For several days, computer models have flirted with the idea of a winter storm in our region next weekend. Some have even projected significant accumulating snow. However, they have wavered on the storm track and, at the moment, place us right on the edge of where meaningful snow starts and stops.
The timing of a storm, if it materializes, would probably be late Saturday night into Sunday, possibly lingering into Monday.
Confidence is somewhat higher that a significant winter storm will affect southwest Virginia (affecting Roanoke, Lynchburg and Blacksburg) and possibly creep into central Virginia (affecting Richmond and Charlottesville). But, even there, it’s not a done deal.
The models have alternated between allowing the storm to track far enough north to hit the Washington region and keeping the storm track suppressed so far south that we escape with just a brush of light snow or even a clear miss.
Much of the forecast problem stems from uncertainty in the jet stream flow over the Northeast. It is the key to whether the storm riding along the southern jet stream has room to track north into our region or gets crushed and forced out to sea to our south.
Leading into the weekend, models agree strong flow from the northwest will pass over the Northeast. If, over the weekend, this flow over the Northeast stays in place, it will probably keep the storm too far south for meaningful snow in the D.C. area. But, if the flow relaxes and shifts east, the storm probably will come close enough to give us snow. Then the question would be how much.
The majority of models tend to hold the flow over New England in place, reducing the chance of a major storm. However, there are enough outliers that we cannot take off the table the chance of a substantial snow event. Also, storm forecasts sometimes shift north with time and a 100-mile shift would move accumulating snow into the Washington region.
Here’s a summary of what the various models predict:
- Operational American (GFS) model: No snow in Washington region. Closest substantial snow in western North Carolina.
- Experimental American (GFS FV3) model: Light snow or flurries reach Washington region, with little accumulation. Closest substantial snow in southwest and central Virginia.
- Canadian model: Heavy snow in Washington region.
- European model: Light snow or flurries reach Washington region, with little accumulation. Closest substantial snow in southwest and central Virginia.
At the moment, the heavy snow scenario presented by the Canadian model seems least likely, but cannot totally be dismissed.
While the main European model keeps substantial precipitation south of Washington, about 25 percent of the 50 simulations in its forecast system predict at least six inches. The American modeling system also offers a full range of possibilities, from a complete miss to a significant winter storm.
At such long time ranges, getting the details right on the interactions of the two streams of flow is extremely difficult, making it impossible to make a definitive call on the storm.
The most we can say is there is a chance of wintry weather between Saturday night and Monday, but there is also the possibility that the storm will slide harmlessly to our south.
We may not obtain a clearer picture of how the storm will evolve and affect us until Wednesday or Thursday. We’ll be monitoring the storm during the week and will provide updates.
Capital Weather Gang’s Jason Samenow contributed to this article.