Technical Discussion

Synopsis:

First cold front moving in later today and tonight with showers and thunderstorms.  Skies clear somewhat and temperatures rise between the two systems on Tuesday.  Strong cold front brings more showers and thunderstorms Tuesday overnight into early Wednesday.  Skies could stay somewhat cloudy through Thursday if the center of the low meanders to the south or a short wave moves through.

Short-term:

The 0Z runs push back the rain until late Monday into overnight hours, while the 12Z runs moved it in during the afternoon.  The complex of storms in Mississippi and Alabama will be what comes first into Pittsburgh.  MOS is about as warm for Monday as the actual temps were on Sunday, so MOS seems pretty good, as more southerly winds are counteracted by less sunshine.  As soon as the low clouds depart from this cold front, high clouds build in ahead of the next system.

Long-term:

This potentially historic gale over the northern Great Lakes will push its very strong cold front across Pennsylvania Tuesday overnight into Wednesday morning.  The model indicates thunderstorms despite low CAPE values, probably because the cold front is just so strong; thunderstorms seem likely.  One thing to watch out for in the future is where the front stalls, as it could stall on the coast and bring more thunderstorms to the Philadelphia area Wednesday afternoon and evening.  The other thing is if the moisture wrapped around the center can get as far south as Pennsylvania, which will increase the clouds and bring showers to northern counties.

Scott Sieron