From the ABC 7 Weather team

Icing likely in parts of the D.C. Metro tonight into Wednesday

February 4, 2014 - 06:20 PM
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Heavy icing is possible across parts of the D.C. area tonight into Wednesday morning.

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Icing has already become a problem across parts of the U.S. today, with reports currently from Arkansas expected to spread east into the Ohio Valley later this afternoon. Below is a look at a tweet from Little Rock, Arkansas of icing on power lines. This kind of precipitation is expected for areas west of D.C. overnight into Wednesday morning.

Low pressure is expected to develop over the Tennessee Valley tonight as precipitation begins in the D.C. area. High pressure located to the north will supply cool, dry air at the surface which will keep temperatures at or below freezing overnight when precipitation begins. This in turn will allow precipitation to start in the form of sleet and freezing rain for the majority of the region.

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Precipitation should start tonight closer to 11pm in the D.C. area. Temperatures are currently at or below freezing from Dulles and Gaithersburg and points west. It will be those locations that see the highest likelihood for accumulating ice on trees, power lines, and roadways.

Winter Storm Warning and Freezing Rain Advisory

A Freezing Rain Advisory is in effect close to the D.C. Metro while Winter Storm Warnings are in effect in areas such as Loudoun, Montgomery and points farther west. Freezing rain is expected to change over to plain rain in the D.C. Metro by the early morning hours closer to sunrise, while freezing rain is anticipated to hang on for a longer duration for areas under the warning.

Precipitation type accumulations by 10am Wednesday per the 4km NAM Model (Courtesy: WeatherBell Models)

Freezing rain may total up to 0.25" to 0.5" in areas under the warning, and closer to 0.1" in areas under the advisory. Looking at the 4-plot chart above of the 4km NAM Model output by 10am Wednesday, it appears like a quarter inch of rain or isolated higher amounts may be possible in Southern Maryland where warmer temperatures shouldn't allow for as much freezing precipitation.

This model still depicts up to 0.1" of ice possible along and just east of I-95 tomorrow morning but once it changes over to rain, ice should be washed away pretty quickly close to the D.C. Metro. For instance, in the potential graphic below, remember that the "up to 0.1" of ice" should change to rain in the early morning.

Icing potential tonight into Wednesday

Our team still thinks there will be a number of delays and cancellations Wednesday and the morning commute will be a mess, so be sure to factor in extra time. Getting up early won't necessarily make it an easier trip with the changeover to rain expected closer to sunrise in the D.C. Metro. Be sure to take it extra slow on side roads and elevated surfaces such as bridges, overpasses and on/off ramps.

Stay tuned to ABC 7 News at 5pm, 6pm and 11pm for Chief Meteorologist Doug Hill's latest forecast and until then please tune in to Newschannel 8 (watch it live online!) for continuous coverage.

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