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Green Christmas: Springlike warmth to swell over Lower 48

It’s the fourth time this month that extremely unseasonable warmth will dominate the nation’s weather

The National Weather Service’s forecast for temperature departures from average on Christmas Eve. (WeatherBell)

If you’ve been dreaming of a white Christmas, it’s probably time to throw in the towel. Most of the Lower 48 will be looking at a spike in temperatures over the coming days that could send highs some 30 degrees or more above normal. In many spots, the weather on Christmas Eve and Christmas Day will be more reminiscent of a typical Easter.

The upcoming warm pulse will be the fourth to take the reins of the nation’s weather this month. The first, which occurred early in December, shattered temperature records in four states. Violent weather, including deadly tornadoes in Kentucky and a record-setting derecho in the central states, accompanied the second and third, respectively.

While this upcoming shot of mildness may bring welcome springlike conditions in some spots, it reinforces the connection between human-induced climate change and the incidence of warm temperatures in the wintertime. Heat extremes have outpaced cold records at a rate greater than 2 to 1 this year, and the holidays are a time of year when that warming is especially pronounced.

Climate change is shrinking the odds of a white Christmas, this year included

Already, the National Weather Service Storm Prediction Center is sounding the alarm that the warmth could brew severe weather early next week, writing, “The quality and spatial extent [of the warmth] for late December bears watching.”

The next batch of heat builds

The heat was gathering over the Four Corners region and the Front Range on Monday, including in Denver, where highs peaked around 60 degrees, as they will every day through Thursday. The average late-December high is 43 degrees. The Mile High City can blame the warmth for elevated fire concerns, which have prompted red-flag warnings in the mountains to the west. Single-digit relative humidities and gusts of up to 60 mph in mountain passes will also play a role.

“A combination of strong winds … low relative humidity … and warm temperatures can contribute to extreme fire behavior,” wrote the local National Weather Service office. The Centennial State has been dealing with a prolonged fire weather season for weeks because of drought on the High Plains and in the Rockies. One person died while fighting the Kruger Rock Fire last month in Larimer County.

That’s just the beginning. On Tuesday, the warmth will expand into the central Plains, including western Kansas, with highs some 20 degrees above normal. Then comes Wednesday, when most of the Rockies, the Plains and the West, including virtually everywhere west of the Mississippi River, will be running a general 10 to 20 degrees above average. While records may not necessarily be in jeopardy, the expansiveness and persistence of the heat are more noteworthy than its magnitude.

Heat into the Christmas holiday

Oklahoma City may be in the mid-60s by Thursday, 16 degrees above average, with temperatures near 60 riding all the way north to the South Dakota border. Denver will see a high around 62 degrees. Dallas could enjoy the mid-70s rather than the mid-50s more characteristic of late December, and then temperatures skyrocket even more.

By Christmas Eve on Friday, Dallas, Oklahoma City and Houston are expected to peak around 80, 78 and 77 degrees, respectively. Nashville will be in the mid-60s rather than its average late-December high of 50, and Kansas City could beat out its record high of 66 degrees, set in 1955, with temperatures nearing 70.

Most of the Mid-South and Mid-Atlantic will be in the 60s on Christmas too, with another resurgence of 70s over the southern Plains.

Looking ahead

Beyond this week, it’s likely that the southern and southeastern United States will remain mild; the National Weather Service Climate Prediction Center has painted above-average odds of mild weather from New Mexico to North Carolina and points southward in its two-week outlook. Below-average temperatures will predominate in the West and especially the northern Intermountain West. In between, temperatures will probably be highly variable.

It’s probable that the seasonal clash could induce some active weather, including bouts of strong to severe thunderstorms, but it’s not clear exactly where yet. That said, the month has been far from typical, and there’s no reason to think the atmosphere’s about to start behaving with just over a week left to go.