Snowfall will depend on how storm tracks north

WASHINGTON — New information Tuesday afternoon showed the rain-snow line moving further west during the storm, which in turn would cut down snow totals around the region.

It is not fair to you for me to produce a snow totals map when my confidence is not high. It is easy to put numbers out there, but once you have them out in the public, it is very difficult to knock them down. It is better to start with high confidence and tweak them as the storm develops.

With that being said, the storm in question hasn’t even formed yet. The two pieces of energy meeting together to generate this coastal low are spinning across Montana and the southwestern portion of the United States. Where these two pieces of energy meet will dictate the path of the low up the coast.

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Water vapor map showing the key ingredients of the storm.

However, what we do know is that the low pressure will develop off the southeast coast Wednesday and travel north up the coast Wednesday night, through the overnight hours, leading into Thursday.

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Courtesy ABC7

Expect the first flakes to fly after sunset on Wednesday. Just to plan ahead, you may want to leave work a little early — since traffic in the D.C.-area tends to be a nightmare. But other than that, I do not anticipate problems with the evening commute on Wednesday.

The commute on Thursday morning may be a different story. Everybody in our listening area will get in on the action from this storm. There is a good chance there will be accumulating snow by daybreak in areas. Heaviest precip is still expected to fall during overnight to early morning hours on Thursday, 4 a.m. to 9 a.m.

The National Weather Service is in the same boat as I am. They are holding off on upgrading us out of a Winter Storm Watch and issuing Winter Storm Warnings and perhaps Winter Weather Advisories because the track of the low is very uncertain, almost a 75-mile deviation with the latest information. And again, that would dramatically cut or raise snow totals depending on locations around the region.

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Still several questions remaining with this storm.

In general, most likely scenario is to expect 5 to 10 inches across the D.C.-metro area. There is about a 25 percent chance of seeing less than 5 inches if more sleet and or rain work into the forecast. And, it is possible that the rain-snow line will set up east of the D.C.-area bringing in 10 to 14 inches of snow — about a 25 percent shot at that.

Here are our best guesses so far for snow totals. Patience is the key with this particular storm and things can absolutely change in the next 24 hours as we are all aware of in the D.C.-area. We will continue to tweak the forecast as the storm continues to come together.

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Snowfall totals map as of 6 p.m. Tuesday

Again, the heaviest bands set up just to the western suburbs of the D.C.-metro area. West of the Blue Ridge Mountains, a lot of that moisture will drop off hence the smaller snow accumulation totals. Southeast of the D.C.-metro area, more of a mix will fall leading to less accumulation.

We will continue to watch where the rain-snow line sets up, but this is what we can work with considering the information we have. I completely understand how frustrating it is not knowing exactly what is going to happen, believe me. The meteorology business is based on uncertainty. However, keep it here and we will update you with the most truthful and analyzed information that we can provide.

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