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Posted at 9:30 AM ET, 01/26/2010

Late-week snow potential grows

By Matt Rogers

Snow chances best late Friday into Saturday

* Return to normal January weather: Full Forecast *

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

A combination of cold air dropping down from Canada and a storm system emerging from the southern branch of the jet stream is brewing potential winter weather mischief for the end of this week. The guidance is converging on the snow threat starting on Friday and potentially persisting deep into Saturday. Snow Friday morning would be light with intensities picking up later in the day and continuing through a part of Saturday based on current estimates.

A Global Forecast System (GFS) model simulation from last night shows a classic Washington, D.C. snowstorm by Saturday morning with high pressure parked to the north feeding cold air into the region while a coastal low pressure system develops to our southeast wrapping in ample Atlantic moisture.

The storm track is very likely to be to our south, which is a favorable course for accumulation potential. But there is still the risk that it could track too far south and only offer a very light amount of snow. And since we are still four days away from the event, it could even track farther north resulting in warmer conditions ( and less snow). As of right now though, the various guidance sources are in good agreement on the late-week snow potential.

Here is the current (VERY EARLY) probabilities on accumulations:

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

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

By Matt Rogers  | January 26, 2010; 9:30 AM ET
Categories:  Snow Lover's Crystal Ball  
Save & Share:  Send E-mail   Facebook   Twitter   Digg   Yahoo Buzz   StumbleUpon   Technorati   Google Buzz   Previous: Forecast: Back to normal January weather
Next: El Niño-linked weather arrives with a vengeance


This is exciting. I wil enjoy watching closely in the coming days to see how this develops. As we are early out, I am restraining my myself and not getting giddy over any snow prospects (although not sure how long my restraint can last!). The timing of the possible storm will mean a lot to me, as both a teacher and a student. It is always tricky when the snow starts falling after 6am....

Posted by: Snowlover2 | January 26, 2010 6:41 AM | Report abuse


I do appreciate the detailed thought you put into your reasoning behind the upcoming system, but I must say I don't fully understand the rationale for the percentages on your crystal ball indicator. I would think that higher snow totals would have a lower percentage. Overall, I think the entire "Gang" does a great job. Keep up the good work!

Posted by: jcmcgrath1969 | January 26, 2010 6:48 AM | Report abuse

jcmcgrath1969, that is a great question. And yes, if we were doing probabilities strictly based on snow event climatology, we would indeed have the lower probabilities for the higher amounts. But right now, the dynamic computer model guidance is suggesting a broad range of potential with some versions showing 8+ and others showing lower amounts. There is even the risk yet that this storm stays suppressed to our south. So we spread the risk out at this early stage and hopefully we can narrow it down in the next day or two here.

Posted by: MattRogers | January 26, 2010 7:04 AM | Report abuse

I am going commit early on this on with a 5-8" forecast. Ideally, I would wait 24-36 hours to see if the NAM is on board with the path of the storm, but that would be too easy! These storms have been tracking a bit northward lately and I think we will track so that the DC area gets 80-90% of the potential impact of the storm. For all of you snow lovers out there lets hope I am right! As for Thinkspring -- start wishcasting against me :)

Posted by: snowlover | January 26, 2010 7:09 AM | Report abuse

5-8 inches sounds great:)

Posted by: celestun100 | January 26, 2010 7:28 AM | Report abuse

My fact-free wishcast is for a snow that begins with the end of the Friday rush hour, leaves us blinking in amazement at a nice blanket of snow Saturday morning, and continues into Saturday afternoon.

Oh, and the usual accumulations -- 10-14" in the burbs, 5" at National.

Posted by: 20009matt | January 26, 2010 7:44 AM | Report abuse

I never, ever take your rational approach to these things for granted. In a world of hype and acromony, this site is (usually) a nice break from pettiness and irrationality. Apart from a few knuckleheads of course.

Have said that, I firmly cast my vote into the fact-free wishcasting camp of six glorious inches of weekend snow, for the sake of my three boys and big dog. Snow comes and goes, but memories endure!

Posted by: curtmccormick | January 26, 2010 8:01 AM | Report abuse

For you wishcasters, the trends in the last 12 hours have been to slow down the snow's onset so that it would either arrive during the day on Friday or Friday evening. So perhaps you'll get your weekend-only storm after all!

Posted by: MattRogers | January 26, 2010 8:16 AM | Report abuse

Matt - is the storm developing later than expected, or slowing down? If the latter, does this mean an extended period of snow for the area?

Posted by: snowlover | January 26, 2010 8:49 AM | Report abuse


Would that also mean that if it moves slower we would get more precip?

Posted by: jpl1019 | January 26, 2010 8:50 AM | Report abuse

The trend is for it to arrive slower, but that is mainly due to additional dry cold air from the North rather than a slower storm system itself. Usually the front end of a storm tends to be the light snow stuff (overrunning) anyway. The heavier potential is Friday night and Saturday at this time.

Posted by: MattRogers | January 26, 2010 8:53 AM | Report abuse

Gfs is certainly looking interesting for the weekend...looks like the good stuff starts to kick in Friday evening and lasts thru the weekend.

That said, I am sitting here in Orlando, FL looking at the sun and chuckling at the "cooooold" comments when it is 47 outside. :-) The locals are dressed like it is Alaska...we are in sweats.

Kim from Manassas

Posted by: ksrgatorfn1 | January 26, 2010 8:55 AM | Report abuse

Teachers like snow days more than their students, and this would be the third weekend storm of the year! I'm holding out for a good Tuesday snowstorm.

Posted by: bbtonbear | January 26, 2010 10:14 AM | Report abuse

I really was hoping to not be snow bound thhis weekend. My god, there isn't even football on!

Posted by: oldtimehockey | January 26, 2010 10:21 AM | Report abuse

I know it is a bit early still, but we have a 2:00 flight on Friday. Is it looking like the storm will hit after that, or should we be considering any earlier flight?

Posted by: ertace | January 26, 2010 10:24 AM | Report abuse

I am really hoping for a 8am flurry developing into solid snow by 12pm, and an early release for Feds by 2pm. Since I don't drive to work and could feasibly walk home I realize how selfish this is.
On more dramatic sites (accuweather) there has been some talk of snow next week. I realize that is way off but I am adding to the wishcast for 8-10inches on Fri/Sat with another 6 (12 in my fantasy land) inches on Tuesday leading to a mid-week snow day and a closing of the Fed.

Posted by: Bainbridge | January 26, 2010 10:29 AM | Report abuse

@ Bainbridge
You are not being selfish at all! I am in the same boat and would love nothing more then to have an early snow day and snowy weekend- who wouldn't?

Posted by: WarderKid | January 26, 2010 10:40 AM | Report abuse

Like ertace, I'm flying on Friday. Do I have anything to worry about for my Friday AM arrival into National? And what are the chances of an early release for government / major employers in DC?

Posted by: mmurphy70 | January 26, 2010 10:41 AM | Report abuse

this is getting exciting...

CWG - matt, you said,
"The trend is for it to arrive slower..."

does that mean it might linger longer? (he pants hopefully...) i like how the NWS "at a glance" now has 60% (!) chance of 5 snowballs (nothing "mixed" apparently?) for both fri and sat! - much more bullish than before.

are chances really improving for a good snow?

Posted by: walter-in-fallschurch | January 26, 2010 10:53 AM | Report abuse

re: questions about flights/closings

It's too early for us to be speculating a lot about this, but the storm onset is trending later, so travel through early afternoon Friday is probably fine, maybe even into late afternoon. Friday night and early Saturday may be another story. But again, details are still coming together here, and a lot can change.

Posted by: CapitalWeatherGang | January 26, 2010 11:01 AM | Report abuse

Why does it always snow when I have travel plans?? :)

Posted by: chass80 | January 26, 2010 11:05 AM | Report abuse

The latest GFS model run simulates the "too far south" scenario Matt described in which we don't get a lot of snow. It's just one model and one model run, but it goes to show a number of possibilities are still on the table.

Posted by: CapitalWeatherGang | January 26, 2010 11:12 AM | Report abuse

I'm hoping that I haven't jinxed the storm by ordering a new snow shovel and rock salt and paying to have it overnighted to my house. We broke our old shovel on the December storm.

Let it snow!

Posted by: bachaney | January 26, 2010 11:52 AM | Report abuse

@bachaney- You totally did. When we don't get big snows we'll know who to blame ;-) j/k

Seriously though, as long as we get a few inches I'll be excited. As much as I love big snows, I also just love snow in general so it doesn't take much to get me excited.

Posted by: kallieh | January 26, 2010 12:17 PM | Report abuse

I put away all my snow stuff so it's gonna snow like crazy now. Unlike you guys, I am ready for spring as of 12/22 of any given year. The CWG does a great job though!

Posted by: joann20657 | January 26, 2010 12:32 PM | Report abuse

Small lunch-time flurry just passed through the Laytonsville area. (Upper MoCo) Nothing but some scattered flakes. (if you blinked, you missed it) What a tease for the weekend storm or 'non-storm' as the case may be.

Oh, and to everyone jinxing this storm: At the beginning of last winter I bought some new truck tires thinking it would be a snowy winter, so last year was my fault. LOL

Posted by: dprats21 | January 26, 2010 12:50 PM | Report abuse

Thanks for the continuous updates CWG!

I wait with bated breath for results from every new model run!

Posted by: hrc2211 | January 26, 2010 1:08 PM | Report abuse

Kind of crazy...seems like this is the 3rd or 4th snow event this season that is starting on a Friday or Saturday, with almost none coming Sun-Thurs.

Posted by: hokiefan1992 | January 26, 2010 1:37 PM | Report abuse

bachaney wrote:

I'm hoping that I haven't jinxed the storm by ordering a new snow shovel and rock salt and paying to have it overnighted to my house. We broke our old shovel on the December storm.

Let it snow!


:slaps own forehead:

That's as sure a jinx as rain comes to DC when I want to see a Nats game.

Thanks for nothing bachaney (grin).

Posted by: Hawaiiexpat | January 26, 2010 2:02 PM | Report abuse

Shoot...sorry to multiple postings. But forgot that I was going to give an unsolicited endorsement to the Capital Weather Gang's Twitter Feed, @capitalweather.

Good stuff, with Tweets pushed directly to my cell phone. Highly recommended.

Posted by: Hawaiiexpat | January 26, 2010 2:04 PM | Report abuse

VIP Dances has their big singles dance scheduled for Friday night the 29th from 8 PM to midnight at the Arlington/Fairfax Elks Lodge.

What are the chances that snow will start early enough Friday so that they can easily make the "cancel" decision on this dance aoa 3 PM Friday afternoon?

Some TV mets are saying "late Friday through Saturday" for this event. Other guidance is suggesting that this storm could pass to the south through South Carolina with little or no impact on us up here in Washington.

What I'm concerned about is a snowstorm which doesn't start up until 9 or 10 PM Friday while everyone's at the dance; then developing into a real mess while we're at the Elks Lodge. What are the chances of that happening? I told them by e-mail earlier today that if there's a winter weather advisory or worse in effect at 3 PM Friday afternoon, to consider postponement/cancellation.

Debra Sternberg of Gottaswing is already implementing contingency plans for possible cancellation of their Friday night dances in the event of a weather situation. They got impacted rather strongly by the Dec. 19th storm.

Posted by: Bombo47jea | January 26, 2010 2:15 PM | Report abuse

Bad news for snow lovers is that model guidance since last night has trended more and more south of D.C. with the most significant snows, including the most recent GFS ensemble data. Good news for snow lovers is that things could just as easily trend back north in the next couple of days. I guess both are bad news for anyone looking for a high-confidence forecast they can make plans based on. We don't seem to be close to that yet.

Posted by: Dan-CapitalWeatherGang | January 26, 2010 2:23 PM | Report abuse

sorry about the jinxing guys, but after getting stuck on our alley street in baltimore after the december storm, I wasn't going to risk facing significant snowfall without a shovel! :-)

I'm right there with everyone rooting for a big one!

Posted by: bachaney | January 26, 2010 2:26 PM | Report abuse

I saw flurries today in Olney, Md.

come on snow, don't trend to the south!!

Posted by: celestun100 | January 26, 2010 2:31 PM | Report abuse

Given that the wise old groundhog is scheduled to appear on Tuesday, could you hold off on the storm another couple of days so there is no chance he will see his shadow? I'm ready to boogie with spring!!

Posted by: eastrnshrsleeper | January 26, 2010 2:46 PM | Report abuse

storm WIll trend back not going to be lucky and catch this one though. O well, being home for the Dec 18 storm was good enough. If this pans out were looking at a lot of areas above average snowfall most have already passed that mark. Very special winter this could turn to be. Were not even in FEB yet. Can anyone verify which winter month has the best chance for snow in this area has it been FEB?

Posted by: jmc732msstate | January 26, 2010 3:12 PM | Report abuse

What does this mean?

There is some divergence in the models of timing/and exact
track of the low center. The GFS has consistently been the model
with the low center closest to the coastline...with the 12z European model (ecmwf)
now coming in slower and closer to the coast than in previous runs.
Predominate ptype is expected to be snow.

Posted by: stinkerflat1 | January 26, 2010 3:17 PM | Report abuse

Has anybody looked at the 12z ecmwf? The website I look at only shows 24hr shots. It is somewhat hard to see what sterling is referring to in its discussion.

Posted by: mciaram1 | January 26, 2010 3:25 PM | Report abuse

Arrrgh, I have very conflicting emotions about this. I love snow, but I have to be down in Blacksburg Friday morning to early afternoon (and had made dinner plans for Friday evening), and I have to be back in Loudoun Co. early Saturday afternoon. I was planning to drive up Saturday morning, but I might have to bail out and drive up 81 as soon as I can get out of town.

CWG, what are your thoughts on timing/amounts for the I-81 corridor?

Posted by: eventual_eventer | January 26, 2010 4:04 PM | Report abuse

Bombo47jea wrote:
What I'm concerned about is a snowstorm which doesn't start up until 9 or 10 PM Friday while everyone's at the dance; then developing into a real mess while we're at the Elks Lodge. What are the chances of that happening?
Based on the most recent data, there is a 0.051413% chance of that happening. Of course, this probability could change as we get closer to the event. Stay tuned... :)

Posted by: prokaryote | January 26, 2010 4:56 PM | Report abuse

Bob Ryan just said, "there are no signs of a major snowstorm in our area this weekend". He thinks it will stay to our south. Big Bummer!!

Posted by: kathyb39 | January 26, 2010 5:25 PM | Report abuse

Where is "south" that these models are saying is the bullseye?

Posted by: morris4903 | January 26, 2010 5:54 PM | Report abuse


Areas in bullseye would be north central North Carolina to southeast Va. We're really on the edge at this point.

Posted by: CapitalWeatherGang | January 26, 2010 6:11 PM | Report abuse

For those "public servants" hoping that the rest of us are snowed in so that they can have a workday off: given your obvious lack of any work ethic, why don't you just pretend to be sick, and leave the rest of us out of it?

Posted by: lydgate | January 26, 2010 8:06 PM | Report abuse

The Bob Ryan jinx is now fully deployed. If he says "it's the big one coming", you can bet the house it's gonna' miss! If he says it's going to miss, I recommend that you begin loading up on TP, bread, milk, beer, chips, etc. starting Thursday. Ryan's declaration of "there are no signs of a major snowstorm in our area this weekend" guarantees a major snow storm for DC this weekend. Spike the football in the end zone, and start your dance. Then locate your snow shovel for a good weekend workout! It's going to be awfully cold, too! A rare "cold" snow, with temps in the low 20's.

Posted by: johnnierat | January 26, 2010 9:35 PM | Report abuse

I'll go on the record to say that I, personally believe that with so much Arctic air barreling into the region, a suppressed storm track is likely (75% chance), with many places in the immediate DC metro area seeing little or no snow. Sorry, snowlovers.

Posted by: Josh-CapitalWeatherGang | January 26, 2010 9:56 PM | Report abuse

CWG: Are we still on the edge? The NWS is saying 60% chance of snow.

Posted by: celestun100 | January 26, 2010 9:57 PM | Report abuse

No snow... too sad, but maybe we will get some. I hate it when it is just cold and no snow. On the other hand, winter is not over yet.

Posted by: celestun100 | January 26, 2010 10:01 PM | Report abuse

Well the 0z GFS certainly keeps hope alive for snow-lovers, at least for moderate amounts, but I'm not going not going to live run-to-run until about 48 hours from now. I still believe the most likely scenario given the overall meteorological setup is one of a suppressed-south system which brings little or no accumulation to, say, downtown DC and points north.

Posted by: Josh-CapitalWeatherGang | January 26, 2010 11:06 PM | Report abuse

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