These were the official snowfall maps and data from last winter's storms:
- #1 Winter Storm Snow Totals Dec. 19-20, 2009
- #2 Winter Storm Snow Totals Feb. 5-6, 2010
- #3 Winter Storm Snow Totals Feb. 9-10, 2010
As you can see from the maps, the first two storms were very unusual, with west-to-east bands of the heaviest snow (both happening to be over the Philadelphia area, leading to some of the biggest storms ever recorded).
The third storm was more classic, with a Nor'easter moving close to the coast. Lowest snow totals were near the shore, and highest amounts were north and west of Phila. Today's storm is more like the third one, except a bit farther offshore, and a bit smaller. As a result, the highest snow amounts should come in New Jersey, and the lowest amounts in places like Berks and Lancaster counties.
The thing that is not classic about the current storm is how the computer models were all over the place for days, only coming to a consensus Saturday morning. Many of the recent storms were well seen by the models days in advance. This one will be studied for years, to see what went wrong.
Now it's time for "nowcasting." Yes, I know, anyone can see what it's doing NOW. But the term "nowcasting" is an official one used by the National Weather Service, and it describes forecasts of the next few hours. In the case of winter storms, we look for the heavy snow bands, and see how they are moving. In some of our biggest storms, those bands stay over the same area for hours, dumping 2-3 inches per hour. We'll watch the radar observations closely during the next 12 hours or so, when we'll find out the exact area that gets the most snow out of this storm.