So it’s time to break out the beach shorts, right? Not quite.
The “warmth” will be driven by one big global player: El Niño, which is already the strongest on record by one measure. The huge pool of toasty tropical water in the Pacific Ocean plays a significant role in wintertime weather across North America. Mainly, it sets up a high likelihood for high pressure to build over much of North America, while cool troughs of low pressure tend to dominate the eastern Pacific Ocean and skirt east across the southern states.
Not one state in the lower 48 is forecast to average below average temperatures during the 6-10 day period. pic.twitter.com/DEhFRvd1ZF
— Michael Ventrice (@MJVentrice) December 2, 2015
That pattern is exactly what the weather models are suggesting — in remarkable agreement — for the month of December. Michael Ventrice, a forecaster at WSI, says he has never seen such a strong signal, nor such consensus between models.
But while this forecast has been pretty mind-blowing for meteorologists, it can lead to misconceptions about what the weather will actually feel like in December.
Warmer than average doesn’t necessarily mean ‘warm’
Don’t be fooled by all of those dark red maps. There’s a difference between warm — let’s say anything over 60 degrees — and warmer than average.
For example, the average temperature in D.C. starts at 44 degrees on Dec. 1 and sinks to 36 degrees by Dec 31. In Minneapolis, it starts at 25 and ends at 16.
It’s also not a forecast for every single day in December. There will be days that are much warmer than average and days where it’s below or near-average. The monthly forecasts describe what conditions will be, averaged over the entire month. There will still be plenty of fluctuation built into our December weather.
— WeatherBELL (@weatherbell) December 2, 2015
All this being said, it seems highly likely there will be plenty of days where it just doesn’t feel like winter, especially in the Midwest, Northeast and Mid-Atlantic. You might get away with a light coat in many places, especially over the next week or two, when temperatures are expected to run as high as 15 degrees above average in the Midwest. For Minneapolis, this will mean temps in the 40s, which, far from beach weather, is much better than the teens or 20s.
It can still snow
Just like there will be variation in temperature over the month, so will there be changes in precipitation. It’s true that high pressure is forecast to dominate the weather pattern over North America in December, but there’s still room for troughs of low pressure to zip across the United States.
This high pressure pattern is something we have already seen this fall, and there were quite a number of snow and ice storms in November. Two storms pushed Sioux Falls, S.D., to its fourth snowiest November on record, and as much as 1.5 inches of freezing rain accumulated on surfaces in Texas, Oklahoma and Nebraska over Thanksgiving weekend.
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In Chicago, it’s already snowed twice this year. But, as longtime WGN forecaster Tom Skilling wrote on Tuesday morning, it’s but an interruption in the abnormally mild pattern that has dominated fall.
“The early season snowfall which hit hit the Chicago area two weekends ago was another and is proof it can still snow during El Ninos,” Skilling writes. “But, the overwhelming fact is that an impressive 64% of Sept, Oct and Nov days finished with temp surpluses and each of the past three months have been warmer than normal — the first time three consecutive months have posted temp surpluses here in more than two years.”
It doesn’t mean the rest of winter will be just as warm
Though we think this pattern has a high chance of holding over into 2016, the truth is second- and third-month forecasts have much lower confidence. But if we’re going to get a big shot of wintry weather, it’s more likely to be after December.
Matt Ross, our seasonal weather forecaster, is predicting slightly elevated chances for a big winter storm this season. “Because we are expecting an active winter with storms approaching from the south and west, it is possible the ingredients for a bigger storm could come together when we do get our cold shots,” Ross says. “The most likely time period for a big storm would be February.”
Really, it’s good news all around; if you enjoy warmer winters, you’re really going to like this one. But if you crave a big, cold winter storm, the window is open for that, too.