Area Forecast Discussion
Issued by NWS Buffalo, NY
Issued by NWS Buffalo, NY
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661 FXUS61 KBUF 241815 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 215 PM EDT Tue Sep 24 2024 .SYNOPSIS... Low pressure will move across the Great Lakes tonight, spreading another round of rain across the region. A trailing front will move slowly across the area Wednesday through Wednesday night and support some additional rainfall. A few showers may linger Thursday, especially east of Lake Ontario. High pressure will then build into the Great Lakes region, bringing a return to mainly dry weather Friday through the weekend. && .NEAR TERM /THROUGH WEDNESDAY NIGHT/... A deep longwave trough will dig across the Great Lakes and Ohio Valley through Wednesday. Large scale forcing for ascent will increase ahead of this trough through tonight. This lift will be supported by DPVA, topped by mid/upper level diffluent flow, and deep moisture transported northward by a 40 knot southerly low level jet. As a result steady showers will continue to spread from west to east across Western NY through this evening. Terrain influences will play an important role in coverage of rain and also rainfall amounts. Persistent south/southeast downslope flow will result in shadows of lower rainfall amounts and diminished rain coverage to the north of terrain and on the lake plains. For these areas rainfall totals will average a tenth to a quarter inch, with the greatest rainfall amounts east of Lake Ontario where around a half inch of rain is expected. Southerly downslope winds will continue Wednesday, and the lake plains may see a period of completely dry weather Wednesday morning due to a mid level dry slot and the drying influence of downslope flow. However, the frontal zone will remain draped from the Ohio Valley to Central NY, and this along with diurnal heating/instability will support an uptick in showers Wednesday afternoon. While there will not be much surface based instability during this event, there will be elevated instability which could support some thunderstorms embedded in heavier showers this afternoon through Wednesday evening. The surface low will track to our north and into southern Quebec Wednesday night, with a trailing cold front moving across our region. This will bring another round of showers to the area, especially east of Lake Ontario which will be closer to the upper level trough. This will bring another half inch or so of rainfall to that region. During this time temperatures will average above normal, especially overnight lows. The lake plains will be the warmest locations due to warming from the southerly flow downsloping. && .SHORT TERM /THURSDAY THROUGH FRIDAY/... Dry air filters into the region Thursday as the mid-level trough axis moves east of the forecast area. The strong ridge will move into the Great Lakes region while the potential tropical storm moves into the southeast U.S. through Thursday night. A strong southeasterly jet will transport moisture into the Mid-Atlantic region and central Appalachians, however the strong ridge will suppress moisture south of the forecast area. By Friday, the remnants of any tropical storm will move northward while high pressure extends into the forecast area from Quebec. Dry weather will continue across the forecast area. Temperatures will be slightly above normal with highs in the low to mid 70s Thursday and Friday and lows in the 50s Thursday night. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... The evolution of the upper low over the Mississippi Valley will be the large scale feature to watch during this period. Ensemble systems show a ridge across the Great Lakes region which should keep the forecast mostly dry, however there are some signals from the ensemble systems that draw the upper low further north and/or open the low into a trough across the forecast area. This could result in increasing moisture and therefore there are low chances of showers across the forecast area through the weekend and into Monday. Temperatures remain above normal through the period. && .AVIATION /17Z TUESDAY THROUGH SATURDAY/... An upper level trough will slowly dig across the Great Lakes through Wednesday. A round of steady rain showers with a few embedded thunderstorms will move from west to east across the area through tonight. Rain will be moderate at times, reducing vsby to MVFR. Cigs will vary, with southerly downslope flow helping to keep the lake plains mainly VFR/MVFR despite the rain. This includes KBUF/KIAG/KROC/KART. Mainly IFR cigs at KJHW, with fog possible tonight. Expect a break in the showers for most locations Wednesday morning as a LLJ exits to the east. However, showers and a few thunderstorms will expand in coverage Wednesday afternoon due to diurnal heating, especially from the Genesee River valley eastward. Outlook... Wednesday night...MVFR/IFR with showers likely. A few widely scattered thunderstorms possible. Thursday...MVFR east of Lake Ontario with a chance of showers. Becoming mainly VFR elsewhere. Friday through Sunday...Mainly VFR. Local IFR in valley fog across the Southern Tier possible overnight into the morning. && .MARINE... A moderate pressure gradient will remain in place over the eastern Great Lakes through Wednesday between persistent high pressure over the Canadian Maritimes and low pressure moving through the central Great Lakes. This will maintain moderate southeasterly flow through Wednesday, with the strongest winds on the east half of Lake Ontario tonight through the first half of Wednesday. 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 Wednesday night 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 from 7 PM this evening to 8 AM EDT Wednesday for LEZ040-041. Small Craft Advisory from 10 PM this evening to 2 AM EDT Thursday for LOZ045. && $$ SYNOPSIS...Apffel/Hitchcock NEAR TERM...Apffel/Hitchcock SHORT TERM...HSK LONG TERM...HSK AVIATION...Apffel MARINE...Apffel/Hitchcock