There is a small chance of winter storminess this weekend in the Washington region


Nearly eight weeks have elapsed since snow was last seen in Washington, but this weekend may finally bring another chance.

Some computer models suggest a storm will develop Friday into Saturday in the South before streaking into the Mid-Atlantic on Saturday night.

If the storm materializes, it would most likely affect the Washington region between late Saturday and Sunday morning — although some shifts in this timing are possible.

How significantly the storm affects our region will depend on its track. Some models still suggest it will pass too far to our south and east to have much effect. But others indicate it has the potential to produce substantial amounts of precipitation.

Because a large area of arctic high pressure over southeast Canada is predicted to feed cold air into the storm, most, if not all, precipitation is likely to fall as snow and/or ice. That said, it is way too early to project how much and where.

If the storm takes a track more to the west (toward Tennessee and Kentucky before re-forming off the Mid-Atlantic coast), we would probably see more of an ice storm. A track to the east (closer to the Mid-Atlantic coast) would produce more snow, whereas a track too far east (out to sea) would mean little or no precipitation for the region.

Capital Weather Gang’s winter weather expert Wes Junker said that the arctic high pressure shown in all of the models is a critical ingredient for supporting winter weather but that variation in predicted storm tracks creates substantial uncertainty in the final outcome.

Here is what the latest models are projecting:

  • American (GFS) model: A storm forms in southeastern Texas and tracks toward Tennessee and Kentucky before re-forming near the Mid-Atlantic coast. It produces moderate amounts of snow, then significant ice.
  • Experimental American (FV3) model: A storm forms in southeastern Texas and tracks toward Tennessee and Kentucky before re-forming along the Mid-Atlantic coast. It produces moderate to heavy amounts of snow, possibly mixed with ice along and east of Interstate 95.
  • European model: A very weak storm forms over northern Gulf of Mexico and tracks to a position east of Cape Hatteras. It produces light snow or flurries with little or no accumulation.
  • Canadian model: A storm develops and tracks along the Gulf Coast before coming up the East Coast, just offshore. It produces moderate snow west of Interstate 95 and a heavy mix of snow and ice east of the interstate.

The bullet points above are forecast summaries for the primary or operational simulations of the models. But some of the models have a larger group of simulations that provide additional forecasts.

For example, the group of 20 simulations making up the American modeling system shows a wide range of possibilities with this storm, ranging from heavy snow to little or no precipitation.

(Note: the snowfall amounts shown above may be overdone in certain cases because sleet is counted as snow. Sleet actually tends to lower snow amounts.)

If you take all of the American model forecasts together, the average snowfall forecast is two to four inches.

The European modeling system is less snowy than the American one. Its 50 simulations indicate a 40 percent chance of at least one inch of snow and just a 10 to 20 percent chance of at least three inches.

On average, the European model is the highest performing. Until and unless its forecast changes, it is difficult to totally buy into the stormier and snowier American model outlook.

We’re still more than five days from the storm possibly affecting the region, so forecasts will evolve substantially. Stay tuned for additional updates as we narrow down the possibilities.

2019-01-07 19:36:57

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