Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 220520 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 120 AM EDT Sun Oct 22 2017 .SYNOPSIS... Beautiful indian summer weather will continue across the region through at least late Monday afternoon...as high pressure along the Mid Atlantic coast will supply us with conditions more typical of late August or early September. A complex storm system will then usher in a pronounced change in our weather...with a soaking rain Monday night into Tuesday followed by much cooler temperatures Wednesday and Thursday. && .NEAR TERM /THROUGH TODAY/... High pressure anchored along the Mid Atlantic coast will provide us with a fine night across the region...as a deepening southerly flow will help to hold our temperatures some 10 degrees higher than those of early this morning. Mins will range from the 40s across the North Country and in the cooler Srn Tier valleys to the lower to mid 50s elsewhere. Sunday will be an encore performance of Saturday`s weather...as sunshine through high clouds will combine with H85 temperatures in the teens Celsius to generate afternoon temperatures in the mid to upper 70s in most areas. Perfect weather for getting out to view some of our picturesque Fall foliage. && .SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/... Pattern change set to take place during the period as the mid level ridge shifts east and a deepening long wave trough settles across the northern tier of states and into the Great Lakes. Latest operational model solutions continue to trend toward a slower onset of precipitation. The development of a cutoff low over the Gulf coastal states will slow the eastward progression of the main upper trough axis limiting the northward stream of gulf moisture until very late Monday into Monday night. Will ramp up precipitation probabilities starting late Monday afternoon in the west with categorical by early Monday night, as negative tilted upper trough swings moves into the Great lakes and surface low moves into the Ohio valley. Due to the uncertainty of the interaction with the cutoff low, confidence in the exact placement of the heavier rain axis is low. Nonetheless, a rainfall event of an inch or more is likely through Tuesday, The longwave trough will settle into the Great Lakes/Ohio Valley Tuesday/Tuesday night. Model solutions have trended deeper with this feature. This will keep a chance/likely showers in the forecast through this time period with the highest probabilities on Tuesday. The delayed onset of precipitation Monday will allow for another well above normal day with most temperatures reaching the upper 60s to lower 70s. Coldest air is not set to arrive until after Tuesday, so likely looking at temperatures Tuesday in the mid to upper 60s across eastern sections, with upper 50s to lower 60s across the west. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... Wednesday through Thursday a sharp mid level trough will very slowly cross the eastern Great Lakes and New England. Cool temperatures aloft, wrap around moisture, and increasing lake induced instability will produce scattered showers and some lake effect rain showers both Wednesday and Thursday. The lake effect rain will likely remain disorganized most of the time, with the placement of the mid level low overhead yielding moderate boundary layer shear and short fetch northwest flow. The lake effect rain showers will end by Friday as high pressure briefly builds over the eastern Great Lakes. Model differences become more significant by Saturday, with the GFS being faster than the ECMWF with the next system. Given the model differences, have just gone with a low chance of rain showers for next Saturday. Temperatures will bottom out Wednesday and Thursday as 850mb temps drop to around 0C. This will support highs in the 50s in most areas, with higher terrain possibly staying in the upper 40s if enough cloud cover persists. Temperatures will begin to warm by Friday and Saturday as southwest flow increases ahead of the next system. This warming trend will be temporary however. Looking a little farther ahead, the overall pattern evolution over the next two weeks will be for a steady turn towards cooler weather as a longwave trough becomes established over central and eastern North America. This pattern change will be in part driven by the poleward movement of the remnants of Typhoon Lan in the western Pacific by the middle of next week. The resulting influx of latent/sensible heat and vorticity into the mid latitude westerlies will strongly amplify the Pacific wavetrain, which in turn will drive amplification downstream into North America. By the middle of next week, a strong Aleutian Low will force a ridge to build over the Gulf of Alaska, which will drift to the west coast of North America by next weekend. This western ridge is forecast to last into the first week of November, and aid in forcing a deep longwave trough over central and eastern North America. This will bring more fall like weather for the last week of October, and the possibility of the first wintry weather during the first week of November. Stay tuned. && .AVIATION /05Z SUNDAY THROUGH THURSDAY/... For the 06Z TAFS VFR flight conditions are found and these flight conditions are expected to continue through the TAF package...with light winds. Outlook... Monday...VFR. Monday night and Tuesday...MVFR/IFR with occasional rain. Wednesday and Thursday...VFR/MVFR with a chance of showers. && .MARINE... High pressure along the Mid Atlantic coast will keep generally light winds and negligible waves in place across the Lower Great Lakes through the remainder of the weekend. Winds and waves will remain well below small craft advisory levels on Monday as a complex storm system will take shape over the Ohio Valley. It will become quite unsettled Monday night into Tuesday though...as notably stronger winds will accompany the passage of the deepening storm system. Small craft advisories can be expected from this event. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...JJR/RSH NEAR TERM...JJR/RSH SHORT TERM...TMA LONG TERM...HITCHCOCK AVIATION...THOMAS MARINE...RSH

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