We have a scenario, call it “A,” which is a spring snowstorm. Rain and snow develop overnight Saturday, becoming all snow by Sunday morning, continuing into Sunday evening. Accumulation would be possible on grassy areas, with even some slick spots possible on the roads, particularly by late Sunday in our colder areas as temperatures fall.
In the second scenario, “B,” a lot of precipitation falls Saturday afternoon and evening as a mixture of rain and snow, with some lingering mixed precipitation Sunday. Minimal snow accumulation would be expected in this scenario, but enough could fall for the ground to turn white.
A final scenario, “C,” brings mostly rain to the region Saturday night and Sunday, with a chance of some snow mixing in, especially in our colder suburbs and toward the end of the event late Sunday.
We somewhat favor the snowier scenario “A.”
“All late March snowstorms are a puzzle, and this one is even trickier than most, because the models still have very divergent solutions,” says Wes Junker, Capital Weather Gang’s winter weather expert.
Junker adds: “For accumulating snows in late March, you usually need to have the bulk of the precipitation fall during the night or have an unusually cold air mass in place and have really intense snowfall rates. It’s not clear how well these ingredients for substantial snow will come together.
“Until we get a better handle on the storm track, precipitation intensity and whether the precipitation will linger into Sunday evening when temperatures drop to freezing, there is no way to make a reasonable guess about accumulations except to say that the best chances for accumulations are on grassy surfaces and to the west and north of the Beltway where there is elevation.”
Let’s break down the different scenarios.
SCENARIO A — Spring snowstorm, mostly Sunday: 45 percent chance
The spring snowstorm scenario seems to be the most likely of the three, by a small margin, because it’s predicted by the European model, which has been most consistent and has the best overall track record.
It forecasts a pretty classic snowstorm, developing low pressure near the Gulf Coast on Saturday and tracking it up the East Coast, drawing moisture into the region and tapping just enough cold air for wet snow to be the dominant precipitation type.
But even though the model shows it being cold enough for snow, most of the snow would fall with temperatures above freezing for the balance of the storm, limiting accumulation mostly to grassy areas.
As the storm is pulling away late Sunday, temperatures might fall enough for snow to accumulate more readily, even on some road surfaces in our colder suburbs. Precipitation would wind down in most spots around midnight, but slick spots would be possible across the area overnight into Monday morning, with temperatures falling below freezing.
Generally, we’d expect up to several inches of wet snow on grassy areas in our colder suburbs in this scenario, north and west of a line from Warrenton to Fairfax to Columbia. Inside the Beltway, snow might paste grassy areas, especially late Sunday afternoon into Sunday evening.
SCENARIO B — Sloppy mix, mostly Saturday: 25 percent chance
In this scenario, the storm zips through the region quickly and it does not rapidly intensify and hug the East Coast. Instead, it scoots off the coast of the Carolinas and tracks more offshore. This limits both the intensity and duration of any precipitation, and hence the snow potential.
A cold rain would develop around midday Saturday before mixing with snow Saturday afternoon as temperatures fell back into the mid-30s.
Precipitation might become all snow, especially in our colder areas, late in the day and overnight, before precipitation tapered off, but temperatures would mostly remain above freezing, greatly reducing accumulation potential.
A bit of light snow might coat grassy areas north and northwest of the District mainly Saturday evening. Amounts would increase toward the Pennsylvania border.
This scenario is best represented by the GFS model forecast. It’s plausible, but we don’t have a ton of confidence in it.
SCENARIO C — Mostly rain, a little wet snow mostly Sunday: 30 percent chance.
The Canadian model, which has fluctuated pretty wildly over the past few days in its forecasts and is generally the least reliable, makes a case for a mostly rain event. It has some support from the U.K. Met model and a few of the ensemble members of the various models.
It shows a similar setup to the European model, but the initial area of low pressure that develops tracks west of the mountains, drawing milder air into the region so that rain falls rather than snow. A secondary area of low pressure positioned off the Mid-Atlantic coast eventually takes over, drawing in enough cold air for the rain to possibly change to snow, especially in our colder areas north and northwest of the Capital Beltway, as the storm is pulling away late Sunday.
This scenario, while least likely, has gained a bit of momentum in simulations today, so we’re not ruling it out.