Snow picking up, heaviest north; ice threat increases tonight (LIVE UPDATES)

** For Sunday morning to Monday morning: Winter Storm Warning west of the District | Winter Weather Advisory for District and points east **


Radar & lightning: Latest regional 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 developing as expected this morning and we could see light accumulations in the metro area by late morning into early afternoon (0.5-2″ generally) – with moderate accumulations in northwest Virginia and northern Maryland (2-4″, isolated 6″+ totals). The bigger deal with this storm is ice, in the form of sleet and freezing rain this afternoon into tonight. That’s when driving conditions should be at their worst, especially west of I-95 and the District, and when some power outages are possible as well. The north and west suburbs of D.C. may hold on to temperatures at or below freezing well into the night, which could mean some school delays/cancellations tomorrow.

Related: Storm timeline, amounts, SchoolCast, other impacts and FAQs | Redskins vs. Chiefs weather forecast | Live game updates | The Grid: Tweets, Instagrams from today’s snow

1:05 p.m. update: This is the last update in this post. We’ve started a new post with live updates here: Snow covering region, heavy north, ice later (LIVE UPDATES)

12:45 p.m. update: Light to moderate snow is falling inside the Beltway and to the south – with grassy areas starting to get covered and a few slick spots on untreated roads. North of the Beltway, it’s moderate to heavy snow, with totals rapidly mounting and hazardous travel. Suffice to say, our forecast for snowfall totals from around Leesburg to Rockville and to the the north and west are likely to turn out too conservative due to the persistent heavy snow bands.

Some reports and pics from around the region:

12:22 p.m. update: It’s snowing to beat the band in Baltimore, where the Ravens host the Vikings at 1 p.m. Same goes in Philly, where the Eagles are playing the Lions. So the Redskins, Ravens, and Eagles will all be playing in snow and sleet this afternoon.

12:10 p.m. update: The National Weather Service forecast office (in Sterling, Va.) has issued a revised snowfall accumulation map. See below. It looks reasonable to us, but we see the potential for even higher amounts in northwest Virginia (around Winchester) and northern Maryland (from Frederick and to the north), where a heavy band has stalled and snow will take longer to transition to sleet and freezing rain. Isolated 6″+ totals are possible.

(National Weather Service)

(National Weather Service)

11:51 am. update: Precipitation has been alternating between snow, sleet, and freezing rain at Fed-Ex field, where the Redskins host the Chiefs at 1 p.m (link: SkinsCast – forecast for game). Roads are probably ok for traveling there right now, just use caution. For the latest happenings at FedEx field weather-wise and otherwise, following this link: Redskins Insider Live Gameday blog

11:30 a.m. update: Radar shows a moderate band of snow, probably mixed with sleet, from southwest of Manassas into Annandale, headed northeast towards the District. This band should get most of the immediate metro region 0.5″ of snow on grassy areas at least, and may also whiten some untreated roads.

 Meanwhile, in Frederick County, Maryland, major and side roads are snow-covered and we recommend avoiding travel there if possible. One to three inches of snow have already accumulated there. Some pics…

 

 

11:13 a.m. update: Reports indicate around 1″ of snow in Great Falls and Frederick, but south and east of there, generally a coating to half inch has fallen on grassy areas. In some areas south of the District – where precipitation changed to sleet for a time (when the intensity diminished) – precipitation has changed back to snow (as the intensity has picked back up). South and east of D.C. – through early afternoon – we may see this kind of alternating precipitation until the eventual changeover to all sleet and freezing rain. 10:53 a.m. update: This is another classic – more snow north and west of D.C. storm. Radar shows heavy snow on I-270 from Germantown to Frederick (where snow is accumulating on roads) and along I-70 from Frederick to Baltimore. Farther to the west, 3″ of snow has piled up around Winchester.

Frederick snow 15 South near 270/15 interchange (Lisa Bolton)

Frederick snow 15 South near 270/15 interchange (Lisa Bolton)

 

 

10:35 a.m. update: Not far south of D.C., snow is already mixing with sleet – even into south Springfield and Old Town Alexandria according to Twitter reports. It’s mostly sleet falling in Warrenton. And, into Fredericksburg, reports indicate no snow, but sleet and freezing rain. This transition from snow to sleet and freezing rain will progress north through the late morning and early afternoon. This reinforces the idea that this will be more of a sleet and freezing storm for most spots, with the window for snow closing rather rapidly.

 

10:20 a.m. update: Northern and northwest suburbs are getting nailed by a heavy snow band. National Weather Service just issued this short term forecast:

.NOW...
A BAND OF HEAVY SNOW WILL SPREAD ACROSS PORTIONS OF EXTREME
NORTHERN VIRGINA AND NORTHERN MARYLAND...STRETCHING INTO EASTERN
WEST VIRGINIA. THE HEAVIEST SNOW THROUGH 11 AM WILL BE BETWEEN THE
INTERSTATE 70 AND 66 CORRIDORS...ACROSS THE NORTHERN WASHINGTON
SUBURBS TO THE NORTHERN SHENANDOAH VALLEY. SNOWFALL RATES OF 1 TO
2 INCHES PER HOUR WILL BE POSSIBLE WITH THIS ACTIVITY...WITH A
QUICK COATING TO AN INCH EXPECTED THROUGH 11 AM WITH LOCALLY
HIGHER AMOUNTS. SLEET MAY PERIODICALLY MIX WITH SNOW. VISIBILITIES
WILL BE REDUCED TO WITH A HALF MILE AT TIMES...AND NEAR A QUARTER
MILE LOCALLY.

But to the south and east of this band, snow is lighter and mainly accumulating on just grassy areas.

10:05 a.m. update: Radar shows snow filling in over D.C. area, but with the heaviest activity from Winchester to Leesburg to Frederick, where it’s really coming down. It may turn out some of the highest snowfall totals are slightly farther north than our forecast map indicated.

 

 

Plot from wxcaster.com, adapted by CWG

Plot from wxcaster.com, adapted by CWG

9:40 a.m. Update: Why do we believe snow will change to sleet and freezing rain this afternoon? Models have been very consistent in showing a layer of above-freezing temperatures developing generally between and noon and 4 p.m. from southwest to northeast. Pictured here is a forecast plot of temperature (horizontal axis) vs. altitude (vertical axis). The dark purple line marks 0 degrees Celsius (32F). The blue curve shows the predicted change in temperature with height at 4 p.m. today in D.C. The area where the red arrow is pointing shows where the temperature is forecast to be above freezing from around 5,000 to 10,000 feet up in the atmosphere. Snow flakes falling through this layer of above-freezing temperatures would melt, and then either re-freeze into sleet as they fall through colder air again closer to the ground, or possibly remain as raindrops before freezing on contact with the cold ground.

Temperature Map

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

9 a.m. Update: Snow that is developing in patchwork fashion should fill in more over the next couple hours. Meanwhile, air temperatures are cold everywhere, mainly in the upper 20s to near 30. Pavement temperatures in the very immediate metro area look to be near or a touch above freezing, so treated roads should stay manageable during the initial period of snow. But they could still become quite slick in any heavier bursts of snow with reduced visibilities as well. And road temperatures are already a couple degrees below freezing as you head north and west from the Beltway.

 

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