Area Forecast Discussion
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000 FXUS61 KPBZ 301614 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1214 PM EDT SAT JUL 30 2016 .SYNOPSIS... Periodic showers and storms will continue through the weekend until high pressure brings the return of dry conditions for much of next week. && .NEAR TERM /THROUGH TONIGHT/...
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As of the early afternoon update time, prior analysis and expectation for shower/storm development and propagation seem to be working out fairly well. Rain rates in excess of an inch per hour have been common, however flooding reports to this point have been rather minor, even in urban areas. Thus, while a flood watch was pondered, it seems spotty advisories for flooding will be sufficient to handle the unfolding scenario at this point. The previous discussion follows with the details... A nearly moist adiabatic profile exists over the CWA as of the 12z KPBZ raob with a freezing level up near 12.5 kft and thus warm rain processes dominating the semi-unstable cloud layer. Steering flow and shear over the area remains rather weak, thus storm movement will be rather slow SW-NE through the day. That said, the sounding PWAT of 1.76 inches is rather soggy, and the presence of a backbuilding 250 hPa jet to the north of the CWA may become problematic during the day. This places the CWA in the right entrance region of said jet with a weak H5 wave approaching from the west. As a result, SWerly propagation of cells is expected during the day with resultant multiple waves of convection likely to move NEward through the area as a result. This will yield the threat of heavy rainfall possibly moving over similar corridors at times during the day. Localized flooding will be possible in this setup, and it has been included in the HWO as a result. Deep moisture in place will keep clouds largely entrenched over the area through the day. While morning lows were elevated because of the clouds, they will not likely be a harbinger of a warm afternoon. Clouds may well keep temperatures largely below normal generally east of New Philadelphia, Ohio. Fries
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... Shower and storm chances will continue on Sunday as the upper trough continues to transition east and the surface low associated with the aforementioned boundary crosses across the north. Drier air will finally begin to move in aloft on the backside of the trough which will bring an end to shower/storm chances by Sunday night. Maintained a dry forecast for Monday under continued dry northwesterly flow, but there is an outside chance of afternoon storms as latest model runs indicate a small jet streak developing Monday afternoon and just enough low-level moisture remaining. May need to include mention of showers/storms in future updates if models show continuity with this feature. && .LONG TERM /TUESDAY THROUGH SATURDAY/... Surface high pressure will build into the area from the western Great Lakes Monday night into Tuesday. This will allow the area to remain in cooler northerly flow even as subsidence builds. A dry forecast will thus be maintained through mid-week. Ridging at all levels of the atmosphere should thereafter increase from mid-week onward as amplification of the pattern is evident on basically all guidance over the upper Mississippi Valley and northern Great Lakes during the second half of the week. This ridge and resultant low level thermal ridge should start to flop over toward our area by Friday, which at this point looks to be the warmest day of the next week or so, when temperatures should push again well above normal. && .AVIATION /16Z SATURDAY THROUGH WEDNESDAY/... General VFR is forecast through the evening with exceptions for isolated convection which will wane with the sun. Mention will be reserved for amendments given the declining coverage and questionable location of cell initiation. Given the frontal position and abundant low level moisture, expect the return of some fog on Saturday morning, although mid level cloudiness is expected to alleviate a widespread IFR threat. Will hedge from previous pessimistic forecast with an MVFR mention. .OUTLOOK /SATURDAY NIGHT THROUGH WEDNESDAY/... Broad upper troughing should maintain periodic shower and thunderstorm restriction potential through Monday. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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