Area Forecast Discussion
Issued by NWS Buffalo, NY
Issued by NWS Buffalo, NY
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900 FXUS61 KBUF 251808 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 208 PM EDT Wed Sep 25 2024 .SYNOPSIS... Weak low pressure tracking by to our west and north today will drag a wavy cold front through the region tonight. While scattered showers will be found ahead of this front today...heavier...more widespread showers can be expected tonight. Areas east of Rochester may experience some left over showers Thursday morning...otherwise high pressure will build across the Lower Great Lakes to support fair dry weather Thursday afternoon through at least Friday. Most... if not all...of the significant rains from Helene should stay to our south. && .NEAR TERM /THROUGH THURSDAY NIGHT/... It will be damp and unsettled tonight...as a storm system pushing north from Georgian Bay will drag a wavy cold front through our region. In advance of this sfc front...a slug of deep moisture (PWAT 1.5") will be lifted by a combination of a 110kt H25 jet rotating around the base of a vigorous northern stream shortwave and convergence in the lower levels. This will result in fairly widespread showers...some of which could be locally heavy. Rainfall amounts tonight are forecast to range from a quarter to a half inch in most basins...with the lesser amounts expected to be over the Finger Lakes region. Elevated CAPE of 200-400 j/kg will be found within this environment...so will maintain the chance for thunderstorms. While the showers will taper off from west to east late tonight as the mid level moisture gets stripped away...a wealth of cloud cover will persist. The slow moving front will certainly take its time exiting the Eastern Lake Ontario Thursday morning...so likely to cat pops will remain in place for the initial daylight hours. Meanwhile...s l o w clearing will start to take place back across the IAG Frontier. As we push through the midday and afternoon...the residual showers will come to an end with more pronounced clearing taking place further west due to more effective diurnal mixing and strengthening subsidence from sfc based ridging. High pressure centered to the north of Lake Ontario Thursday night will then guarantee fair dry weather...although some cloudiness may still linger near the Pennsylvania border. It will be notably cooler...with mins forecast to be in the low to mid 50s...rather than the 60s from the previous two nights. && .SHORT TERM /FRIDAY/... Friday...the Lower Great Lakes will be in a squeeze play between an evolving mid level low over northern New England and the Canadian Maritimes, and another closed low over the south central US. Between these two large systems, a narrow ridge of high pressure surface and aloft will build over the Great Lakes and support dry weather for our region. Temperatures will continue to run a little above average with highs in the low to mid 70s for lower elevations and upper 60s for higher terrain. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... A complex pattern will evolve over the eastern US Friday night through the weekend. A mid level low over the Canadian Maritimes will move slowly southeast and into the North Atlantic Friday night through Saturday. Meanwhile, another large mid level closed low over the south central US will interact with the remnants of Helene Friday through Friday night, with a classic Fujiwhara interaction as the remnants of Helene first move in a cyclonic loop around the mid latitude closed low, and then eventually become absorbed into the closed low by Saturday over the Tennessee Valley. The vast majority of the greater impacts with the closed low and remnants of Helene will remain well southwest of our area across the Ohio Valley. Expect an extensive shield of mid/high clouds to stream northward into the eastern Great Lakes later Friday through the weekend as the upper level outflow of Helene`s remnants spread northward. Latest model guidance suggests the northern extent of light showers wrapping around the system may clip the western Southern Tier later Friday night through Saturday, with mainly dry weather elsewhere. Sunday through Monday, model and ensemble guidance show the mid level low containing the remnants of Helene moving east across the Ohio Valley to the Mid Atlantic states. This track would keep the majority of the rain south of our region, but it would not take much of a northward shift to bring higher rain chances to our area and this will need to be monitored through the coming days. Tuesday, a strong mid level trough and associated cold front is forecast to dig southeast across the Great Lakes, bringing an increasing chance of showers. The airmass is quite cool behind this cold front, with a trend towards below average temperatures for at least a few days starting around the middle of next week. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... A slow moving cold front will produce fairly widespread showers throughout the region tonight...with most areas experiencing MVFR to IFR cigs...the latter of which will be focused across the Srn Tier. While showers will persist east of Rochester Thursday morning...fair dry weather will return to the region. Cigs will improve to VFR levels by late morning/midday...then most areas will lose their cigs altogether by the end of the day. Outlook... Thursday night...Mainly VFR. Friday...Mainly VFR...but with a chance of showers across the western Southern Tier. Saturday through Monday...VFR. && .MARINE... A moderate pressure gradient will remain in place over the eastern Great Lakes today through tonight between persistent high pressure over the Canadian Maritimes and low pressure moving through the central Great Lakes. This will maintain moderate southeasterly flow today, with the strongest winds on the east half of Lake Ontario today. The southeast wind direction will continue to push the greater wave action into Canadian waters, but the offshore winds will become strong enough to require a Small Craft advisory for the eastern ends of Lake Ontario and Lake Erie. Winds will gradually become southwest and then west tonight through Thursday as a trough crosses the eastern Great Lakes from west to east, with wind speeds decreasing with the passage of the trough. Northeast flow will then pick up Friday, possibly requiring small craft headlines on Lake Erie and western Lake Ontario. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...Small Craft Advisory until 2 AM EDT Thursday for LOZ045. && $$ SYNOPSIS...RSH NEAR TERM...RSH SHORT TERM...Hitchcock LONG TERM...Hitchcock AVIATION...RSH MARINE...Apffel/Hitchcock/HSK