Tuesday morning update on snow totals

With snow likely to arrive in Mecklenburg county near noon Wednesday (tomorrow) here's a Tuesday morning update. Two systems will be responsible for ushering in the white stuff. A surface low pressure crossing the Gulf states before exiting off the South Carolina coast tomorrow will bring the first round. That precipitation will taper off Wednesday evening, but some flakes are likely to continue falling.

Then round two arrives early Thursday morning as an upper level shortwave trough scoots across Virginia. That system will move quickly off the coast, and Thursday afternoon will wind up mostly sunny but still cold and breezy. Temperatures during both events will be in the 20s, which will result in a dry fluffy snow instead of the heavy wet stuff. 

Snow forecasts are always tricky since it doesn't take much variation in liquid amounts to change accumulations. It's not always true, but typically one inch of atmospheric liquid equates to ten inches of snow. So a change of a few tenths of an inch in available liquid can mean very different snow totals. 

For those that remember their statistics classes weather forecasts are usually couched in probabilities instead of firm absolute numbers. This doesn't mean forecasters don't know what they're doing (a tired and very incorrect old bromide), that's just how forecasting works. With that in mind here are two graphics from NWS Wakefield to illustrate. First, the chances of locations seeing at least 4" of white stuff this week:

Then, the chances of the same locations seeing at least 8":

The official forecast for Mecklenburg county is for 4-6" of snow. Per these graphics it's obvious that areas east of I-85 will see deeper amounts.

Why probabilities? Forecasting the future is difficult. Folks who will be filling out "March Madness" colllege basketball brackets will find that out very soon!!