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Will Work Week End as it Began?

Dan Stillman @ 2:03 AM


Noon Update: I don't see anything new in this morning's model runs to warrant any changes to the storm probabilities outlined below, although I am growing more confident that north and west of town will see mainly snow, which means accumulations there are likely to be closer to 5 inches than to 3.

The second winter storm this week is taking aim on Washington and is expected to impact the area Thursday night into Friday. Here's what we can say with some confidence:

  • Most of the precipitation will probably fall between 11 p.m. Thursday night and 9 a.m. Friday morning.
  • Areas north and west of D.C. have a better chance of seeing more snow than sleet or rain, while the District and points south and east could see a more evenly mixed bag.
There's still a good amount of uncertainty as to how close the rain-sleet-snow line will get. Nevertheless, we're going to take a crack at accumulation probabilities and an overall storm assessment. We think the most likely scenario is 3-5 inches of a snow-and-sleet combination, probably more snow than sleet:

Overall storm assessment

Storm Impact:
(for Friday)

Differences From Last Storm

  • Monday's storm was primarily an all-snow event for D.C. and vicinity. The track and nature of the approaching storm has the potential to give us a combination of snow, sleet and rain.
  • This next storm looks to be juicier, stronger and faster than Monday's. That means the potential for higher precipitation rates, but lasting for a shorter duration.
  • On Monday, the highest snow totals were to the south and east of town, which is unusual. This time I think we'll see a more typical pattern of colder and snowier north and west of town, and warmer and slushier south and east.
  • Temperatures will be colder in the days leading up to this storm than they were before Monday's storm. The high reached 51 on Sunday, while temps will max out only in the upper 30s today and tomorrow. Because of that, and because it looks like much of the precipitation will be falling before the sun rises, it shouldn't take as long for any frozen precipitation to stick to road surfaces (assuming the air temperature is at or below freezing).

Living on the Edge

Monday's storm brought a lot of nervous nellies to our comments section. During the late afternoon, as the storm was just starting to get its act together, several posters keeping their eye on radar feared that the precipitation was moving off to the east more quickly than expected, and that the storm would come to an end before producing the forecasted accumulations.

Without an understanding of the big picture, radar can be misleading during winter storms here. While precipitation tends to flow steadily from west to east, or southwest to northeast, that doesn't mean the overall storm is moving off at the same speed. The key to watching radar is to observe the back edge of the precipitation. As long as new precipitation is being regenerated along the western or southwestern edge -- in other words, as long as the back edge is holding its ground -- then there's no reason to worry about precipitation ending prematurely.

The above image is a radar loop from Monday that goes from 7 a.m. to 11 p.m. Even though bands of snow were flowing from southwest to northeast, you can see that the back edge -- stretching southwestward from the panhandle of Western Maryland through West Virginia -- remained largely in tact throughout the day. It's only once that back edge begins to progress east and north that the end of a storm is in sight.

Image courtesy Intellicast.

Last Call for Snowfall Reports

We're still ready and willing to accept your snowfall totals from Monday's storm. Please submit them using our online form, which can be found here.

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