Are you enjoying the (sort of) warm weather we've seen for the past day or two? Don't get used to it. A surge of Arctic air will deliver subfreezing highs for most of the country early next week. It won't be anywhere near as bad as last winter's "polar vortex" panic, but it'll be a miserable cold spell just in time for the new year.
Almost everyone who lives east of the central Plains has experienced downright comfortable temperatures for the past day or two, with high temperatures coming in 10 to 20 degrees above normal for this time of the year. Yesterday's high in New York City was 63°F—tying the record for the date—clocking in nearly 25 degrees above average for Christmas. Montreal, Quebec has already blown past its record high of 28°F for December 26, sitting at 41°F as of the writing of this post.
Why are we seeing such a relatively warm spell this late in December? A large ridge in the jet stream is facilitating a center of high pressure at the surface over the southeastern United States. Winds flowing clockwise around the high are dragging warm air from the Gulf north into the United States and Canada, creating a highway of comfort, to put it in the cheesiest terms possible. The above map shows surface pressure (contours) with winds (shading)—winds roughly follow the contours.
While some of these temperatures are approaching record territory, Christmastime-ish warm spells like this have happened before, most notably back in 1982.
Many cities like Chicago and New York City set record highs on this date 32 years ago thanks to a low pressure approaching from the Rockies and a high pressure sitting over the Atlantic. The enhanced southerly winds between the two features pulled very warm air north from the tropics, bringing temperatures in the mid- to upper-70s as far north as southern Ohio. Buffalo—tropical paradise that it is—recorded a high of 62°F.
After that nice trip down memory lane, let's talk about the frozen hellscape that will unfold next week. No, it won't be frigid on the levels that we saw last year, but it'll get cold, especially after we were spoiled by this welcomed warm spell.
Unfortunately, and as expected, the warm-up will be short lived. A cold front currently sitting near the Mississippi River will slowly make its way east over the weekend, bringing bitterly cold Arctic air with it. High temperatures in the northern Plains along the border will struggle to climb above zero on Monday, and by Wednesday, high temperatures will be at or below freezing from central Texas through Tennessee and into the Mid-Atlantic.
Even in Minneapolis this weather will be relatively cold. The average high/low for Minneapolis around this time of the year is 22/7—beginning next week, the GFS model and its ensembles are predicting a prolonged period of highs in the teens with temperatures a few degrees on either side of zero.
Chicago will see a prolonged period of highs in the low- to mid-20s with lows in the teens, while New York will find itself a little more mild, with highs for the next week or so hovering in the 30s.
Winter is returning to the United States after a short vacation. Even if it's going to get a little colder than normal in spots, we've been spoiled this year with the amount of open window time we've enjoyed. When it comes time to warm up, maybe burn some of that coal you got as a gift yesterday. (And if push comes to shove, ugly sweaters burn well, too!)
[Images: Tropical Tidbits x2, NOAA, WeatherBELL x2]