Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
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303 FXUS61 KPBZ 040046 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 846 PM EDT Wed Jul 3 2024 .SYNOPSIS... A series of disturbances will create periods of scattered thunderstorms tonight through Friday, offering low probabilities for localized flash flooding and gusty wind. Dry weather with seasonable temperature are expected to return Saturday into Sunday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... KEY MESSAGES: - Isolated to scattered showers and possible thunderstorms expected through the overnight period. ------------------------------------------------------------------- 845 PM Update... A broken line of showers and thunderstorms continues to advance across the Upper Ohio Valley region this evening, ahead of a shortwave trough/vorticity maximum. The latest mesoanalysis shows most of the ML CAPE has waned across western PA, with levels around 500 j/kg across eastern Ohio. The 00Z PIT sounding also indicated poor mid level lapse rates, with warm temperatures aloft. Radar continues to show the line of showers/storms weakening and dissipating as it tracks eastward and outruns the instability. Isolated to scattered showers will continue overnight as the shortwave completes its passage. A rumble of thunder will also be possible with minimal elevated instability, though this potential appears low. Otherwise, mostly cloudy skies are expected overnight. Patchy fog is possible, especially across the PHD-ZZV area, where thunderstorms occurred today. It will be a warm night, with temperatures around 10 degrees above average. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... KEY MESSAGES: - Scattered to numerous showers and thunderstorms are likely Thursday, favoring locations along and south of I-70. These storms may pose a localized flash flood threat. - More widespread coverage is expected Friday, with damaging wind and flash flood threats remaining possible. ------------------------------------------------------------------- Broad west southwest flow will remain in place over the Upper Ohio River Valley region as the main trough axis sits over the Central Plains Thursday and Friday. A series of shortwaves will traverse the region within this flow and tap into the warm, humid environment to create periodic shower and thunderstorm chances. For Thursday, a stationary boundary laying roughly along the I-70 corridor will serve as a focus for convective development throughout the day; areas to the south are thus more likely to see convection while a gradient of decreasing probabilities exist to the north. Modest instability (around 1000 J/KG), weak lapse rates, and weak forcing should limit concerns for damaging wind and localized flash flooding but low probabilities remain given near record PWAT values, enough column shear, and potential for some storm training with parallel storm flow and surface boundary. The afternoon to evening period, where surface based instability is maximized, is likely when those threats are maximized before trending down overnight. For Friday, a more organized shortwave will lift the stationary boundary northward as a warm front and push through a late day cold front. Increases in storm motion and lack of parallel boundary flow should temper flash flood risks, otherwise the environment should resemble that of Thursday`s but for most of the forecast region. The afternoon/evening timeframe remains the most likely period of impact of hazardous weather. Passage of the surface cold front and upper shortwave will diminish storm chances Friday night and initiate a period of drier and more seasonable weather. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... KEY MESSAGES: - High probability for dry weather and slightly above average temperature the rest of the weekend. ------------------------------------------------------------------- Confidence remains high as ensembles show strong agreement of dry and seasonable weather developing Saturday and Sunday. This is a result of upper troughing persisting over the Central Plains and the Upper Ohio River Valley within the dry slot of southwest flow (plus surface ridging). Expect near to slightly above average temperature Saturday and Sunday before temperature returns well above normal Monday (think upper 80s to lower 90s) as warm, moist advection increases ahead of the next low pressure system set to cross Tuesday into Wednesday. && .AVIATION /01Z THURSDAY THROUGH MONDAY/... Deeper convection has remained near ZZV while updrafts to the northeast from PHD-FKL have weakened considerably as they encountered diminishing buoyancy. Storms will affect ZZV thru 04/0100-0200 UTC before they continue ewd into increasingly hostile environment. Weakening showers are likely to affect HLG thru 04/0300-0400 UTC. In the wake of the evening convection, mid-level clouds are anticipated, and perhaps a scattered lower deck around 4 kft. By morning, MVFR cigs (1.5-2.5 kft) are anticipated with high likelihood (70-80% probability) for a few hours in advance of an approaching series of troughs, which seem poised to invigorate showers near the srn terminals (ZZV/MGW) around sunrise. Cigs should lift to higher MVFR/VFR by late morning, when broader coverage of showers and storms begins in the early afternoon. Greatest coverage appears to be focused from ZZV-LBE during the 04/1900-2300 UTC timeframe before diurnal stabilization weakens their potential. .Outlook... Additional rounds of showers and thunderstorms (with occasional restrictions) are then expected episodically through early Sat as a cold front slowly crosses. VFR should return Sun amid high pressure. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...Frazier NEAR TERM...WM/Frazier SHORT TERM...Frazier LONG TERM...Frazier AVIATION...Cermak/Kramar/Rackley