Tuesday, February 21, 2012

Friday's Storm Brings Mildness, Rain To Region

Today marked the transition into a milder regime in Philadelphia that will last for Wednesday through Friday. Temperatures, as discussed in Brian's forecast earlier today, are targeted to reach the 60's at least once during the upcoming stretch as we have our first legitimate tease of Spring-like warmth. It's not unusual (not stealing a phrase from Tom Jones) to get a Spring Fling in February.  Spring Flings are multiple back-to-back days of 60 or milder in the month.  We already had one such fling bookending January and February, including that 67 degree high on the 1st, but we've been here and done that in late February a few times.  Last year, the 17th and 18th featured highs over 65 degrees both days (67 and 69, respectively) and only three years since 2000 have not featured at least two days of 60 or warmer (2003, 2007, 2010).  So far, we've only been there once...that will change.

The warmest day sets up on Thursday in all likelihood but Friday could come darn close depending on how fast the front gets here.  Computer modeling is in pretty good agreement that low pressure will track to our north and west and that the low will intensify as it moves through the Great Lakes.  There is some question on track with the low -- the GFS is a bit more aggressive in pulling the low into Canada earlier in the day and simply zipping the front through the region in the mid to late afternoon hours with some showers.  The Euro handles things a little bit differently...taking the southern energy and thunderstorms (severe weather event for the South) and pulling those up the frontal boundary, fusing that energy into the low as it moves a bit more slowly.  The result is a slower frontal passage which may linger into Friday night or even Saturday morning before moving through, a bit more wind, and more rain than what is promoted on the GFS.  The Euro even suggests the possibility of some thunder...not likely, but merely possible in some spots.

Both scenarios suggest a breezy Friday with mild breezes ahead of the front and a slap of late winter returning Friday night.  The question comes down to how much of that southern energy can ride up the front and how quickly that takes place.  The GFS generally keeps the threat of those southern storms confined to the Carolinas on southwest as the energy from the South doesn't phase into the low, merely bringing us a round of showers with the front that will not impact us too terribly much while the Euro brings those thunderstorms into the Mid Atlantic as a wind and rain (perhaps even some thunder) event.  In terms of modeling trends, the GFS has trended away from the windswept East Coast rain event through this morning's runs while the Euro has held steady.

In any event, Friday does bring the threat of at least some showers -- whether we get into the heavier, steadier rain from that severe thunderstorm line that will track through the South or if we merely get a run-of-the-mill spread of showers with the front remains to be seen.  In any event, Friday also brings warmth but it will be fleeting as the front marches through in the afternoon and sends us back to reality for the weekend.