Winter weather advisory through Tuesday morning  (see map) | Winter storm warning from Winchester to Hagerstown (I-81) and west *

11:15 a.m. NEW FORECAST UPDATE: Second wave of storm: Snow accumulation possible through tonight, PM commute could be slick (UPDATES)

9:50 a.m. update: As we expected, precipitation is starting to decrease in coverage and intensity as the disturbance sweeping through the area transfers its energy to the massive coastal storm expected to wallop the Northeast. Radar shows mainly light activity west of the District and it’s contracting with time. For the next few hours, expect mainly just light, patchy snow from Rt. 50 north, and rain or a rain/snow mix to the south. Not much additional accumulation is likely from this batch, maybe just a coating to – at most – an inch in our colder northern suburbs.


Temperatures and radar at 9:45a (Weather Underground)

However, new model information is suggesting chances are decent the second phase of the storm, starting mid-to-late afternoon, will deliver some accumulating snow to the region.

This is the last update in this post – please scroll down for the full forecast through the weekend. Follow this link for the latest update on this afternoon’s and evening’s snow potential: Storm’s second wave: Snow accumulation possible through tonight, PM commute could be slick (UPDATES)

8:40 a.m. update: The position of the rain-snow line has seemingly stabilized and it appears to span from around Manassas in Va. to Upper Marlboro in Md, with snow to the north and rain to the south. Snowfall rates are pretty light at the moment, and the heaviest precipitation is actually south of Dale City where it’s mainly rain. Due to the light snow intensity, accumulation is mostly restricted to grassy areas except in our colder areas from northern Montgomery County to the north and west where there have been some reports of accumulation on untreated paved surfaces.

7:45 a.m. update: The rain-snow line continues to make good progress south of the District (see graphic below), although I wouldn’t be surprised if it slows in the next couple hours. Many areas (from NW D.C. and north) are seeing a coating on grassy areas, and a couple inches could fall in our northern suburbs this morning – especially in areas already down to freezing. Again, we expect main roads to be mostly ok, although we can’t rule out slick spots and reduced visibility during heavier bursts. Side streets, sidewalks and driveways may become covered, especially in our colder areas north of town.


(Weather Underground)

7:20 a.m. update: Radar shows some heavier rain and snow southwest of the Beltway lifting north. This could produce a burst of accumulating snow – especially in our western suburbs over the next hour or two. Visibility could be reduced and some slick spots could develop. We’ll keep an eye on it.

7:10 a.m. update: The rain-snow line has seeped into the District and Fairfax County, with many reports of light snow or mixed precipitation.

Again, we expect the best accumulations prospects from upper Montgomery County to northern Loudoun County and to the northwest, but some slushy accumulation cannot be ruled out to the south and east.

6:30 a.m. update: This map from Weather Underground nicely shows the rain-snow line (just after 6:20 a.m.) and regional view of temperatures which range from the low-to-mid 30s to the north and northwest where it’s snowing, and upper 30s to the south where’s raining. Again, look for this rain-snow line to ooze south, but it may have trouble getting south of D.C. this morning.


(WeatherUnderground)

In our northern suburbs where it’s snowing, some light accumulation is likely over the next few hours as snow continues, especially on grassy areas and untreated surfaces.

6:00 a.m. update: Cold air is seeping south and reports indicate the rain has transitioned to snow around Columbia, Md. and is changing to snow in central and northern Montgomery County and northern Loudoun County. We may start seeing the rain mix with snow into the northern part of the Beltway area over the next hour, but the push south may stall some after daylight arrives. So far, reports indicate just wet roads, but use caution where it’s snowing…

5:30 a.m. update: In the immediate D.C. area, mostly rain is falling with temperatures in the upper 30s to around 40. However, rain turns to snow around I-70 and points north. BWI Airport, Frederick, and Hagerstown were all reporting snow at 5 a.m. The rain-snow line will try to shift south through Howard and Montgomery County and into Loudoun County over the next hour or so, but may face some resistance reaching the District. We’ll keep an eye on this and provide updates.

Roads should be just wet around metro D.C., but look out for slicks spots from I-70 and to the north and northwest – mostly on untreated areas (side roads, driveways, and sidewalks). We’ll have more specifics on road conditions in our next update.

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

3/10: Probably not enough snow to appease snow lovers, and otherwise cold and raw.

EXPRESS FORECAST

Today: Snow and/or mixed precipitation at times. Highs: 32-37
Tonight: Snow showers likely. Lows: 25-30
Tomorrow: Morning flurries, then slow clearing, windy. Highs: 30-35

FORECAST IN DETAIL

Radar: Latest regional radar shows movement of precipitation over past two hours. Refresh page to update.

Some snow, rain, and mixed precipitation are with us at times today, but this evening and tonight may hold the best chance for snow accumulation in the immediate metro area as temperatures fall below freezing.  Snow showers and flurries could linger into Tuesday morning, before the monster storm off New England is out of our face.  The remainder of the week is chilly and we’ll have to watch two more clippers for some light snow potential Thursday and Sunday.

Today (Monday): Snow, rain, and/or mixed precipitation are likely this morning between about 5 a.m. and 11 a.m.  The steadiest and heaviest activity is likely northwest and west of the immediate metro area towards northern Fauquier, Loudoun and Frederick (Md.) counties (where mostly snow is favored). These areas have the best chance of some accumulation.

Closer to the city, precipitation is generally lighter and temperatures are a bit warmer, so we may have rain at times, and snow accumulation becomes more challenging.  However, there’s an outside chance that some heavier snow bands sneak into the area which could whiten the ground, reduce the visibility and even cause a few slick spots.  The precipitation type may very between snow, sleet and rain, with snow favored during heavier periods of precipitation.

Note that precipitation is likely to coincide with the morning commute and it doesn’t take much to cause travel issues. Most main roads should be ok, but use special caution on untreated roads, driveways and sidewalks.

From late morning to mid-afternoon, precipitation may taper off a bit with just scattered areas of light snow, sleet and/or rain, with temperatures into the mid-to-upper 30s.


Snow accumulation forecast for through Monday afternoon. (Capital Weather Gang)

By late into the afternoon, we may see bands of snow cycle back into the area with slowly falling temperatures.  This could lead to some delays and slick spots for the evening commute.  ConfidenceLow-Medium

Tonight: Areas of snow are likely but exactly where and how heavy are hard to pin down. We tend to favor areas east of I-95 getting more snow; however, some models have forecast a band farther west from near Sterling Va. out towards I-81.  Generally, there’s the potential for a coating to a couple inches – but we may not have a great idea of exactly what to expect until this snow starts developing.  Temperatures drop back below freezing in most areas with lows in the upper 20s to near 30. Confidence: Low-Medium


Snow accumulation forecast for Monday afternoon to Tuesday morning. (Capital Weather Gang)

For related traffic news, check out Dr. Gridlock. Keep reading for the forecast through the weekend…

Tomorrow (Tuesday): Snow flurries or scattered snow showers are possible in the morning but should end pretty quickly.  The sun should come out by the afternoon as a strong wind cranks up.  Highs are only 30-35. Confidence: Medium

Tomorrow night: Mostly clear, windy and very cold.  Lows range from the upper teens in our colder suburbs to the low-to-mid 20s downtown.  Wind chills dip into the teens and single digits. Confidence: Medium-High

A LOOK AHEAD

Wednesday should be mostly sunny, breezy in the morning, and cold. Highs aim for 30-35. High clouds increase late Wednesday night, with lows near 20 downtown with some teens in our colder suburbs. Confidence: Medium

Another clipper zooms through the area Thursday and, depending on its exact track, could produce a period of snow or mixed precipitation. It doesn’t look like a big deal and it may deposit its narrow stripe of snow to our north, but it’s worth keeping an eye on. Highs reach 35-40. A few snow showers or lingering flurries could linger into Thursday evening, with overnight lows in the 20s. Confidence: Low-Medium

SNOW POTENTIAL INDEX
A daily assessment of the potential for at least 1 inch of snow in the next week, on a 0-10 scale.

7/10 (): If we find a way to not pick up an inch by Tuesday morning, clippers Thursday and Sunday may offer 2nd and 3rd chances.

Cold high pressure builds into the region for Friday and Saturday. Under partly sunny skies, highs are only in the low-mid 30s, with overnight lows in the 20s. Confidence: Medium

The third clipper of the week could race into the region on Sunday and bring another round of snow or mixed precipitation, the specifics of which will depend on its exact track. High should be in the 30s. Confidence: Medium