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Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
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001 FXUS61 KPBZ 122342 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 742 PM EDT Mon Aug 12 2024 .SYNOPSIS... Surface high pressure will keep mostly dry conditions and slowly warming temperatures in the forecast through mid-week. Rain chances increase by the end of the week as a more unsettled weather pattern develops. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... KEY MESSAGES: - Temperatures will remain near to below seasonal averages. - Dry weather is forecast, with patchy valley fog north of Pittsburgh. ------------------------------------------------------------------- Update... Cumulus will continue to dissipate this evening as temperatures fall below convective thresholds. No other changes for the evening update. Previous discussion... Some mid and upper clouds may stream across locations mainly south of Pittsburgh tonight, as weak shortwave energy rotates through the approaching main trough axis. To the north, some patchy valley fog will be possible due to relatively clear skies, light wind, and the near to just below normal temperatures expected. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/... KEY MESSAGES: - Temperatures will show a slow warming trend into midweek. - An isolated shower or two is possible Tuesday, with a dry Wednesday. ------------------------------------------------------------------- The main trough axis swings through the region on Tuesday. A marginal moisture increase may be enough to help generate a few light rain showers during the peak heating hours. Still, the presence of warm air in the mid-levels, as well as surface high pressure providing subsidence, should keep this activity isolated at best, as well as prevent the occurrence of thunder. Temperatures may run a degree or two warmer as compared to today. Forecast soundings on Wednesday indicate that a touch of warming and drying will occur off of the surface due to mid-level subsidence behind the departing trough. With high pressure still in control at the surface, another dry day is forecast, with a continued slow warming trend thanks to the rising 500mb heights. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... KEY MESSAGES: - Dry and warm weather is forecast for Thursday. - Forecast uncertainty increases toward the end of the week with a shift to a more active pattern. ------------------------------------------------------------------- The upper trough axis will be off of the Atlantic Seaboard come 12Z Thursday, putting the Upper Ohio Valley in northwest flow aloft ahead of an advancing Great Lakes ridge, while surface high pressure begins to depart. Cluster analysis shows good model agreement to this point. One more dry day and a continued warming trend are forecast with reasonably high confidence. Thereafter, differences do start to increase among the ensemble guidance, although the overall spread seems a bit less than yesterday. The next trough advancing from the western CONUS is expected to bump into the advancing ridge, and the models begin to disagree on timing, as well as to the degree that the ridge is impacted by the trough. Model clusters still show some variance, depicting either quasi-zonal flow or troughing aloft into the weekend, with ridging solutions becoming a bit less likely. Nevertheless, the overall depiction shows a more active weather pattern overall, with rain chances in the forecast for Friday into early next week. The possible range of 500mb heights suggests that daytime temperatures will generally remain near or just a touch below normal through this period, while the active weather points to minimums a bit above normal. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... VFR is expected for most airports through the TAF period. The exception is FKL and DUJ, where IFR to MVFR river valley fog is possible Tuesday morning. Otherwise, expect an increase in mid and high clouds overnight ahead of an approaching shortwave trough. In addition, a scattered to broken diurnal cumulus layer is expected on Tuesday as convective temperatures are reached, and as the shortwave crosses the Upper Ohio Valley region. The cumulus should dissipate by Tuesday evening, with mainly clear skies expected under high pressure. .Outlook... VFR is expected through Thursday under high pressure. Periodic restriction chances return Friday through the weekend with slow moving low pressure. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...22/MLB NEAR TERM...WM/CL SHORT TERM...CL LONG TERM...CL AVIATION...WM