Friday, February 08, 2013

Soggy To Snowy This Evening

Today's storm is pushing in from the south, spreading rain into Philadelphia this morning, with a mix of rain, snow, and sleet across the northern burbs as it moves north.  As warmer air pushes north and northeast along the coast with southern energy later on, we'll see the rain/mix line push north into the upper burbs for a while, with the mix/snow line likely to hold in the Poconos or across the northern edges of the Lehigh Valley.  Across the Lehigh Valley, some mixing of rain and snow looks likely.  Perhaps a bit more snow in heavier periods of precipitation, rain in the lighter periods into afternoon.

Anything that falls this morning from a snow standpoint, at least around the immediate Philly metro, will be short duration and will not amount to much other than driving headaches and hallucinations that more snow than reality will ultimately fall.  Rain takes over for most of us later on, some of it rather heavy later on this morning and into the afternoon as the southern energy pushes up the coast.

By late afternoon, some lulls will develop in precipitation.  Rain will remain along the coast and to the city's east.  To the west of the city, the northern piece of this storm will begin to push in from the west with snow falling across Central Pennsylvania and into Berks County.  The changeover from snow to rain will take place during this timeframe, during this lull in the late afternoon and evening.  If this high res modeling is correct about the lull taking place, we will dodge a bit of a bullet on the PM drive home since precipitation will not be falling at a significant clip, meaning impacts may not be terrible.  It won't be a walk in the park going home but it could be worse.

Snow spreads in from west to east during the latter half of the PM rush hour and by 7 PM the northern and western burbs are in on the snowfall.  In areas where rain is falling, we should see the transition take place from rain to snow during the latter half of the PM rush hour as well although it may take until after 7 PM for everyone in the region (including the coast) to see snow.

The largest chunk of snow with this storm falls after 7 PM, some of it heavy and steady at times across the Lehigh Valley and up into Central and North Jersey overnight.  In these areas, an inch or two per hour of snow are possible after 7 PM.  Locally, half inch amounts per hour aren't unreasonable and some spots could probably top that across the northern and eastern suburbs (Bucks County, Burlington County, the 5-9" zone outlined at the bottom of this forecast).

We'll see snows begin to wind down after Midnight from west to east, with some lingering light snow possible around the area as dawn breaks on Saturday.  Snow quickly winds down from there.  You can also see during the evolution of the storm how much of a pounding the Boston area and Southern New England will take from this storm, while New York gets hit hard but not quite as bad as those in Boston will.

For the city and immediate burbs -- no major changes on the snowfall projections.  3-6 in most of the city, 5-9 across Bucks, and Montco above the PA Turnpike and east of 476.  We trimmed the 7-13 zone back just a touch but Central into North Jersey are still in line for a major snowstorm.   We have nudged Delco completely into the 3-6 zone but snow totals in Delco will be closer to three inches of snow than to six.

Occasional updates through the day today on twitter and Facebook. A more thorough update this evening.