Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
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972 FXUS61 KPBZ 250105 AAA AFDPBZ Area Forecast Discussion...UPDATED National Weather Service Pittsburgh PA 905 PM EDT Tue Sep 24 2024 .SYNOPSIS... Scattered showers and a few thunderstorms will move across the area at times through Wednesday, ahead of a slow moving cold front. Rain chances return Friday into the weekend with low pressure. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... KEY MESSAGES: - Scattered showers and possible thunderstorms tonight ------------------------------------------------------------------- The latest surface analysis shows surface low pressure across Michigan, with a warm front extending through NW PA. A cold front extends south from the low. The latest mesoanalysis shows ML CAPE decreasing over the past few hours, with a diminishing trend in the 0-6km shear as well. A shortwave trough/upper low remains across the Midwest. Individual shortwaves embedded in SW flow ahead of the trough will maintain isolated to scattered showers at times overnight as they track across the Upper Ohio Valley region. With the waning instability and shear, the severe weather potential diminished. The potential for thunder will continue mainly west and south of PIT early this evening, before that also ends. Similar to recent nights, temperatures will average around 10 degrees above seasonable levels with cloud cover in place. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/... KEY MESSAGES: - Rain chances continue through mid-week. ------------------------------------------------------------------- Showers and weak thunderstorms will likely be ongoing early Wednesday morning as a trough continues to move across the Ohio River Valley. The potential of strong storms will be considered low given weak instability and the absence of a lifting mechanism. By 8am Wednesday, the cold front will likely be positioned in western Ohio and stall due to the mean flow orientated parallel to the boundary. Showers and storms may redevelop in eastern Ohio along the stalled frontal boundary and along any moisture/temperature gradient boundaries that develop after 12pm. Shower and storm potential is expected to decrease after 10pm with the loss of surface heating. Above average temperatures are expected through this time period under deep southerly flow. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... KEY MESSAGES: - Uncertainty increases greatly for the end of the week with Tropical Storm Helene. - Rain chances will continue through the end of the week. ------------------------------------------------------------------- The central CONUS trough may interact with Tropical Storm Helene as it moves inland out of the Gulf. Meanwhile, the northern stream trough will be sliding across the Northeast states. Ensemble clusters all show that the remnants will be absorbed by the trough but with much uncertainty after that. The highest probability scenario at this time is that the northern stream trough deflects the remnants off to our west and rain chances stay low. There are potentially wetter solutions with a track further east; one of the members depicts 2-3 inches of rain with this outcome. However, there is a 10% chance of exceeding 2 inches of rain in 24 hours with 13Z NBM run. If impacts do evolve from Helene, it would likely be Friday into Saturday. By Monday into Tuesday, the remnants of an upper-level low associated with Helene will weaken near our southwest of the Ohio River Valley and drift east as a trough over the Dakotas ejects southeast. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/... Scattered showers will continue to cross the area through the evening and into the early overnight. Some minor instances of restrictions are possible through the evening. Deteriorating conditions are expected late tonight into Wednesday morning with ensemble guidance suggesting a greater than 70% chance of MVFR cigs (30-50% chance of IFR) at all terminals by or shortly after sunrise. Additionally, any locations that saw heavy rain today will likely see some amount of fog development overnight, further impacting flight categories at area airports through sunrise. Another round of showers and thunderstorms are expected through dawn and through midday. This will impact cigs through the coming day as well. Expect intermittent restrictions through the day tomorrow with passing thunderstorms. .Outlook... Some improvement is expected Wednesday, with a 80% chance of VFR everywhere except FKL/DUJ, though very isolated showers and storms may bring temporary cig/vis drops. Widespread restriction chances increase again Thursday morning, before VFR returns to close out the work week. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...WM NEAR TERM...WM SHORT TERM...Hefferan LONG TERM...Hefferan AVIATION...Cermak/Shallenberger