Wednesday, March 06, 2013

Updating The Storm As Of This Morning

Radar early this morning shows the precipitation with today's storm pushing north off of the Atlantic as the storm pushes towards the coast.  Low pressure as of 6 AM is centered in northeastern parts of North Carolina, pushing east-northeast towards the coast.  This low will gradually, steadily intensify through the course of the day, continuing to push precipitation north off of the Atlantic and into the region.

Today's rule of thumb is that snow is more likely the farther west and southwest you travel, with rain more likely the farther east your live or travel.  The Philly metro resides in the "more rain than not" category for today but will see periods of snow mixing in from time to time depending on intensity of precipitation.  We won't rule out times during the day where it's halfsies between rain and snow but the majority of what falls until 5 PM will be on the rainier side of the fence before the transition to snow takes place this evening.

That said, the storm probably will surprise a bit at times and in various locations, with the best chance of any surprises generally across the northern suburbs down 476 through Delco down into Delaware where that transition from mostly rain to mostly snow exists.  It's possible some of you may see more snow than rain in various spots in that transition zone between mostly rain and mostly snow, mainly in hilly areas.  Farther to the west, over the hills of Chester County on west through Lancaster County on southwest, snow will fall, probably accumulating on nonpaved surfaces although some periods of rain mixing in from time to time are possible.  The valleys of Chester County will probably deal with a mix through the day.

For those in the city and points east, please note that the lion's share of the snow that's projected to fall does so tonight...we've pointed this out since yesterday that the bulk of whatever snow falls does so this evening as the storm intensifies and pulls in colder air from aloft and that transition from rain to snow takes place.  Modeling is still all over the place on snowfall potential, with the NAM toning down its antics somewhat for tonight and now "just" calling for three to six inches in the city.  The SREF is still aggressive.  For those who don't know, the number we're using for the SREF is an average of 15 different variants of the model...the SREF spread is 1.2" to 16.4" but the average of those 15 is between five and six inches.   The "big" models -- the GFS and Euro -- still hold to an inch, maybe two, for the city.

We're holding to one to three inches for Philadelphia -- with up to five inches possible in a stripe across South Jersey -- it's the same map from last night.

We'll provide an update this evening as the transition from rain to snow takes place.  Occasional updates on Twitter and Facebook as time permits.