609 FXUS61 KBUF 220046 AFDBUFArea Forecast Discussion National Weather Service Buffalo NY 846 PM EDT Sun Sep 21 2025
.SYNOPSIS... A slow moving trough of low pressure will finally bring beneficial rain to the region Monday through midweek, with several rounds of showers and scattered thunderstorms. Another low pressure system will move into the Great Lakes late in the week, with additional rain chances in an unsettled pattern.
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.NEAR TERM /THROUGH MONDAY/... A band of showers and a few thunderstorms is holding together despite nocturnal stabilization of the boundary layer, with convection likely being maintained by elevated instability. This line of showers and a few storms will likely hold together long enough to enter far Western NY late this evening before weakening by around midnight.
A broad southwesterly flow will develop across the region tonight. Mid-level moisture will increase ahead of an approaching mid level trough. This will continue to support a chance of a few showers overnight across Western NY, with mainly dry weather east of the Genesee Valley.
Broad southwest flow continues on Monday, continuing to transport moisture into the region. Shortwave expected arrive into the region Monday afternoon. This jet-induced lift combined with a seasonably warm and moist airmass should lead to at least scattered convection as diurnal instability increases. Moderate instability, and a modest shear environment could lead to low end severe threat, especially across far western New York. Would not rule out a localized heavy rainfall potential, though dry antecedent conditions and progressive storm motion should greatly reduce any flood concerns.
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.SHORT TERM /MONDAY NIGHT THROUGH THURSDAY/... Several distinct shortwaves north of the Gulf states will form an aggregate, positively tilted troughing pattern across much of the CONUS through midweek. Deep southwesterly flow of moist air into the eastern Great Lakes (PWATs increasing to 1.5-1.75") combined with weak but favorable upper level jet dynamics will bring periods of rain and possibly a few thunderstorms to the region. The complex nature of the partially phasing shortwave pattern lends overall lower confidence in the more granular forecast details with large run-to-run jumps noted among the deterministic models, especially in regards to QPF magnitudes and placement. Fairly widespread total rainfall amounts of 0.5-1" inch seem probable through Tuesday, though higher end totals will certainly be possible where embedded heavier convection ultimately sets up. Based on NBM ensemble probabilities, chances for rainfall >1.5" appear low across the North Country while highest (20-30%) from roughly the Buffalo Metro area southward to the NY/PA border.
Shower coverage and intensity will trend downward Tuesday night through Wednesday as the eastern portion of the trough and deeper plume of moisture shifts eastward, though with one of the aforementioned shortwaves still hanging over the Upper Great Lakes lower-end chances for showers will linger. As this shortwave begins to merge with additional energy rippling eastward from the central Plains, the system will likely form a cutoff low somewhere over the Mississippi Valley. Uncertainty remains high in the evolution of this system, though after a brief period of mostly dry weather between Wed - Wed night, chances for rain increase again through Thursday as it tracks eastward and deep moist SW flow is reestablished across the region.
Otherwise...temperatures this period will be cooler than early in the week though still average above normal. Daytime highs will be seasonable within a few degrees of climatological averages, though with nighttime lows on the warm side owed to southerly flow and/or increased cloud cover.
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.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... Longwave troughing initially centered over the Mississippi Valley will slowly cross through the Great Lakes this period, forcing a broad wave of sfc low pressure through the region. Model certainty remains quite low in how this system ultimately evolves, with some depicting an initial cutoff low as opposed to an open wave, though a general weakening trend with time is noted among the long range solutions. Greatest chances for additional appreciable rainfall and possibly some isolated deeper convection will be Thurs night - Friday, though given low confidence will maintain NBM`s chc PoPs into Saturday night, with lower-end sChc/Chc PoPs lingering through Sunday.
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.AVIATION /01Z MONDAY THROUGH FRIDAY/... A band of showers and a few thunderstorms is holding together despite nocturnal stabilization of the boundary layer, with convection likely being maintained by elevated instability. This line of showers and a few storms will likely hold together long enough to enter far Western NY late this evening before weakening by around midnight. This may bring TSRA and brief CIG/VSBY restrictions to KBUF, KIAG, KJHW for a few hours late this evening.
Overnight, the approach of a mid level trough and increased moisture will continue to support a few scattered showers and isolated thunder, mainly across Western NY. MVFR CIGS will likely develop across the higher terrain of the western Southern Tier, with mainly VFR elsewhere.
Monday, increasing low level and deep moisture combined with limited instability and modest forcing from the approaching trough will support scattered to numerous showers and a few embedded thunderstorms, especially later in the afternoon and evening. Expect areas of MVFR CIGS across higher terrain and in any heavier showers, with mainly VFR for lower elevations outside of the showers. Some heavier showers will also bring brief/local VSBY restrictions.
Outlook...
Tuesday...VFR/MVFR with showers likely along with a few thunderstorms.
Wednesday through Friday...Scattered showers and thunderstorms with restrictions possible.
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.MARINE... A moderate southeasterly flow is expected to veer more southerly and picking up a bit across both Lake Erie and Lake Ontario tonight. Speeds should remain below 15 knots through this evening, though winds will increase to up to 20 knots tonight, especially in the eastern basins of Lake Erie and Lake Ontario. A Small Craft Advisory is in effect for the eastern basin of Lake Erie and the eastern shore of Lake Ontario tonight.
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.BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...Small Craft Advisory until noon EDT Monday for LEZ040-041. Small Craft Advisory until noon EDT Monday for LOZ045.
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SYNOPSIS...Hitchcock NEAR TERM...Hitchcock/TMA SHORT TERM...PP LONG TERM...PP AVIATION...Hitchcock MARINE...EAJ/HSK/TMA
NWS BUF Office Area Forecast Discussion