From the ABC 7 Weather team

Snow on Sunday in D.C.

February 17, 2012 - 08:48 AM
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ABC7 meteorologist Adam Caskey is back with a revised look at our chances for snow this Sunday...and he says the outlook is looking rosier for those who appreciate winter weather.

Adam Caskey's 'snow excitement factor' has steadily increased throughout the week. (Photo: ABC7)

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• Snow Chance: Likely
• Time: Sunday
• Forecast Confidence: Average to Below Average
• Snow Excitement Factor: 3 out of 10
• Snow Amount: TBD (read below for possibilities)

It’s now fair to say that snow is likely on Sunday, but what remains a mystery is the amount of snow that will fall upon Washington.

Model guidance is still in some disagreement on the exact track of the storm and certain interactions in our atmosphere, which will be critical in determining snow totals. I’ll break it down for you in simple terms regarding the computer models and odds in terms of snow totals.

This will be a coastal storm, which is the type of storm that generates the highest snowfall in the Washington area, however, Doug Hill stated an important point this morning, “…this will NOT be another Snowmageddon.” It’s also important to note that we’re trying to predict the outcome of a storm that has yet to develop, nevertheless, I can provide preliminary odds of snow amounts.

As of now, I think this will be a low to moderate impact storm system for Washington, and I’m currently leaning towards “low impact.”

 

 

 

Before jumping into some of my rationale, above is a graphic indicating the odds of getting various accumulations in the D.C. metro area. I do think a trace to 2 inches is likely (60 percent) with 3 to 6 inches possible but unlikely (30 percent) and more than 6 inches highly unlikely but possible (10 percent).

It’s more than just figuring out how much moisture will be squeezed out of the clouds and how that translates into snowfall. Other factors such as surface/ground & road temperatures, phase changes, crystal composition, timing, intensity and more needs to be determined.

 

 

Model guidance has yet to be very reliable this winter, and this situation is no exception, which is why my confidence is “average to below average” but rising. The projected tracks of various models are shown in the graphic below and while it may look like they’re pretty close, in fact, the disparity is significant in terms of the overall effect on our region.

Basically, fellow snow lovers need to hope for the most northerly track (white - NAM), and snow haters need to pull for the southerly track (DARK BLUE – NAVY). Neither of which are guaranteed, of course.

 

 


As much as I’d love to, I can’t buy into the northerly & very snowy track as I’ve notice poor performance and great inconsistencies in this model beyond 18 hours all winter, and the most southerly track is a bit of an outlier. In turn, a blend seems in order as is the case is many situations. However, I have more confidence in the yellow track (CMC) as it has shown more consistency over the past few days.

 

 

In regards to precipitation type, I do think it will mainly be snow in the D.C. area with a rain to snow transition likely south of D.C. However, I must go back to persistence like in my previous posts and note that model guidance has had a tough time nailing precipitation type all winter.

Nonetheless, should we see rain, it would be brief in the metro area with a quick changeover to snow. This is just a basic assessment, and remember that we will have updates all day and through the weekend here on wjla.com.

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