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A winter weather advisory was in effect until 9 p.m. for the entire D.C. metro, northern suburbs and Baltimore. It does not include Charles, Calvert or St. Mary’s counties.


9:45 p.m. update: Precipitation is pulling away from the area, with some rain still falling across southern Maryland, where temperatures have been closer to 40. Temperatures have warmed into the mid-and-upper 30s for much of the immediate area and to the south. This is probably about as mild as temperatures get before falling back off through the night.

Plan on ice if you are out and about. It might not be everywhere, but you’re likely to encounter some if you travel far enough. A number of locations will continue to see dangerously slippery conditions through the sunrise period. It is particularly problematic that in some places much of the area will be treated, but a curve or side street might be an ice rink. Take it slow and easy.

8:10 p.m. update: Not to be a broken record, but the ice is quite problematic out there despite temperatures that have now warmed up a little bit again across much of the area. For instance, National Airport is up to a balmy 37 at 8 p.m., its highest temperature of the day. Yet, ice is dangerous in many places.

The slight temperature rise is not doing much because much of the region was below freezing for nearly two straight weeks. It’s an odd case where ice is most prevalent right at the ground. Usually, trees and other elevated objects will also gather ice. Here, not as much, except in the north and west suburbs.

The bottom line is that ice is going to be a problem on untreated surfaces until the sun comes out tomorrow and we begin some legitimate warming (to the 40s!!). Slippery conditions are a bigger problem in and around D.C. and to the north than to the south, but they are possible just about anywhere, which means you’ve got to keep taking it slow if you are out.

Precipitation is ending out west and it will do so in the Interstate-95 Corridor as well, probably sometime in the 9 to 10 p.m. time frame or so. Even though the precipitation ends, winds are likely to stay light enough to not help dry out surfaces much. At least patchy ice will remain likely through morning, even in places to the south that have mainly been wet, as temperatures cool into dawn.

7:10 p.m. update: There has been an uptick in reports of iciness across the immediate area lately. It does seem that the loss of daylight has helped the cold ground show off a bit more than it was earlier. Even in places with temperatures above freezing, you may run into extremely slippery conditions, especially on steps, sidewalks, parking lots, driveways, and untreated side streets.

6:20 p.m. update: As the sun dips farther below the horizon, temperatures have mostly fallen a degree or two across the area over the last few hours. While most spots outside the northwest suburbs are near freezing to a few degrees above, some ice continues to form even in those places, especially where there has not been treatment. This is thanks to the very cold ground. At elevation to the northwest, it’s more widespread iciness that is ongoing. A similar story is likely across much of northern Maryland and our western suburbs.

The heaviest and most consistent part of this second round of rejuvenated light precipitation is focusing over the southern half of our area, but we will continue to see rain, freezing rain, and sleet fall areawide (at least at times) for the next hour or two, before it more noticeably tapers off later this evening.

4:15 p.m. update: A wintry mix of sleet and freezing rain continues in the northern suburbs, but things in the Beltway are fairly quiet and look like they will remain that way through at least the first part of the evening commute. In Montgomery, Frederick and Loudoun, side streets and untreated sidewalks are still icy and with temperatures beginning to drop as the sun sets, we can expect more patches of ice forming as the evening wears on.

The temperature downtown peaked at 35 degrees but is starting to drop now. Be aware of wet, untreated roads as you head out the door. Sidewalks are heavily salted in the District, so your walk home should be ice-free.

3:30 p.m. update: The second wave of precipitation is moving into northern Montgomery County. Side streets and sidewalks are “messy and slippery” according to readers in Germantown and Gaithersburg. I-270 will probably be okay through the duration of the evening commute since it’s already treated and has so many cars on it. The good news is road crews seem to be out en masse laying down salt to prevent ice from forming.

We’re keeping an eye on temperatures, which are in the mid-30s in the Beltway and hovering around the freezing mark in the north and west suburbs. When the sun goes down, we’ll see temperatures drop and wet, untreated surfaces will be more likely to freeze.

2:30 p.m. update: The wintry mix is steadily easing up in the northwest suburbs and will exit the Beltway in the next hour or two. There’s a second round of precipitation that some models are predicting will come through between 6 and 9 p.m., although we’re not yet seeing evidence of that on radar. In short — be prepared for some more rain and wintry mix this evening, and we will continue to update on the second wave as it approaches (or fizzles).

That all being said, main roads look good in terms of traction despite being bad in terms of traffic. We expect the main treated roads to be okay through the evening commute in the immediate metro, with some slick spots possible in north and far west suburbs.

1:50 p.m. update: Temperature update — still above freezing in the District , Arlington and southern suburbs, but it’s below freezing north of the District. This includes Bethesda, Silver Spring and Rockville, where untreated roads are starting to become slick. We’ve already seen reports of icy untreated roads in Rockville and points north.


Temperatures as of 1:50 p.m. (Weather Underground)

1:32 p.m. update: Freezing rain is confirmed in some of the north and west suburbs. I-270 is at risk for icy spots, although thankfully it’s treated. Untreated roads in Rockville up to Germantown are apparently quite icy.

1:20 p.m. update: There’s significant sleet accumulation in the north and west suburbs, including what’s being reported in this photo (below) from a Reston reader. This strange, icy, pellet-like precipitation is technically sleet. We’re watching temperatures and reports carefully for freezing rain, though, which is far more dangerous for motorists since it can coat the roads in a thin layer of ice that is nearly imperceptible.

1:05 p.m. update: Sleet reports are coming in from North Bethesda, Falls Church and Arlington. Temperatures are a little above freezing in these regions, but we’re expecting it to drop as precipitation falls. Treated roads appear to be okay for now, but untreated (and infrequently traveled) roads could become slippery.

12:50 p.m. update: We’re watching temperatures carefully as precipitation inches toward the Beltway. North and northwest suburbs are still below freezing, and will probably remain that way though most of the afternoon now that sleet is falling. Temperatures are up to 33-36 degrees in the Beltway, which will initially preclude icy accumulation, but it will get colder as the rain and/or sleet falls.


Temperatures at 12:50 p.m. (Weather Underground)

12:00 p.m. update: Sleet is falling in the far northern suburbs, including Frederick, Gaithersburg, Germantown and Leesburg. Sleet and freezing rain is moving into the Baltimore area from west to east, coating the untreated surfaces with ice. As the hours pass, the rain and sleet will creep farther south toward the Beltway. Temperatures could drop, making it more likely for ice to develop on untreated roads.

The Monday evening rush could be hazardous as a wintry mix skirts through the D.C. region just as commuters head out the door, especially in the northern suburbs.

Snow is not really going to be the issue tonight — the concern will be the chance of icy roads due to sleet and freezing rain. Temperatures seem likely to rise above the freezing mark this afternoon, which would preclude icy accumulation. However, as the precipitation falls, it will cool the air, which could drag the temperature back down below freezing. That in combination with very cold roads (thanks to the recent prolonged cold snap) suggests untreated surfaces could become slick.

In many ways, this so-called wintry mix can be more dangerous than snow. Be prepared for icy roads — particularly side streets — and sidewalks. Allow extra time for the commute.

Timing: Monday from 3 p.m. to 7 p.m.

Hazard: Light freezing rain, sleet and snow

Impacts: Icy glaze on untreated surfaces, including roads, sidewalks, driveways and parking lots

Confidence: Medium

Forecast details

The main uncertainty in this forecast is the temperature. If it stays above freezing through the duration of the event, there will not be hazardous accumulation. If it drops below freezing then ice could start to develop on the roads. The forecast is right around 32 degrees, so it could go either way.

These are a few reasons we are concerned about ice this evening:

1) The air will initially be dry. So any rain falling through it will evaporate, which will cool the air. Even if the temperature gets up above freezing this afternoon, it could drop rapidly once the precipitation arrives.

2) Arctic air often holds on a little longer than forecast, and we are only just coming out of a prolonged cold snap. In these situations, the coldest model forecast usually ends up being closest to reality unless strong surface winds are present. The high-resolution NAM model suggests, despite the lack of a high pressure system to our north to promote cold air damming, temperatures will stay at or below freezing for most areas north and west of the city.


NAM temperature forecast for 4 p.m.

The NAM also indicates temperatures will fall back to freezing even around the Capital Beltway once the precipitation starts. The NAM is predicting below-freezing temperatures as far south as the District. By 7 p.m., the model drops the temperature to 33 degrees as far south as Waldorf and Dale City.

Other models forecasts are a little bit warmer — notably the GFS, which keeps the District at 35 degrees at 4 p.m. With light winds being forecast, it is hard to rule out the NAM’s colder, icier prediction.

3) The ground and untreated surfaces are likely to remain well below freezing because of the extreme cold of the past couple of weeks. If that is the case, rain would freeze on contact, even if the air is warmer than 32 degrees. For that reason, even folks living in areas where the temperature rises a little above freezing south and east of the city should not let down their guard and should monitor road conditions.

The precipitation should clear out from west to east but could linger across our eastern areas into the evening hours. Precipitation will be over well before tomorrow morning, but temperatures will drop below freezing again tonight, which raises the potential for icy patches in the morning commute.

The Capital Weather Gang takes us through their predictions for the upcoming 2017-2018 winter weather in Washington, D.C. (Joyce Koh/The Washington Post)