Forecast Discussion

Synopsis...

High pressure to our south will continue to keep summer-like conditions across the region. As Hurricane Earl moves closer to shore on Friday (not expected to make landfall), an upper level trough will be approaching from the west dragging a cold front across the state. The trough axis passes on Saturday meaning the chance for showers will continue until then. Conditions improve for Sunday.

Short Term (through Thursday)...

Other than a few fair weather cumulus, the weather for Wednesday and Thursday seems to be calm. High pressure to our south is fairly strong (around 1022 mb) and will help to keep us stable. Temperatures will generally be the same as they were on Tuesday which  is consistent with the GFS MOS. Early morning fog will be likely in the valleys as well.

Long Term (Fri-Sun)

Here is where the forecast gets fun/tricky! On Friday, we have Earl to our east and a cold front to the west. Current thinking is that Earl does not make a landfall in the Northeast US, but it will throw some clouds and showers in our SE zones. Cold front passes through the west in the late morning on Friday, through central PA during the afternoon and through eastern PA in the evening. This is consistent with the 0Z run of the GFS. While the previous disco kept most of PA dry, we thought there was still enough energy with the front to at least mention the chance of showers and storms with the FROPA. Temperatures on Friday will vary depending on where you are in the state. The axis of warmer air will stretch from the Capital region to NE Pa while clouds from Earl will keep SE PA cooler. The cold front will drop temperatures in the west before daytime heating can max out. Temperatures behind the front will drop our highs on Saturday a good 15-20 degrees. Saturday, the 500mb vort max finally leaves PA by the afternoon which is why we kept mostly cloudy skies and the chance for showers into mid-day Saturday. After the upper level trough lifts out of the region, high pressure starts to build back in for Sunday helping to clear us out and bring temperatures closer to average. 

-Adam Del Rosso