Area Forecast Discussion
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000 FXUS61 KPBZ 200109 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 909 PM EDT Fri May 19 2017 .SYNOPSIS... Shower and thunderstorm chances will continue ahead of a stalled boundary into tonight. Rain chances will increase by the end of the weekend ahead of an approaching frontal system. && .NEAR TERM /THROUGH SATURDAY/...
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As of 9pm, a severe thunderstorm watch remains in effect for south central portions of the forecast area, including some WV and PA counties. The east-west line of thunderstorms from this afternoon has fallen apart, and the north-south line of thunderstorms has weakened considerably as it moved across Ohio. Although the chance for a severe thunderstorm remains quite low at this point across the watch area, still felt it was prudent to keep the watch at least a little bit longer. Nearly all locations will at least receive some minimal rain as the line continues to weaken and move east. Once the line pushes into central Pennsylvania, an isolated shower cannot be ruled out farther west, but any widespread precipitation chance will be done. 500 mb heights start to rise again Saturday over our area in response to a trough moving into the Mississippi Valley. This will start to push the boundary north again as a warm front. The increase in moisture will allow for scattered showers and storms across mainly the southwest half of the CWA during the afternoon. Severe risk again looks marginal in weak flow. Temperatures will be near normal across the north, and a few degrees above normal in the south.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... This period will feature a healthy amount of rainfall, particularly during Sunday afternoon and evening, where categorical PoPs are appropriate. A shortwave over the upper Midwest will rotate a surface low across the Great Lakes, driving a frontal boundary towards and across our region. Southwest flow will push a very moist air mass over us ahead of the front, with precipitable water values rising to between 1.5 and 1.75 inches. This would be near the top of climatology. Given the relatively slow movement of the front, several rounds of showers and storms are possible, which could leave to heavy rainfall, perhaps even excessive in a few spots. Not enough confidence for an HWO heavy rain mention yet, but will continue to monitor. Above-normal temperatures will continue. && .LONG TERM /MONDAY THROUGH FRIDAY/... Behind the front, near to below normal temperatures will take hold in a general troughing pattern. A couple of systems will provide shower and thunderstorm chances through the period, with chances decreasing toward the end of the period. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
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As of 9pm, current forecast keeps VFR conditions overnight except for a short period of MVFR/IFR conditions associated with a line of showers and thunderstorms. However, widespread MVFR/IFR ceilings are beginning to set up across Indiana into central Ohio. With ZZV already dropping to IFR ceilings, will need to further investigate whether these ceilings will persist and possibly affect sites farther to the east. .Outlook... Restrictions are possible again late Sat thru early Mon with crossing fronts.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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