Friday, March 16, 2012

Weather History: Beware The Ice Of March

One of the cruelest realities of March weather in Philadelphia was five years ago today...the Ice of March snow and sleet storm that brought anywhere from a couple of inches of sleet to as much as a foot and a half of snow to the highest elevations in the Poconos.   Occurring just two days after temperatures reached 80 degrees in Philadelphia, the Ice of March began as a cold rain during the evening hours of the 15th in the wake of a cold front that slid through the region around midday.   Low pressure had organized along the front overnight to our southwest, lifting northeast and enhancing precipitation while continuing to draw down low level cold air into our region.  

By morning, temperatures had dropped to near freezing in the city with a rather cold rain that was mixing with sleet in spots.  That transition from rain to mainly sleet in the city took place by mid morning, with sleet accumulating by late morning in many locations and falling at a heavy clip throughout the course of the storm.  In higher elevations north of the city, rain transitioned to sleet for a brief period of time and then snow as air over the Poconos was cold enough to support snow all throughout the atmosphere.

Sleet (and higher elevation snow) continued through the course of the day before ending around Midnight.  By the time the storm subsided, between three and six inches of sleet fell from I-295 on northwest through the Pennsylvania suburban counties, with 1-3" of sleet falling south and east of the city down to within twenty miles of the coast in South Jersey and Delaware where rain was the dominate precipitation type.

Over the Poconos, as much as eighteen inches of snow fell in Carbon and Monroe Counties.  Between six and ten inches of snow and sleet fell across the Lehigh Valley from this storm system.

In terms of precipitation itself, between one and three inches of liquid fell across the region overall if the snow and sleet were melted...and it was the second "mid-month" major storm the region experienced in three consecutive months as the region got popped in mid April with a significant nor'easter as well.

In terms of slaps in the face from Mother Nature, this storm was one of the crueler twists of fate in our local weather history -- it's the rare instance where Philadelphia went from 80 to frozen precipitation in just under 48 hours.

The National Weather Service has a really good write-up on this coastal storm and the impacts that it brought to the region.