Thursday, January 17, 2013

Update on Tonight's Rain to Snow

Pictures sometimes explain reality much more eloquently than verbose paragraphs. Tonight's weather is illustrated with the graphic below.

Long story short, the stuff on the Dover radar image from just before 5 PM shows a batch of light and moderate precipitation across New Jersey (north of 195) and Pennsylvania.  Almost all of that is not reaching the ground as the lower atmosphere is a bit too dry, which is known as virga. There might be a sprinkle, a sleet pellet, a flurry but the odds of getting much more than that this evening and tonight are remote.

The precipitation that IS reaching the ground is currently across Virginia, Maryland, and is just entering SW Delaware.  That is falling as rain, sleet, and in the heavier batches a little bit of snow.  This precipitation will continue to push east over the coming hours, falling generally south of the Dover-Atlantic City line we've illustrated earlier this morning.  This batch of precipitation extends back into Virginia, where it's falling as snow across Lynchburg and Roanoke.  In fact, heavier snow is falling in Southwestern Virginia, with three inch per hour rates falling around Roanoke.

That type of snow doesn't appear likely in Delaware but later this evening, as colder air works in and precipitation reintensifies, the rain/sleet mix that's been falling down there will likely transition over to snow and begin to accumulate.  Best chances for snow will likely be between 7 and 11 PM before things taper off...and hence, the potential for one to three inches south of that line but with most of you south of that line seeing an inch or perhaps two.  The best chances for that three inch total will be in Sussex County, Delaware, likely closest to the southern end of the county.

For us in Philly, clouds rule the roost tonight until later this evening.  We could see a round of clearing after Midnight after a cold front slips through the region.  This front may bring a flurry along with it but odds don't favor many seeing snow.