Synopsis
With Sandy finally dissipating and merged within a weakening trough, her remnants will remain in the form of scattered showers throughout the Northeast. Our concern for the upcoming weekend will be the possibility for lake effect precip throughout the northeast area of the state. Beyond this, an approaching surface ridge will work to bring the state some much needed sunshine for the latter part of the weekend.
Short-term (Now through Overnight Friday into Saturday)
Currently, the state is under the influence of a moderately tight (moderate in comparison to Sandy) pressure gradient that is forcing a mean westerly wind across the state. This will help influence gravity wave clouds over the ridges, but more importantly, lake effect precipitation over northwestern portions of the state. Erie is already seeing some lake effect rain, something that only the 12z 4km Nam was able to resolve. Based on its resolution, the most intense lake effect showers will occur along the eastern coast of Lake Erie, with 850 winds helping to extend light showers all the way to Central PA. Overnight Thursday into Friday, scattered light showers will fall along the sloping edges of the ridges leading up to State college, and then dissipating later in the night as clouds become broken. Friday will show the heaviest lake effect rain in Erie and near Bradford, but areas south and east of them will see lighter showers during the afternoon. With the 540 dam line far to our south by then, a viewing of the forecasted soundings show us the potential for mixed precip further away from the lake, with potential for that occurring overnight tonight into Friday for parts in the Northwest, North Central, Ridge/Valley, and Laurel Highland regions. Squall lines perpendicular to the ridges are being resolved for overnight Saturday, but with no convergence of surface winds and NVA, that could end up being just scattered showers along southwestern PA. the east side of the state will enjoy no precip the mean downsloping wings will favor cloud breaking for Friday, with decreasing clouds Saturday as the trough pushes away as well as a weakening surface pressure gradient.
Long-Term (Saturday through Monday)
With the trough aloft receding in conjunction to an approaching surface high, the cloud fraction over eastern PA will decrease as the day rolls along. The influence of lake effect will diminish with weakening surface winds, but the will still be enough energy both in the trough aloft and with the onshore flow to allow for mostly overcast cloudswithin Western PA. as the ridge slowly weakens the pressure gradient, the presence of sun will be felt statewide by Sunday, with more clearing and sun for Monday.
During this time, positive vorticity will get cutoff from the trough aloft and sink toward the south, leading into the development of a potential Nor'easter looking to make landfall next Wednesday. The 12z GFS throws it into New England, but the 12z Euro throws it into us, so keep a watchful eye on the models as we look toward next week!
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