from the Corn Belt, courtesy of evapotranspiration, and that moister air combined with daytime heating allow CAPE, including elevated CAPE, to increase. The rest of the forecast remains valid. Please see discussion below for further details. && .KEY MESSAGES... 1) Showers and scattered thunderstorms late this afternoon through Sunday afternoon. 2) Cool, upper level low to bring lake effect rain Sunday afternoon through Tuesday night. Cool Sunday night through Monday night. 3) Showers and isolated thunderstorms Monday with the passage of Upper level trough axis. && .DISCUSSION... Key Message 1...Showers and scattered thunderstorms late this afternoon through Sunday afternoon. A deepening area of low pressure, advancing from Michigan this morning to just north of Lakes Erie and Ontario Sunday morning- afternoon will push a warm front across our region today, followed by a cold front late tonight through midday Sunday. Instability will increase to around 500 to 1000 J/KG of MUCAPE late this afternoon and through the evening hours which will support scattered thunderstorms. A modest wind flow through 10K feet could bring a few stronger storms with damaging wind gusts, though the overall warm, moist environment with a 10K warm cloud depth is not the greatest for large hail growth. Combined with peak heating of the day, a few stronger storms will exist across our region (marginal to slight risk level west of the Genesee Valley), before overnight convection and instability begins to wane. Any storm in this increasingly moisture rich environment could bring a locally heavy downpour. Additionally, as increasing EL heights force the convective cloud depth to grow to over 25K feet, combined with a deepening 850 hPa to lake surface temperature gradient, a few waterspouts may form under the approaching upper level low. A shortwave trough within the base of the negatively tilted upper level low early Sunday combined with the occluded front will pass across our region early Sunday. Showers and a few thunderstorms will be likely ahead of the frontal boundary Sunday...these within a typical summer humid airmass. A few stronger storms will be possible, especially along and south of the NYS Thruway along with the potential both damaging wind gusts and hail as lapse rates steepen. PWats around 1.5 inches will allow for a few drenching downpours of rain as well. Expect the rain showers to end from west to east through midday...though attention will quickly turn to a lake effect response. Key Message 2...Cool, upper level low to bring lake effect rain Sunday afternoon through Tuesday night. Cool Sunday night through Monday night. An early taste of fall Sunday night through Monday night as a cool upper level low rotates across our region. Temperatures at 850 hPa will plummet towards +7 to +8C across the eastern Great Lakes. This will generate a lake effect rain response with the cool air flowing over the very warm lakes. Broken bands of lake effect rain will become disorganized through the day Monday with daytime heating and the passage of a trough, but both Sunday night a decent plume of lake effect rain, centered just near and south of Buffalo and Watertown, and Monday night into Tuesday centered ESE of the Lakes is expected. This rain will diminish Monday night off Lake Erie, and Tuesday and Tuesday night off Lake Ontario. In addition to the rain, there will be the potential for waterspouts along lake convergent boundaries with tall EL heights combined with the cool air associated with the upper level low over the warm lakes. Overnight lows will be some 5 to 8 degrees below normal Sunday night and Monday night, while high temperatures Monday will be some 10 to 15 degrees below late August normals. Key Message 3...Showers and isolated thunderstorms Monday with the passage of Upper level trough axis. A surface trough, combined with an axis of an upper level low will pass across the eastern Great Lakes region Monday. Instability is not too impressive, generally under 300 J/KG of MUCAPE, but increasing low level lapse rates of 6.5 to 7.0 C/km will aid in the generation of more widespread shower activity through the late morning and early afternoon hours. Behind the initial cold front PWATs will not be as great, generally around an inch which will keep any heavier downpours limited, but the increasing lapse rates and lowering wet bulb zero heights could bring small hail within any stronger convective cell Monday. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... For the 12Z TAFs VFR flight conditions are found, with upstream convection over Lake Erie dwindling as cloud tops warm. These flight conditions will persist for the next 6 to 12 hours. A warm front extending eastward across the TAF region will also usher in deeper instability and moisture that will bring showers and scattered thunderstorms to the TAF region by mid afternoon. The greatest threat for storms along with localized gusty winds will be WNY. Then as activity pushes eastward through the evening and overnight waning instability will begin to limit the thunder threat. Isolated showers will likely remain through the balance of Saturday night. Outlook... Sunday through 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. && .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 may bring small craft 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 tall EL heights combined with the cool air associated with cyclonic flow around the upper level low over the warm lakes. Initial waterspout development will be as early as tonight over Lake Erie...and later tonight over Lake Ontario. This threat will continue through at least Monday night. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ DISCUSSION...Jaszka/Thomas AVIATION...Thomas MARINE...Thomas