March 8, 2018 at 1:32 PM
Computer models have backed away from the idea of a significant winter storm for the region, although the possibility is not completely dead.
A storm may still track across the Carolinas to the coast, which, historically, is a favorable course for snow in the Washington region. However, the latest models are forecasting a weaker storm tracking a bit farther south compared with Wednesday.
Depending on the model, the storm either misses Washington entirely or just skirts it — with the zone of precipitation barely edging into the region.
Riding along a storm’s edge in March will typically not result in meaningful snowfall in Washington. Because of milder temperatures at this time of year, snow must fall heavily to cool the air and ground enough for it to accumulate. The light precipitation that falls along the edge of storms, for the most part, just won’t stick.
Ultimately, how far north the storm tracks and whether it develops quickly once it reaches the coast will determine whether we see significant snow. A decreasing number of simulations from the American and European modeling systems still support a major storm.
In some storms this year and in previous years, model forecasts have tended to shift north as storms draw closer to the East Coast — so we cannot take the chance of a significant storm completely off the table.
Here are four possible scenarios, based on the latest models’ forecasts:
Scenario 1, nonevent — 50 percent chance.
The storm stays too far south and remains too weak to give us any accumulating snow. In such a scenario, we might see a brief period of light rain or snow, or the storm could completely miss us to the south. Surface temperatures might never fall below freezing, and any precipitation would fall as sloppy wet flakes or even light rain. Such a scenario would be just another cruel tease for snow lovers.
The European, NAM, UKMet and Canadian models present this scenario.
Scenario 2, minor event — 30 percent chance.
The storm tracks just far enough north to spread a period of light to occasionally moderate precipitation across the region, with the heaviest precipitation staying to our south. In such a scenario, light rain or snow would overspread the area Sunday afternoon and continue, at times, into Monday morning. Temperatures would possibly remain above freezing except over higher elevations. Accumulation, if any, would be light and probably limited to grass and mulch.
The American (GFS) model presents this scenario.
Scenario 3, substantial snow — 15 percent chance.
The storm tracks across North Carolina and then strengthens along the North Carolina coast. In this scenario, snow or a mix would spread into the region Sunday afternoon, with the precipitation changing to snow that could become heavy at times.
Snow accumulation would be maximized in our colder, higher-terrain areas north and west of the city, and depend heavily on the intensity of snowfall. But there would be the chance of substantial amounts of snow all the way to the Interstate 95 corridor if heavy snow materialized. Temperatures would be just marginally cold enough for snow, meaning accumulation would tend to favor grassy areas around the city. However, because a good portion of the storm would move through at night, roads could become snow-covered during heavy bursts.
A few simulations out of 20 in the American (GEFS) modeling system support this scenario.
Scenario 4, heavy wintry mix — 5 percent
The storm rapidly intensifies near Cape Hatteras and roars up the coast. Inland areas near Interstate 81 get a crippling snowstorm, while enough mild air would get drawn into the Interstate 95 corridor for precipitation to alternate between heavy snow, sleet and rain. Such a storm would also present strong winds and coastal flooding concerns. It was on the table Wednesday, but modeling has mostly backed away from this scenario.