Area Forecast Discussion
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973 FXUS61 KPBZ 300944 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 544 AM 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 /UNTIL 6 PM THIS EVENING/...
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Minimal change needed at this time to the ongoing forecast based on latest observations and trends. The previous discussion follows.. An approaching shortwave will help lift a stalled surface boundary north across the forecast area today and upper level divergence will also increase as the area transitions to a more favorable position under the jet. This combined with a moist and unstable boundary layer will in more convective coverage today. Progged instability is marginal with slim profiles and even the chronically overdone NAM forecasting cape values to remain under 1000, so the severe threat is low. Forecast precipitation amounts over the 24 hour period will range from a quarter inch across far southwestern zones, increasing to the northwest up to three quarters of an inch on average over Jefferson and Forest counties where the greatest synoptic lift will be. Locally higher amounts will be possible at locations that see deeper convection with PWATs around 1.75" on average and warm cloud processes dominating but overall rain rates should remain reasonable given the marginal instability.
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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 FRIDAY/...
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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.
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&& .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
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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.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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