The Saturday and late-Tuesday-Wednesday systems appear to have the most wintry potential locally, but they are also far from sure bets.
From the three systems combined, the chance of at least an inch of snow is around 50 percent. The chance of four inches or more of snow is 25 percent. These numbers are somewhat conservative since even the first of the three systems is still 72 hours from arriving.
The event slated for Saturday has the potential to produce accumulating snow in our area, especially if the system’s low-pressure center tracks to our south. But because the storm is relatively weak, the sweet spot for getting a stripe of moderate-to-heavy precipitation is likely to be narrow.
Slight changes to the storm track north or south could be the difference between receiving heavy-enough snow with cold-enough temperatures for accumulation vs. being fringed or even missed by the storm.
The various simulations of the European model, shown below, exhibit enough differences to allow for several possibilities. Each L in West Virginia, Virginia, North Carolina and nearby states is the possible location of the storm’s low-pressure center at 7 a.m. Saturday, as predicted by different simulations of the model.
The low-pressure positions in northern North Carolina and southwest Virginia are most favorable for snowfall in Washington. If they end up to the south, we might just get skirted by the storm. If they are more to the north, enough warm air could be drawn into the region for a rain-snow mix or rain.
There are three main scenarios in play at this time.
- Scenario 1 — Several inches of snow possible (45 percent chance): Low pressure takes a near-perfect path across northern North Carolina or southern Virginia, placing our area under the precipitation sweet spot. In such a scenario, precipitation would probably start as light rain Saturday morning and change to snow as the storm draws in cold air from the north and falling precipitation helps lower temperatures to the low 30s. Rain would probably change to snow across the north and west suburbs by mid-to-late morning and across the rest of the area by early afternoon, with snow ending from west to east during the afternoon into evening. Several inches of snow (models have suggested anywhere from around two to six inches) could accumulate in the zone of heaviest precipitation and coldest temperatures, potentially leading to slick roads, sidewalks and driveways.
- Scenario 2 — Little or no snow accumulation (45 percent chance): The low tracks far enough south to fringe or miss the local area. Light precipitation probably moves into our far southern suburbs during the day on Saturday, with the northern edge of the precipitation shield just touching the immediate area. Northern suburbs might receive little or no precipitation. Surface temperatures across the area probably remain above freezing, even if light snow is falling, resulting in little or no accumulation.
- Scenario 3 — Mostly rain (10 percent chance): The low takes a northerly track, moving into West Virginia and then across central Virginia. In this scenario, the system doesn’t track far enough south to drag enough cold air into the area to support snow inside the Beltway. The likely result is a light cold rain, except for the typically colder locations north and west of the city, which could see some snow accumulation, particularly across northern Maryland and points north.
The latest weather models generally track the low-pressure center for this second system to our west and north, suggesting a mix-to-rain scenario is more likely than snow, with temperatures during the day Sunday rising well above freezing. The most likely timing for any precipitation would be Sunday afternoon and night.
That said, things could still a change a bit, and it’s hard to rule out some brief snow and perhaps slick spots, especially north and west of the city. But as of now, this event looks more like a conversational one or a nuisance event, rather than a significant winter weather threat.
Late Tuesday into Wednesday
The third storm in this series has potential to be the most significant, however it’s also the lowest-confidence of the forecasts, given we’re almost a week out.
As low pressure approaches from the southwest, high pressure is forecast to be to our north in a favorable position to lock cold air over our region, with a cold front having pushed well to our south before the storm’s arrival.
It’s way too early to get into specifics about this system, other than it has the potential to produce significant snow or a wintry mix if the colder and moister model forecasts are correct.
We’ll be closely monitoring all three systems over the next several days.