* Winter weather advisory midnight to 9 a.m. Thursday *

A moisture-starved, but energetic ripple in the atmosphere will zip across the Mid-Atlantic tonight, producing areas of snow showers. Given very cold temperatures near 20 degrees, every fluffy flake will stick.

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A dusting to just over 1 inch of snow is the most likely scenario for most of the Washington, D.C. metro region and a few slick spots are possible early in the morning.

Heaviest amounts are favored south and southeast of Fairfax county, where up to an inch or even a little more snow is possible. North of Montgomery county, amounts are likely to be somewhat less.

Chance of 1 inch or more of snow

Immediate Washington, D.C. area: 50 percent
North of Montgomery county: 40 percent
South of Fairfax county: 60 percent

Timing: 11 p.m. Wednesday to 6 a.m. Thursday

“My feeling for amounts would be in half inch to 1.5 inch range for most of the area with the lighter amounts north and the higher amounts south,” said Wes Junker, Capital Weather Gang winter weather expert.

Junker cautioned a few flakes could linger into the very early part of Thursday morning’s commute and that slick spots are possible on area roads.

With very compact weather systems like this one, the exact location of the heaviest snowfall is difficult to pin down until the snow is actually falling. Somebody could get 2 inches of snow. On the other hand, because the ribbon of snow that develops will be relatively narrow, some areas may see just a few flurries and awaken to bare ground.

Schoolcast commentary: Although a few slick spots are possible early in the morning, this will be a light, powdery snow that will quickly exit the region and probably be fairly low impact. For those areas that get up to an inch or so of snow, a one or two hour delay is possible.

Technical discussion

Upper level disturbance passing thru Fredericksburg area early Thursday morning (WeatherBell.com)

This system is a classic “clipper”, moving along the jet stream (region of fast upper level winds) from northwest to southeast. Ordinarily, the heaviest snow in such systems falls just north of the track of the upper level disturbance.

But models are suggesting, in this case, heaviest amounts will be just south or southeast of the upper level disturbance or just north of a weak area of low pressure at the surface pushing east along the Virginia/North Carolina border.

Low pressure passing over Virginia/North Carolina border early Thursday morning with simulated precipitation having fallen just to its north. (WeatherBell.com)

It is from north central Virginia into southern Maryland where the temperature contrast is steepest and heaviest precipitation is simulated.

For the D.C. area, models are spitting out about 0.0-0.1 inch of liquid equivalent precipitation which would translate to no accumulation to over an inch of snow. We slightly favor the more aggressive models precipitation-wise because - despite the lack of moisture - the upper level system is energetic and the air is cold.