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Area Forecast Discussion
Issued by NWS Buffalo, NY
Issued by NWS Buffalo, NY
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033 FXUS61 KBUF 150759 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 359 AM EDT Thu Aug 15 2024 .SYNOPSIS... High pressure draped across the central and eastern Great Lakes will bring fair dry weather to much of the area today...with just a few isolated to widely scattered showers and storms possible at times across the North Country. The high will then exit to our east tonight, paving the way for a large, slow moving storm system to affect our region from Friday afternoon through the weekend. The most unsettled conditions will be Saturday and Sunday...when we can expect occasional showers and scattered thunderstorms. && .NEAR TERM /THROUGH TONIGHT/... Today surface high pressure will remain nearly stationary across the central and eastern Great Lakes...and will provide continued fair dry weather to western New York. Meanwhile further east...the eastern Lake Ontario region will remain on the western fringes of the upper low over the Canadian Maritimes. Spotty showers and thunderstorms that developed overnight across the North Country will drift southward and wind down early this morning...before the combination of daytime heating and another disturbance rotating around the backside of this low bring the chance for a few more isolated to widely scattered showers and thunderstorms this afternoon...with the best chances of these found across Lewis county. Otherwise it will be a little warmer than yesterday...with highs ranging from the upper 70s across the higher terrain and along the southern/eastern shores of Lake Ontario to the lower to mid 80s elsewhere. Tonight the axis of the surface high will drift east into central and eastern New York...while weak ridging builds in aloft. Coupled with nocturnal stabilization...this will bring an end any lingering convection across our far eastern zones...with a dry and quiet night otherwise expected. Later on in the night some high clouds should begin to arrive across far western New York...with some patchy valley fog again becoming possible across the Southern Tier. Overall...low temps will be a touch milder than those of the previous night...ranging from the mid 50s across the interior of the Southern Tier and North Country to the upper 50s to mid 60s elsewhere. && .SHORT TERM /FRIDAY THROUGH SUNDAY/... The longwave pattern across the CONUS will amplify over the weekend as a ridge builds over the Rockies, forcing a downstream trough to carve out over the Great Lakes, Ohio Valley, and New England. The digging trough and ample moisture will bring an extended period of unsettled weather starting Friday night and lasting through early next week. Friday, a narrow ridge surface and aloft will drift slowly east from the eastern Great Lakes to the Mid Atlantic, sandwiched between a closed low moving into the upper Great Lakes and another over the Canadian Maritimes. The wedge of dry air and subsidence will keep dry weather in place for much of Friday, with a chance of a few spotty showers and thunderstorms later in the afternoon or evening across Western NY as height falls start to spread east across the Great Lakes. Friday will be quite warm, with highs in the mid 80s for lower elevations and around 80 for higher terrain. Friday night, the initial push of height falls, DPVA, and moisture transport supported by a 30+ knot low level jet will gradually cross the area from west to east, likely producing an area of showers and a few scattered thunderstorms first in Western NY, and then overnight from the Genesee Valley eastward. Saturday through Sunday, the closed low over the upper Great Lakes will move slowly east, becoming and open wave by late Sunday over the eastern Great Lakes. A weak surface low vertically stacked beneath the mid level feature will also move slowly east across the Great Lakes. Plenty of moisture will be available with PWAT values averaging 1.5"-1.75" both weekend days. Height falls and diffluent mid/upper level flow will continue to gradually spread east across the area, with enhanced periods of ascent from difficult to time and place convectively generated vorticity maxima. The forcing and moisture will bring an unsettled weekend, with occasional showers Saturday through Sunday. There will be a chance of thunder much of the time, but the coverage of thunder should generally peak in the afternoon and evening each day as diurnal instability develops. PWAT values are not overly high, but nonetheless the persistence of the pattern and moisture suggest some potential for locally heavy rainfall both days, especially in areas where convection develops. Temperatures will pull back a little over the weekend, with highs both days in the 75-80 degree range for lower elevations and low to mid 70s for higher terrain. It will be muggy, with dewpoints in the 65-70 degree range much of the time. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... The very slow moving mid level trough will linger across the eastern Great Lakes Sunday night through Monday. The weakening surface low approaching the eastern Great Lakes Sunday night will give way to weak secondary cyclogenesis along the New England Coast Monday. There will still be more than ample forcing and moisture to produce occasional showers Sunday night through Monday across the eastern Great Lakes. Thunder chances will gradually wane from northwest to southeast as a cooler and more stable airmass arrives behind the slowly advancing cold front. The mid level trough axis will finally drift east of our longitude later Monday night and Tuesday, with the plume of deeper moisture gradually moving off the eastern seaboard. This will bring a return to mainly dry and seasonably cool weather for the middle of next week. && .AVIATION /08Z THURSDAY THROUGH MONDAY/... Fair dry VFR weather will prevail across the majority of the region today...with two exceptions. The first will be some localized reductions to IFR/MVFR in patchy valley fog across the Southern Tier early this morning. The second will be brief localized restrictions in some widely scattered showers and storms across the North Country early this morning...and again this afternoon and early this evening. Tonight will then feature fair dry weather...with some high clouds beginning to arrive across far western New York late. Some patchy valley fog/MVFR vsbys will also become possible across the Southern Tier again overnight. Outlook... Friday...VFR...with scattered afternoon showers and thunderstorms/ localized restrictions from a KROC-KDSV line westward. Saturday and Sunday...MVFR to IFR with occasional showers and thunderstorms. Monday...VFR to MVFR ceilings with scattered to numerous showers and possible thunderstorms. && .MARINE... High pressure draped across the central and eastern Great Lakes will maintain quiet conditions on Lake Erie and Lake Ontario today...with the weak pressure gradient supporting the development of lake breeze circulations this afternoon. A modest southeasterly to southerly flow will then develop later tonight and Friday as a warm front approaches the region...however wind speeds should remain less than 15 knots. Following the warm frontal passage...a general south to southwesterly flow should then ensue for the weekend...though winds should again generally remain below 15 knots. Of greater concern to marine interests will be the potential for scattered thunderstorms with locally higher winds and waves...with this beginning Friday afternoon across Lake Erie and western Lake Ontario...then spreading east across the remainder of the region over the weekend. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...JJR NEAR TERM...JJR SHORT TERM...Hitchcock LONG TERM...Hitchcock AVIATION...JJR MARINE...JJR