Is Winter Cancelled??

No, but it’s about to go on hiatus for a while. A month after the issuance of our original Winter Forecast, let’s see where we stand now and talk about the needed changes to the outlook.

The Original Forecast

Temperature-wise, the overall idea with the forecast was that the season would feature some hefty cold snaps but also some significant periods of warmth (compared to average), especially later in January and February. When averaged out, the 3 month period would likely come out as pretty close to “normal”.

With a very balmy mid-December pattern ahead of us, we have to adjust course. The updated forecast now tilts odds in favor of a warmer-than average season:

The important thing to keep in mind is the fact that not EVERY day or even week will be warm. In fact, I think there is room for a pretty cold period during the first part of January.

Another important caveat: mild Winters can still have a healthy amount of snow! In a mild-flavored Winter, you have to rely on moisture and cold air being synced up more than in Winters in which the presence of very cold air is usually already a given.

Confidence remains reasonably high that overall precipitation will be above average this Winter.

The Balmy Mid-December Pattern

So I outlined the overall seasonal forecast change above….what about back here in the near term? Well, mid-December is going to be very balmy. The jet stream will be very amplified next week, with a deep trough of low pressure over the western United States and a stout ridge over the East:

This results in a rare-looking 8-14 day outlook from the Climate Prediction Center: slam-dunk odds of it being warm over a huge area:

Before we even get to the sustained warmth that’s coming our way next week, a very Spring-like day is ahead on Saturday. Ahead of an approaching cold front, temperatures will surge into the 60s, probably breaking the daily record high of 61, set in 1979. There will also be some showers around, mainly early in the day and again late in the day. There may even be rare December thunderstorm! As if that were not enough, the afternoon may be quite windy…especially if the Sun comes out for a time.

Back To The Winter Forecast: Why Is The Pattern This Warm?

The warm December east of the Rockies is not something most meteorologists expected. With this year’s atmospheric/oceanic background state (La Nina, etc), the odds should be heavily in favor of a fast start to Winter. BUT! There’s one monkey wrench.

The North Pacific Cold Pool

A pool of colder-than-average water in this part of the Pacific (south of Alaska) is not all that unusual, especially in a La Nina. But this Fall/early Winter, the cold pool, and the atmospheric response to it, has been pretty impressive.

During Autumn, a very persistent upper-level low pressure area existed almost right over that cold water, resulting in cold and stormy weather for Alaska and western Canada. Eastern North America was very mild during September/October:

The western North America pattern persisted into November, although thanks to a “blocking pattern:” in the northern Atlantic, the eastern part of the continent was sharply colder than earlier in the season:

That blocking has broken down of late and the pattern for much of mid-December will snap back to the one that dominated in September/October.

There Are Signs The Pattern Will Change By Around Holidays/Early January

The highly anomalous warmth won’t last forever and the main drivers of atmospheric patterns are likely to start steering some cold into the region by the end of the month and into January. Some weather models suggest the period between Christmas and New Year’s will be at least more “typical” of the season and maybe even colder than average.

A colder “flip” around that time would remind us of the winter of 2017-2018, which one of our analogs for this winter. Much like this December, it was a very warm start to the month:

A dramatic change occurred by the holidays and a pretty severe cold snap unfolded:

We don’t know yet if a redux of December 2017 will occur but it certainly can’t be ruled out at this point.