Update: Sunday storm shows increasing snow potential

The models coming in this evening, thus far, have trended colder - which is critical for Sunday’s snow prospects. And while some earlier model runs showed the storm just grazing us, according to this evening’s runs, it now delivers a pretty good blow. So it looks like the necessary moisture and cold air may be coming together for accumulating snow Sunday. But - with the storm still 60-70 hours away - significant fluctuations to the forecast are possible.

This evening’s NAM model, which weather geeks are salivating over, simulates moderate to heavy snow during the day on Sunday, with significant accumulations and temperatures falling below freezing. The GFS run is actually quite similar to to the NAM, just a little warmer and with less moisture (about one third less total precipitation).

The bottom line is that the chances of accumulating snow Sunday have increased. We’ve raised our Snow Potential Index to 6, and the odds of at least 1” of snow are now better than 50/50.

Here’s how I’d characterize current snow probabilities for inside the beltway:

At least 1”: 55%

At least 3”: 40%

At least 5”: 20%

These probabilities are higher to the west and southwest. We’ll release an initial accumulation map tomorrow by midday.

Jason is currently the Washington Post’s weather editor. A native Washingtonian, Jason has been a weather enthusiast since age 10.

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