Friday, March 22, 2013

Slushy, Perhaps Sloppy Sunday Night & Monday

We continue to keep an eye on the Sunday night and Monday storm system and there haven't been any marked changes in the storm's modeling over the past day. Timing still looks on board for a Sunday night into Monday impact on our region with some wet snow for many spots, with light rain likely for those east of I-95, with the city sitting on the fence but leaning on the rainy side outside of the elevated areas of Mount Airy and Chestnut Hill that can coax a bit more snow.

There are still some detail issues to be worked out, mainly with the intensity of the low pressure systems, and that will mean all the difference between any snow, mixed bag, and nothing.

West and southwest of the city, this has some potential to be a decent late season snowfall if everything comes together correctly (temperatures in the lowest parts of the atmosphere plus precipitation intensity).  Unlike the storm system that moved through on March 6th and 7th, the timing for this system is predominately at night.  That wasn't the case with the aforementioned storm, which moved in during the day.  Similar to the last system is that most of the precipitation will be south of the city, which places us on the fence for much if any snowfall potential unless some of the heavier bands work into the region.

The GFS is suggesting a chance of some of that steadier precipitation working into the region, with about ah half inch liquid equivalent at the Airport, between a third and a half inch in the suburbs to the north and west. On the GFS, that falls as mostly rain at the Airport but in Pottstown it's snow on Sunday night, transitioning to a cold rain during Monday, with a couple of inches of snow accumulating out there.  The Euro is far less robust on precipitation intensity than the GFS (shown above) and the result on the Euro is a mixed bag with coating type accumulations west and southwest of the city, with light rain (perhaps mixing with snow at times) in the city and points east and south.

The temperature profile in the bottom atmosphere is somewhat marginal, which means it comes down to precipitation intensity.  The GFS has it, for now, since it is strengthening the coastal low a bit more robustly than the Euro.

Putting all that breakdown together, it's important to note that this does not look like a major league snowstorm locally or even to our immediate or nearby west but some snowfall could result IF we get enough steady, heavy precipitation to move north into the region on Sunday night. That is a big IF since we are straddling the fence.  However, it will be raw, damp, and for some, potentially snowy.