If the storm comes up the coast, it could be a substantial snow producer, although there’s also some chance it draws in enough warm air for a wintry mix or even cold rain.
It will take at least a couple more days to have a good idea what scenario is most likely.
At the moment, we’d say there’s about a 40 percent chance of at least an inch of snow and 20 percent chance of at least 3 inches. These numbers are on the conservative side because the storm system is still about six days away and a lot of ingredients have to come together for this storm to meaningfully affect the area.
As of Tuesday afternoon, three of four major modeling systems simulate a major storm affecting the Mid-Atlantic on Sunday into Monday. Here’s what they are projecting:
- The primary American (GFS) model simulation shows a major storm that produces heavy snowfall in the region; however, the storm becomes so intense it draws in some milder air off the Atlantic Ocean and precipitation flips to rain for a time along and east of Interstate 95 before it changes back to snow. The modeling system has 29 alternative simulations, about half of which show significant snow, while the other half suggest the storm would mostly miss to the south and east. It gives the District about a 50 percent chance of at least one inch, 40 to 50 percent chance of at least three inches and 30 percent chance of at least six inches. It even shows a 10 to 15 percent chance of a foot.
- The Canadian modeling system also suggests that a significant storm system could take a track favorable for snow in the region. Its group of simulations indicates about a 60 percent chance of at least an inch, 55 percent chance of at least three inches, and 33 percent chance of six inches or more. Like the American modeling system, it also gives a 10 to 15 percent probability of at least 12 inches.
- The European model is on board with the idea of a major storm as well and, like the American, it suggests that it could draw in enough mild air for snow to change to a cold rain or wintry mix, especially from Fairfax and Montgomery counties eastward. Its solution would plaster the Interstate 81 corridor with heavy snow. Its group of 50 simulations indicate about a 40 percent chance of at least one inch of snow, 25 percent chance of three inches and 15 percent chance of six inches.
- The UKMet model suggests that the storm is a near miss, battering the beaches but just giving the D.C. area a little light snow.
The forecast is complicated for several reasons. The models need to resolve three different features to lock into the correct forecast: (1) the low-pressure system tracking through the Southeast toward the Carolinas that could be our snowmaker; (2) a zone of low pressure in northeast Canada; and, (3) a third zone of low pressure over north-central Canada that will be digging southeastward. The strength and position of any one of these three systems could change the forecast.
Ultimately, how much snow we see or don’t see will depend on the approximate position of the storm center or zone of low pressure relative to Cape Hatteras. If the storm is centered near Cape Hatteras on Sunday, it will favor significant snow in our region.
The map below shows the predicted positions of the low pressure from the 30 American model simulations Sunday evening. You can see that there is a large amount of spread. The lows west of Cape Hatteras would favor a snow-to-rain scenario, while the low positions well east of Cape Hatteras may suggest more of a glancing blow from the storm.
No one solution is yet off the table. The National Weather Service noted that energy that will drive the storm system tracking through the Southeast “remains over the Aleutians, a fairly data sparse area, which means guidance could change significantly.”
Why snow chances are elevated for the next two weeks or so
The models are displaying a pattern conducive to colder-than-normal temperatures across much of the country through the end of the month. That alone raises our potential for more snow or frozen precipitation.
The jet stream will be displaced well to the north over western North America, poking into Alaska, before diving southeast over the eastern United States. This jet stream configuration suggests that storm systems will generally track to our south instead of passing to the north like they typically do during La Niña winters. The models even suggest cross-polar flow will develop, which would tend to aid in the development of high-pressure systems over Canada that can supply cold air when storms approach our region. But sometimes the high-pressure zones can push the storm track too far south, keeping us dry.
High temperatures on most days in the next two weeks are projected to be about 35 to 40.
After the chance of storminess Sunday and Monday, there may be another opportunity for wintry precipitation around Jan. 21 or 22.
The 9.6 inches of snow that have fallen in D.C. so far this January, double the norm, is the most during the month since 2019, when 11.5 inches fell. There is certainly the chance the current January total could climb. We would have to see a good deal more, though, to match the output of 2016, when 18.8 inches fell, most occurring during the “Snowzilla” storm of Jan. 22-23.