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(CNN)A mammoth storm is threatening to paralyze parts of the Midwest and South with ice, snow, dangerously cold temperatures and possible power outages starting Wednesday.
Ice accumulation is expected across the South, including in the Dallas-Fort Worth region and Memphis, with effects that could linger into the weekend. Overall, more than 100 million people are under winter weather alerts that stretch from the Rockies to New England.
“A corridor of heavy ice accumulation (exceeding a quarter of an inch) is likely from Texas through the Ohio Valley,” the Weather Prediction Center said early Wednesday. “Locations impacted by snow and/or ice are expected to have temperatures remain below freezing, and well below average for at least a couple of days after the wintry precip(itation) ends.”
About 3,000 US domestic flights have been canceled Wednesday and Thursday because of the storm, according to FlightAware. Airlines including Southwest, American, United and Delta Air will let travelers impacted by bad weather rebook for free.
Recalling the deadly outages of last winter, Texas Gov. Greg Abbott assured residents Tuesday that the power grid — Electric Reliability Council of Texas, or ERCOT — is in a better position to handle the potential impact of the storm.
“Right now, the prognostication is that ERCOT will have an access of 15,000 megawatts of power available even at time of highest demand. So ERCOT is well-prepared for conditions as they currently stand but remains flexible in order to be able to be responsive to power demand needs,” Abbott said during a news conference.
Still, power may go out because of problems unrelated to the grid’s capability, including falling trees or icy power lines, the governor warned.
In the Midwest, the governors of Missouri and Oklahoma declared states of emergency until Thursday due to the storm.
Oklahoma City could see up to 8 inches of snow as well as ice accumulations in the quarter-inch range, with some places seeing up to half an inch of ice, the National Weather Service said.
In St. Louis, heavy mixed precipitation is possible, with ice accumulations up to two tenths of an inch.
“The winter storm is expected to include a mix of freezing rain, sleet, snow, strong wind gusts and low temperatures across the state beginning Wednesday, which may result in power outages,” Oklahoma Gov. Kevin Stitt said in a news release.
In addition to declaring the emergency, Missouri Gov. Mike Parson activated the National Guard, saying it will be ready to help the state’s highway patrol with stranded drivers.
Ice is this storm’s biggest threat
Forecasters predict heavy snow, with some places in the Midwest due for 15 to 20 inches, CNN meteorologist Dave Hennen said.
But the bigger threat will be ice accumulation.
“I do think that ice will end up being a bigger threat due to the more lasting impacts of ice on power lines and tree limbs,” CNN meteorologist Robert Shackelford said. “Ice accumulations are usually very small — we are talking about fractions of inches. Yet, these accumulations can bring widespread power outages and impossible travel conditions.
“These forecasted snowfall totals are not to be taken lightly” either, he said.
After the storm pushes south and east from its origin in the Rockies region, conditions are expected turn more icy than snowy, with the threat of significant ice accumulation for millions. The impacts could linger, especially in the South and Mid-South, until Saturday or Sunday, according to forecasts.
In Arkansas, Gov. Asa Hutchinson has deployed some 88 members of his state’s National Guard. He also signed an executive order that will allocate $250,000 for recovery efforts.
In Illinois, Gov. JB Pritzker also activated the National Guard and issued a disaster declaration. The state Department of Transportation will also deploy more than 1,800 trucks and equipment to plow, treat roads and respond to weather emergencies, it said.
Meanwhile, areas north and east of the Dallas-Fort Worth metropolitan region are expected to bear the brunt of this storm.
“The primary impact would be ice accumulation that may lead to very dangerous travel Thursday and Friday particularly on high-rise overpasses,” the National Weather Service office in Dallas-Fort Worth said.
“A quarter-inch or more of ice accumulation on utility lines and trees with winds gusting to 30 mph would likely lead to power outages and tree damage.”
School closed for some in Texas and Missouri
The potentially dangerous conditions have led the Dallas Independent School District to close Thursday and Friday, and schools are not expected to make up those days, officials said Tuesday.
In Kansas City, Missouri, the school district also moved to shut its doors Wednesday due to the storm’s potential impact.
“Students are not expected to log into virtual learning. Enjoy your old-fashioned snow day, and be safe!” the district said in a Facebook post.
CNN’s Monica Garrett, Jennifer Gray, Gregory Lemos, Dave Alsup, Joe Sutton, Ed Lavandera, and Amy Simonson contributed to this report.