Network News

X My Profile
View More Activity
The new Washington
Post Weather website
Jump to CWG's
Latest Full Forecast
Outside now? Radar, temps
and more: Weather Wall
Follow us on Twitter (@capitalweather) and become a fan on Facebook
Posted at 9:00 AM ET, 01/27/2009

Forecast: Some Shovelable Snow, Then Ice & Rain

By Capital Weather Gang

Winter Storm Warning through 12 p.m. tomorrow for Loudoun and Montgomery counties and N & W

Winter Weather Advisory through 12 p.m. tomorrow for the rest of the metro area

So far, this has been the winter of the snow flurry or non-accumulating snow shower. Finally, we have a shot at some honest-to-goodness snow today into this evening. But before it piles too high, the snow is likely to change to ice tonight and eventually rain tomorrow. The worst of the storm's impacts will probably be felt tonight into early Wednesday -- in the form of some significant icing, especially for D.C. and points north and west.

ACCUMULATION MAP AND TIMELINE

4 AM to 10 AM
Light to moderate snow develops SW to NE. Dusting to 1" possible. Temps 25-30.
10 AM to 4 PM
Intermittent snow. 1" of snow possible--heaviest snow south of DC. Temps 28-32.
4 PM to 10 PM WED
Intermittent snow. 1-2" possible. Temps 27-31.
10 PM to 4 AM WED
Snow to ice from SE to NW. 1-2" possible (highest amounts N & W) Temps 28-32.
4 AM to 10 AM WED
Ice to rain in District and N & W. Rain S & E. Temps 32-36.
10 AM to 4 PM WED
Rain, gradually tapering off. Temps 34-38.

IMPACT FORECASTS (FOR TODAY - UPDATED)

STORM FAQ

How confident are you in your forecast? As usual, these complicated storms with various precipitation types can reduce forecast confidence. We are confident that the two major commute concerns will be this evening and tomorrow morning. Confidence is moderate that most areas will see some accumulation of snow today into early evening before the switchover begins from southeast to northwest.

Radar: Latest D.C. area radar loop shows movement of precipitation over past two hours. Powered by HAMweather. Refresh page to update. Click here to see radar bigger. Or see radar bigger on our Weather Wall.

Confidence is low regarding the exact timing of a complete turnover to plain rain Wednesday AM. Areas north and west of DC have the best chance of holding onto frozen conditions beyond the morning rush hour tomorrow.

Where is the precipitation right now? Track the precipitation's progress using regional and local radar. Note that parts of the leading edge of the precipitation seen on radar may be virga -- precipitation that's in the air but not yet reaching the ground.

Keep reading for answers to more FAQs about the storm ...

When will the snow start? The current thinking is that light snow will develop from southwest to northeast between 4 a.m. and 10 a.m. this morning. [7:30 a.m. update: The snow has already started throughout the area]

How much? There should be sufficient snow during the first half of the storm to yield 1-3" inside the beltway. We could see 3-4" north and west of the beltway. There may also be some ice accumulation with up to 0.2-0.4" possible (southeast to northwest) before it's washed away by rain during the day Wednesday.

Will the frozen precipitation stick? Conditions have been quite cold around the area for the past few weeks, so the ground is sufficiently cold for all precipitation to stick today and tonight. Temperatures should climb above freezing during the day Wednesday across the entire metro area allowing untreated surfaces to gradually melt.

When will travel be most difficult? Much will depend on how much snow occurs this morning and afternoon, but with below freezing temperatures, today's morning evening rush hour may have some slowdowns -- particularly if it coincides with steady snow. Rush hour tomorrow morning also be problematic especially in areas north and west of the city where temperatures may remain at or below freezing.

What about precipitation type? What a mess! We believe precipitation will fall as snow through around midnight, followed by a mix of sleet and freezing rain late at night, before a changeover to plain rain in most locations around the morning rush hour, except perhaps after the morning rush in areas north and west of the beltway.

When will conditions improve? They should improve from southeast to northwest during the first half of tomorrow. Tomorrow evening's commute should be just wet.

What could go wrong? Plenty. Mixed precipitation events are notorious for complication and potential changes. Let's try to quantify some of the change risks to this current forecast:

Probability that snow will arrive too late or weak for much lower accumulation: 40%
Probability of snow arriving stronger/faster with more than 3" local accumulation: 30%
Probability of significant ice accumulation tonight (more than .25"): 30%
Probability of a change to plain rain before tomorrow's AM rush hour everywhere: 45%

What will conditions be like after the storm? Temperatures will slip below freezing again tomorrow evening so any wet areas will turn back to ice (watch out for black ice!). The rest of the week should be dry and cold with highs in the 30s and lows in the 20s for most locations.

What are other forecast outlets calling for?
National Weather Service: 1-3" DC and close in, 3-5" N & W
NBC4: 1-2" DC and close in, 2-4" N & W
WUSA-9: 1-3" Metro Area, 2-4" N & W
WJLA-7: 1-2" Metro area. 3-4" N & W

By Capital Weather Gang  | January 27, 2009; 9:00 AM ET
Categories:  Forecasts, Winter Storms  
Save & Share:  Send E-mail   Facebook   Twitter   Digg   Yahoo Buzz   Del.icio.us   StumbleUpon   Technorati   Google Buzz   Previous: Snow Forecast May Cause Dilemma for Schools
Next: Snow Bursts Onto Scene; Turns to Ice Tonight

Comments

Woo first!

Posted by: Havoc737 | January 27, 2009 4:19 AM | Report abuse

snow flakes falling in Chevy Chase, deck turning white and were now under a winter storm warning in montgomery county, this is exciting

Posted by: cjespn | January 27, 2009 5:10 AM | Report abuse

Snow on the ground, everything white (just) here in G'burg.

Posted by: MDScot | January 27, 2009 5:37 AM | Report abuse

And no school in MoCo - this had to be because

a) No days used so far
b) 2nd Semester just starting today

But if the forecast is even close to being correct, this will probably cover tomorrow as well.

Posted by: MDScot | January 27, 2009 5:40 AM | Report abuse

Snowing enthusiastically here in Leesburg. Everything white already with enough to require sweeping the walkway to let the wife get her work shoes to the car unscathed

Posted by: mandarb77 | January 27, 2009 5:47 AM | Report abuse

27.8 here in culpeper va with light snow/sleet. Yes there is sleet mixing in.

Winter storm warning in effect.

Posted by: clintonportis17 | January 27, 2009 5:56 AM | Report abuse

Officially the biggest snowstorm of the season for Chevy Chase with about 1//4 of an inch...thats sad

Posted by: cjespn | January 27, 2009 5:58 AM | Report abuse

Where is the Snowcam?

Posted by: Bitter_Bill | January 27, 2009 5:58 AM | Report abuse

Why does the radar animation change abruptly from rain to snow and ice around 5 am?

Posted by: jethro1 | January 27, 2009 6:35 AM | Report abuse

Schoolcast needs an update ;)

Posted by: Kmlwx | January 27, 2009 6:36 AM | Report abuse

Posted by: cjespn | January 27, 2009 6:55 AM | Report abuse

moderate snow/SLEET in Culpeper. Temp 28 degrees.

Posted by: clintonportis17 | January 27, 2009 6:56 AM | Report abuse

Good morning capital weather-ers!

I guess that answers that question. Jason and I discussed last night how long it would take to actually start snowing and get this storm going. Computers were showing 7amish, but so much was up in the air, we had to take a later start into account. I guess the early snow won out!

Other news: Snow Cam! http://www.washingtonpost.com/wp-srv/mmedia/webcams/snowcamLG.htm
Looks like a dusting is already on the ground in Arlington.

Suprised to see how many schools already punted this morning. Not a bad decision, but very suprised. I guess my contrary thoughts last night sealed the deal for kids all over the region. Thank me later

Posted by: JJones-CapitalWeatherGang | January 27, 2009 6:57 AM | Report abuse

JJones-As an adult, I'll thank you now- for a day sledding and making snow angels with my daughter

Posted by: mandarb77 | January 27, 2009 7:02 AM | Report abuse

Its snowing!!!! :) FINALLY! Alexandria has a nice little dusting so far. Spoke to me parents down in Occoquan and they said they have a coating of sleet on the ground. yuck!

Keep it coming!! Productivity will be at a halt for me today :)

Posted by: AnneinSand | January 27, 2009 7:04 AM | Report abuse

AnneinSand - Occoquan has a coating of snow - not sleet. Currently snowing at a good clip.

Posted by: ZmanVA | January 27, 2009 7:08 AM | Report abuse

something is wrong with the radar, in bethesda it was showing mix then rain but it has beeen snowin not sleeting the whole time!

Posted by: samdman95 | January 27, 2009 7:17 AM | Report abuse

Looks like some patches of sleet mixing in from about Warrenton east and south (as noted in Culpeper too). Warm air should not make too much progress northward until late this afternoon for majority of DC area, but we'll need to watch it. For now, the flakes will fly! -Matt Rogers

Posted by: mrwx1 | January 27, 2009 7:25 AM | Report abuse

Closing schools is always a tough call. Driving from Old Town, Alexandria into Arlington this morning with barely a flake (at 6:45am), but now the grass outside my window is white and snow is sticking to sidewalks. I really hope there are not dangerous conditions for students heading home today.....

Posted by: Snowlover2 | January 27, 2009 7:34 AM | Report abuse

@samdman95

You're right. That radar had a problem. I changed to a different one which seems to be working correctly.

Posted by: Jason-CapitalWeatherGang | January 27, 2009 7:40 AM | Report abuse

Snow falling at a really nice rate here in Rosslyn. Beautiful! I get to wear my new winter boots. Shallow, I know, but I've been waiting all winter for this.

Posted by: phanieb | January 27, 2009 7:46 AM | Report abuse

forecast amount of snow is going up! fox just said 3-5 inches for places north and west! also i saw Jasons comments in the washington post metro section. Youre famous!!

Posted by: samdman95 | January 27, 2009 7:55 AM | Report abuse

CWG - Two things. First, I feel that the Winter Storm Warning will be eventually extended to Howard, PG and Anne Arundel counties in MD; thoughts? I also think that storm will track just enough south so that we see the higher end of your snow total predictions, if not a bit higher before any change over occurs. Comments? Thanks!

Posted by: snowlover | January 27, 2009 7:56 AM | Report abuse

heaviest stuff is definitely south of the city...as is mentioned in the forecast above. I hope it moves north...

Posted by: Kmlwx | January 27, 2009 8:03 AM | Report abuse

To All

New update post here.

Posted by: Jason-CapitalWeatherGang | January 27, 2009 8:06 AM | Report abuse

NBC has upgraded NW DC and Mont. Co. from 2-4" to 3-5."

Posted by: lioninzion | January 27, 2009 10:22 AM | Report abuse

The comments to this entry are closed.

 
 
RSS Feed
Subscribe to The Post

© 2012 The Washington Post Company