Area Forecast Discussion
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000 FXUS61 KPBZ 230638 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 238 AM EDT Wed Aug 23 2017 .SYNOPSIS...
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Quieter weather today before showers return Thursday. Cooler and less humid are the themes through the weekend.
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&& .NEAR TERM /THROUGH TODAY/...
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A cold front extends from around Seven Springs toward Hundred, WV, as of 230 AM. This should continue to hold itself together fairly well as it transits to the southeast given the rather abrupt density discontinuity along the front in the lower levels as dewpoints drop from the 70s in the 50s over a fairly short distance between northern WV and Cleveland. With the drop in dewpoints in mind, while some fog has developed, once northwesterly dry advection begins in earnest in the boundary layer, it would seem additional fog development will become unlikely fairly rapidly. While some 3-5 mile visibilities will be possible through morning, dense fog seems unlikely given isallobaric flow and drier air moving in. With drier air in most of the column for today, skies should start out mostly sunny across the board save for departing clouds in the southeastern reaches of the area. However, even with a rather dry atmosphere aloft, the mid-level cold pool does transit the southern Great Lakes. This will lead to enhanced lapse rates in the mid-level and some cumulus development. While showers will be most likely generally near and north of Lake Erie, it seems more unlikely that they would spread as far south as I-80. PoPs were kept non- zero, however a mention of showers will not be added to the forecast at this time. Fries
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&& .SHORT TERM /TONIGHT THROUGH SATURDAY/...
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Large scale troughing will be the theme through the short term forecast. With this, one decent wave embedded in the large scale cyclonic flow over the area looks to impact Thursday. A decent chunk of mid-level cold air drops toward the area on Thursday. With this, a fairly vigorous short wave trough will also transit. Moisture content in the layer is lacking, and jet support is modest, so deep convection seems unlikely, however a shower or two with its passage seems plausible. PoPs were thus adjusted to chance levels, skies increased a bit in the peak heating/destabilization hours, and high temperatures knocked back a few degrees due to cloud expectations. Beyond Thursday, northwesterly flow will remain entrenched. As such, continental dry air will maintain sway over the area. This will limit precipitation chances and keep temperatures largely below normal with a fairly wide diurnal spread due to a dry boundary layer. Fries
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&& .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
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The departing mid level trough and associated low pressure system owes to several nice weather days late this week through the weekend. Surface high pressure builds south from the Great Lakes and with northerly flow on the front end expect below normal temperatures to continue into the middle of next week. Toward the end of the forecast /next Tuesday/, moisture from the Gulf resulting from Harvey may provide a canopy of high clouds, but still plenty of time to resolve that over the coming days.
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&& .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... Remaining showers SE of PIT should end overnight as a cold front completes it`s passage. Otherwise, mainly VFR conditions are expected through the TAF period with diurnal CU and SC under building surface high pressure. .Outlook... No widespread restrictions expected under surface high pressure. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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