Sunday, December 09, 2012

Monday's Rains Could Include Thunder?

The stalled front that is bringing today's damp and raw weather will lift north through the region over the course of tonight and cross through Philadelphia on Monday morning. It will be a mild, perhaps even warm Monday as the warm front pushes up along the East Coast through the course of the day with southwest breezes aloft and at the surface helping push warmth along.

How warm could Monday get?  Well, the higher resolution modeling like the NAM are suggesting middle 60's for highs from Philadelphia and Southeast Pennsylvania on south.  Monday's record high is 71 so it'll be pretty tough to reach that in the city...but we'll still get within a few degrees of it.   While it will be mild, sunshine will be a bit of a premium locally...might be some sun down in Southern Delaware or down towards Washington but we will probably be stuck locally under gray skies.

However, with the warm push that will occur ahead of an approaching cool front the odds for some thunder along the cold front are possible.  It's not a high chance but Monday evening could include a gusty shot of thunder within the rain band that moves through.  The frontal boundary timing varies from between 5 and 10 PM depending on the various models -- given it's December, the timing won't be critical from a wind/thunder standpoint since we're relying solely on dynamics and energy with the storm system and not on sun-generated atmospheric instability.  That said, there is a slight chance for a rumble or two of thunder with the front as it moves through on Monday night.  Severe weather is not likely but some gusty winds cannot be ruled out with the frontal boundary passage.

Rainfall with the front will vary -- some spots could pick up locally heavy rains and could see over a half an inch on Monday, especially if the modeled line of heavier rain projected on the NAM model up above does indeed develop -- other spots will get a modest amount of rain on the order of a quarter inch or less.

In the wake of the frontal boundary passage will be a gradually cooler temperature pattern for Tuesday through the balance of the week but temperatures will step down to normal or just above that for the balance of the week after Monday's front moves through.