Area Forecast Discussion
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000 FXUS61 KPBZ 220513 AAC AFDPBZ Area Forecast Discussion...UPDATED National Weather Service Pittsburgh PA 113 AM EDT Thu Jun 22 2017 .SYNOPSIS... Chances of showers and storms will continue into the weekend. Cooler weather arrives next week. && .NEAR TERM /THROUGH TODAY/...
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Only changes to the overnight period, is the addition of slight chance PoPs over the southern half a few hours before dawn. Models are all hinting at light showers developing ahead of a weak shortwave moving southeastward in the northwest flow aloft. Currently, the upper level wave is not producing showers, but as it moves over the Upper Ohio Valley, it will encounter an atmosphere of higher moisture content with surface dewpoints well into the 60s. Additionally, we still have a surface boundary laying over the area, which is discernible by a wind shift and dewpoint differences. The wave will clear the area shortly after dawn. Upper level heights will rise today, which will assist in dragging the stalled boundary northward. This will in turn allow the more humid air to overspread much of the region by late in the day. As heights rise, another shortwave will ride over top of the weak ridge and provide the risk for afternoon showers and storms, mainly north of PIT. This wave will also flatten the ridge by late in the day. With the increasing humidity, surface temperatures will rise with warm advection and increasing mixing heights.
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&& .SHORT TERM /TONIGHT THROUGH SATURDAY/...
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More substantial upper level energy will stream northward from the lower Ohio Valley tonight. These waves will follow the intensifying southwest flow aloft, as the remnants of TS Cindy move over the Lower Mississippi Valley. Deep moisture, tropical in nature, will also stream northward which will bring widespread rain to the area Friday and Friday night. Warm rain process will develop on Friday, creating a scenario for very efficient rainfall. As the rain overspreads the region, a surface cold front will move across the Upper Midwest, reaching Western Ohio by late in the afternoon. It is a good bet that rainfall will intensify ahead of the boundary Friday afternoon, so the eastward progression of the front will need to be monitored closely in future model runs. Currently, models are showing the highest risk for heavy rain, arriving late Friday afternoon and Friday night. In addition to closely watching the progression of the front, where the remnants of TS Cindy go, once they phase in with the upper level flow, will also be critical. It will take all of Friday night for the front to exit to the east, meaning the risk for heavy rain will continue into early Saturday. Drier air sags through the area on Saturday behind the exiting front. This will allow for the area to finally start to dry out and cool down.
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&& .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... A stark shift in the upper level pattern looks to occur by early next week. Model and ensemble projections all favor deep troughing settling over the region by that juncture. With this, much colder air aloft combined with northwesterly surface flow will mean temperatures well below normal with chances of showers as cold air aloft migrates through the region. && .AVIATION /05Z THURSDAY THROUGH MONDAY/... Showers have moved east of terminals for the evening, and general VFR is expected through the period. Frontal boundary near ZZV and MGW will be pulled northward on Thursday with the chance for scattered convective activity continuing. .OUTLOOK... Widespread restrictions are likely Friday and Friday night with the encroachment of a cold front. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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