|Wind||10mph from the ENE|
... Confidence is increasing that well above average temperatures and significant rainfall will overspread the Ohio River Valley this weekend as a deep and slow moving trough builds to our west.
NEAR TERM /THROUGH FRIDAY/... Precipitation chances are decreasing early this morning as dry, warm air advances from the south. The PIT 12Z sounding shows a layer of deep dry air between 1,500ft to 6,000ft. Therefore, a lot of the radar returns from KPBZ are not reaching the surface due to evaporating. In fact, a lot of the low-lvl clouds are mixing out and dissolving based on METAR ceilings across the region.
Warmer temperatures aloft will filter into eastern OH/western PA from the west with a building ridge throughout the rest of the evening. Confidence is high that temperatures will be near or a few degrees above normal this afternoon, ranging in the mid-40s to upper-40s in the lower elevations and upper-30s/low-40s in the higher terrain.
SHORT TERM /FRIDAY NIGHT/... 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 THURSDAY/... 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.