Area Forecast Discussion
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000 FXUS61 KPBZ 230530 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 130 AM EDT Fri Jun 23 2017 .SYNOPSIS... Downpours are possible through Friday night with a tropical airmass in place. A cold front sweeping through early Saturday will return comfortable humidity levels by the weekend. && .NEAR TERM /THROUGH TODAY/...
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Rain showers associated with an upper-level shortwave are entering our southern zones as of 1am. These light to moderate showers will slide north-northeast this morning following the shortwave, bolstered by mid-level speed convergence and upper- level divergence. Despite any evidence of embedded thunderstorms, rain rates may increase with this activity in the pre-dawn hours as it lifts northward. This is due to an increasing 850mb jet that will continue to feed moisture into this already moisture-laden atmosphere. This will pre- condition much of the Flash Flood Watch area with around a half an inch of rain, before the heavier rain chances arrive later today. The already hard hit areas of Armstrong and Indiana Counties will also see this rain before daybreak. Flash Flood Warnings continue for these locations. The remnants of Cindy pass Friday afternoon and evening. This will bring a widespread area of showers and storms to the region especially south of I-70. There should be not a lot of precipitation around during the morning and early afternoon hours, however with the approach of a the cold front during the afternoon hours this will trigger storms and interact with moisture associated with Cindy.
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&& .SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
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The cold front crosses during the overnight hours Friday night so come daylight Saturday any measurable QPF should be east of the mountains. Clearing will rapidly take place before 15Z then a cu field will develop during the afternoon hours. Humidity levels will be noticeable lower as dewpoints drop into the 50s some 20F lower than today. Benign weather Saturday night with moisture arriving from the northwest ahead of the next upper disturbance.
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&& .LONG TERM /SUNDAY THROUGH THURSDAY/... Highlights: - Cooler weather - No signs of a high water threat Full latitude trough will bring a period of below normal temperatures to the region. Afternoon high temperatures will be running nearly ten degrees below their normal benchmarks Sunday - Tuesday. With the trough axis overhead, scattered showers and perhaps a thunderstorm are possible through mid week, but with low level moisture lacking due to the placement of high pressure southeast of the western Great Lakes. A transitory high pressure takes over at weeks end bringing temperatures back to their normal location and returning dry weather. && .AVIATION /05Z FRIDAY THROUGH TUESDAY/...
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Most ports begin the 06z TAF period with VFR conditions, but these should deteriorate rather quickly. An upper-level shortwave trough will spread light to moderate rain north- northeast in the pre-dawn hours, lowering ceilings to low MVFR and perhaps IFR. Keeping most ports in low MVFR through daybreak, with gradual lifting through the afternoon. Restrictions will likely continue through Friday as the remnants of Tropical Storm Cindy merge with an approaching cold front. Showers, thunderstorms, and low ceilings will be common Friday afternoon through the evening. Wind will remain WSW through the period, with gusts expected Friday afternoon. .OUTLOOK... Widespread restrictions are likely through Saturday morning with the passage of a cold front.
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&& .HYDROLOGY... A flash flood watch has been issued for areas along and south of interstate 70. Allegheny and Westmoreland counties are also included because of lower guidance in the urban areas, as well as Armstrong and Indiana county because of flash flooding that already occurred Thursday afternoon. The main concern would be QPF Friday afternoon and evening. Meteorologically values all point to high water issues with PWATS over two inches, warm cloud depths above 13KFT, and a strong low level jet. GEFS M-Climate values are near or at record levels for PWATS on return interval, and climate anomaly. && .PBZ WATCHES/WARNINGS/ADVISORIES...
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MD...Flash Flood Watch through late tonight for MDZ001. OH...Flash Flood Watch through late tonight for OHZ057>059-068-069. PA...Flash Flood Watch through late tonight for PAZ021>023-029-031- 073>076. WV...Flash Flood Watch through late tonight for WVZ002>004-012-021- 509>514.
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&& $$

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