728 FXUS61 KPBZ 111501 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1101 AM EDT Thu Oct 11 2018 .SYNOPSIS... A crossing cold front will end rain showers from west to east today. Temperatures will become much cooler tonight, and remain below normal through the weekend. The next good chance of rain arrives with a Friday night disturbance. && .NEAR TERM /THROUGH TONIGHT/... Previous forecast remains on track. The back of the primary shield of precipitation currently stretches along an axis from the Ohio River in WV towards Pittsburgh and areas NE. A few scattered showers remain towards the west... but will diminish through the morning hours as they move eastward. The front currently (as of 12z) lags just behind the precipitation from near Erie PA towards Columbus Ohio and will push through the Allegheny Plateau through the remainder of the morning and clear the ridges by the afternoon. The heaviest rain will fall in the eastern CWA, with around an inch possible. Some brief downpours may be observed with high PWAT and deep warm cloud depths, but the overall progressive nature of the system will keep rainfall totals in check. Temperatures will steady out, or perhaps even fall a bit this afternoon behind the front, but the strongest cold advection will wait until the nighttime hours. Expecting the radar scope to be clear at 00Z Friday. However, as low-level flow turns northwest during the evening, cold advection ramps up and opens the door to our first round of subzero 850mb temperatures of the season. This with lingering low-level moisture will allow isolated showers to bloom, especially north of Pittsburgh and along the ridges. Model soundings come tantalizingly close to allowing for a few flakes, but the boundary layer should remain warm enough to keep precipitation liquid. Likewise, lingering clouds and a stirred boundary layer should keep frost possibilities in check across Ohio. Nevertheless, low temperatures Friday morning will end up 20 to 25 degrees colder than those this morning. && .SHORT TERM /FRIDAY THROUGH SATURDAY/... Subsidence and thinning moisture will shut off the isolated showers by midday Friday, although enough moisture will remain trapped underneath a stout inversion to keep clouds around for a while. Some locations will struggle to reach 50 degrees during the day. A fairly potent shortwave will cross Friday night into Saturday morning, bringing the next chance of rain showers. Precipitation will be light, but likely PoPs are appropriate. Model soundings are showing a bit more moisture in the dendritic growth layer, and sufficient depth of cold air, to allow for a few flakes to mix in across the higher ridges above 3000 feet. However, no accumulation will be mentioned. Precipitation departs with the shortwave by midday, and some sunshine should be seen areawide by afternoon as surface high pressure builds in. Much below normal temperatures will linger. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... A general troughing pattern will remain in place through this period, keeping temperatures below normal. If clear sky can linger Saturday night, Sunday morning may represent our best chance of seeing some frost. Temperatures may recover a bit Sunday afternoon as flow turns southwest around the departing high. However, a frontal boundary will bring renewed rain chances by Sunday night, with temperatures dropping back well below normal behind the front on Monday. Continued disturbances moving through the trough will keep some low shower chances going into midweek. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... Varying ceilings from 500 to 1500 feet will continue through much of the region through the remainder of the morning and into the early afternoon hours. A cold front will pass through the area and most terminals by late afternoon, with improving ceilings west to east as it passes. A cool NW flow will commence later this evening, bringing MVFR ceilings with a lake-enhanced stratocumulus deck. Outlook... Periodic restrictions are expected Fri/Sat with cool NW flow and a crossing trough. Restrictions potential returns with a late Sun/Mon cold front. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$