From the ABC 7 Weather team

Wintry weather still a likelihood Sunday in the D.C. area

December 5, 2013 - 03:10 PM
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A winter storm is impacting many parts of the country today and latest guidance is indicating a wintry mess for the D.C. area by Sunday.

Winter storm warnings and ice storm warnings are posted for parts of the Deep South east into the Mississippi and Tennessee Valleys today and tomorrow and reports of icing and major traffic complications are already beginning to pile in through social media.

Above is a look at just one of the highways in Oklahoma where reports of up to a quarter of an inch of ice has built up causing multiple accidents.

Here's a look at all of the watches and warnings across the U.S. from the National Weather Service. They stretch from Texas all the way to Ohio, with the shade in pink Winter Storm Warnings and in deep purple Ice Storm Warnings.

Take a look at this tweet below showing the difference in temperature across Texas.

It gives you an idea of just how much cold air is involved with this system. The cold air is undercutting the warmer air aloft, and with precipitation falling through the warm layer above it melts precipitation to rain which will then either refreeze into sleet before hitting the ground or freezing on contact with the surface in the form of freezing rain.

Below is a nice graphic showing this type of scenario.

Courtesy NWS

One of the biggest questions for the D.C. area will be how cold it is at the surface, how deep that cold layer is, and how big is the warm layer aloft. This will all determine the precipitation type at the surface.

When there is a warm layer aloft, often times if that layer is greater than 600 ft deep or if it exceeds 3-4°C, then complete melting will occur. The next problem is figuring out how deep the cold layer is at the surface, as even if the precipitation melts aloft, it may refreeze into sleet if there is a cold layer greater than 800 ft deep at the surface.

Little nuances like that make it fun for us forecasting such a delicate process. A matter of 1 to 2 degrees are all that it takes to differentiate snow, from sleet, to freezing rain and plain rain. And you say meteorologists have it easy!

What we can give is our best guess this far out. Right now, we think hazardous conditions will be likely through the day on Sunday. Here's our current thoughts as to the timing.

Start Time Frame: 7am - 11am

-Taking a look at some of the guidance, the starting time has been delayed just a bit to the mid-morning hours on Sunday. This could be bad news for people headed to the Redskins or Ravens games as it may be quiet when you wake up but treacherous by the time you exit the game. Keep that in mind for now and stay tuned to the latest updates.

850 Temperatures Sunday Evening

Changeover to Rain: 5pm (East) - Overnight (West)

-A changeover from snow and sleet early on to plain rain is still expected, but it appears like it will be a slow progression from east to west with some western areas hanging on to freezing rain through the overnight on Sunday. This will be the toughest part of the forecast and has the least confidence at this point.

Our thoughts are that D.C. and points east will change to rain after sunset and points north and west will hang on to freezing rain overnight. This may lead to delays or possible closings Monday morning.

System Exits

-The system won't exit the region until Monday or Tuesday as the cold front moves off the east coast. Rain will fall during the day on Monday and temperatures will rebound into the mid and upper 40s. Much colder air will filter into the region Tuesday and Wednesday with highs in the mid 30s each day and lows into the teens possibly by Tuesday night!

Impacts

-Areas of light snow are expected to develop in the morning hours, changing to sleet and eventually freezing rain later into the afternoon and evening. Light accumulations may be possible, though they are too difficult to pinpoint at the moment. Regardless, we think it will be enough to cause slick road surfaces and enough of a travel issue that you might want to stay home Sunday afternoon and evening.

Depending on the amounts of snow, sleet and icing, power may be lost, so be sure to just keep that in the back of your mind in the case of the worst scenario.

We will have full updates tonight on ABC 7 at 5, 6 and 11pm and will continue to update you on each live newscast. In addition, we'll be updating our website around the clock tonight and tomorrow and will continue to substantial updates through the weekend.

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