Area Forecast Discussion
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000 FXUS61 KPBZ 231154 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 754 AM EDT Wed Aug 23 2017 .SYNOPSIS... Quiet weather today before a small chance of showers return Thursday. Cooler and less humid are the rule through the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 8am update... Showers have exited the southeast counties as the front exiting the area. Mid and high clouds in its wake for a few hours but otherwise widespread sunshine with scattered CU. Previous Discussion... With the drop in dewpoints in mind, while some fog has developed, by and large the boundary layer has remained fairly mixed due to advection. Further, mid and high clouds in the wake of the front have been limiting radiational cooling. Thus, any fog should be fairly local and minimal. With drier air in most of the column for today, skies trend rapidly toward mostly sunny across the board once clouds depart 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 && .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/... 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 && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... 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. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... Isolated morning fog through 14Z, VFR conditions are expected through the TAF period with diurnal CU and SC under building surface high pressure. Some MVFR restriction are possible Thursday morning. .Outlook... No widespread restrictions expected under surface high pressure. MVFR possible in morning fog Friday through Saturday. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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