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Posted at 1:50 PM ET, 01/10/2011

Snow map, accumulation timeline & FAQs

By Jason Samenow

The South has been slammed and the Northeast is poised to be pummeled. What happens in between? Will the D.C. area be left in the snow hole once again? It'll be close, but we think the storm will redevelop just in time to produce a light to moderate snowfall across the area mostly Tuesday late afternoon and evening.

Use the information below to help you prepare for this storm, but note that we may need to adjust the accumulations in the map below in either direction as the storm is still about 24 hours away from impacting us...


10 AM to 1 PM TUES
Chance of light snow developing, mostly south. 28-32.
1 PM to 4 PM TUES
Chance of light snow, mainly south. Little/no accumulation. 29-33.
4 PM to 10 PM TUES
Light snow west, moderate snow east. Accumulation likely, esp. after sunset. 26-30.
10 PM TUES to 2 AM WED
Accumulating snow ends from southwest to northeast. 25-29
Overall Forecast Confidence: Medium


SchoolCast (for Wed.)

FedCast (for Wed.) capitol-black.jpgcapitol-black.jpgcapitol-gray.jpgcapitol-gray.jpg


Where is the storm now?

Follow the progress of the storm on national radar, regional radar and satellite.

How confident are you in your forecast?

Forecast confidence is moderate. Model guidance has been pretty consistent for the last day or so in simulating a 1-3" storm for D.C. and to the southwest, and 2-4" storm east and northeast of D.C. And that supports our overall thinking given the setup since Friday. However, because the storm will redevelop just as it's approaching us, slight changes in the speed of development could mess up our forecast.

Keep reading for more FAQs...

What does Wes Junker, CWG's winter weather expert, think about this storm?: Wes tells us...

The models have come into pretty good agreement during the last few runs. The overall differences in their forecast precipitation amounts is minor over the Washington metro area. I still like our forecast from yesterday. Snowfall totals looks like they will be in the 1-3 inch range west of the city and 2 to 4 inch range to the east and northeast. The storm threatens to produce significant snowfall for cities farther north such as New York and Boston.

What are the chances of lower or higher amounts of snow than forecast?

We think there is a 20-30% chance the storm will re-develop too slowly or too late such that accumulations would be less than 1" similar to the 12/26 storm. There is also 20% chance the storm re-develops quicker and earlier, offering the region a 3-6" type of snow event. Because the storm will be moving so fast, we don't think there's much of a chance for more than that.

Where and when will conditions be the worst?

The window when moderate, accumulating snow is most likely starts late tomorrow afternoon and continues through around midnight, or maybe a little after as you head northeast. The afternoon/evening rush hour could be impacted.

Will the snow stick?

While temperatures have been cold, light snow that falls early on during the event Tuesday afternoon may not be intense enough to appreciably accumulate. However, as it becomes dark and the snow intensity picks up after 4 or 5 p.m., that's when accumulation is most likely.

How will travel be impacted?

After 4 or 5 p.m., slick spots could begin developing on roadways from south to north. So allow extra time for the evening commute or leave early. There may be some flight delays and a few cancellations Tuesday evening if moderate snow materializes, but this is not a crippling storm and we do not advise changing flights at this point.

What about schools?

The snow may well start late enough not to impact schools too much Tuesday. However, delays and closings are possible Wednesday due to snow Tuesday night.

What will conditions be like in other I-95 cities?

The storm is likely to intensify as it heads northeast meaning significant snows for Philadelphia, New York , and Boston. Philly might expect 4-8", with 6-10" in New York and 8-12"+ in Boston. The snow will begin in those cities mainly Tuesday night and continue through Wednesday afternoon in New England.

What are other forecast outlets saying?

NBC4: 1-3" with sleet DC and east; 2-4" north &west
ABC7: 1-3" (2-4" east)
FOX5: 1" Tuesday, more Tuesday night
WUSA-TV9: 2-4"
National Weather Service: 2-4"
AccuWeather: 1-3"

What's the forecast for the rest of the week and weekend, after the storm?

In a word - cold. Here's our forecast for Wednesday through the weekend.

Finish this sentence, #WinterinDC ...

Does winter/snow in D.C. drive you batty? Or is the whole thing just a bit overblown? Share your thoughts with us in the comments below or by using #WinterInDC on Twitter. We'll post some of the responses back here on the blog later...

Follow the action here:

By Jason Samenow  | January 10, 2011; 1:50 PM ET
Categories:  Forecasts, Latest, Winter Storms  
Save & Share:  Send E-mail   Facebook   Twitter   Digg   Yahoo Buzz   StumbleUpon   Technorati   Google Buzz   Previous: Update: Snow chance Tuesday night steady
Next: PM Update: Waiting on tomorrow's snow


Great write-up! Exactly the info we need to plan our work days. Keep us posted if there are any changes.


Posted by: ThinkSpring | January 10, 2011 1:59 PM | Report abuse

I realize the NAM is giving us a bit more QPF than the globals are and some think it is a bit overdone. The 12Z NAM is showing some incredible snow ratios, as high as 28:1 at the end of the storm. I know CWG has mentioned more than once that ratios are probably going to be near 10:1. A little difference in the ratio won't matter much in the total accumulation but the difference between 10:1 and 28:1 can be significant. What are your thoughts on the NAM's output, ratio wise?

Posted by: pjdunn1 | January 10, 2011 2:03 PM | Report abuse

pjdunn1, yesterday I thought the snow ratios might only be 10-1 but think they will be higher than that now. The models are suggesting a mix of plates and dendrites so we probably can get ratios in the 12-14 range. If we end up getting pure dendrites or they become much more numerous than the plates, then maybe the ratios could be higher. However, ratios are also dependent somewhat of snowfall intensity too. 28-1 ratios show up more on the Bufkit output than actually is observed. At least that is my perception.

Posted by: wjunker | January 10, 2011 2:16 PM | Report abuse

CWG - Thanks for the detailed accumulation timeline and FAQ. I know this is splitting hairs a bit, but is the Columbia, Maryland area (where I am) going to get closer to 1-3 in or 2-4 in? Asking because, from my past experience, 3 to 4 in of snow is when I start to need to first shovel my driveway before driving out - and that's a royal pain when you have to get going.

Posted by: creativekev | January 10, 2011 2:32 PM | Report abuse

*Praying for the four inches in Ellicott City*

Intensify early and often baby.

Posted by: bbirnbau | January 10, 2011 2:32 PM | Report abuse

As a summer lover, my wife had the audacity to tell me that in her mind, this winter is already nearing its completion. She states that it is her belief that we won't get much snow this year and that the cold will shortly cease. She is no meteorologist and she likes getting under my skin. As a fan of winter, give me something to fire back at her. I'd really like to win one for the guys and/or winter lovers.

Posted by: authorofpoetry | January 10, 2011 2:36 PM | Report abuse

Thanks Wes. Much appreciated.

Posted by: pjdunn1 | January 10, 2011 2:43 PM | Report abuse

to me the WSW up for howard county is kind of sketchy. When you travel north along maryland from howard county the watch continues, but then all of the sudden you hit PA and none of those counties along that line are under any type of a watch. Unless the criteria for a WSW doesn't apply enough to those counties it kind of seems incongruent to me.

Posted by: bbirnbau | January 10, 2011 2:52 PM | Report abuse

Please lob some gentle snowballs at your wife later tomorrow.

Posted by: FIREDRAGON47 | January 10, 2011 2:54 PM | Report abuse

Last year I left DC on the Friday morning that Snowmageddon started.

On December 26, 2010 I was here.

On Saturday, it started snowing precisely when my bus to NYC left (7:45 am). And of course, not one half an inch of snow fell on New York City over the weekend.

Now I'm back and I will be here all week.

I'm sorry Washington, your local snow repellent is home, no snow tomorrow. :(

Posted by: dantebouchot | January 10, 2011 2:55 PM | Report abuse

Firedragon - You got it! But only because I have a nice couch!

Posted by: authorofpoetry | January 10, 2011 2:58 PM | Report abuse

"Will the snow stick?

While temperatures have been cold, light snow that falls early on during the event Tuesday afternoon may not be intense enough to appreciably accumulate. However, as it becomes dark and the snow intensity picks up after 4 or 5 p.m., that's when accumulation is most likely."

Awww.. you do love snow. :)

Posted by: RedCherokee | January 10, 2011 3:02 PM | Report abuse

During the past 18 hrs., the SREF's have dried and suppressed to the south and east. Since they usually have a higher QP verification short range than the GFS or NAM, I feel that the 1 inch or less area will expand in the final solution.

The exception would probably be east side of Baltimore toward Dover and Atlantic City.

Is my reasoning flawed?

Posted by: AugustaJim | January 10, 2011 3:15 PM | Report abuse

Hey Guys... Is it just me or does the precipitation down south getting smaller and smaller, I'm now concerned about this so call dry slot not unless it will fill in as times goes by when the "Low" hits the ocean...

I'm hoping something will hapenned, getting nervous now about this, I'm hoping this isn't a BUST II...

Posted by: Michael_Nguyen | January 10, 2011 3:21 PM | Report abuse

i look forward to Wes' reply to Augusta Jims post as ive heard the same thing about the SREF and that T - 1 inch expanding farther east thru PG county. Bust potential is written all over this storm even tho its already a minor to moderate event.

Posted by: KRUZ | January 10, 2011 3:24 PM | Report abuse

The new Nam run was good for our area. Hoping to get the higher end of the 2-4. May even need to bump up the numbers alittle.

Posted by: dannythe357 | January 10, 2011 3:27 PM | Report abuse

Amazing when you look at the National Watches and Warnings map on the main page, you AGAIN see literally a hole around Washington DC!!!

I've been a weather-addict living in this area for almost 20 years, and I can't remember seeing this with multiple storms in the same winter. It's all around us.

Literally a hole! It's amazing. Amazingly sad and disappointing. Boy we were spoiled last year...

Posted by: HurricaneSpud | January 10, 2011 3:28 PM | Report abuse

I know I'll get hammered by snow lovers - I used to be one of you - but last year's experience has made me a reformed snow freak, so I'm glad these storms keep wimping out here. Just the thought of my foot plunging into a foot of icy dirty slush every time I step off the curb gives me chills....

Posted by: dwt301 | January 10, 2011 3:31 PM | Report abuse


The fact that the precip to the south is shrinking has been forecast by the models for days. That's why this isn't going to be a huge storm.

Posted by: Jason-CapitalWeatherGang | January 10, 2011 3:34 PM | Report abuse

Yes we were spoiled last year. I am hoping for snow but I'd rather have these little ones this winter. Last winter is to fresh to repeat it again.

Posted by: maestrojmk | January 10, 2011 3:37 PM | Report abuse


The precip in the South now isn't really "our" snow, and in fact it may look weaker and weaker tonight into early tomorrow as the surface low transitions from over northern Florida to off the Carolina coast. Our snow may not fully blossom until basically right over us tomorrow late afternoon/evening (so, radar early to midday tomorrow may not the best indicator of accumulating snow to come late afternoon/evening), once the moisture associated with the coastal surface low meets up with the energy from the upper-level system (which is associated with the precip you see out over the Midwest now). -Dan, CWG

Posted by: CapitalWeatherGang | January 10, 2011 3:37 PM | Report abuse

AugustaJim, The euro verifies best. I don't see the less than 1" area growing. This is not a case like dec 25, we have a really vigorous upper low coming towards us, we probably wont get into the comma head but its close enough to us to put us in the comma. I see no reason to change our forecast. The 1*Z nam looks pretty much like the 12Z except for a hair more precipitation west of DC

Posted by: wjunker | January 10, 2011 3:42 PM | Report abuse


Good point -- but the Evening News won't make that distinction.

Posted by: jaybird926 | January 10, 2011 3:44 PM | Report abuse

Thanks for your professional insight.

Posted by: AugustaJim | January 10, 2011 3:57 PM | Report abuse

that map is disgusting.

Posted by: walter-in-fallschurch | January 10, 2011 4:05 PM | Report abuse

UGH! Look at the NWS warning map...DRY SLOT!

Posted by: joshvt | January 10, 2011 4:11 PM | Report abuse

The NWS doesn't have even a Winter Weather Advisory for DC yet. When are those usually issued?

Posted by: SouthsideFFX | January 10, 2011 4:22 PM | Report abuse

A new update has just been posted; let's move the discussion over there...

Posted by: BobMiller2 | January 10, 2011 4:28 PM | Report abuse

Idle question ... why isn't there an L with the snow in the midwest? Looking at the most current weather channel surface map.

Posted by: AdmiralX | January 10, 2011 4:32 PM | Report abuse

I hope that 2-4in moves further west at the last minute.
Whats the schoolcast for Mont.CO

Posted by: redskins-95 | January 10, 2011 4:42 PM | Report abuse

Great page! I particularly like the accumulation map and the links provided to view the progress of the storm. NWS has so many graphics out on the web it can be hard to find the really interesting ones (particularly the animations).

Posted by: NM1964 | January 10, 2011 6:17 PM | Report abuse

This winter (lack of snow) is payback for last years abundance of snow.
I base this on absolutely no scientific evidence ;-)

Posted by: bodyiq | January 10, 2011 6:19 PM | Report abuse

Great page! I particularly like the accumulation map and the links provided to view the progress of the storm. NWS has so many graphics out on the web it can be hard to find the really interesting ones (particularly the animations).

Posted by: NM1964 | January 10, 2011 6:19 PM | Report abuse

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