While January should still be warmer and wetter than normal thanks to El Niño, the odds of a record-warm month are much lower. Overall, I expect a slightly warmer than normal month with below normal snow.

Here are the numbers…

The temperature forecast

I’m calling for the average January temperature to be 37 to 39 degrees, which is 1.5-3 degrees above the January 30-year normal of 36.0 degrees. My confidence is medium to high that it will be milder than average, but I’m not as certain about the magnitude.

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Our most recent super El Niño of January 1998 was much milder than normal with an average temperature of 43 degrees (7 degrees above normal), but the next most recent super El Niño in 1983 averaged 38.1 degrees, which is closer to our outlook.

The precipitation forecast

Precipitation (rain and melted snow) should be near average, with approximately 2.5-3.0 inches of rain (the average is 2.81 inches). Confidence in the precipitation outlook is low

Other super El Niño January periods have produced varying precipitation amounts ranging from 1.69 inches (Jan. 1983, below normal) to 5.43 inches (Jan. 1998, much above normal).

The snow forecast

Sorry, snow lovers. I’m calling for just a trace to 3 inches (the normal is 5.6 inches). However, confidence is just low to medium – meaning there’s a decent chance I could be wrong.

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The past super El Niño January periods both recorded just a trace, so there’s little precedent for a snowy January under such a regime, though the sample size is small.

January snow in the 2000s has ranged from zero in 2006 to 14.5 inches in 2000 with that year’s surprise snowstorm event. In 2015, we only managed 3.6 inches in this month. With a super El Niño, the odds seem better for another no-snow result. However, we do have some cold air in the pattern mix unlike December, so we should at least include the odds of up to 3″inches as a possibility. Half of the years during 2000s saw 3 inches or less during this month.

January forecast rationale

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A milder start

While not as crazy warm as the December kick-off, we are still seeing the first third of January highly favored to verify warmer-than-normal for Washington D.C. The New Year’s holiday weekend (first three days of month) averaged just shy of 5 degrees warmer than normal, a fairly decent head start. And while we go colder early this week, there is another round of warming coming just beyond that into early next week that should also average 5-10 degrees warmer than normal.

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El Niño

We continue to track a very powerful event in the Tropical Pacific that is a major driving force for our winter weather pattern. The latest view (from satellite estimates as shown below) continues to highlight this monster with warmer than normal water temperatures from the International Dateline to South America.

Like we saw in December, El Niño forcing works to flatten the jet stream and send warmer Pacific air streaming across the U.S. to limit access to colder air from Canada. We may occasionally see some colder weather, especially due to a new feature arriving- described next- but El Niño forcing should limit the duration and intensity of that cold.

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Blocking

A new kid has shown up on the block for January and it’s known as “blocking”. This signifies large areas of high pressure stalling out to our far north, for example in Alaska, the North Pole, and Greenland. When that happens, it helps transport cold air southward in our general direction.

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In a normal winter, we would be blasting headlines about a massive, sustainable cold winter pattern. But this is not a normal winter and the powerful tropical Pacific super El Niño should frequently act to offset the typically colder blocking influences. This happened in January 1998 too when blocking over the North Pole (negative Arctic Oscillation) was prevented from affecting the U.S. as much and the pattern stayed warm-dominated. We expect this blocking to bring some cold into our area (like early this week and again later next week), but its duration and intensity should be more limited thanks to El Niño.

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Long-range models

The CFS model from the National Weather Service has mostly featured a warm and marginally wet pattern for our area, but it has been much less consistent in portraying this pattern compared to what we saw in December. This suggests to me that January will be “noisier” with both colder and warmer periods at times, but thanks to El Niño, the warmer periods should win…again.

National Weather Service

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The National Weather Service presents a more complicated January outlook than what we saw last month. A newly-active feature called the Madden-Julian Oscillation (MJO) has set the stage for more high-latitude blocking influences that send cold air southward from Canada, but at the same time, we still have fairly strong El Niño forcing, which is a warm influence.

Its forecast splits the difference and favor typical El Niño warmth to the north and cooler conditions to the South, while keeping the middle part (including the Mid-Atlantic!) on the fence. They also keep the Mid-Atlantic on the fence with respect to precipitation. You can read the Weather Service’s January forecast discussion here.

Review of December’s forecast

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Our forecast for December performed well with regard to our call for a warm-dominated month with little to no snow chances. However, precipitation was ultimately underestimated as was the massive magnitude of the warmth.

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December average temperature forecast

We called for an average temperature of 42 to 44 degrees, which is 2.3 to 4.3 degrees above the December average of 39.7 degrees. The right answer was 51.2F, 11.5F above normal. So we were correct on direction, but quite a bit off on the magnitude.

December precipitation forecast

We predicted 2.75 to 3.25 inches of rain, which is right around the average of 3.05 inches. The right answer was 4.84 inches, which was more than expected but we conveyed low confidence in this part of the outlook.

December snow forecast

We called for no snow or a trace (normal is 2.3 inches) with medium to high confidence and we were right.

Summary review

Overall, I’d grade our December outlook a “B”, particularly since the no-snow forecast worked out well.