925 FXUS61 KPBZ 071030 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 530 AM EST Thu Dec 7 2023 .SYNOPSIS... Light snow over northwest Pennsylvania this morning should rapidly push east and be out of the area by midday. Southerly flow will then take hold and result in warming trend through Saturday. Widespread rain will arriving ahead of a strong cold front Saturday and Sunday. && .NEAR TERM /THROUGH TONIGHT/... Warm air over the central states is pushing northeast across the Great Lakes and setting up strong warm advection into the New York and northern Pennsylvania areas. Snow is evident on radar across northwest Pennsylvania and HRRR takes this precipitation southeastward along the thermal gradient into the far northeast forecast area during the morning. A dusting of snow is possible in that area but the lift should push rather rapidly to the east by the midday hours. && .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/... Upper ridge crosses the Mississippi River valley this afternoon and heads for the Ohio River Valley. 500 mb heights will rise about 50 meters and readings should climb to near normal this afternoon. Ridge moves overhead later tonight and Friday with 500 mb heights building to near 5700 meters. Temperatures will climb well into the 50s as a result, roughly 15 degrees above normal. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Guidance came into better agreement yesterday and continues to show the same scenario on latest runs where a strengthening short wave trough lifts north across the western Great Lakes on Saturday. Deep southwest flow and continued warming pushes readings to about 60F or nearly 20 degrees above normal as a result. A surface low will likely track from near Chicago into central Ontario on Saturday and push associated cold front into Ohio by evening. This cold front will then sweep across the forecast area Saturday night and Sunday morning, bringing moderate to heavy rain to the entire area. 500 mb heights drop about 100 meters Sunday and another 150 meters Sunday night. Rapid cooling of the airmass is expected during the afternoon and the guidance has been persistent in changing the precipitation to snow before it ends. Experience suggests that this rarely results in significant snow accumulations as the precipitation tends to shut off rapidly in the cold advection regime prior to the column cooling enough to produce snow. The exception may be over the Laurel Highlands and Preston/Tucker Counties in West Virginia where the higher elevations will favor a faster turn over to snow. Several inches of accumulation are possible Sunday evening before the precipitation ends there, but most lower elevations would be at most 1-2 inches. High pressure builds into the Ohio Valley on Monday with northwest flow and some upslope snows continuing over the ridges. 500 mb height rises on the order of 150 meters occur, setting the stage for a return to near normal temperatures for Tuesday and Wednesday as surface high settles over the eastern states. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... Warm-advection driven light snow north of PIT, aided by lift from left exit region jet dynamics, will depart the region during the morning hours. DUJ should be the only terminal to experience brief visibility restriction through 14Z or so. Several terminals have MVFR ceilings currently. These will improve this morning as well as height rises continue from the southwest. The onset of daytime mixing will aid in this process as well. This, combined with a continued surface pressure gradient, will help to support wind gusts of 20 to 25 knots out of the southwest from late morning into late afternoon. Skies will be mostly clear by evening as surface ridging rides north into the Upper Ohio Valley, with diminishing wind as decoupling ensues. VFR conditions and generally light wind will continue through the night. .OUTLOOK... VFR conditions will prevail through Saturday morning. The next impactful system with associated restrictions and rain is expected late Saturday through Sunday. && .HYDROLOGY... Widespread rain of 1 to 2 inches is expected for most of the Upper Ohio River Valley Saturday night into Sunday, with 1.5 to 2.5 inches over the Laurel Highlands and mountains of northern West Virginia. A few inches of snow are on the ground in those mountain areas, which will add to the runoff over the weekend. NBM 90th percentile 72 hour PQPF is in the 2 to 3 inch range. Even with lower amounts, significant rises are expected on area rivers. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...Craven NEAR TERM...Craven SHORT TERM...Craven LONG TERM...Craven AVIATION...CL HYDROLOGY...