Thursday, May 03, 2012

Updating Tonight's Thunder & Low Clouds

We never were fully able to shake the overcast north of the city as the stubborn marine layer was quite stubborn despite a sun angle equivalent to that in early August...so much for that "strong" sun. Stable air can win out just above a frontal boundary! It is warming aloft and that inversion or temperature differential between surface and aloft is aiding in the low clouds having a very slow burn across the region today. Where it did burn off temperatures jumped quickly into the 70's...and farther west...80's.

Around here? Mid 60's.

That warmer air out west is also unstable -- and the result is thunderstorms that have popped in scattered fashion across New York, Pennsylvania, and Maryland...all of which are moving southeast and east.  The batch in Central PA, which you can see below as of 7:15 PM, is working towards Harrisburg and I-81 and pushing more southeast than east.


The best chances for thunder reside west of the city this evening -- there's more unstable air out there and as these storms continue to work east they will push into further stabilized air and continued loss of daytime heating.   Adding more "fuel" to the fire of low clouds is the continued push of stable air from the Atlantic overnight...we should see more fog and low clouds overspread the region tonight and be a factor into tomorrow morning.

Of course, that all will play a hand in tomorrow's forecast -- how quick does the fog burn off and how much sun do we get...assuming we finally break out into sunshine.  It *should* happen tomorrow as the atmospheric flow from the southwest is strong enough to push the low clouds offshore.  The only question is how quickly it happens...we'll have some handle on it in the morning...hopefully...but this pattern has been a humbling one for many a forecaster as the warm front is in no hurry to push on through.