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Posted at 1:45 PM ET, 01/ 6/2011

Tuesday snow threat: On the edge again?

By Jason Samenow and Dan Stillman

Like the previous significant snow chances we've had this season, the one we're tracking for Tuesday (possibly into early Wednesday) may have us on the edge of our seats until the very end.

We're dealing with essentially the same set of issues we wrestled with for the Dec. 26 storm (and to a lesser extent, the threat before that). The key question, once again, is: Will a disturbance cutting across the South merge with a disturbance dropping down from the northwest in time to spin up a coastal storm that tracks close enough to shore to give us substantial snow?

The latest guidance leans toward a miss or just light accumulation, but if history is any indicator, it's probably not game over.


After showing a major snowstorm for the mid-Atlantic in both runs last night, the latest GFS model (from this morning) and most of the GFS ensemble members now push the storm far enough out to sea to deliver only a glancing blow. Though the major snow scenario could easily return in upcoming model runs - such fluctuations are common several days ahead of a potential storm.

Credit: NCEP.

In the earlier runs, the GFS was holding back the southern disturbance which allowed a phase (or merger) with the northern disturbance. But in the latest run, the southern disturbance gets too far out in front of the northern disturbance and the merge occurs too late. The timing of the merging or phasing is important, because an early phase helps amplify the jet stream - effectively shifting the storm track more south to north up the coast, rather than southwest to northeast out to sea.

Wes Junker, our winter weather expert, provided this comment after seeing the latest model runs: "This year, systems have had trouble phasing early enough to hold the low close enough to the coast for us to get significant snowfall. Because of the inherent difficulty in getting phasing, the more likely scenario is for the storm to scoot out to sea. However, we're still looking so far in the future that we cannot rule out a solution that stays closer to the coast which would offer DC accumulating snow."

The European model has consistently simulated the phase happening too late, resulting in just a graze from the storm in several consecutive model runs, though the latest run from this morning brings the storm a touch closer to the coast. The Canadian model - which we trust least because it's erratic - has tended to show an earlier phase and hence a storm track more conducive to significant snow up and down the East Coast.

In light of the various guidance and the seasonal trend, we're tilting the early odds toward a lower impact, more out to sea track. But the situation still bears plenty of watching.

Stay tuned tomorrow for a full analysis from our winter weather expert Wes Junker.

By Jason Samenow and Dan Stillman  | January 6, 2011; 1:45 PM ET
Categories:  Winter Storms  
Save & Share:  Send E-mail   Facebook   Twitter   Digg   Yahoo Buzz   StumbleUpon   Technorati   Google Buzz   Previous: Amazing images of D.C.'s extreme 2010 weather
Next: PM Update: A few Friday morning flakes


This is awesome analysis! Thank you Jason and Dan for continuing the tradition of Wes of stating the what but then following up with the why :)

Posted by: kolya02 | January 6, 2011 2:02 PM | Report abuse

This is 5 days from now.
That's like a billion years in snow forecast time.
People get nutz over this. They'll stay up all night watching those cursed models.
Unless you're actually collecting a salary for doing that sort of thing I suggest you get some sleep.
Wait at least for the SLCB.

Posted by: FIREDRAGON47 | January 6, 2011 2:19 PM | Report abuse


Thanks for the nice words.


Good words of wisdom. Will probably wait another day or two before doing any late night live blogging on this threat...

Posted by: Jason-CapitalWeatherGang | January 6, 2011 2:30 PM | Report abuse

Henry Margusity thoughts just posted on F.B. about the storm next week:
"You have to ask yourself, if the trough axis is so far west, why would a storm run out to sea and not come up the coast. This is the same issue with the big blizzard where the models try to run the storm out to sea and not hook it into the trough, which is what will happen. I have no worries at all right now on the storm situation next week."

For us the issue will be will it skip over DC/Baltimore and take aim at NYC?

Posted by: greg2010 | January 6, 2011 2:52 PM | Report abuse

Wes says: "This year, systems have had trouble phasing early enough to hold the low close enough to the coast for us to get significant snowfall."

Any ideas on why that is the case this year?

Posted by: petworthlad | January 6, 2011 3:06 PM | Report abuse

Greg, can you link me to Henry Margusity's FB page? I want his head on a platter when he's dead wrong about this. I'm not saying he will be. I'm just saying he's basing his information on the "assurances" of the tilt of the current trough and the positive turning NAO. But at the same time Joe Bastardi pontificated his "assurances" about the Dec. 26 blizzard that it wouldn't hit because of a lack of blocking high.

I wish I could seperate the truth from Accuweather's commercial, sell out garbage.

Posted by: bbirnbau | January 6, 2011 3:15 PM | Report abuse

Great post guys. Does this also look like a situation where DC will get no snow but then points north (Philly, NYC) will get hammered? Or are we all in the same boat in terms of a hit-or-miss?

Posted by: jms12 | January 6, 2011 3:21 PM | Report abuse

This was a helpful post...look forward to another informative article from Wes! I'll keep reading, but I have VERY little confidence in any significant snowfalls this year due exactly to Wes's quote in this post. Any models hitting the coast are just a tease this year. We had a TON of snow last we're in an 'averaging out' period...ugh!

Posted by: parksndc | January 6, 2011 3:34 PM | Report abuse

petworthlad, part of the problem is there have been so many shortwaves and features that have to be timed almost perfectly to get phasing. Last year with the strongest southern stream and the block centered a little more over greenland made it easier. The other reason is probably just plain bad luck with the timing. That asie, if we keep it cold and have multiple chances at phasing, we could get a big storm. Heck that could even happen with this one. We're still talking about 5 days inn the future.

Henry M's take on the trough is interesting and if indeed the trough were to take on a negative tilt, we'd have a much better chance of getting a big snow. We're still 5 days from the event so nothing is set in stone.

Posted by: wjunker | January 6, 2011 3:43 PM | Report abuse

parksndc, great observation. If one looks at the "snow hole" from the previous storm, it was where there was the most snow last year. We have to spread the wealth, or the snow, around! We hit gold last year with snow, this year, we might have to settle for scraps. It would be interesting to know if any of the very snowy DC winters (say top 5) were followed by a snowy winter.

Posted by: cloudking1 | January 6, 2011 3:50 PM | Report abuse

i don't buy the "averaging out" theory. if you flip a (not loaded) coin and it comes up heads 5 times in a row, the next time you flip it you still only have a 50% chance of it coming up tails. the coin doesn't "know" it's supposed to even things out.

Posted by: walter-in-fallschurch | January 6, 2011 4:28 PM | Report abuse

@cloudking1, Ian or others would know better than I but my recollection is there were some back-to-back prodigiously snowy years early in the 20th century. I may have the data bookmarked on my home machine, but I'm at work.

Posted by: JerryFloyd1 | January 6, 2011 4:28 PM | Report abuse

Wes... your forcasting approach is similar to the GFS flip flops accept you provide your flip flops in one statement. you go from no snow at all to an all out blizzard...

"...Because of the inherent difficulty in getting phasing, the more likely scenario is for the storm to scoot out to sea. However, we're still looking so far in the future that we cannot rule out a solution that stays closer to the coast which would offer DC accumulating snow."

"...The other reason is probably just plain bad luck with the timing. That asie, if we keep it cold and have multiple chances at phasing, we could get a big storm."

I could do your job... it seams like all you have to do is state all of the possible scenarios and in the end you are right!!! Good Job on that.

The funny thing is is that you probably just hate snow. Deep down in your heart you dont want it to snow at all and that is what drives the pesimism.

Posted by: jac8949 | January 6, 2011 4:48 PM | Report abuse


yeah i feel that way too honestly with most pro mets... it really is a gravy job.

But i wouldnt go so far as to say Wes is saying this because "he hates snow" LOL. I think hes saying it because storms on these type tracks the past couple of times have all done the same thing just about which is too far south and OTS and then too far east to give us any real snow.

Posted by: KRUZ | January 6, 2011 5:15 PM | Report abuse

I just love it how some people hide behind their anonymity on here and claim they could do Wes' (or Jason's, Dan's, Ian's, Cameron's, etc) job.

Posted by: natsncats | January 6, 2011 5:43 PM | Report abuse

Thanks so much, Capital Weather Gang, for your great analysis. I loved reading your blog during the crazy winter of 2009-10, and this winter, it's just as fun and informative to read. Thank you!

Posted by: DianaJeaninArlington | January 6, 2011 5:57 PM | Report abuse


Thanks. Getting a meteorology degree is tough-- it requires 4 semesters of calculus, 2 semester of calc based physics, 2 semesters of chemistry, taking stats, mathematically intensive dynamics classes, computer programming, and a lot of technical meteorological coursework. And the job market for meteorology is extraordinarily competitive. There's no doubt it's a fun job and you do still get paid when you're wrong (but don't economists, stock brokers, doctors, and many other professionals????), but most folks I know in the field work really hard and put in a lot of hours. So I don't mind being a little defensive when folks try to trivialize what we do. It's a tough road and you've got to really love it to stick with it.

I think maybe we're getting criticized for how we communicate highly uncertain information, but the truth is if I knew of a better way, we'd do it. We just try to be honest and we're always open to suggestion for ways to do communicate uncertain information better. Some folks would prefer we just go out on an limb because we can...but we're philosophically against that.

Posted by: Jason-CapitalWeatherGang | January 6, 2011 6:08 PM | Report abuse

Some people want forecasters to hype their hopes & opinions. They find the "highly uncertain information" aspect of weather prediction unsatisfying.
In this world of news as entertainment that's kind of understandable.

Posted by: FIREDRAGON47 | January 6, 2011 7:13 PM | Report abuse

@Jason --

Yikes...calculus...physics...chemistry...I already know I couldn't do your job! ;-)

Posted by: natsncats | January 6, 2011 7:55 PM | Report abuse

I think your explanations are great. There's uncertainty, it's that simple. But instead of leaving it at that, you give us your best call (or say it's just uncertain), you explain the models in an understandable way, you explain why things are uncertain.

I guess I'm just saying, I think you actually do a good job communicating the highly uncertain info. Keep up the great work.

Posted by: perdog05 | January 6, 2011 8:36 PM | Report abuse

I also think some people come on and make inflammatory, ridiculous statements to get attention through response.

It is very silly to imply mets are not skilled professionals and much of the criticism stated on this thread today is poorly constructed.

Posted by: Snowlover2 | January 6, 2011 8:41 PM | Report abuse

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