Tuesday, March 29, 2011

Winters Revenge (Part 5)

When I started the winters revenge blogs 11 days ago I knew we were going back into a snowy and cold pattern but nothing like this. Last week NW Jersey added up 6"-15" inches of snow and I still have 3.5" on the ground today! That tells you that it's been very cold for March snow to stick around this long, it's almost April for crying out loud! Now we are going to add more, and possible A LOT more. The tanking of the NAO is to blame.

Let's look at all the models at Fridays storm system.





I think I have made my point. A storm is coming up the coast and it's seen on every model except the NAM. Currently I'm waiting for the 00z NAM to come out to see if it has changed to come in line with every other model.

The problem with this storm is that it needs to pass through the "key hole", a track where it doesn't bring us too much rain yet not to far out to sea to bring us little snow. I think this will happen and that means most of NW Jersey will get significant snow accumulations. The higher up you go, the more you will get.

Right away we should look at the precip type, and we will do that using a sounding.

The yellow line is the freezing mark and the blue is the cold air. The long pink lines are the temperature and dew point and both remain below freezing in the entire air column all the way to the surface for all hours of the event except the first few hours of light precip, which may fall as rain. We just determined that this is a mostly SNOW event! Let's figure 10" inches of snow per 1" inch of liquid because the ground did refreeze and it's snow covered still in most areas.

Time to look at total QPF, remember we have 10:1 ratios.

With around an inch of liquid forecasted you do the math...

Check back tomorrow for my preliminary snow map and update on the situation. By then the exact track should be determined and snowfall amounts can be forecasted.

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