Unsettled weather tomorrow, then pleasant again

Synopsis:

The essentially rain-free conditions that we have been experiencing for the past week will end tomorrow. A strong cold front that is advancing from the upper Midwest will give all areas of PA rain for tomorrow, along with a few isolated thunderstorms. There will be some pretty heavy amounts of rain - the models are agreeing on 2-3" for many areas of PA - and the thunderstorms could be quite strong. However, once the front passes through, we can expect more sunshine and pleasant temperatures through the end of the work-week. A couple of upper-level lows will roll through to the NW of us, possibly giving extreme NW PA an isolated shower or two on Thursday and Friday. Saturday, the 500-mb heights dip down a fit further south, and force the next system to move further south, giving some areas of PA a better chance of a few showers.

 

Short-term (Monday and Tuesday):

 

With high pressure moving eastward away from us, two systems will be allowed to move towards the Commonwealth. One is a slow-moving front in the deep South that is throwing some moisture northward towards PA. The second system is a cold front advancing from the upper Midwest. The slow-moving front has a lot of moisture to work with (drawing it up from the Gulf of Mexico). The cold front has some moisture with it, but not as much. With the 500-mb heights the way they are, the cold front is moving along faster than the system in the South, so the two are expected to merge sometime late Tuesday. The SREF 03Z run seems to slightly reduce the amount of rain forecasted for this system - more in line with 2-3" expected where there will be the most rain, as opposed to 3-4" with the 21Z run. All in all, though, it will be a soaker for tomorrow, so be careful out there.

 

Long-term (mid-week into the weekend):

 

Once the cold front passes, expect drying conditions overnight Tuesday into Wednesday, with more sunshine and cooler temperatures. Considering that we currently in a relatively zonal pattern in the upper levels (500 mb), we will not see any really cold air being drawn down from Canada, but temperatures will be cooler than we've seen recently (a few 50s, but mostly 60s). The upper-level heights will lift somewhat later in the week, as milder air is drawn up again. We will see temperatures in the upper 60s and 70s by Friday before our next system arrives on Saturday. However, with a fairly persistent area of upper-level high pressure, the showers won't be really widespread. Sunday looks to be a little more wet, however. But before then, we should see pleasant conditions and temperatures for the last week of summer!