From the ABC 7 Weather team

Major winter storm organizes across the country

December 4, 2013 - 11:27 AM
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A major winter storm will affect a large part of the U.S. over the next few days. A mix of snow, sleet and freezing rain may even pay a visit to the D.C. area late this weekend.

Numerous weather alerts are posted through the country, with heavy snow falling in the Rockies to the Midwest, and the potential for a dangerous ice storm shaping up for parts of the Central Plains and Mississippi Valley.

This will be a high impact system with numerous travel complications likely through the weekend.

Watches and Warnings as of 11am Wednesday

Flight Aware Misery Map

Heavy snow has already been reported across parts of the U.S., with some of the heaviest totals so far seen in Minnesota. Below is a tweet from Susie Martin.

For those of you that are looking forward to ski season, it's already looking good in the Rockies, with reports of over 10" of snow so far in locations and the possibility of 1 to 2 feet more. Here's a look at the Vail Mountain Cameras. I wish I was out there with them today!

Snow isn't the only issue in the forecast, as freezing rain will become a big problem from Texas and Oklahoma, east to the Ohio Valley.

Below is a look at the probability of more than 0.1" of freezing rain across the U.S. from a 48-hour period Wednesday night through Friday night.

Graphic from the WPC

This shows a 80-90 percent likelihood of greater than 0.1" of freezing rain accumulating across parts of southeast OK, much of AR and points northeast through the Mississippi and Ohio Valleys. This storm will affect those regions through Friday night into Saturday morning.

The next threat will move in behind this system and will bring an additional chance for frozen precipitation into the weekend for the D.C. area.

This has been a relatively consistent forecast since the beginning of the week and the chance for a wintry mix at the onset of precipitation and possibly a good amount of Sunday is increasing.

(Courtesy: WeatherBell)

Above is a look at the forecast MSLP, 3-hr precipitation and 850mb temperatures for Sunday around lunch time per the GFS model. If you take a look at the northeast, you see the blue H over Canada representing a large area of high pressure.

You also see the black lines which are constant lines of pressure (called isobars) dipping on the east side of the Appalachians. This is showing cold air damming, as the cool, dry air from the high over Canada is pushing air into the D.C. area from the NE and trapping it against the mountains.

As warmer air and precipitation moves over the cold pool at the surface, the air will begin to saturate and temperatures will more than likely be below or near freezing through much of the D.C. area.

Depending on the depth of the warm air layer above the surface, precipitation may either fall as snow, melt some and refreeze in the cold pool to sleet, or possibly melt aloft and fall onto a frozen ground in the form of freezing rain.

This could cause travel complications across the D.C. area Sunday, but don't expect to have Monday off, as warmer air is expected to move into the region late Sunday into Monday morning changing everything over to rain.

Places that will hang on longest to the wintry precipitation will be in areas to the northwest such as the Shenandoah Valley. We will have further updates on this developing situation in the D.C. area over the next few days.

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