Saturday, February 25, 2012

Lake Effect Driven Snow Band

11:00 A.M. Update: A small, intense snow shower is now moving through Burlington County as the streamer is falling apart closer to the coastal plain. A few additional snow showers and flurries are possible N&W of the city throughout the rest of the afternoon. An isolated new snow streamer cannot be ruled out. For live weather images and updated tweets...go to the left side of our page.

10 A.M. Update: The snow streamer is continuing to drift southeast and it is now impacting most of the Pennsylvania Turnpike. The band, if it holds together, will begin to close in on the greater Philadelphia area. Surface temperatures are a bit milder around Philly than N & W of the city….but this band has been so impressive…that it has resulted in a quick one to two inches of accumulating snow north of the city. With the combination of 1” per hour snowfall rates and wind gusts of over 40 MPH…rapid and sharp reductions of visibility are quite likely. Actually, some of the greatest momentum could be within the snow streamer.

(Image above around 9:00 a.m.)

Maybe it is being snow starved that prompted this post! But anyhow, I just wanted to focus on the areas south of Allentown and Interstate 78 and north of Lancaster…including Interstate 76.

It appears around 8:15 a.m. a lake-effect snow streamer developed and it is now drifting southeast. These are not common in these parts, but fueled in part today by the strong winds. This squally feature of snow may quickly coat the ground with snow and sharply reduce visibility (due the wind combo) to below one-quarter of a mile. This will result in tricky travel for these areas.

Forecasting how far south and east such a band will move before falling apart can be relatively tricky. From a climatological standpoint, they tend to break apart when they move closer to the coastal plain. But with the strong winds, this feature could survive to some extent…perhaps in the form of showers. Surface temperatures are also a bit milder to the south of the current area and unless the intensity is persistently moderate to heavy, rain will mix with the snow based on the atmospheric profile and it could even be all rain if intensity is light enough.

Additional activity is possible as long as those winds remain brisk.