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Posted at 3:45 PM ET, 12/21/2010

PM Update: Cold transitions to cool

By Jason Samenow

For the first time in more than a week, we escaped the 30s. But the (unofficial) high of 41 (at Reagan National) is still four degrees below average. We remain locked in a cold pattern which shows no immediate sign of meaningfully relaxing. As such, a chilly evening and Wednesday lie ahead.

Through Tonight: A very weak disturbance - which looked like it might bring us snow a few days ago - harmlessly slides by to the south. It spreads considerable cloud cover but, in all likelihood, no snow. Lows range from the low-to-mid 20s in the colder suburbs to near 30 downtown.

Tomorrow (Wednesday): Some morning sunshine is possible, but clouds probably increase in the afternoon as another disturbance ripples through from the northwest. Highs should be around where they were today, in the upper 30s to near 40. Winds from the northwest blow at a manageable 10 mph.

See Matt Rogers' forecast through the weekend. And if you haven't already, join us on Facebook and follow us on Twitter.

Mammoth snow: Jesse Ferrell at AccuWeather reports California's Mammoth Mountain's four-day snow total, spanning Friday to Monday, was an incredible 186 inches or 15.5 feet. Was that any kind of record? Ferrell writes: "The only one possibly in jeopardy is the 3-day snowfall record, if it is confirmed." See also our post from yesterday about the storm.

By Jason Samenow  | December 21, 2010; 3:45 PM ET
Categories:  Forecasts  
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Next: Weekend storm: Glancing blow or blizzard?


So, from what I am hearing on Am WX, there are two model sets each with a lot of support and very consistent unto themselves. Fascinating.

The funny thing is, I keep reminding myself this is Tuesday, and the discussion is for weather Saturday. In fact, some things are pushing it more into Sunday. That is really a lot of time between now and then for weather to do stuff

Posted by: AndrewRockville | December 21, 2010 4:21 PM | Report abuse

You may have gotten out of the 30's but I haven't. Dulles only made it to 37.

Posted by: rwalker66 | December 21, 2010 4:25 PM | Report abuse


Do the long term models show any chance of an above normal (43 F or better) day the rest of the calendar year? It seems that the odds of having just 2 days out of 31 reach "normal" are astronomically low (I came up with 1/2.1M on the back of the envelope, but my math skills have atrophied a bit. :) )

Posted by: vtavgjoe | December 21, 2010 4:30 PM | Report abuse


The next week looks cold. After that, the signals are mixed.

Posted by: Jason-CapitalWeatherGang | December 21, 2010 4:54 PM | Report abuse

I'm surprised I haven't seen anyone mention how dry the last few runs of the GFS have been.

Posted by: JTF- | December 21, 2010 5:28 PM | Report abuse

After a blockbuster 12z ECMWF, the 18z GFS is in and again saying, not so fast.

As I said in comments within Wes's post at 8:52 last night: the 50/50 hybrid low pressure in the north Atlantic is too strong and too far west, with no high pressure from northern New England to the upper Lakes to help funnel moisture in off the Atlantic.

Unless this giant Atlantic storm relaxes or shifts east, we are probably looking at a "garden variety" 1-3 inches.

Next few days will be interesting!!

Posted by: AugustaJim | December 21, 2010 5:42 PM | Report abuse

It does get more quiet when model runs favor little to no snow ;-) I conclude we have a community of snow lovers who are silently disappointed ...

Posted by: Camden-CapitalWeatherGang | December 21, 2010 5:50 PM | Report abuse

Snow is an exciting event around here. People get goofy.
I am tired of the cold & wind; the scant 2 inches of old snow in our shaded front yard has hardly melted.
Snow down or warm up.

Posted by: FIREDRAGON47 | December 21, 2010 6:14 PM | Report abuse

People are in traffic heading home after sitting in front of their computers all day on this site. 8:00pm things will ramp-up again.

Posted by: greg2010 | December 21, 2010 6:19 PM | Report abuse

Right now it seems like the bulk of the snow will be down in the carolinas. Well, a lot can change still.

Posted by: Finn1917 | December 21, 2010 6:32 PM | Report abuse

How has nobody mentioned that there seems to be model consensus that this will end up going out to sea? NOGAPS, GFS, Canadian...they are all showing the same thing.

Don't get me wrong, I think the EURO looks wonderful :) It just seems to be the outlier right now.

I'll still hold out hope, of course, but it is looking very similar to this most recent storm that missed us.

Posted by: 4seams | December 21, 2010 6:32 PM | Report abuse

I was silently disappointed- afraid to say anything lest I carry over the silly snow love/hate debate to this new thread ;)

It is so far out still I suspect a few more highs and lows for both camps. I'm trying to take a reasonable approach and just enjoy trying my hand at interpreting data.

Posted by: Snowlover2 | December 21, 2010 6:36 PM | Report abuse

You can not discount the Euro model, the UKMET model, and the Canadian model which all show us with at least a disruptive 4 or 5 inches. Of course, the Euro shows hell breaking loose. All of these models are so much better at long range forecasting (84 hours or more) than the GFS. Snow lovers, do not despair. We are not done with this storm yet.

Posted by: Formerwxman | December 21, 2010 6:46 PM | Report abuse

If you want to hold out hope for a big storm this weekend, then Bastardi's blog is what you want to read. Personally, I think we're in for several days of model flip flopping...but am certainly rooting for a White Christmas!


It is like it is from another planet.. a bit slower meaning the white Christmas is still south of the big Northeast cities, but then its 965 mb low just east of ACY by Monday morning would have meant everything gets shut down Sunday into Monday anyway..timing more like 1969 event.




I am coming off of a beating on a storm that wound up too far east. But the error analysis of that storm indicates that the problem was that the storm developed too far southeast relative to the upper height fall center. Also, if one looks at the initial 500 mb this morning we see the upper ridge is flatter and much farther east than what will occur this weekend.

The northern Plains clipper is unloading according to plan in the plains and lakes but does fade southeast. It does bring fresh cold air into much of the target area for the Christmas period storm, and in the end that will be its main function in the east.

Both the major model solutions have problems with me. The European and its idea holds the southern max back too much, though has so much northern energy that it still bombs the storm out for the major event, first west-east in the plains but as close to I-40 as I70 to the Appalachians. I think this is an error and the max comes out faster, much like the GFS. That being said, the GFS tries to hurry it off the field so its co-ordination with the northern branch is not correct. This results in a widespread light snow event in the East, not the monster I am thinking. So my correction, as stated yesterday, and as seen on the 00z run is to pull that back west and allow the phasing and the classic Hatteras (Christmas night) to the Benchmark (Dec. 26 at 7 p.m.).

This would put the heavier snow in the plains farther north, near I-70 all the way to around DC from Topeka with an area of 10 to 1 ratios near the -3 isotherm but then 20 to 30 to one near -8 at 5k. Hence the idea of the 6- to 12-inch band. The idea then is the turn northeast. Obviously, given the model uncertainty and the bust I had, you probably won't trust that.

However, if we look at the ridge when the storm is near the East Coast, it is much farther west than this last storm. The Canadian 12z run, driving the storm far enough west for rain in southern New England Sunday night, looks overdone. However, this has the kind of baroclinicity available for the monster deepener, a blockbuster pressure by the time it is near 40 north, much like the Midwest monster two weeks earlier.

The Big Dog looks at all this from the prism of the overnight runs, while the long ranger reviews the flip of the winter of 1950-1951.

Thanks for reading, ciao for now

Posted by: DLO1975 | December 21, 2010 6:51 PM | Report abuse

Several mesonet stations in the sierra reported 190-200+ estimated snowfall. Top seems to be 204. I don't know if/how these are verified.


Posted by: Ian-CapitalWeatherGang | December 21, 2010 8:58 PM | Report abuse

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