Saturday morning forecast

Synopsis:

 

We are in the midst of a calm weather pattern (pretty unusual for March). A high-pressure system centered over Ontario is funneling in unseasonably cold air, which will continue through Monday. High temperatures will be only in the 30s and 40s for most of the Commonwealth, with lows in the teens and 20s (and possibly a few single-digit readings). There could be a snow shower or two near the PA-MD border overnight towards Sunday morning, but otherwise, nothing to speak of. Tuesday, we begin to see slightly milder temperatures, ahead of a warm front, which will move into Pennsylvania during the night and Wednesday. By Wednesday, expect widespread precipitation - a wintry mix in the morning, but mainly rain in the afternoon. Also, temperatures will be milder in the warm sector of the storm system, but then they will drop again behind the cold front. It will not be as cold, however, as it is going to be this weekend. We will not see any really warm weather until possibly a week and a half from now.

Short-term:

 

A decent ridge of high pressure is currently parked over Ontario, which will be the main influence of our weather for the next four days. We will see January-like temperatures under mostly sunny skies through this weekend and into the beginning of the upcoming work week. A 510-mb. area of pressure will sit over central and southern Ontario and upstate New York today (we usually don't see this this time of year), but it will gradually shrink, and then disappear by tomorrow (according to the 00Z and 06Z extended GFS loops). That doesn't mean that our cold weather will disappear, however. The 540-mb. line will stay well to our south until Tuesday, again keeping most areas only in the 30s and 40s during the day, with teens and 20s at night. This persistent cold, clear, and calm pattern will break beginning on Tuesday, however, as the next storm system makes its' way towards the Commonwealth.

Long-term:

 

The 540-mb. line will cross through Pennsylvania sometime Tuesday evening. The GFS runs have the line crossing through between 18Z Tuesday and 06Z Wednesday. The 06Z GFS run does not have the 540 line cross all the way through PA until about 12Z Wednesday, as it tries to keep the Canadian high (and cold air) parked over the region a little bit longer. This could spell trouble Tuesday night - if the cold air stays entrenched at higher levels, many areas could see sleet or freezing rain. By Wednesday, however, the warm sector of the system will be over the state, and most areas should see just rain during the afternoon. Then, the cold front will pass through the state sometime Wednesday night. The 06Z GFS run is the slowest (in terms of when the front will pass), suggesting that it will not move out of Pennsylvania entirely until 12Z on Thursday morning, whereas the other two runs have the front out by 00Z Wednesday evening. So, we'll have to watch the timing of the FROPA. Precipitation amounts from this system will be light to moderate - nothing too extreme. After the cold front, a few systems will affect PA - including another cold front further south, giving a reinforcing shot of colder air for Friday, and a Canadian clipper for next Saturday. Otherwise, expect temperatures to stay below normal for at least the next week and possibly week and a half.