The December Outlook stands to be Cooler than normal and slightly wetter than normal
The first 2 weeks of December feature our favorite issue where “precipitation is chasing cold”. A series of cold air dams will set up beginning this Tuesday bring us cold air…highs in the low 40’s. Another will setup on the 9th. The real news maker will be another round of Arctic Cold outbreaks around the 18th and then again around the 24th.
Precipitation is nearly impossible to forecast this far out but we can use other indicators to suggest precipitation and should it occur, what type it might be. See below.
Note: The absolute best presentations comes from the European (ECMWF) model, however new licensing prohibits distribution. In working with the provider, using GIS to create a depiction of the model output is acceptable so this season many custom maps will be made available from that model.
CFS V2 Temperature Anomaly
Shown here is the temperature anomaly for December or the departure from normal. The Piedmont stands to be cooler than normal which for December is already quite cold. Two Polar outbreaks on the 18th and again around Christmas contribute to the drop in monthly average.
CFS V2 Precipitation Anomaly
This is the departure from normal for precipitation for December. Shown for our region is a near normal month for precipitation. This model output does not consider precipitation types or amounts, so all we can say is that normal precip is expected.
CFS V2 Snow Maximum
Considering our lower than normal temperatures, our near normal precipitation amounts, and the potential for 2 polar outbreaks in December, IF by chance it did snow, this is the maximum we could see. Shown for our region, the worst case scenario would be 1-2 inches.
Using a tried and true method for converting rainfall amount to snow amount, begin at 1:10 where 1 inch of rain would equal 10 inches of snow. These models suggest a very dry month which NC Weather Happens feels is under done.
Our normal liqud precipitation is about 3 inches for December. Considering two polar ourbreaks and below normal temperature, the thinking here is that there will be some snow opportunities for us in the middle and end of the month. How much would be impossible to say but those would be the best times should it arrive here.
Again, it’s impossible to say a month in advance but we are giving it a fairly decent chance this year… What we can say with authority is that time will tell and NC Weather Happens will be there!