Winter is coming. Finally.

After months on end of warmth across the country, cold air will finally arrive for much of the U.S. next week. The chill will start in the West as Arctic air spills down and turns the map blue from Alaska to the Southwest and then migrates eastward as the week goes on.

Temperatures could dip down to 30°F below normal, with the coldest air centered over the Northern Rockies and High Plains by midweek. Highs will be in the single digits and low teens for much of the area, and in the mountains, they could bottom out below zero. By the end of the week, the Northeast is likely to feel the effects of the cold snap, though temperatures will be a little less extreme and likely in the 8°-14°F below normal range.

Winter weather

The midweek forecast temperature anomalies for the U.S. using the NAM model.

The Climate Prediction Center’s 8-14 day forecast shows the entire U.S. will have increased odds of colder than normal temperatures. The last forecast of that kind for the U.S. came in December 2013, according to Brian Brettschneider, a climate researcher based in Alaska (you may remember that polar vortex thing).

The impending cold spell will come after a year-to-date of abnormal warmth across the country. There have been multiple stretches this year where the entire U.S. has been warmer than normal for weeks on end.

CPC forecast outlook composite
CPC forecast outlook composite

Every CPC 8-14 day outlook over the past year. Increased odds of warm weather has been forecast more often than cold weather, including a number of spells forecast to be all warm across the U.S.

Daily record highs have outpaced record lows at a rate of 5:1 this year, including an insane November when daily high maximums and minimums outpaced their low counterparts by a whopping 44:1 according to the National Centers for Environmental Information. Every state is having a top 10 warmest year-to-date, a pattern which has the U.S. as a whole on track to have its second-hottest year on record (the planet is also having its hottest year ever recorded).

All this is to say that the incoming cold blast, which could set a few daily record lows, is going to be stepping out of a sauna and into a walk-in refrigerator.

The chill is likely to linger out West for the entire month. It will also be accompanied by a more stormy weather pattern across the northern half of the U.S. That would be a boon for ski areas in the Northern Rockies, which have been languishing due to warm temperatures and very little snow. That weather pattern is indicative of the weak La Niña, which tends to create cooler, wetter conditions in the region.

In the Northeast, the CPC indicates that December as a whole is likely to be warmer than normal and longer term patterns may favor a return to unseasonable temperatures for the back half of the month.

Signs also point to a wet spell for the Southeast, which is atypical for La Niña. Residents of the region won’t complain, however, as exceptional drought now covers an area that’s 50 percent larger than the area of exceptional drought in California.