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Snow Lovers: The Trend is Not Your Friend
But Game is Not Over

Jason Samenow @ 10:15 AM

A significant shift in the forecast guidance now suggests the likelihood of a major winter storm on Monday has decreased. But the situation still bears watching as forecast confidence remains low. Meanwhile, after a cold afternoon today, we may see a bit of the white stuff tonight before warmer air moves in, bringing a wet (not white) Sunday.

The Scoop on Monday

Overall storm assessment

Storm Impact:
Travelcast (for Monday):
Schoolcast (for Monday):

For the last several days, we have been talking about a 50% chance of a significant snowstorm on Monday. Dan's comments on Wednesday were especially prescient when he said the Monday storm "has the potential to be ...a blockbuster, but depending on the exact track it could be an all-or-nothing situation for the Washington area." "Nothing" may now be closer to reality than "blockbuster."

The image below shows four consecutive model forecasts for 1pm Monday. The first forecast (far left) came out Thursday night, the next two during the day on Friday, and the last forecast arrived at press time (around midnight Saturday). Notice how the area of low pressure (aka the storm center) shifts southeastward over time. The first forecast (and the second for that matter) is dumping snow over us, whereas the final forecast shows almost all of the precipitation missing us to the south and east.

When you forecast you have to pay attention to trends, particularly when one model "trends" toward the solution of other models. There are a number of other models which have been consistent in keeping the storm to the south and to the east. Now that this model is agreeing with the others, I must begin backing away from a snowy forecast.

I would caution that since the storm is still over 2 days away, the models could shift back towards a snowy solution. But that appears less likely than the alternative: another snow miss for DC.

10am Saturday: Stricken text may have been premature. Model trends seem to be reversing a bit. I'll write more in my PM update. See also comments.

Today and Tomorrow

This morning it will be mostly sunny and quite cold when you get up and head out, with temperatures in the mid 20s. By afternoon, clouds will increase and it will remain chilly, with highs only near 40.

Tonight, snow will move in around midnight and will mix with and change to sleet and then rain as a warm front crosses the area. Little or no snow accumulation is expected and temperatures will gradually rise in the early morning hours -- so any freezing should be isolated to the extreme north and west suburbs.

Rain should continue until around noon on Sunday, followed by mostly cloudy skies and the passage of a cold front. Highs should be in the mid to upper 40s.

Snow Lover's Crystal Ball

Next Chance of Snow: Monday, Dec 5
Probability of Accumulating Snow: 50%
Potential Impact:
Commentary:Notice I've downgraded the potential impact by one flake, based on the analysis shown previously. And the 50% probability of accumulating snow may be generous. There may be another storm that could affect the area in about a week, but I'm not ready to analyze that yet.

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