FXUS61 KBUF 240117 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 917 PM EDT Sun Aug 23 2026 .WHAT HAS CHANGED... Minor changes with this forecast update. && .KEY MESSAGES... 1.) Cool weather and periodic showers and thunderstorms, some of the lake-effect variety, are expected through Tuesday. 2.) Dry weather expected region-wide this Tuesday night through Wednesday. && .DISCUSSION... Key Message 1...Cool weather and periodic showers and thunderstorms, some of the lake-effect variety, are expected through Tuesday. Aloft, a low should wobble ENE'ward from the northern Great Lakes to near the Gulf of St. Lawrence the rest of today through Tuesday. In response, cyclonic flow, initially SW'erly to W'erly over our region, veers to NW'erly overnight tonight into Monday and then remains NW'erly through Tuesday. Shortwave disturbances embedded in the cyclonic flow will continue to impact Western and Central NY. At the surface, a cold front was located near I-81 at 1:35 PM EDT. This front will continue moving E'ward and should exit the rest of our CWA by 4 PM at the latest. Behind the front, a lake-aggregate trough is expected to persist through Monday night and then a high pressure ridge will begin to build from the western and central Great Lakes on Tuesday. Net low-level CAA will impact our region behind the cold front. Accordingly, late afternoon highs should reach the mid 60's to mid 70's today and Tuesday, respectively. In between, Monday is expected to feature highs only in the 60's to lower 70's courtesy of colder 850 mb temperatures and rather abundant cloud cover, including diurnal cumuliform clouds. Overnight lows should reach mainly the upper 40's to upper 50's around daybreak Monday, Tuesday, and Wednesday, respectively. Outside lake-effect precip (details below), isolated to scattered showers and thunderstorms are expected the rest of today through Monday night as low-level convergence/moist ascent along the cold front and surface trough axes accompanying the shortwave disturbances release at least weak potential instability in the lowest ~1 km AGL and weak boundary layer CAPE stemming from daytime warming through this early evening and again late Monday morning through early evening. Behind the cold front, scattered lake-effect rain showers and thunderstorms have already developed over/downwind of Lake Erie and over much of Lake Ontario. Lake-effect rain showers and thunderstorms with periods of heavy rainfall will continue through Monday night as synoptic-scale low-level moisture remains deep/abundant and 850 mb temperatures around 8C to 10C continue to become established over/downwind of ~23C to ~24C Lakes Erie and Ontario, behind the cold front. Those factors will yield sizable lake-induced CAPE and lake-induced EL's around 20kft to perhaps 30kft above lake level. The passage of the aforementioned shortwave troughs will cause mean low-level flow direction to vary over and downwind of Lakes Erie and Ontario. Accordingly, lake-effect precip should primarily stream ESE'ward or SE'ward from Lake Erie through Monday night. However, a period of W'erly to WSW'erly mean low-level flow should allow lake-effect precip to stream E'ward or ENE'ward from the lake during most of the predawn and daylight hours of Monday. This lake-effect precip should remain south of Buffalo. As for Lake Ontario, mean low-level flow should allow lake-effect precip to impact locations generally northeast of the lake through Monday afternoon, before the precip shifts S'ward and eventually settles southeast of the lake Monday evening through Monday night as a shortwave trough axis passage causes mean low-level flow to veer from SW'erly to NW'erly over/downwind of the lake. Note: lake-effect precip is expected to be most-organized tonight into Monday morning and again Monday night into Tuesday morning, when nocturnal cooling will allow Lakes Erie and Ontario to be the primary sources of warmth, moisture, and instability. On Tuesday, lake-effect rain showers and thunderstorms are expected to stream generally SE'ward from Lakes Erie and Ontario, but decrease in coverage/intensity and end by nightfall as the building surface ridge is accompanied by synoptic-scale low-level dry air advection, a lowering subsidence inversion, and increase in directional low-level vertical wind shear, which will all act to decrease lake-induced CAPE. Primarily dry weather is expected outside the lake-effect precip, but a few showers may accompany the passage of additional shortwave troughs/attendant surface trough axes coinciding with weak potential instability in the lowest ~1 km AGL. Key Message 2...Dry weather expected region-wide this Tuesday night through Wednesday. The high pressure ridge at the surface and aloft will build from the central Great Lakes Tuesday night and then begin to exit toward New England on Wednesday. Dry weather is expected as stabilizing subsidence accompanies the ridge. Considerable clearing, low humidity, and weak surface winds should allow lows to reach mainly the mid 40's to mid 50's around daybreak Wednesday. Mainly clear to party cloudy sky and net low-level WAA along the western flank of the surface ridge should allow highs to rebound to mainly the mid 70's to lower 80's late Wednesday afternoon. && .AVIATION /01Z MONDAY THROUGH FRIDAY/... A mid-level low will continue to meander eastward across southern Ontario through the nighttime. This will keep colder air aloft and shower activity around, though not to the degree it has been during the daytime. As diurnal heating returns on Monday, shower and even some thunderstorm activity will increase. As cold advection continues, cloud bases will likely lower to MVFR at all sites during the day on Monday as well. Outlook... Monday night through Tuesday night...Lake effect rain, mainly east and southeast of the Lakes with associated restrictions diminishing off Lake Erie Monday night into Tuesday and off Lake Ontario Tuesday/Tuesday night. Otherwise mainly VFR. Wednesday...Mainly VFR. Thursday and Friday...Mainly VFR, except MVFR/IFR conditions possible from scattered showers and thunderstorms each afternoon. && .MARINE... Behind a cold front passage today, an upper-level low will bring an early taste of autumn with brisk winds developing, courtesy of a decently strong pressure gradient and moderate instability over the lakes. SW'erly to W'erly winds around 15 to 25 knots will result in choppy waters through Monday night on Lake Erie and through Tuesday on Lake Ontario. Small Craft Advisories and Beach Hazards Statements remain in effect. Lake- effect rain showers and thunderstorms may produce waterspouts through Tuesday, amidst sizable lake-induced instability as cool air associated with cyclonic flow around an upper-level low crosses the warm lakes. Quieter marine conditions are expected Tuesday night through Wednesday as a high pressure ridge builds from the western and central Great Lakes. During Wednesday night through Thursday, the ridge should exit E'ward, allow a warm front to sweep NE'ward across Lakes Erie and Ontario, and cause SE'erly winds around 5 to 15 knots to veer to S'erly to SW'erly. Waves should be 3 feet or less. On Friday, a cold front should sweep E'ward across Lakes Erie and Ontario and cause S'erly to SW'erly winds around 5 to 15 knots to veer to W'erly to NW'erly. Waves should remain 3 feet or less. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...Beach Hazards Statement through Tuesday evening for NYZ001>007. Beach Hazards Statement through late Monday night forNYZ010- 019-085. MARINE...Small Craft Advisory until 2 AM EDT Tuesday for LEZ040-041. Small Craft Advisory until 8 PM EDT Tuesday for LOZ042>045. && $$ DISCUSSION...Jaszka AVIATION...Fries MARINE...Jaszka/Thomas