Wednesday, December 23, 2015

The Winter Storm Outlook

Whew! This is a tough one. Normally, I would not have tried to forecast the winter storm six days in advance but there is tremendous interest due to Christmas travel. Unfortunately, there is little confidence in this forecast.

Here's why. The low pressure system that will turn into our winter storm is over the Gulf of Alaska (pink circle showing storm at 15,000 feet). While there is useful weather satellite coverage, there are no weather balloons and few aircraft sampling the atmosphere. So, the computer models have a difficult time when there is low confidence in their analysis of the current state of the atmosphere.

The storm now over the Gulf of California is forecast by the models to move over far northern Mexico Sunday night. Snow is likely in El Paso (while it is raining in Toronto)! A second storm should get close enough to the first (i.e., within 1,500 miles) that it will "kick" the first storm northeast (purple arrow). If so, there will be a major snow storm in the Plains. 
However, if the storm is not "kicked" by the second, it will take a much more southerly path (green arrow) and there will be little or no snow! Note: Snow falls to the north and northwest of an upper level low. The detour into Mexico creates a longer path for the low to cover and so causes the low to slow down a bit.

So, here is the likelihood of 6" or more of snow Saturday afternoon through Monday.
Check your local AccuWeather forecast for specific amount for your location.