678 FXUS61 KBUF 211711 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 111 PM EDT Sat Aug 21 2021 .SYNOPSIS... A warm and humid airmass will remain in place for the rest of the weekend, allowing for a few scattered showers and thunderstorms mainly during the afternoon and early evening today and again Sunday. Heat and humidity will continue through the middle of next week, along with the chance of a few spotty showers and thunderstorms. && .NEAR TERM /THROUGH SUNDAY/... Radar imagery showing a few diminishing showers over the Niagara Frontier and western Lake Ontario, with developing heavier showers east of Lake Ontario and across Central NY. A weak mid level closed low over West Virginia and southwest PA this afternoon will drift east into the Mid Atlantic through Sunday, with a weak inverted trough in the mid levels extending northward into the eastern Great Lakes. Weak vorticity maxima will continue to drift north and west across our region in response to flow around this weak mid level low, and a feed of Atlantic moisture will also continue. Given how weak the forcing is, most of the showers and thunderstorms through the rest of the weekend will be closely tied to the diurnal cycle, with peak coverage during the afternoon today and Sunday. Hurricane Henri will also move northward to the east of this system, but have no direct impact on our area. This afternoon and early evening expect showers and a few thunderstorms to continue to develop as diurnal heating peaks, with the best coverage across the eastern Lake Ontario region and the western Finger Lakes where the deepest moisture resides and forcing ahead of a weak vorticity maxima provides an added boost. Coverage of rain will be more sparse across far Western NY near Lake Erie, but a few showers are still possible here as well. The showers and storms will taper off by mid evening as the boundary layer stabilizes. Plenty of low/mid level moisture will remain in place overnight with partly to mostly cloudy skies. Despite the cloud cover, abundant low level moisture and weak surface winds will allow for patchy fog to develop. The most widespread fog will be across the valleys of the Southern Tier and western Finger Lakes. The fog will dissipate by mid morning Sunday. The abundant low level moisture will combine with diurnal heating to support scattered showers and thunderstorms in the afternoon, mainly across the higher terrain inland from Lakes Erie and Ontario. Developing north/northwest flow will allow stable lake shadows to spread inland across the lake plains in the afternoon, decreasing the chance of rain close to the lakes. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... Sunday night, showers should diminish from west to east with the loss of daytime heating, but with the tropical airmass and the tropical storm to the east, showers should still linger through the night for the eastern portions of the area. Monday, again another active day, with showers and thunderstorms possible, especially for the eastern portions of the area. But daytime heating and a tropical airmass will provide for the chance of showers and storms across a good portion of the area. The track of Tropical Storm Henri will be monitored closely as the western edge of the storm may approach the North Country during the day on Monday. Most guidance doesn't push the system that far west, but a few global models continue to push the system slightly closer to these eastern portions of the forecast area. If Tropical Storm Henri does end up tracking east a bit quicker on Monday, then that will also pull the upper level trough east as the storm gets phased into the upper level pattern. This would result in less showers overall as well for the entire area as some of the moisture will push east and the upper level support of the trough will exit the area. Monday night, any showers and storms should taper off from west to east after sunset. Tropical Storm Henri should track away from the area on Monday night, further reducing the potential for showers/rain associated with the system. Daytime temperatures on Sunday and Monday will be in the upper 70s to mid 80s with humid conditions making both days uncomfortable. Night time lows will be in the low 60s to near 70 each night. && .LONG TERM /TUESDAY THROUGH FRIDAY/... A shift in the upper level pattern will lead to some quieter weather for most of the long term period. Warm temperatures and fairly humid conditions will persist through the week before a cold front moves through late Wednesday into Thursday. This will also provide the best chance for showers and thunderstorms during the long term period. Behind the passing cold front, temperatures will cool to near normal and humidity levels will also lowers as an area of high pressure over southern Canada tracks east along the international border. Temperatures will be in the low to upper 80s for Tuesday and Wednesday, and cool some to the upper 70s to mid 80s for Thursday. Once the cold front has fully crossed the area, and cold air advection cools temps, highs on Friday will be in the low to upper 70s. && .AVIATION /17Z SATURDAY THROUGH WEDNESDAY/... Scattered showers and thunderstorms will expand in coverage through mid to late afternoon with the peak of diurnal instability. The best coverage is expected to be east and southeast of Lake Ontario where the best forcing and instability reside. A few of the heavier showers will reduce visibility to MVFR or lower briefly, otherwise VFR will prevail outside the showers through this evening with plenty of diurnal cumulus inland from the Great Lakes. Most of the showers will end by mid to late evening as daytime instability wanes. This will leave partly to mostly cloudy skies overnight. Abundant low level moisture and light winds will allow for patchy fog to develop, with the fog widespread across the valleys of the Southern Tier and western Finger Lakes. Areas of IFR will be found in the fog. Fog will dissipate by mid morning Sunday, with low level moisture evolving into a diurnal cumulus field. The cumulus field will briefly have MVFR bases late morning through midday in some areas before lifting into VFR in the afternoon. Widely scattered showers and thunderstorms will develop again in the afternoon, especially across higher terrain well inland from the lakes. Outlook... Monday...Mainly VFR with the chance of mainly afternoon and early evening spotty showers and thunderstorms. Tuesday...VFR. Wednesday and Thursday...Mainly VFR. A chance of showers and thunderstorms. && .MARINE... Winds will remain light through early next week with negligible wave action. There will be a few scattered showers and thunderstorms each afternoon and evening which may produce locally higher winds in a few locations. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...Hitchcock NEAR TERM...Hitchcock SHORT TERM...SW LONG TERM...SW AVIATION...Hitchcock MARINE...Hitchcock