Severe storm possibility Wednesday

Just three days ago, we were dealing with sleet, freezing rain, school closings, and hundreds of motorists smashing into guardrails and other vehicles.

Now we're talking about 70 degrees and a chance of damaging winds and tornadoes in two days.

A brief switch in the upper atmospheric steering currents will allow a return of very warm weather to the Carolinas for about 48 hours, starting later today. But that will end Wednesday with a strong cold front and the threat of severe weather.

After another cloudy and cool afternoon today, with high temperatures probably only reaching the upper 40s, the pattern change will start tonight. Warmer air will arrive from above, probably trapping cooler air near the surface and causing fog in the early-morning hours.

But once the sun rises, mixing the atmosphere Tuesday morning, the fog is expected to dissipate in a hurry, and we'll see temperatures reach the upper 60s.

Wednesday also will be warm, but a strong cold front will be approaching the region by late morning and afternoon.

Harry Gerapetritis, of the National Weather Service's office in Greer, S.C., said there will be very strong winds in mid levels of the atmosphere in advance of the front, and some computer models indicate those winds will be transported to the surface as the front approaches.

In addition, heavy rain is possible in the mountains and foothills, and those areas already have received 6 or more inches of precipitation in the last few weeks. So flooding also will be a threat.

"Both a flash flood watch and a high wind watch could be needed" in the mountains for Tuesday night and Wednesday, Gerapetritis said.

In the Piedmont, the threat is expected to develop after midday Wednesday, when the cold front approaches.

Gerapetritis said a few of the thunderstorms could become severe, especially in the Interstate 77 corridor of North Carolina, and in the South Carolina upstate.

"Damaging wind gusts will be the primary threat, but isolated tornadoes will be possible as well," he said.

His assessment is supported by the Storm Prediction Center in Norman, Okla.  In fact, SPC meteorologists have painted a large area of the South and Midwest -- stretching from Texas to central Illinois and Indiana -- for a threat of severe weather Tuesday. Then on Wednesday, the severe threat area stretches from the Gulf Coast to Virginia and southern Kentucky.

Behind all this will be a return to cold and stable conditions for several days.  High temperatures will only reach the middle and upper 40s Thursday through Sunday, but there are no signs of low pressure areas that could bring another threat of frozen precipitation.

In fact, some of the longer-term models point to a rather mild (even warm) period for at least the first half of February. We'll be talking more about that in coming days.