National Harbor at sunrise from Jones Point Park in Alexandria, Va., on Dec. 29. (Carol Jean Stalun via Flickr)

The punishing cold pattern that closed December shows little sign of relenting as we start January.

Get ready for more winter as we’re forecasting January to run 2 to 4 degrees colder than normal (normal is 36 degrees) with near normal snow (around 5.6 inches).

Precipitation overall, factoring in rain and mixed precipitation in addition to snow, should end up slightly below normal (0.25 to 0.75 inches below the average of 2.81 inches).

After two really warm winters, many of us may have forgotten what real cold feels like. The current weather pattern, which we expect to continue, is offering us a stinging reminder.

The chill in the final week of 2017 should tip the scales to provide the first colder-than-normal December since 2010.  Interestingly, of the six colder-than-normal Decembers since 2000, all but one presaged a cold January.

So the odds appear elevated that we’ll continue this cold narrative for the new month ahead.

Since 2000, we’ve experienced a genuinely cold January once every three years on average. Our most recent notably cold January was 2014, infamous for the polar vortex blast. This January might bring back those memories.


Chart showing the percentage of Januarys above, below, and near normal since 2000.

Snow

Washington’s 30-year (1981 to 2010) average snow in January is 5.6 inches. With all of the cold air in place, we have a reasonable chance to reach that amount.

Getting much more than that may be a challenge. We’ve only exceeded normal snowfall in January six times since 2000. The last time we did it was just two years ago with the one-time super El Niño snowstorm, which we named Snowzilla. We have more difficulty getting big snowstorms during La Niña years (we are in a weak to moderate La Niña right now), although we did it big-time back in January 1996 — never say never!

January outlook rationale

Here are the different factors we used to develop our January outlook. …

Impressive cold pattern to dominate first half of January.  After two warm-dominated winters, it seems like the colder base state that influenced our 2013-14 and 2014-15 seasons has returned. That includes a resurgence of the “ridiculously resilient ridge” pattern over Alaska that causes the jet stream to crash back down over the eastern United States, unleashing Arctic air.

The various weather models have tried to kill this western ridge pattern off a few times in the past few weeks, but it keeps coming back!

The 15-day forecast from the European modeling system is shown below.


You can see the strong high pressure ridge feature over Alaska and the Gulf of Alaska.  Like a seesaw, big high pressure warmth over Alaska displaces big cold air downstream over the eastern Lower 48.

CFS model shows mixed signals. The National Weather Service’s CFS long-range model is currently struggling to get a grip on the forecast. It has shown both warm and cold outcomes for January, but it is recently trending back colder again and leans mostly to the drier side.

National Weather Service provides tantalizingly close calls for Washington.  Its forecast maps shown below show the Washington area right outside the magical criteria for snow-lovers — above normal precipitation and below normal temperatures.  This might suggest that we’ll have some reasonable chances for snow, but that they’ll be hit or miss.



While the National Weather Service predicts a very cold start to January, it does suggest a thaw is possible in the second part of the month while ramping up precipitation chances some:

If the cold comes as advertised during the first half of the month, we’ll be ready for some relief.

The torrent of arctic air that poured into many parts of the United States this week tightened its grip on Dec. 30 and brought record cold to some areas. (Reuters)