Thursday, February 23, 2012

Fine Line Separating March & May

Tomorrow is shaping up as one of those days that forecasters can earn their paychecks...or strike out badly...on.   A stalled out front just to our south is poised to lift north tomorrow into the region as warm air pushes northeast ahead of a stronger cold front that moves through tomorrow night.  The push of warmth into the region may not be as potent as first thought to the north of the city as rain, drizzle, and low clouds linger behind the push of warmth aloft thanks to east winds off of the Atlantic.'s that time of the year...time for marine influence (winds off of the Atlantic) and some cold air damming in the lower levels of the atmosphere to ruin forecasts!

We're not certain just how far north the warm front will get -- and while earlier data suggested we would see it blast through the region, giving everyone low 60's to low 70's (depending on location) we're not confident the front gets much north of Philadelphia or even to the city.  The NAM's higher resolution variant (below) shows the extreme in temperatures that are being anticipated tomorrow afternoon...low 40's in the Lehigh Valley during the mid to late afternoon, 70's in Delaware and South Jersey.  We could be flirting with records in Atlantic City and Dover while cursing out low clouds in Doylestown.

Philly sits right on the cusp...and 20 miles separates 50 for a high from 70 in the city.   Needless to say, it's not going to be fun forecasting our weather over the next 24 hours.  The bad news is that the NAM tends to do a great job of nailing down temperature gradients...the good news is that it's the only model that's this aggressive and has this much separation in temperatures over a short for those of you who do get into the warm sector tomorrow afternoon it'll be like May while the rest of the region is in varying stages of March-like weather.

The fine line between warmth and loathing the cruelest times of the year.

Along with the fun will be a threat for thunderstorms as the cold front moves through the region tomorrow afternoon.  The best chances for thunder will be in the warm sector -- south of wherever the surface warm front ends up setting up shop.  Wouldn't surprise me if some spots get in on gusty winds with the frontal boundary thunder threat tomorrow afternoon and evening but the best chances for this will be Delaware and Maryland.  South Jersey doesn't have as good a shot as Delaware but you're in the game for some gusty winds and thunder.  IF the warm front lifts north of the city, the city stands a chance as well but all of this is dependent on the warm front lifting through and a decent amount of sunshine breaking out in the warm sector.

This will be a fun day to track weather from a meteorological perspective but north of the city it's going to stink from a "spring fever" perspective unless the warm front decides to cooperate and move north.