Friday, March 23, 2012

This Is It For Warmth, For A While

We're starting off with more fog around the region -- thankfully, this is not the marine-induced variety of fog but merely the old fashioned "radiational cooling" type of fog that we're apt to get around the region more often.  This fog should be quicker to burn off than past days and we should see a good deal of sunshine by late morning across most of the region.  Fingers crossed, again, that takes place.  Today's forecast is based on the "assumption" that we get several hours of midday sunshine to help us make a run at record highs around the region -- today's record in Philly is 78.  If everything breaks right, we should reach 80 in the city.  Considering few things have broken right in the weather department lately, temperatures are still very much on track for tying or approaching the record in Philly -- some places could reach 80 though...keep that in mind.

The problem for the past few days with getting fog to burn off north and west of the city has been due to a bit of a temperature inversion between surface and aloft -- we've had a bit of a damming situation to the west of the city due to a persistent southeast to south flow off of the Atlantic, which has allowed moisture and low clouds to pool east of the Appalachians.  The low level moisture has not scoured out as effectively as it has in other places because the moisture is trapped and there is nothing to scour it out from aloft -- the result is the low cloud morass that continued to reside across Eastern Pennsylvania the past two days, one that allowed weather forecasters to rip up their forecasts in partial agony.   Thankfully, the flow aloft will be a bit more westerly today and feature a bit more oomph (at least on paper)...that should get the scouring to take place.

The fly in the ointment today is a cool front that's over New York State and New England, dropping slowly southward.  The front will begin to drop through the region after Noon today, reaching Philly around 3 or 4 PM.  Once the front crosses, winds will veer to the east and northeast and the Atlantic is open for business again as cooler air will push southwest into the region.   The best shot for any record highs will take place in the early to mid afternoon....and generally across Southeast PA and Delaware.

Temperatures will begin to trend cooler by evening, with a more marked dropoff as those east breezes bring reality back into the mix.  No more 70's for a while as our taste of May ceases after today.