December Outlook

11/27/21 Saturday 9:40 am

The next 12 or so days are going to have people wondering where winter is.  Especially all of the new residents who moved here since Covid. Those of us who have lived here for a while know that for the most part, winter does not usually get going until mid to late December.

I have the distinct advantage of being able to look at the long-term weather models. There is good agreement right now that we will start to transition into a wetter pattern after December 9th. The longer-term Euro weekly model and GFS extended model concur and they then show us entering a cooler and wetter pattern beginning around December 12th.

The model shows that pattern continuing for the duration of the run which concludes January 9th (Euro). To clarify, that is the end of the model run, not necessarily the end of the cooler wetter pattern. What is significant about this is that even with the first 12 days of the model runs showing basically ZERO precipitation, we end up with average precipitation for the lower elevations with above-average precipitation in the mid-and higher elevation areas.

The ridge should have a dominant hold on our weather for the foreseeable future. The transition that occurs is that the ridge begins to flatten out. This opens up the storm track, but it will take a few days before we see cold working its way down to the Western United States.

There is still some speculation out there that the cold may be in response to a stratospheric warming event that is coming. Stratospheric warming events often lead to the displacement or split of the polar vortex–a term we get used to hearing about in the winter. The polar vortex is nothing more than the low pressure that keeps our polar regions cold.

Stratospheric warming events often displace the polar vortex and drop it further south in the northern hemisphere. Determining where it will end up is tricky.

In December 1967, after a stratospheric warming event, extremely cold air led to snow in La Jolla, California. The cold air and storm track moved onshore and led to the biggest snowfall in history for Flagstaff and other areas of northern Arizona. Snow fell for 8 days. Flagstaff received 86 inches of snow during that period. Over 100 inches fell in some mountain locations. The storm tracked east into New Mexico and it was one of their worst winter disasters ever.

Colorado did not escape the storm, although the impacts were not as great/severe. The only storm data I have on it was that Grand Junction received 16 inches of snow during that storm. I do know that Durango reported 46 inches of snow for the month of December. Rico reported 62 inches of snow for the month. The towns of Telluride and Silverton both reported 45 inches of snow for the month, but I am not sure how much of it was attributed to this storm.

I forgot to mention the date all of this occurred: December 12th, 1967 through December 20th, 1967…

By the way, did you hear that Antarctica had its coldest winter on record this year? The average temperature at the South Pole during polar darkness (April through September) was -77 degrees. It was attributed to a stronger than usual polar vortex.

Time to look at some precipitation maps.

As I said, nothing to talk about between now and December 8th.

GFS ensembles mean through December 7th.

GFS extended ensembles mean December 7th through December 30th.

Euro ensembles mean through December 7th.

Euro extended model December 7th through December 31st.

The Euro extend model has a longer forecast period. Here is the projection for December 7th through January 9th.

Euro extended snowfall December 7th through December 26th.

Euro extended snowfall December 7th through January 9th.

My next update will be Tuesday, November 30th-unless I see something cool before that. Thanks for following and supporting the site!

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