* Winter storm warning 2 a.m. to 8 p.m. Wednesday for entire region | School closings | Icy conditions bring crashes in D.C. area | Photos of the snow | Snowfall totals *

Key points

  • Heaviest snow, with highest chance of accumulation and effects on roads, is likely through early-to-mid-afternoon.
  • Snow likely to continue into evening but lessen in intensity, becoming more spotty between 4 and 6 p.m. from southwest to northeast. Accumulation will slow, allowing road conditions to improve.
  • Worst conditions generally will be away from the urban core.
  • Total accumulations mostly in the 2-to-6 inches range, but isolated higher amounts possible, especially east and northeast of Washington.
  • Reagan National Airport received 4 inches, its heaviest snowfall so late in the season since 1964.

Updates

4:30 p.m. update: The band of heavy snow on the west side of the Chesapeake Bay, which was remarkably persistent, is finally showing signs it should cave over the next couple of hours. This signals the start of the end of this event. While snow showers and flurries may linger well into the evening, most if not all accumulating snow is finished in the region.

Link: Snowfall totals

This concludes our updates on this storm. Stay tuned for our PM Update which will be posted between 5 and 5:30 p.m.

Capital Weather Gang's Jason Samenow provides an afternoon update on the springtime storm that is hitting the D.C. region on March 21. (Claritza Jimenez,Jason Samenow,Daniel Mich/The Washington Post)

2:45 p.m. update: Mostly light, non-accumulating snow is falling in much of the region. But right along the Chesapeake Bay, from Lexington Park to Annapolis, snow continues to fall hard enough to accumulate some. These areas could pick up another inch or so before the snow starts letting up after 5 p.m.

We’ve received a good number of questions about whether roads will refreeze tonight. We expect temperatures to remain near to a little above freezing through around midnight. Once skies clear, temperatures should fall to near 30 downtown and from 25 to 30 in our colder suburbs. This would allow wet spots to ice over – meaning the likelihood of some slick spots in the morning in areas that are not treated. However, we are not expecting a hard, fast freeze that turns everything into a sheet of ice.


High-resolution NAM model forecast of temperatures overnight.

We’ll take all of this into account when we post our SchoolCast late this afternoon.

1:30 p.m. update: We’re continuing to see this pattern of moderate snow, accumulating some, along and east of Interstate 95, and lighter snow, not accumulating much, west of Interstate 95. Also, the snow is compacting because of its weight and temperatures rising above freezing. Except where it’s snowing at least moderately, snow is mostly not sticking to pavement where it has been plowed or treated. What we’re seeing now will continue to be the case for the next few hours.

Here are some of the latest accumulation totals we have in, mostly in the 3-to-6-inch range:

  • 2.5 to 3 inches in downtown Washington
  • Falls Church, Va: 3 inches
  • La Plata, Md.: 3.5 inches
  • Annandale, Va.: 4 inches
  • Crofton, Md: 4 inches
  • Glenmont, Md.: 4 inches
  • Silver Spring, Md.: 4.5 inches
  • Herndon, Va: 5 inches
  • Takoma Park, Md.: 4 to 5 inches
  • Severn, Md.: 4 to 5 inches
  • Springfield, Va.: 4 to 5 inches
  • Fairfax, Va.: 4 to 5 inches
  • Olney, Md.: 5 inches
  • Bowie, Md.: 5 inches
  • Leesburg, Va.: 5 inches
  • Dunkirk, Md.: 5.5 inches
  • South Laurel, Md.: 5.5 inches
  • Odenton, Md.: 6 inches
  • Savage, Md.: 6 inches
  • Waldorf, Md.: 6 inches
  • Greenbelt, Md.: 6 inches
  • University Park, Md.: 6 inches
  • Berwyn Heights, Md.: 7 inches

Because the rate of melting and compaction is greater than the rate of snowfall in many places, these totals may be as high as they get with a few exceptions (mainly northeast of Washington).

For earlier reports, scroll down to the bottom of this post.

A spring nor'easter is dumping moderate snow in the D.C. region on March 21. (Claritza Jimenez/The Washington Post)

Original forecast posted at 5 a.m.

TODAY’S DAILY DIGIT
A somewhat subjective rating of the day’s weather, on a scale of 0 to 10.

7/10: It was a long wait, but finally significant snow for the kids and snow lovers out there! A few points off for spoiling our start to spring, though.

EXPRESS FORECAST

Today: Wintry mix changing to all snow. Highs: Low 30s.
Tonight: Snow tapers early. Lows: Upper 20s to low 30s.
Tomorrow: Partly sunny, cold, gusty wind. Highs: Upper 30s to low 40s.

View the current weather at The Washington Post headquarters.

FORECAST IN DETAIL

After waiting all winter, it’s our first full day of spring that finally brings a significant snowfall — possibly the biggest of what has been an anemic season for snow. Accumulating snow should come to an end by this evening. But we remain quite chilly through the weekend with, believe it or not, a chance of light snow late Saturday into Sunday.

Listen to the latest forecast:

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Today (Wednesday): A wintry mix changes to all snow from west to east across the area around 5 to 8 a.m. And then the snow accumulates into and through the afternoon, anywhere from 2 to 8 inches across the D.C.-Baltimore area as shown in our forecast map below. More snow will stick to the grass than pavement, thanks to the high March sun angle. But with temperatures hovering right near the freezing mark, the snow should manage to stick to many road surfaces, especially during heavier bursts. The breeze is chilly and around 10 to 15 mph from the north. Confidence: Medium-High


Tonight: The snow should taper from west to east by around 5 to 8 p.m., though it may continue lightly later into the evening, but with little additional accumulation. Winds remain breezy, from the northwest around 10 to 20 mph, as lows in the upper 20s to low 30s. Confidence: Medium

Follow us on Facebook, Twitter, and Instagram for the latest updates. For related traffic news, check out Gridlock. Keep reading for the forecast through the weekend.

Tomorrow (Thursday): Partly sunny skies and temperatures rising above freezing get the melting process going, but it doesn’t feel anything like spring. Highs reach only the upper 30s to low 40s, with winds gusting from the northwest near 35 mph. Confidence: Medium-High

Tomorrow night: Winds diminish, although we should maintain a breeze from the northwest around 10 to 15 mph. Otherwise skies turn mostly clear, with chilly lows down to the mid-20s to low 30s. Confidence: High

A LOOK AHEAD

Friday looks only slightly warmer, with highs in the low to mid-40s under partly cloudy skies and still a noticeable breeze from the northwest. Could see a flurry or snow shower, as well. Friday night lows drop back to the mid-20s to near 30. Saturday may start on the sunny side but should see increasing clouds as highs stall in the 40s again. Confidence: Medium-High

Another system may try to bring light snow Saturday evening into Sunday, although some models keep the precipitation mainly south of the D.C. area. This system should be weaker than today’s but bears watching. Saturday night lows dip to the upper 20s to low 30s, with continued chilly Sunday highs in the upper 30s to mid-40s. Confidence: Low

SNOW POTENTIAL INDEX
A daily assessment of the potential for at least one inch of snow in the next week, on a 0-10 scale.

9.5/10 (): Wednesday snow prospects push the SPI sky high! (There is even a chance of light snow this weekend, too.)


Snow in Hagerstown, Md., March 20. (Merry Sushi via Twitter)

Earlier short-term snow updates (now out of date)

12:15 p.m. update: We’ve now reached midday, when accumulation will become more challenging for three reasons:

  1. The sun is high in the sky.
  2. Snow, except along and east of Interstate 95, is trending downward in intensity.
  3. Related to 1 and 2, temperatures are inching up. We’re seeing an increasing number of locations above freezing, in the 33-to-34-degree range.

It’s going to keep snowing, for a number of more hours, probably not tapering off substantially until between about 4 and 6 p.m. But where it’s not snowing at least moderately, it is not going to add much accumulation. In other words, a lot of locations west and southwest of Interstate 95 have already seen most of their snow accumulation.

Along Interstate 95 and to the east, another one to three inches are possible, with isolated higher amounts not out of the question near the Bay and into northeast Maryland.

11:30 a.m. update: Reagan National Airport checked in with 3.0 inches at 11 a.m., which makes today’s storm the heaviest since 1964 so late in the season. However, to break Washington’s snowfall record for March 21, set in 1924, the total would need to increase to 5.3 inches, which is unlikely.

Here are a few more snow totals that  have come in on the heavy north and east side of the storm: Greenbelt: 5 to 6 inches; Poolesville: 6 inches; Odenton: 4 inches.

11:00 a.m. update: It’s becoming apparent that our eastern areas, from southern Maryland to Baltimore, are going to hit the snowfall jackpot with this storm; a number of places are likely to see “boom” totals exceeding 6 inches. Radar shows the heaviest snow there, and short-term models (see update below this one) show it lasting there longest.

Here are more snowfall totals received in the last hour from around the region, mostly in the 2-to-4-inch range:

  • Alexandria, Va.: 3 inches
  • Reston, Va.: 3 inches
  • Franconia, Va.: 3 inches
  • Fairfax, Va.: 3 inches
  • Falls Church, Va.: 2.5 inches
  • Woodbridge, Va: 4 inches
  • Leesburg, Va.: 4 inches
  • Herndon, Va.: 4 inches
  • Waldorf, Md.: 2 inches
  • Takoma Park, Md.: 3 inches
  • Columbia, Md.: 3.5 inches
  • St. Charles, Md.: 2 inches
  • Washington, D.C. Mall: 2.5 inches
  • Capitol Hill, D.C.: 3 inches
  • Mechanicsville, Md.: 4 inches
  • Northern Calvert County, Md.: 3.5 inches
  • Cheverly, Md.: 4.25 inches
  • Silver Spring-Wheaton, Md.: 2 to 3 inches

10:10 a.m. update: So how much more snow are we talking about (beyond what has already fallen)? Here’s what two different models project, the HRRR and the NAM.

HRRR


Snowfall forecast 10 a.m. to 10 p.m. from HRRR model.

NAM


Snowfall forecast 10 a.m. to 10 p.m. from NAM model.

Note that both suggest around 2 to 4 inches; however, these models assume every flake sticks and, as temperatures rise a bit this afternoon, accumulation will become more difficult, especially on pavement. So we would shave 25 percent or so off these totals.

You may notice there are some 6 inch-plus totals on the east side of town. That is not out the question. Radar shows the heaviest activity there, and the American (GFS) model, which has been most consistent for this storm, has been predicting some of the highest totals in that area since yesterday.

9:40 a.m. update: The snow is really coming down at a good clip, around half an inch to an inch an hour, and this should continue through midday at least. Snow falling this fast will tend to stick to pavement, so take it slow or stay off the roads. A number of locations from  now have at least an inch of snow, with up to three inches in our southwest suburbs. Some early totals, including locations well to our southwest:

  • Takoma Park, Md: 1 inch
  • Laurel, Md.: 1 inch
  • Fairfax: 1.5 inches
  • Dale City: 2 inches
  • Dulles Airport: 2.2 inches
  • Bull Run, Va.: 3 inches
  • Charlottesville, Va.: 4 inches
  • Crozet, Va: 5 inches
  • Staunton, Va.: 6 inches

9 a.m. update: Radar shows areas of moderate snow now covering much of the area, including inside the Beltway. Many roads are becoming snow-covered, even inside the District. We’ll continue to see hazardous road conditions into the afternoon, especially during periods of moderate to heavy snow. Alternatively, when the snow lightens up, it may tend to melt on treated surfaces, before perhaps whitening up again with the next heavier pocket of snow. Scroll below for more details on our forecast through the rest of the day.

8:10 a.m. update: A solid area of snow has developed across the DMV with snow starting to accumulate nicely. As the sun rises higher in the sky, the snow may tend to melt on road surfaces when falling lightly. But during moderate to heavy bursts, even treated roads may become snow covered, and expect lowered visibility as well. Based on radar and short-term modeling, we think the morning hours through around 1 p.m., perhaps a bit later north of the Beltway, are probably our best window for accumulating snow, with snow continuing but more lightly thereafter.

7:30 a.m. update: Snow now picking up nicely across the area, starting to cover grassy areas, sidewalks and untreated road surfaces. Radar and short-term models suggest that areas of light to moderate snow will continue through much of the day. So while we don’t see the “boom” scenario playing out, we do think there’s a decent chance we’ll see accumulations near or into at least the lower end of our most likely amounts in the forecast map down below.

6:45 a.m. update: Radar has started to fill in with a mixture of sleet and snow across the area. We think, based on the latest information, that we may be looking at the lower end of our forecast map below but need to see how things play out with radar and temperatures over the next few hours. See tweet below for commentary on the timing of things thus far…

5:45 a.m. update: Precipitation arriving on schedule, likely in the form of a sleet-snow mix, as it moves in generally from south-southwest to north-northeast over the next 30 to 45 minutes. Temperatures are right around 29-32 across the area, so beware of slick spots if you must be out early this morning, especially on untreated roads and sidewalks.