D.C. area forecast: Showery evening, a few slick spots north and west; breezy Sunday

December 14, 2013

* Winter Weather Advisory Saturday for Frederick and Carroll counties *

7:45 p.m. update: The winter weather advisory has been lifted in Loudoun and northern Fauquier counties (it continues in northern Maryland, but even there snow has mostly turned to rain – although some areas are holding around freezing…so some slick spots will linger). The entire region – by and large – is just seeing rain showers – but with wet roads and fog, use caution if out and about tonight. The back edge of the precipitation is in central Virginia and rain is expected to end from southwest to northeast between 11 p.m. and 1 a.m. Unless conditions warrant, this is the last update. Scroll on down for the forecast into early next week.

6:50 p.m. update: With temperatures settling near the dew point, visibilities have come down this evening across most of the area. In general, they are running around 2-5 miles locally, but patches of lower visibility have developed. Spots of fog are possible overnight, particularly in areas where winds are calmest.


Surface visibility in miles (iPhone Surface Weather App)

5:45 p.m. update: More of the region continues to flip over to rain and drizzle as temperatures steadily warm aloft. At the surface, we’re probably going to continue with readings about where they are now through a good portion of the night. There may be some slight fluctuations upward before trending back down heading toward sunrise. Places above freezing now shouldn’t worry too much the next few hours, though a few slick patches are possible closer in to the city in any places that got extended sleet earlier. The precipitation pattern also remains more showery than it was, and that should persist before the storm winds down later this evening.

We will probably slow the pace of info here given that precipitation coverage is decreasing and most of it is rain, but will update as necessary.


Temperatures across the region taken in the 5 o’clock hour. (Weather Underground)

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.

4:50 p.m. update: As skies turn dark, mainly elevated locations that have seen temperatures fall near freezing are reporting more in the way of snow covered roads. This is still well off to the north and west of the city and was furthered along by a heavy band of precipitation that just rotated through. There are still heavier showers around, but overall radar has trended more patchy again, especially west. Temperatures should remain fairly steady in the 32-38 range across most of the area in the hours ahead. Overall, trends should be more showery, and more rain, though stubborn spots may hold a mix a bit longer. A few pockets of freezing rain could also develop north and west and some sleet may still occur in heavier activity.

 

4:13 p.m. update: As heavier precipitation envelops the region, we’re seeing reports of rain and/or sleet in the District and points south and east, and more sleet and snow west and north.  With the sun going down and temperatures just a degree or two above freezing in some of the colder suburbs, be a bit careful in case there’s a slick spot or two. That’s not out of the question if a heavier band of frozen precipitation moves through.  By around 6 p.m., per the update below,  reports of snow and sleet – even north of town – will become even fewer as precipitation becomes mostly rain throughout the region – although some of the colder spots towards I-81 could have freezing rain.

 

 

 

3:20 p.m. update: A large area of moderate precipitation is about to move into the area from the south. This will probably come as as a mixed bag, with more rain and sleet in the District and south and east, with wet snow (mostly non-accumulating) to the north and west. (Again, we don’t see much of a risk for accumulation until you get north of I-70 in Maryland) But even in north and west areas, the window for snow will rapidly close as the afternoon and evening wears on. The temperature at 5,000 feet is warming fast, and once it gets above freezing, the snow will change to sleet and/or rain. As shown in the animation below, temperatures warm above freezing at 5,000 feet everywhere except northern Maryland by 6 p.m. and even into central Pennsylvania by 8 p.m.


Temperatures at 5,000 feet (850 mb) at 4, 6 and 8 p.m. as simulated by the HRRR model. The white and gray shaded areas are below freezing and red and blue are above. The divide between these two zones is a rough approximation of the rain-snow line. (WeatherBell.com)

And even though temperature at 5,000 feet may be below freezing right now around D.C. – meaning it’s cold enough to snow – temperatures near the surface are so warm flakes are melting before hitting the ground in many spots. 2:20 p.m. update: The precipitation hole has closed over the District and Fairfax County and snow and/or rain has moved in. Temperatures are cold enough at high altitudes for snow, but near the surface they range from the upper 30s to low 40s – so some of the flakes are melting before reaching the ground. We’ll continue with this conversational snow and/or rain through late this afternoon, when temperatures at high altitudes will warm enough for just plain rain. The snow that does fall will mostly not stick until you get into some of the colder areas of Montgomery and Loudoun counties and even there sticking should mostly be on grassy areas (except a bit of slush possible on roads in heavier bursts). Accumulating snow (of at least 1″) will mostly be confined to northern Maryland, north of I-70.

1:20 p.m. update: Snow is returning to the region, with big fat flakes being reporting in Montgomery County.  There’s a bit of a snow hole inside the Beltway, but it should fill in.  Temperatures are above freezing so this should be “conversational” snow by and large, with any sticking mainly on grassy areas.  If it snows hard enough, a little slush could build-up on roads, so keep that in mind.  A changeover to rain is still likely as the afternoon wears on.

 

11:50 a.m. update:Winter Storm Warning for Frederick and Carroll counties now downgraded to Winter Weather Advisory. Also, the Winter Weather Advisory for Montgomery and Howard counties has been dropped.

11:15 a.m. update: Radar continues to be fairly quiet around the area, with temperatures in the mid-30s to near 40. You have go out around Frederick and Winchester and points north and west of there to find temperatures down near freezing. So, nothing to worry about as far as roads go in the greater metro area. Precipitation should pick up again mid-afternoon into evening, but that should be in the form of plain rain.

9:15 a.m. update: Snow showers have remained rather patchy, though more consistent activity is now northwest of the city. Around Dulles, a brief period of moderate snow passed by recently, causing a dusting or a little more of snow in spots. Temperatures remain in the mid-30s most of the region, minimizing the risk of anything more than a grassy coating of snow unless in elevation. For the most part, we are into a bit of a lull in the next few hours, but a few snow or rain showers remain possible during this time.

 

7:10 a.m. update: A band of mainly light scattered snow is pushing into the area from the south and west. This activity is pretty minor overall with possibly a brief patch of heavier. Reports of a dusting or so have come in from places like Winchester, Va. in elevation off to the west. Much of the immediate area is actually running a tad mild this morning, with many temperatures in the mid-30s. Temperatures could cool a bit with any onset of precipitation, but perhaps not much, as anything falling from the clouds should remain pretty spotty for the coming period and the sun is now rising.

Today’s Daily Digit

A somewhat subjective rating of the day’s weather, on a scale of 1 to 10.

3
Light mixed precip changing mainly to a cold rain. Blah. Ian, CWG

Express Forecast

Today: Wintry mix changing to rain, slowest in elevation well north and west. Highs: Mid-30s to near 40.

Tonight: Rain and pockets of freezing rain ending around midnight. Lows: Near 30 to mid-30s.

Tomorrow: Clearing, breezy. Highs: Near 40 to mid-40s.

FORECAST IN DETAIL

Temperature Map

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

5:00 a.m.: Remember last Sunday? Well, the onset of this one is somewhat similar, although it ends up a good deal less problematic around here. A storm system approaching from the southwest will ultimately redevelop around the Mid-Atlantic coastline, leaving us kind of in the middle. That means we get a smorgasbord of weather. But it’s generally the type that is more wet than anything else, and it doesn’t cause widespread headaches locally.

Today (Saturday): The first area of precip may be pushing in somewhere around sunrise. If so, it will have to overcome some surface dry air. Anything falling early should be snow or sleet, with temperatures near freezing north and west of I-95 and the low-or-mid 30s southeast. Those temps go up slowly with the sun. Any accumulation in most of the region should be limited to grassy surfaces and amount to a dusting or so, perhaps up to around 1″ in the higher elevations north and west, with more north and west of that. Many of us just see conversational flakes or even mainly sleet before the change to rain — much of the precip could be light and spotty. By the time we get past noon, pretty much everyone should be rising past freezing. A transition to rain is ultimately likely in most spots, perhaps staying mixed well north and west. Highs mainly end up in the mid-30s to near 40, with some elevated areas north and west closer to freezing. Confidence: Medium


Snow Potential Index

A daily assessment of the potential for *accumulating* snow for the next week on a 1-10 scale.

3 (→) A few well north and west may eke out 1″ or so Saturday. Most folks see a little grass slop or no stickage.

Tonight: Showers or a period of mainly light rain with embedded heavier activity may continue through as late as about midnight, but don’t be too surprised if it cuts off earlier in the evening. Pockets of freezing rain are possible well north and west, but even there it should be somewhat isolated as readings stay mostly above freezing until precip ends. Eventually we should settle into lows in the near 30 to mid-30s range prior to sunrise, so there could be some fresh slick spots for early risers. Confidence: Medium

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

Tomorrow (Sunday): Clouds break as we get through the day, and we end up partly to mostly sunny on the whole. A bit windy as well, as gusts blow in from the northwest on sustained winds around 15-20 mph during the midday. Highs rise to near 40 in the coldest spots, perhaps reaching the mid-40s downtown. Confidence: Medium-High

Tomorrow night: The area ends up fairly clear overnight. With those clearer skies, and cooler air moving back in, we should see lows in the 22-28 range most locations. Confidence: Medium-High

A LOOK AHEAD

On Monday we see temperatures a bit colder than the weekend as air from Canada filters in temporarily behind the storm system. Highs could be down as low as near freezing to the mid-30s, but hopefully we’ll trend a tad warmer. Skies are sunniest the first half of the day, and there may be a snow flurry or snow shower late, particularly northwest portions of the area. Probably still a bit breezy as well. Confidence: Medium

Tuesday brings a warm up but, it’s likely also somewhat be brief with a system moving through the Great Lakes poised to send us another cold front as soon as Tuesday night. Not a bad day at all with partly to mostly sunny skies and highs rising into the low-and-mid 40s. Confidence: Medium

Jason Samenow and Dan Stillman contributed to this post.

Ian Livingston is a forecaster/photographer and information lead for the Capital Weather Gang. By day, Ian is a defense and national security researcher at a D.C. think tank.
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Jason Samenow · December 13, 2013