Wednesday, November 25, 2020

History of Snow Between Thanksgiving and Christmas: Are Our Chances Higher This Year?

In late October, we issued our WINTER WEATHER OUTLOOK for 2020-2021.  The general idea is for a backloaded winter with shorter "teaser" periods of cold and snow in December.  So far (as of this writing before Thanksgiving, we've had under an inch of snow). 

Sledding with my kids when they were much younger!

How much snow do we typically get between Thanksgiving and New Years' Eve? We average around 10" over the last 10 years although the trend for early season snow has dropped over the last 15 years.

How about actual snowfalls?  We average around 4 one-inch snowfalls during the holidays.

Snowfall is one thing. But snow on the ground during the holidays is entirely different. More days with snow on the ground, the better chance we will remember it as a "snowy" holiday. We average around 8 days with snow on the ground over the last 10-15 years. 

As of this writing we are watching for changes in the pattern that strongly show more cold.

* Ridge developing across central Asia
* Jet stream across the North Pacific changing
* More frequent lows across Northern Pacific

All of this is resulting in the high pressure across the western US/North America with low pressure across eastern US. We call this a +PNA pattern (Pacific North American)

The super-long range model output into Christmas week is also strongly hinting at this eastern TROUGH/COLD lasting beyond December 20th. While I think this is probable, my confidence is high ONLY through the first two weeks of the month.

Animation from Thanksgiving to December 21st

Historically we average 15 days with temperatures in the 30s or COLDER over the last 10-15 years. Last winter we had 14 days in the 30s or COLDER before December 31st

Either way, cold and BELOW NORMAL temperatures are coming the first week of December with good chances of accumulating snow along with lake effect multiple times! Winter is coming everyone...