** Winter storm warning Tuesday evening through Wednesday afternoon for Montgomery, Loudoun, Carroll, northern Fauquier counties and points north with freezing rain advisories for most other areas **

11:50 p.m. update: Light freezing rain/drizzle continues to fall and produce very icy sidewalks across the region and some icy spots are also forming on roads. So far, the NAM model – the coldest – has been most correct and would suggest temperatures may not budge much during the night. So ice will continue to accumulate. A strong enough push of warm air from the south may help temperatures rise a bit towards morning (5-8 a.m.). But – before then – use caution out there.

Given temperatures are on the low end of forecasts and as ice is affecting most of the region, we would not be surprised if more schools delay or close than we indicate in SchoolCast below. Going to catch some sleep, but we’ll be back online providing updates starting between 5 and 6 a.m.

11:10 p.m. update: Temperatures around the region at 11 p.m. are in the upper 20s in our colder north and west suburbs (28 at Frederick and 29 at Dulles) to near freezing at Reagan National and south and east of town (31 at Annapolis, 32 in Fredericksburg). Patchy freezing drizzle and light freezing rain is occurring with reports of some sidewalks becoming a bit icy as well as some light ice accumulation on elevated surfaces. Roads – by and large – are mostly wet, but use caution – especially on bridges, ramps and overpasses.

10:30 p.m update: Much of the area is now near or below freezing, with light freezing rain the predominant precipitation type, but some plain rain falling as well. After an initial batch of showers, there’s a bit of a radar break ahead, although precipitation will continue to fill in and stream northeast from the southwest. Temperatures have perhaps reached their lowest point or close in many spots. It appears the focus of the icing risk in the next batch will be west of I-95 around here, but some icing remains possible in the next few hours just about everywhere and on elevated objects in particular.




10:00 p.m. update: NOAA’s Storm Prediction Center has issued a technical “mesoscale discussion” for the region, highlighting a growing ice threat mainly covering our western and northern suburbs, but closing in on D.C. itself. Here’s a brief snippet, see the whole thing for more:


9:15 p.m. update: Showers of freezing rain and rain are breaking out over parts of the area, with DCA now reporting 34 with light rain. This trend is expected to continue over the coming period.

9 p.m. surface analysis of the local mid-Atlantic. (WeatherScope)

Above is a 9 p.m. analysis of the area that includes temperatures at that time as well as winds (in knots and direction), and an estimated wet bulb line of 32 degrees. With a fully saturated air mass that’s in theory about how far south could end up at freezing. For the next few hours at least, this includes the entire area. It does not mean all spots will get to or below freezing though, especially near the edges, and it is dependent on precipitation. Places near or just below freezing will accrete ice considerably less efficiently than those in the 20s.

8:00 p.m. update: Freezing rain advisories have been extended south and east to cover the entire region through 6 a.m. Given temperatures near freezing in those zones, it does appear some light icing is possible even into Calvert and St Mary’s counties, but only a trace to a few hundredths of an inch. The forecast remains on track in general, with temperatures perhaps on the cold side of the expected envelope thus far.

Regional radar at 7:30 p.m. ()

7:35 p.m. update: Still dry. In fact, I saw the moon for a while in the last hour here in D.C. Precipitation should begin to develop and increase across the region over the next several hours, and there are some early hints of that with very light radar echoes starting to show up between Richmond and Fredericksburg (likely not reaching the ground for a while).

Short-term models have been consistently slowing the start time a bit, but it still looks like light freezing rain and rain showers want to break out by 10 p.m. or so in the immediate area. Temperatures that quickly dropped to a range between the upper 20s and mid-30s should remain fairly stable, though may fall off a bit once precipitation starts.

From 5:30 p.m…

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.

Highs mostly made the mid-30s to near 40 today, with many spots already falling back closer to freezing thanks to the loss of any sun earlier. We won’t head too much further down temperature-wise in most locations, but there won’t be any hurry to get readings back on the rise until around sunrise either. With that, the stage is set for some iciness overnight into early Wednesday, particularly north and west of the city.

Through Tonight: Showers of rain and freezing rain, possibly some sleet to start, push in from the south/southwest late this evening, covering the whole area by midnight or a little later. Start time currently appears a bit pushed back compared to earlier, but activity should develop or move in by 10 p.m. or thereabouts, and some showers are possible prior.

Related: Ice issues mainly north and west of D.C. tonight

Once underway, periods of mainly light (some moderate+ pockets) rain and freezing rain are likely through the night, with spots generally near or below freezing from the city and to the west of I-95, while near or above freezing south and east. Readings may begin to rise even before sunrise, especially around D.C. and east of I-95.

20z HRRR radar panel for 2 a.m. tonight shows the freezing line already north of the city. Not our specific forecast, but certainly possible. (Weatherbell.com)

Tomorrow (Wednesday): Freezing rain continues to be likely in the morning, but the freezing line pushes north and west with time. Pretty much everyone should be above freezing within a few hours after sunrise. Some of the heaviest precipitation locally may come in the morning, mainly after temperatures rise. Total ice accretion of 0.20″+ is possible in the far north and west suburbs, with 0.05″-0.15″ or less more likely around the city, and about trace or even none east.  As much as 1″+ of liquid equivalent precipitation may fall overall, generally favoring northern spots.  

As precipitation clears in the midday, we end up trying for a brief push of warmth into at least parts of the area, but that aspect of the forecast has high bust potential. Heading to or through the 40s might be the way to term it, though that could mean low 50s southwest and upper 30s northeast. Above freezing, at the least.

See Matt Rogers’ forecast through the weekend. And if you haven’t already, join us on Facebook and follow us on Twitter . For related traffic news, check out Dr. Gridlock.

SchoolCast, FedCast, and TravelCast

Wednesday SchoolCast

(Loudoun and Frederick, and counties N/W)

(2.5 apples)A bit more than 50/50 chance of delays, or even no school. Do your homework!

(Montgomery and Howard counties)

(2 apples) Impacts are less here than further northwest, but can’t rule out delays or even a closing due to morning iciness.

(Everywhere else)

(1.5-1 apples) School should go on as scheduled except perhaps in counties with a history of playing it extra safe. 1.5 apples most spots, but 1 apple for those furthest southeast. Keep an eye on conditions as small changes may have impact.

Wednesday FedCast

(1.5 domes) Less than 50% chance of unscheduled leave policy. Shut down unlikely.

Wednesday TravelCast

(2 airplanes) Minor-significant airport delays or cancellations expected, mainly in the morning to midday, but this storm is impacting the entire northeast corridor so they may linger.