Precipitation start time: Between mid-afternoon and early evening Sunday
Precipitation end time: Between early Monday morning and midday
Precipitation type: Snow, possibly changing to mixed precipitation
Chance of at least one inch of snow: 70 percent
Chance of at least two inches of snow: 55 percent
Chance of at least four inches of snow: 40 percent
Chance of at least eight inches of snow: 20 percent
(Note the above probabilities are conservative since the storm is still four days away. The same model forecasts at this time tomorrow would merit higher probabilities.)
Over the last two days, computer models have trended toward a storm track scenario more favorable for snow in the D.C. area. Earlier forecasts had suggested the storm might track to our west and north, allowing it to draw in enough warm air for snow to change over to ice and rain. Current forecasts tend to track the storm to our south, which allows cold air — supplied by high pressure over eastern Canada — to hold in place and for mostly snow to fall.
But not all model simulations favor all snow. Some continue to stick with the idea that the storm tracks to our west and it’s more of a snow-to-wintry-mix situation. Others track the storm so far south that we would be brushed by just light amounts of snow.
To summarize, here are the three scenarios and their likelihood:
Scenario 1 – Substantial snow (40 percent chance): The storm tracks to our south across southeastern Virginia, with the low strengthening enough to spread heavy snow across the region. The GFS and European model supports this scenario. Within this scenario, a track farther to the north across Virginia might offer a snow-to-mix situation across the southern suburbs and all or mostly snow from the District and to the north and west.
Scenario 2 – Light snow (30 percent chance): The storm stays suppressed farther to the south. Such a scenario would result in lighter snow but probably still some accumulation. The Canadian model supports this idea.
Scenario 3 – Wintry mix (25 percent chance): The storm tracks through West Virginia or western Pennsylvania before reforming along the coast to our north. Such a scenario would probably offer some accumulating snow before a transition to sleet, freezing rain and rain. Last night’s Canadian and some of the various ensemble members of the GFS and European model forecast this solution.
You could add a fourth scenario — that the storm misses us to the south entirely (see some the storm positions south of the North Carolina border in the above image) — but that has only about a 5 percent chance of happening.
The bottom line is there is still quite a bit of uncertainty about the exact evolution of the storm, but we believe chances are very good for some accumulating snow Super Bowl Sunday evening into Monday morning. This could interfere with plans to travel to and from Super Bowl parties, as well as Monday morning’s commute — when school delays and cancellations are a possibility.
We will attempt to narrow down the scenarios and issue more specific forecasts as the storm draws closer.