Area Forecast Discussion
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000 FXUS61 KPBZ 231730 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 130 PM EDT Wed Aug 23 2017 .SYNOPSIS... Calm weather is expected today before a low chance for showers returns on Thursday. Below-average temperature and less-humid air will continue through the weekend. && .NEAR TERM /THROUGH TONIGHT/... Steep low-level lapse rates will support modest instability sufficient to generate a cu field by early afternoon, but the lowering inversion height will limit vertical depth and any chances for precipitation. If a fetch off the lake can inject a moisture plume into this environment, isolated showers will be possible, but the probability is too low to mention. A low-amplitude shortwave trough is depicted in most models to move through this evening, grazing the nrn section of the forecast area and generating light precipitation. Minimal PoPs were included with this feature, which primarily will offer increasing cloud cover. Overall, today`s temperature will end up below seasonal averages with maxima in the mid 70s and lows in the upper 50s. && .SHORT TERM /THURSDAY THROUGH SATURDAY/... A broad upper trough in the ern CONUS will dominate the wx pattern through much of the remaining forecast as an upper ridge amplifies in the central CONUS. On Thu, a shortwave trough will impact the Ohio Valley, leading to increased cloud cover and slightly-increased chances for rain showers. Coverage and amount of rain will depend on atmospheric moisture return, which will be meager amid sfc high pressure. So, PoPs were increased, but QPF remains light. Beyond Thursday, northwesterly flow will remain entrenched. As such, continental dry air will maintain sway over the area. This will limit precipitation chances and keep temperature largely below seasonal average with a fairly-wide diurnal spread due to a dry boundary layer. && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... Surface high pressure builds swd from the Great Lakes. With northerly flow on the front end, temperature below seasonal average is expected to continue into the middle of next week. By next Tuesday, moisture streaming from the Gulf in association with tropical system Harvey may provide a canopy of high clouds, but still plenty of time to resolve that over the coming days. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... VFR conditions are expected through the TAF period with diurnal CU under building surface high pressure. Some MVFR restriction are possible Thursday morning with isolated morning fog through 14Z. .Outlook... No widespread restrictions expected under surface high pressure. MVFR possible in morning fog Friday through Saturday. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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