Midwest blizzard to usher in polar vortex cold snap
A bomb cyclone that will bring "life-threatening blizzard conditions" to Iowa was beginning to form in the Southwest on Thursday, and is set to move across the Plains before dramatically intensifying over the Midwest.
The big picture: The third in a series of major storms to hit the U.S. in the past 10 days, the bomb cyclone will usher in the coldest air of the winter so far, which will envelop much of the country, from the northern Plains to the Gulf Coast.
- On Monday during the Iowa caucuses, for example, temperatures will be stuck in the single digits or below 0°F. Wind chills will be dangerously cold.
- First, though, the next intense storm needs to wind up and wallop a huge swath of the central and eastern U.S.
- On Thursday afternoon, there was not a single state in the Lower 48 without some form of weather watch, warning or advisory.
Driving the news: Computer models are unanimous in showing a rapidly intensifying storm system, likely to qualify as a bomb cyclone, over the Great Lakes region Friday into Saturday.
- It will feature powerful winds, given the steep differences in air pressure over short distances, and heavy snow, mixed precipitation and rain.
Threat level: The National Weather Service issued blizzard warnings for much of Iowa on Friday into Saturday for "life-threatening blizzard conditions" as winds up to 45 mph combing with heavy snowfall to produce near-whiteout conditions.
- Wind chills in Des Moines are forecast to plunge as low as minus 30°F to minus 45°F.
- Chicago could be in the snow/mix/rain transition zone for a time on Friday into Friday evening, but the city, and particularly areas away from the immediate Lake Michigan shoreline, is still likely to pick up 8 or more inches of snow.
- Blowing and drifting snow could lead to blizzard conditions at times Friday night into Saturday, and travel may come to a virtual standstill well into Saturday.
- On the warmer side of the storm, yet another round of severe weather is expected across the South and Southeast.
Zoom in: On the back side of the storm, a stout high pressure area will slide south, enveloping the Central U.S., parts of the South, Rockies and Pacific Northwest in Arctic air.
- This cold snap will come courtesy of a lobe of the polar vortex that has split off from the Arctic, and barreled south from Canada.
- The polar vortex is an area of low pressure high above the Arctic during the winter, with counterclockwise winds swirling around it. When these winds slacken or become stretched into an oval shape, rather than moving in a circle, it can allow cold air to escape the Arctic into the midlatitudes.
Details: While dozens if not hundreds of daily temperature records may be broken during this cold snap, few all-time records are likely to fall.
- This is partly because the winter is the fastest-warming season, and climate change makes it more difficult to manufacture true ultra-cold air.
- Still, this cold snap looks to bring the lowest temperatures some areas have seen in a few years, with temperatures as cold as 40 to 55°F below average for this time of year in the northern tier, such as Montana.
Of note: In Texas, this is likely to bring some of the coldest air, and for the longest duration, since the cold snap of February 2021 triggered cascading failures of the state's electric grid. (That threat is far lower with this event.)
- According to the National Weather Service, wind chills colder than minus 30°F are expected this weekend in the northern Plains and northern Rockies.
- "Have a cold survival kit if you must travel," the agency stated.
- Already, 15.6 million people in the Lower 48 states are under wind chill warnings, watches and advisories.
Here are a few forecasts for cities during the heart of the cold snap:
- Chicago: Minus 10°F with a high of 3°F on Monday
- Kansas City: Minus 12°F with a high of 4°F on Monday
- Dallas: A high of 23°F on Monday with a low of 12°F on Tuesday
- Denver: Minus 7°F with a high of 7°F on Saturday
- Des Moines: Minus 17°F with a high of minus 1°F on Monday
- Seattle: 14°F with a high of 24°F on Saturday
What's next: In general, the weather pattern across North America and the North Atlantic will be favorable for cold and snow well into next week, and possibly through late January.
The bottom line: The storm and Arctic outbreak will continue the extremely active period of winter weather in the U.S., with the polar vortex and El Niño fighting for influence.
Editor's note: Jacob Knutson contributed reporting. This story has been updated to reflect additional developments.