From the ABC 7 Weather team

Snow in the forecast for the D.C. area Thursday

January 16, 2013 - 10:36 AM
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Snowfall is finally in the forecast for the D.C. area Thursday, as a Winter Storm Watch has been issued for the greater Washington area.

The Winter Storm Watch takes effect on Thursday morning. Photo: Richard Reeve

As of January 15, Reagan National Airport has recorded 0.2 inches of snow so far this winter, which is 4.8 inches below the seasonal average, and January is down 2.2 inches for the month.

These numbers are likely to change, however, with a snow-maker developing for Thursday. An evolving low pressure system looks like it'll take a turn closer to Washington, and with plenty of cold air in place, the region may be in for a messy commute home on Thursday.

The National Weather Service has issued a Winter Storm Watch for the greater D.C. region starting Thursday morning.

This system has been on our radar (figuratively speaking) all week, as it has shown up on every single model run and has been a part of every single forecast. The problem is that earlier this week, this low had been expected to stay south of D.C. with the northern extent of the precipitation to brush Fredericksburg and Southern Maryland.

Since then, there has been a trend in the models to take the main area of low pressure a bit farther to the north.

500mb vorticity plot showing the main energy over the Deep South

As a result the current trend is to push the precipitation northward over D.C., with areas north and west of the city (Frederick, Md. to northern Loudoun County, to Frederick, Va.) not really expected to see much precipitation at all. The D.C. metro area and points south should have some measurable snow to contend with by midday Thursday.

What can be expected Thursday:

The morning commute should be cool with temperatures starting in the mid to upper 30s with spotty light rain showers. Once everyone gets settled in at work and school, it appears the system will start to make its way into the D.C. area and start the change over to snow.

Here's something everyone should take note of: precipitation should start falling in the form of rain in the morning but change to sleet and snow throughout the morning and midday.  The heaviest snow should fall during the afternoon and evening drive home.

Winter Storm Watch issued for Thursday

A cold front will be pushing into the area midday and colder air will be sliding into the region which will help turn everything over to snow. The timing of the change over to snow will vary across the ABC7 viewing area and happen a little later south of Washington. 

There will be a sharp difference in snowfall totals north to south due to a steep gradient in precipitation associated with the low pressure system.  This and the timing of the change over to snow is the biggest forecast challenge at this time.

Snowfall Amounts:

Forecasting snowfall amounts for this system is very challenging because of the aforementioned phase change, the exact track of the low, and the location of the sharp precipitation gradient/cutoff along with a few other factors.  As of now, we expect 2 to 4 inches around the D.C. metro area with the potential for higher totals south.  These numbers hinge on a few factors that will become more clear later today.

Snow forecast for Thursday
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