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Posted at 10:00 AM ET, 01/27/2010

Late Friday-Saturday snow threat still evolving

By Dan Stillman

Cold enough for snow, but amounts hinge on storm track

* Calm into tomorrow, then action begins: Full Forecast *

Next Chance of Accumulating Snow: Friday PM-Saturday
Probability of Accumulating Snow (1" or more): 60%
Most Likely Potential Impact:

What we're fairly confident of is that: 1) A storm center tracking eastward along the Gulf Coast during the day Friday will then track northeastward toward the North Carolina/South Carolina coast Friday night; 2) The cold air needed to support a mostly snow or all-snow event is likely to be in place both near the surface and higher up in the atmosphere; and 3) The timing for snow in D.C. and vicinity looks to be late Friday and Saturday.

But from its position off the North Carolina/South Carolina coast, does the storm turn up the coast and bring moderate to major snow accumulations to the D.C. area? Or does it take a track more out to sea with the potential for only minor accumulations across the region, with heavier stuff staying south of the metro area?

Frankly, we don't know the answer yet. While yesterday's computer model runs tended to shift the more significant snows south and away from the area, that trend may now be reversing back to the north. Here are the accumulation probabilities based on analysis of the latest data. These will likely continue to evolve:

40% chance: Less than 1"
25% chance: 1-4"
20% chance: 4-8"
15% chance: 8"+

Note: While the highest percentage for any one category is the 40% for less than 1", taken as a group the three highest categories indicate a 60% chance for 1" or more.

The Snow Lover's Crystal Ball appears when the potential exists for accumulating snow beyond 24 to 36 hours.

By Dan Stillman  | January 27, 2010; 10:00 AM ET
Categories:  Snow Lover's Crystal Ball  
Save & Share:  Send E-mail   Facebook   Twitter   Digg   Yahoo Buzz   StumbleUpon   Technorati   Google Buzz   Previous: Forecast: Calm into tomorrow, then action begins
Next: Ann and Antarctica: How's the air down there?


How fun were those passing snow 'showers' yesterday? It was snowing at a good enough clip (in Laytonsville, MD) to obscure the houses across the street and cause a meeting to pause so everyone could look outside like kids. So glad it was above freezing.

Last year we would have been so excited to have the potential of a few inches of snow. The snowpocolypse really spoiled us.

Looking forward to the discussion in the next few days!!!

Posted by: dprats21 | January 27, 2010 6:53 AM | Report abuse

come on shift to the north!

Posted by: bachaney | January 27, 2010 7:31 AM | Report abuse

Temps in the 20's, with a 60% chance of 1" or more...I like it. Homemade chicken soup and cinnamon rolls are planned, plenty of hot chocolate is stocked, and a good book awaits Saturday afternoon. Sunday, it's outside to play!

Posted by: --sg | January 27, 2010 8:26 AM | Report abuse

As a newbie here, I always here people talk about the weather models they look at. Can someone tell me where I could go to look at them? I won't understand it, but I'm curious.

Posted by: jase700 | January 27, 2010 8:28 AM | Report abuse

Jase700, there's a link to Models & Discussions on the left panel of this page.
Here's a page with simple instructions.

dprats21, the snow showers were a bit fun. Actually was able to measure 1/8th inch...

Posted by: spgass1 | January 27, 2010 8:49 AM | Report abuse

"While yesterday's computer model runs tended to shift the more significant snows south and away from the area, that trend may now be reversing back to the north."

and the dance begins.... or maybe it's like musical chairs?: hopefully the music stops while the models show "significant snow" right on top of us!

Posted by: walter-in-fallschurch | January 27, 2010 9:30 AM | Report abuse

...of course when i say "us" i mean "ME" - west of the city inside the beltway...

Posted by: walter-in-fallschurch | January 27, 2010 9:32 AM | Report abuse

The 12Z GFS is really suppressing the qpf and keeping most of it south of DC. 12z NAM is actually giving DC metro more liquid now. If we are approaching 15 or 20 to 1 ratios, that's still significant enough to cause problems. Lets see how things look in about 24 hours before we go one way or the other.

Posted by: DullesARC | January 27, 2010 11:10 AM | Report abuse


Are you suggesting the models are diverging? That would be odd, no?

Posted by: oldtimehockey | January 27, 2010 11:42 AM | Report abuse

Grrrrr! Wish these things would come into clearer view. Supposed to to go to Hershey for the Bears' game against Albany on Saturday, making use of the tickets we couldn't use the weekend of the LAST snowstorm. So it figures to be a repeat performance....

Posted by: ValleyCaps | January 27, 2010 11:43 AM | Report abuse

DullesARC, (others?)

who says we'll get 15 or 20:1 ratios? isn't 10 or less more typical?

Posted by: walter-in-fallschurch | January 27, 2010 11:50 AM | Report abuse

Accuweathers Henry Margusity's newest blog saying 6-12 inches for Central VA and about 6 for the DC area. Hype it up baby!

Posted by: crozet | January 27, 2010 12:02 PM | Report abuse

Still waiting for the timing on this potential dance-wrecker...would be OK this time if it holds off till early Saturday...or "busts" to our south.

Posted by: Bombo47jea | January 27, 2010 12:02 PM | Report abuse

Walter - oh yeah, 10 to 1 is our normal, but if the Sterling temp forcast of about 21 for a high on Saturday verifies, we'll be in a very cold column of air...especially with the thickness value looking so low. That 540 line is way down south and that 522 line heading our way, even mid-day. I did see one of the Sterling discussions mention high ratios on Monday or Tuesday this week. Not saying that we will get an inch or a foot, but what does fall wont be good for snow sculpting!

Posted by: DullesARC | January 27, 2010 12:02 PM | Report abuse

NAM has been the best model for predicting these snow events SO FAR this winter (past does not determine future, however.) Still concerned about the wide range of solutions this close in. 20:1 makes sense to me in a "cold" storm like what's coming.

Since in the end the strength of the pressing cold will determine our final accumulations, anyone looking at any particular data to check how strong the cold high is in reality vs. predictions? I think watching the high is the trick on this one, and I was trying to figure what which specific data to watch. Thanks.

Posted by: curtmccormick | January 27, 2010 12:07 PM | Report abuse

I love comments where people wish for snow and have their snow day planned out drinking hot chocolate and reading books.

But not everyone wishes for snow, because some of us have to work our butts off salting and plowing snow all day and night. Because those same people who wish for the snow, are the same ones who go out driving in the snow and cause mass amounts of accidents.

Enjoy the snow.... sea!

Posted by: KRUZ | January 27, 2010 12:53 PM | Report abuse

I do feel bad when the weather makes it difficult for people, however, wishing for snow is not what causes it to snow. I do like snow, so I am glad when it does snow. I do not drive in it, I do have to shovel, but I think it is nice to bake on a snowday, if you can.

I hope that if you are out salting and plowing you are being paid to do so.

Posted by: celestun100 | January 27, 2010 1:08 PM | Report abuse

extremely good point about those out plowing being PAID to do so - hardly a hardship... probably plenty of people who would happily collect that extra paycheck. as far as accidents and so careful. better yet, stay home, bake, drink irish coffee, go for a walk. i suppose there are a few people (doctors, maybe) who HAVE to go out in it, but almost all who do so CHOOSE to do so.

what's the 540 and 522? are those air pressure? cold temp and low (?) pressure makes high ratios?

CWG, others,
you guys keep saying the models are all over the place on this one. when's the next batch of model runs due?

Posted by: walter-in-fallschurch | January 27, 2010 1:37 PM | Report abuse


I deeply value those who are out salting, plowing and shoveling during snowstorms. I recognize that I am very, very lucky to be able to plan to stay indoors with hot chocolate and a book during a storm. As those are my plans, I think it's pretty clear that I will not go out and drive in it, and certainly will not get in the way of those of you working to clear it.

Please be careful when you're out salting and plowing. And please be aware that none of us here wishing for snow are hoping to make it hard on you. We know it's a burden for many, and many of us do our part to assist and support those for whom snow in any amount is a negative event.

Posted by: --sg | January 27, 2010 1:43 PM | Report abuse

All essential types of personnel have to go out in it, people tend to forget that. This includes people who work in pet boarding, pet sitters, police officers, fire fighters, EMTs, etc.
Also, shift workers usually have no choice but to try to drive because they don't have the option of calling in and the places they work at stubbornly stay open even with crappy roads. For example, Lowe's during the Dec09 storm- stubborn because they were determined to try to make Christmas sales.

My husband is a police officer and hates snow because he has no option of staying home. But...he never takes it personally when I'm wishing for it, he realizes that it's fun for me and most others. Lighten up.

Posted by: kallieh | January 27, 2010 1:49 PM | Report abuse

walter- the lighten up wasn't to you, it was in general. I was just responding to your "doctors, maybe?"

Posted by: kallieh | January 27, 2010 1:49 PM | Report abuse

I don't like the way the models are trending. We may end up dry and very, very cold.

Posted by: bdeco | January 27, 2010 1:58 PM | Report abuse


The Euro model just ran and it's a complete miss. (Which is a-ok with me as a snow hater.)

Posted by: oldtimehockey | January 27, 2010 1:58 PM | Report abuse

i would include police, emts those who HAVE to go out. shift workers and so forth...uh...i don't know...

i am always disappointed when kruz or one of his ilk (all in good fun, kruz) plows our street. it goes from looking so clean and white, a "winter wonderland" i call it, to...well...yuk...brown or black. the plowing event marks the end of a certain phase of the storm.

i remember as a kid (in this area) how it would take many days or a week for the plows to come. after a few cars had driven on them and packed them down, the roads would ice up and be great for sledding (on a flexible flyer type sled with "runners"). wow that was fun....! i still have my old sled, but my daughter's NEVER done that kind of sledding because the darn plows get here so soon these days....

Posted by: walter-in-fallschurch | January 27, 2010 2:08 PM | Report abuse

I only include shift workers because they don't get paid if they don't work. Most of them do not have the means to just choose not to work. If the decision is taken out of their hands (the business closes) they'll stay home, otherwise they'll go.

I remember that- it was like that when I was a kid too. My street never gets plowed so kids were sledding on it after the Dec storm. It's a narrow street and since no one has driveways everyone parks on the sides of the street. Too narrow for a plow to fit down without risking hitting into cars. They don't risk it. By Wed after the last storm, we just went out and shoveled out a path to get cars out.

Posted by: kallieh | January 27, 2010 2:14 PM | Report abuse

bdeco, oldtimehockey,

re those model runs: a big HARRUMPH...

Posted by: walter-in-fallschurch | January 27, 2010 2:14 PM | Report abuse

IT's a miss! Pack it in! Enjoy the snow - RICHMOND AND THE N.C. Piedmont!

Posted by: stinkerflat1 | January 27, 2010 2:44 PM | Report abuse

A shift back to the north that occurred in the models last night has reverted back to the south on model runs today -- a good example of why you don't want to change a forecast too dramatically based on just one or two model runs. Maybe things will again shift northward tonight. If they don't come back north at least a bit, either tonight or by tomorrow morning's runs, then we may be looking at minor accumulations (at most).

Posted by: Dan-CapitalWeatherGang | January 27, 2010 4:55 PM | Report abuse

Not surprisingly, Joe Bastardi has a very different take on this storm, he sees it tracking north and putting the D.C. area in the heavy snow band with something in the neighborhood of a foot:!

Posted by: jdtdc | January 27, 2010 5:05 PM | Report abuse

I'm scheduled to drive to Charlotte NC Friday evening--it doesn't look like a sound idea, even if DC gets "skipped." How much of a nuisance will this weather be further south?

Posted by: norsemanpilot55 | January 27, 2010 5:51 PM | Report abuse

My sister lives in Charlotte and she told me that they are expecting 1-4 inches. To us that is cake, to them it is a massive storm.

Posted by: FusilliJerry1 | January 27, 2010 10:11 PM | Report abuse

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