Forecast Discussion
Summary
SYNOPSIS
... Rain chances will be primarily focused south of Pittsburgh today as a front remains stalled across West Virginia. The front will shift back north tonight, returning rain areawide into Saturday. Showers will begin to clear after a cold front Saturday, leaving dry weather for Sunday.
NEAR TERM /THROUGH TONIGHT/... Latest surface and radar analysis shows the nearly stationary cold front continues its slow descent into the Mountain State. This has granted a brief reprieve from rainfall north of the Mason-Dixon, but additional rainfall will shortly expand across southern portions of the area (generally Pittsburgh, south) ahead of another shortwave crossing just north of the front. However, the highest threat for heavy rain overnight continues to be south of the forecast area, closer to the frontal boundary.
As the shortwave exits the area this morning and drier air pushes into northern OH/PA, focus for rainfall will shift south once again, closer to the frontal boundary. This will keep most rainfall for the morning (after sunrise) generally Pittsburgh south, shifting even farther south by early afternoon -- mainly south of the Mason-Dixon. Rain will once again begin to overspread the region from the south this evening as the boundary lifts back northwards as a warm front.
Periods of moderate-to-heavy rain are expected overnight as the warm front lifts north, particularly across eastern OH, which will see mod/heavy rain from the warm front quickly followed by mod/heavy rain ahead of the approaching cold front. Fortunately, this will occur during a brief window, over areas that have seen less rainfall so far than areas farther south. In collaboration with neighboring offices, opted not to expand the Flood Watch into this area. However, this will need to be monitored as the situation evolves.
With the front to our south, area temperatures will be much cooler today than yesterday... topping out in the 40s for most. Temperatures will drop this evening, but begin to rise again overnight with warm advection behind the lifting warm front.
SHORT TERM /SATURDAY THROUGH SUNDAY/... The surface low will cross into the Great Lakes on Saturday, pushing a cold front across our region by Saturday evening. A pre-frontal line of showers and possibly a few thunderstorms will cross the area early Saturday morning. Lingering showers will gradually diminish through the day, clearing with cold frontal passage late afternoon/evening. Behind the front, cooler, drier air will infiltrate the area, leaving dry weather for Sunday.
As the low shifts northeastward on Saturday, tightening pressure gradient will bring the potential to mix down strong wind gusts in the warm sector. Forecast gusts remain just under wind advisory criteria for now (40 kt), but this will need to be monitored. Winds will likely peak later Saturday afternoon with cold frontal passage. With southeasterly winds in place across the ridges, there is also some potential for enhanced downsloping winds early Saturday morning just outside the higher terrain in Westmoreland/Fayette/Indiana counties. This, too, will bear watching, though the signal is not as strong as more recent downsloping events.
Temperatures will warm back into the 60s with perhaps a few 70s in WV with continued warm advection behind the warm front. More seasonable temperatures are expected on Sunday with clearing skies.
LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Generally quiet weather is expected to start the week, though a series of weak shortwave troughs will cross the area and bring slight chances for showers Monday/Monday night. A more vigorous shortwave will cross on Tuesday with PoPs slightly higher in the Chance category. Broad high pressure will return dry weather for Wednesday before much better rain chances return Thursday night into the weekend in advance of the next system.
Temperature through the long term will remain near-normal.