The frontal passage and thunderstorms in Philadelphia expected today will be well-handled by the NWS.

So, what value-add can I offer this early in the day?

Reviewing the models from earlier this morning, the following characteristics and trends exist:

There’s a possibility of some earlier scattered showers and thunderstorms as early as 12-2PM.

Increasing  areal activity is expected between the hours of 4 PM and 8 PM.   A line of storms should develop by 5-6 PM and move through the Philadelphia area, according to the latest RAP and HRRR models.

The severe weather parameters (cape, helicity, shear, precipitable water) are all elevated, but not as elevated as seen a few weeks ago with the tornado development.

Some low pressure centers are expected to develop in this line of storms and additional activity may linger until after 8 PM.

This afternoon’s models have backed off on the extreme weather just a bit.  Most of the severe activity will move in between 8-12 midnight.  Accumulated precipitation values have come down a bit to 1-2 inches of rain with additional rain on Thursday afternoon and evening.

Shear, Helicity and Vertical Velocity values have reduced a bit from yesterday’s posted graphics with the heaviest activity now predicted to occur in the northern suburbs of Philadelphia, Berks, Lehigh and Bucks counties and into central/ northern NJ and New York City.

That said, these locations are hard [impossible] to pin down precisely in advance.  There are differences in the models.

It’s a good thing I don’t usually “do thunderstorm forecasts”.  This would have to become a full-time job!