Area Forecast Discussion
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603 FXUS61 KPBZ 251826 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 226 PM EDT Thu Aug 25 2016 .SYNOPSIS... Showers and thunderstorms will move through the area this evening and tonight with very warm conditions continuing through the weekend. && .NEAR TERM /THROUGH TONIGHT/... Scattered to broken cumulus remains over the area late this afternoon with dewpoints generally in the 70s across the board. Convection is starting to develop from Indiana into lower Michigan and southwest Ontario ahead of an eastward moving short wave trough. The vast majority of large scale ascent associated with this wave will move to the north of the area, however the trailing edge of the wave combined with an uptick in shear late this evening and CAPEs still elevated due to very high dewpoints will mean a pretty good chance of showers and thunderstorms traversing especially the northern reaches of the CWA late this evening. SPC maintains a slight risk for severe thunderstorms with damaging wind gusts and isolated tornadoes as the predominant threats. In examining the 12z raob, PWATs were already 1.6 inches at that time and KILN revealed 1.9 inches. As soupier air moves in, this will mean that any storms that do develop will likely be copious rainfall producers due to warm rain processes and a very high freezing level. Likewise, this means hail will be a minimal threat as the system moves through. Fries && .SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
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Upper ridge of high pressure centered over the Mid-Atlantic will continue to build through the weekend. This, and a broad area of surface high pressure drifting across our north will keep our area dry through a majority of the weekend with a warming trend. Dewpoint temperatures will drop back down to around 60 by Friday night, but will slowly creep back up through Saturday and into Sunday. By Sunday, the very humid air mass will return with dewpoints in the mid to upper 60s common. This, and a draw of warmer air from the south will combine for high heat indices that may near 100 degrees. How warm we get Sunday may largely depend on the arrival of clouds associated with a disturbance passing well to our north. Model guidance indicates the potential for afternoon/evening showers and thunderstorms as a mid-level wave tries to flatten the upper ridge. With the best forcing riding over the ridge and staying to our north, coverage of showers may be limited. Tax
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&& .LONG TERM /MONDAY THROUGH WEDNESDAY/... Little change in pattern is indicated through the first half of next week with the southern U.S. upper high maintaining grip, but with tropical system encroachment toward the Southeastern Coast. Shortwaves with the zonal flow over the immediate area would support periodic, and diurnally-supported precip chances for the long term. Low-confidence slight to chance POPs were maintained for that eventuality as per the latest Superblend guidance. Warm temperature can be expected given the lack of any significant airmass alteration. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... Showers and a few thunderstorms will encroach from the west during the early portions of the forecast. Expect coverage and intensity to continue to decrease overnight, so have only included restrictions in a tempo group. Shortwave that has sparked the activity will clear the area quickly this morning. Expect a quick return to vfr conditions after sunrise. .OUTLOOK /FRIDAY THROUGH MONDAY/... Periodic restriction chances should persist through Friday with the approach and passage of a cold front. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.