Radar & lightning: Latest D.C. area radar shows movement of precipitation and lightning strikes over past two hours. Refresh page to update. Click here or on image to enlarge. Or see radar bigger on our Weather Wall.

Overview: Snow is moderate to even heavy at times tonight.  Temperatures near and above freezing limited early accumulations to grass and sidewalks. But as pavement temperatures have cooled, even main roads have now picked up snow cover, and should continue to worsen into the overnight. By morning, we generally expect 3-6″ of snow in much of the metro region, and 4-7″ in our colder western suburbs, with a slow morning commute and numerous delays and cancellations. But road conditions should improve by late morning.

Scroll down for our latest snowfall forecast map | Closings and delays

4:00 a.m. update: Federal offices are closed today due to the snow. It keeps on coming. 2″ new reported last hour at Reagan National! The back edge of the steadiest snow appears to be heading this way from the southwest, but we’ll have to watch to see if it fills in or not. The next few hours is about when we were expecting things to begin to wane a bit. We’ll be ramping coverage back up in about an hour.

4 a.m. radar snapshot in the region. (NOAA)

1:25 a.m. update: No sign of slowing just yet as another hefty band rolls into D.C. On the whole, radar has filled in a bit in between bands lately, so there’s little reason to think that things wind down super quick. Short-range models still continue to indicate that process begins once we get toward 4 a.m. or so, taking longer further east. After that, snow appears to persist in a showery fashion into the early morning at least, and perhaps into the midday. By the time most folks are waking up, the worst should be over.

Radar loop ending at 1:17 a.m. shows snow continuing across the area, with embedded heavy bands. (Weather Underground)

Given where everyone stands on snow totals thus far, it’s hard to see how this storm won’t be classified as a “boom” in almost all categories. At least another 1-3 inches is likely through sunrise in most spots, and anyone who hangs out under a band for a while could see even more. With road conditions now poor across the area, both FedCast and SchoolCast from earlier should probably be bumped a bit, with widespread school closures (many have already done so) likely at the least.

We’re going to sign off for a few hours, but we’ll be back around 5 a.m.

12:45 a.m. update: We promised a white St. Patrick’s Day, and it’s more than delivered thus far. Here’s a post-midnight sample from folks who have helped us ring it in on Twitter.

12:20 a.m. update: A fresh list of snow totals is out from NWS Baltimore/Washington. They range from about 3 to 5 inches in many spots, with maximums in the suburbs just north and west of D.C. in particular. Current leaders include: Purcellville, Va. at 5.2 inches; Chantilly, Va. at 5 inches; and 5 inches 1 mile NNW of Dalecarlia Reservoir just across the D.C. line in Montgomery County. Reagan National was up to 2.6 inches as of 12 a.m.

Let us know your totals in the comment section as you measure!

Radar grab from 11:55 p.m.

11:55 p.m. update: The band of heavy snow that recently pushed through the city continues to head north, and it’s dumping very heavy snow across Loudoun and Montgomery counties as well as places east and west. Reagan National reported an astounding 1/8 mile visibility as it passed — about as heavy snow as you see around here. Here’s the METAR, with the important part in bold: (how to decipher in full)

SPECI KDCA 170325Z 01009KT 1/8SM R01/3500VP6000FT +SN FZFG VV004 M01/M02 A3011 RMK AO2 P0006 $

These intense bands are helping to quickly pile up the snow in a lot of spots, and another is roaming off to the south. But, in between snow is relatively light. Hi resolution models indicate we’ll be dealing with periodic banding through the next few hours, but that things may start to lessen and pull to the east as we get toward 3-4 a.m. or so. Snow persists after, but appears lighter on these models. That more or less backs up the ideas of when the heaviest should begin to wind down from earlier.

HRRR simulated radar at 4 a.m. shows the heavier snow beginning to push east of the area. (Weatherbell.com)
Radar from 11:19 p.m. (Weather Underground) Radar from 11:19 p.m. (Weather Underground)

11:30 p.m. update: A recent radar snapshot shown here shows a solid swath of snow over the area going nowhere fast, including areas of moderate to heavy snow across much of the area. Main roads even in the District are snow covered as seen below, always a sign of an impressive storm especially in March. Most spots locally are now up to ~3″+ and counting.


11 p.m. update: Snow is now sticking to roads pretty much everywhere, even many main roads, as some bands with moderate to heavy snowfall rates move through. As the saying goes, don’t go out if you don’t need to. Sounds like most spots in the immediate metro area have accumulated 2-3″ thus far, and as much as 4-5″ in parts of Loudoun County, with a few more inches to come. You can pretty much bank on a rough morning commute.




10:15 p.m. update: Accumulations across the area have reached the 1-3″ range in many spots according to reports, including 2.7″ at Dulles. Until this point, sticking on roads has mainly been confined to Loudoun County, western Fairfax County, northern Montgomery County, northern Howard County, and points north and west. That will change over the next hour or so. With temperatures now below freezing everywhere, side roads even near and inside the Beltway should see snow cover soon. Main roads may hold out a bit longer before they go from wet to snowy.



9:30 p.m. update: With temperatures having dropped a little faster than expected and grassy accumulations already up to an inch some spots locally and a few inches in western Loudoun County, we are making one final change to our snowfall forecast map, which is to bump totals up by an inch or two. Instead of 2-4″ across the bulk of the metro area, we’ve upped to 3-6″. And instead of 1-3″ in the urban core near downtown D.C./Arlington/Alexandria and across the far northern suburbs, we’re now going 2-4″. We’ve changed the western suburbs “jackpot” from 3-6″ to 4-7″. These changes don’t change the general idea of our forecast or the expected impacts from the storm. And in fact the extra inch we’re adding may manifest itself on grass more than anything else. Below is a our revised and final map.

CWG snowfall forecast (final call), issued Sunday at 9:30 p.m.

8:30 p.m. update: Not much has changed over the last hour. Snow continues to fall, accumulating mainly on grass and a bit on sidewalks in the colder suburbs, with temperatures generally near freezing. Most roads remain just wet. Main roads and highways should remain that way for some time. Side roads will be the first to get a coating over the next few hours as pavement temperatures continue to chill. While some school cancellations were anticipated for tomorrow, it seems a few school systems are throwing in the towel a bit earlier than we expected. What do you think?

7:30 p.m. update: Temperatures are now in the 30s everywhere — including 38 at National, 32 at Dulles and 34 at BWI — a bit colder a bit faster than forecast. As readings continue to chill and with snow falling moderately at times over the next couple hours, expect grassy accumulations to increase nicely. Some roads, especially side roads and untreated surfaces, may start to become slick as well. We hear that snow is even starting to stick around sidewalks downtown, but highways are just fine (and should be for a while).



6:45 p.m. update: Snow is falling pretty much everywhere in the metro region now, with temps falling to near freezing in order colder spots well west of the District to just 40 near the city. No reports of snow sticking on streets yet, mainly just grassy areas and elevated surfaces in our colder areas. Expect road/pavement issues to start developing after dark from west to east. Start to be alert for slick spots.



6:00 p.m. update: There’s a pretty big difference in temperatures and conditions between the District and our western suburbs. The 6 p.m. temperature at Reagan National is 42 with cloudy skies, meanwhile it’s snowing and 34 at Dulles. The cooling should begin in earnest even around the city once the snow gets going, which should be over the next hour or so.

5:40 p.m. update: Snow continues to fill in and is picking up in intensity to our west and southwest where some slushy accumulations are beginning on grassy areas. As the snow gets going, temperatures are quickly falling off, already into the mid-to-upper 30s in central and western Virginia. Accumulation on grassy areas could begin in the D.C. area between 6:30 and 7:30 p.m., but shouldn’t be an issue on roads until after 8 p.m.




Temperature Map

Temperatures: Latest D.C. area temperature map. See interactive map on our Weather Wall.

5:00 p.m. update: Many areas report light precipitation has already begun, mostly in the form of snow – although we’ve seen a few reports of rain drops mixing in near I-95 and to the southeast.  The very cold air at high altitudes is supporting snow flakes even with temperatures in the low 40s near the ground.  These temperatures will steadily fall this evening, but it’s going to take several hours before they get cold enough for accumulation, especially around the city.

The period to watch for accumulation to begin is around 8-10 p.m. (perhaps a bit later in the District and south and east)  It’s also at that time when snowfall rates are predicted to pick up.  The National Weather Service Storm Prediction Center posted a special discussion highlighting the potential for snowfall rates of 1 inch per hour after around 10 p.m.

The National Weather Service predicts the possibility of heavy snow starting around 10 p.m. in the region. (National Weather Service Storm Prediction Center)
The National Weather Service predicts the possibility of heavy snow starting around 10 p.m. in the region. (National Weather Service Storm Prediction Center)

It’s the window from roughly 10 p.m. to 2 a.m. or so when this storm has the best chance to produce some meaningful snow.