Much of the country's midsection will face severe storms and a high risk of tornadoes. NBC's Brian Williams reports.
By John Newland, Staff Writer, NBC News
A storm system stretching across much of the U.S. brought snow to the Mountain West on Tuesday, with forecasters warning severe thunderstorms and tornadoes will this week present a hazard from Texas to the Southeast.
Blizzard warnings were in effect in Utah and Colorado, and winter storm warnings stretched northeast to Minnesota. As much as two feet of snow was possible in South Dakota by Thursday morning.
Temperatures dropped dramatically as the system moved into the Mountain West. In Denver, it was 71 degrees at 2 p.m. local time Monday (4 p.m. ET), according to the weather service. By 7 a.m. ET Tuesday, it was 16 with a wind chill of 1 degree. ?
As of 5:30 a.m. local time (7:30 a.m. ET), 238 flights had been cancelled since Monday night at Denver International Airport, according to?FlightAware.com.
A strong dip in the jet stream has shifted west and is pulling arctic air deep into the country, where it is colliding with warm, moist air pushing north from the Gulf of Mexico. This is creating instability that will ?bring a variety of hazards,? the National Weather Service said.
Seth Wenig / AP
Kids including Branden Rivera, 9, spray each other with water from a drinking fountain while enjoying the warm weather in New York on Monday. Things may not be so pleasant later this week, as a massive storm system moves east.
Earlier in the week, with the jet stream dipping in the East and down to the gulf, severe weather was largely confined to parts of the Deep South. Its move westward allows the gulf?s hot, wet air to assert itself and bring what the weather service termed ?a plethora of interesting weather conditions.?
That means storms, and lots of them.
?We?re looking at the gamut today for severe weather,? Weather Channel meteorologist Kevin Roth said Tuesday.
While the Southeast and Mid-Atlantic north to Washington may see their first 90-degree highs of the year on Tuesday, blizzards were forecast from Utah to South Dakota.?
Between the extremes of hot and cold, where the systems collide, ?is where we should see the storms start to fire,? Roth said.
As Roth runs through the week?s forecasts, the predictions aren?t for the timid: ?Damaging wind gusts, very large hail ? baseball-size or larger ? and also the threat of tornadoes. ? And we have the potential for a foot or more of snow from eastern Wyoming and northwest Nebraska all the way to Minnesota.?
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An area including Wichita, Kan., Oklahoma City and north-central Texas should be prepared for severe thunderstorms and possible tornadoes, Roth said. On Wednesday, severe storms are likely to strike in the Mississippi Valley, from St. Louis to northern Louisiana. And on Thursday, powerful storms will threaten a broad area from the Ohio Valley to the Southeast, including Florida.
Meanwhile, during that same period, heavy snow should make its way from Colorado and Wyoming through Minnesota and into Wisconsin and the Upper Peninsula of Michigan, Roth said.
While the outlook ? particularly in areas threatened by tornadoes -- is severe, it?s not uncommon for a spring storm, he added.
?Be careful what you wish for,? Roth said. ?With spring, with the warmer weather, comes the threat of severe storms and tornadoes.?
This story was originally published on Tue Apr 9, 2013 4:59 AM EDT