Monday, January 17, 2011

Snow then more snow

It hasn't really been a "snowy" season here in North West Jersey. It's actually just average as of right now. Another snow event is coming through tonight, but it will mix and eventually go over to just rain in some places. First off the system will come up from the south and precipitation will be heavy to start, accumulations will range from around 2" inches at lower elevations to as much a 6" inches above 1000 feet.

Here is the sounding a few hours into the storm for Andover airport:

The red line is the freezing line and long blue line are temperature and dew point. The two blue lines are close together meaning the atmosphere is moist, and the fact that it is primarily below freezing means this is a snow sounding. The only problem is a little layer of the atmosphere is above freezing (in the yellow circle), which would indication a few sleet pellets are mixing in.

The next sounding is a few hours out:

Now this time a large layer of the atmosphere is above freezing which indicates the melting of all the snow on it's way down. Now the surface has a thick layer of cold air, this would be mostly sleet with freezing rain mixing in as the liquid precipitation freezes in free fall.

Most sounding data supports the idea that the surface will remain below freezing all day long above 500 feet, which means most areas in North West Jersey with stay wintry. A solid 3"-5" inches of snow will fall before the change over to sleet. Once the sleet starts to fall the snow will get compacted down into a hard, durable, and thaw resistant surface. The freezing rain will follow and put down a good layer of ice on top of the snow cover.

I know it's not the best storm, but by tomorrows end we will have a few inches on the ground that we didn't have today. So it's a good thing.

The snow map:

After this mess is all over with another storm potential for Friday could bring another plowable snow event.

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