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Posted at 2:15 PM ET, 01/ 6/2010

Still cold, but not too cold for a little snow

By Dan Stillman

Chance of light accumulations late Thurs. into early Fri.

* Consistent cold continues, even colder this weekend: Full Forecast *

Next Chance of Accumulating Snow: Thursday Evening-Friday Morning
Probability of Accumulating Snow (1" or more): 70%
Most Likely Potential Impact:

When you're this cold for this long, it's almost inevitable that the chance of at least a little snow will come along eventually. That's exactly what we have facing us for Thursday evening into early Friday, as an Alberta Clipper is expected to swoop down from Canada and carry the potential for light accumulations in the D.C. area.

How much snow are we looking at?


Global Forecast System precipitation forecast for the 24 hours ending 1 p.m. Friday. Darker colors represent higher precipitation amounts. See adjacent text for more commentary. Credit: NOAA/NCEP.

Except in relatively rare occasions, Alberta Clippers tend to move too quickly, and lose too much of their moisture as they cross from west to east over the Appalachians, to give us much more than a few inches of snow. The precipitation forecast from the Global Forecast System model (at right; one of the main weather forecast models for the U.S.) for the 24 hours ending at 1 p.m. Friday hints at a D.C. 'snow shadow,' with higher amounts of snow west of the metro area toward the mountains, higher amounts off to the east as the storm transitions into a stronger system off the coast, and lower amounts in the metro area.

Nonetheless, we should be cold enough at all levels of the atmosphere for all snow, and any flakes will likely be the drier, powdery kind that pile up higher than ones that are of the wetter variety. So, there's the potential for a period or periods of mostly light snow Thursday evening (starting from west to east probably sometime after 5 p.m.) through Friday morning (ending from west to east, probably sometime before 10 a.m.) that could amount up to a few inches. Here are the accumulation chances as we see them now:

30%: ~1" or less
35%: 1-2" (most likely)
25%: 2-4"
10%: 4"+

Check back for updates as we try to better hone in on accumulation and timing.

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

By Dan Stillman  | January 6, 2010; 2:15 PM ET
Categories:  Snow Lover's Crystal Ball  
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Next: Forecast: Snow tonight, then more wind & cold

Comments

Meh, this amount of snow barely seems worth commenting on. Barely.

Posted by: crzytwnman | January 6, 2010 2:29 PM | Report abuse

Is it just me or does latest 12z model trend show low forming I'm deep south seems to pull more moisture from gulf & then sliding off NC /VA coast in a more favorable track for snow

Posted by: StormChaserMan | January 6, 2010 2:33 PM | Report abuse

What's funny is that during last year's crackpot snowless winter we would have been so excited to get even an inch of snow. Starting off the season with over a foot has kinda ruined it ;-) everything else seems like nothing.

Posted by: kallieh | January 6, 2010 2:34 PM | Report abuse

I Just checked Joe Bastardi from Accuweather.Com Professional Site. Joe thinks that we'll get 4-8 inches from the storm Thursday night. He thinks that the GFS is making it's normal mistakes.

Posted by: rginsburg | January 6, 2010 2:36 PM | Report abuse

This is a good bit stronger at upper levels than many clippers around here so I'd tend to think we have a better shot at not hitting the low end in this case.

Posted by: Ian-CapitalWeatherGang | January 6, 2010 2:44 PM | Report abuse

LOL at Bastardi.

On the contrary, I think HE is making his normal mistakes. :)

Posted by: ThinkSpring | January 6, 2010 2:46 PM | Report abuse

hey guys, nice map...thanks! darn "snow shadow"...

Posted by: walter-in-fallschurch | January 6, 2010 2:46 PM | Report abuse

Thinkspring
You may be right, but let's see how much snow we get. Bastardi has been predicting that this will be a serious snowstorm since last Thursday. He said that the GFS will keep downplaying the storm until it becomes obvious that it's mistaken. He's saying it will be 4-8 inches. Let's see who ends up being right.

Posted by: rginsburg | January 6, 2010 2:53 PM | Report abuse

No schoolcast? They still haven't finished clearing the roads from the last storm!

Posted by: pxl4 | January 6, 2010 2:57 PM | Report abuse

is there a chance of a delay friday if it ends thurs nite or will it end late so either schools are open or closed ?

Posted by: samdman95 | January 6, 2010 2:57 PM | Report abuse

rginsburg, the problem for him is that the GFS has company (though is still drier) with other models at this point. 4-8 is a bit ridiculous as far as I am concerned. It's one thing to stick to a forecast it's another to ignore the facts as they come in.

Posted by: Ian-CapitalWeatherGang | January 6, 2010 3:07 PM | Report abuse

Regional ensembles give a 50-60% chance of 1-2 inches and 0.0% for anything more. But this is at the limit of this systems range, so check again tomorrow.

BTW: Anchorage Alaska has temperatures today in the low 30's, about 12 deg above it's normal for the day. DC today is in the in the upper 30's, about 5 deg below its normal. It's not unusual for Alaska to be anomalously warm when it's cold in the eastern U.S.

Here in Ft. Lauderdale the morning low was 36, 23 deg below normal. The highs this afternoon are in the mid 50's, which would be a heatwave now in DC but nightmarishly cold for Floridians.

Posted by: SteveT-CapitalWeatherGang | January 6, 2010 3:07 PM | Report abuse

Yep, that is most often true Steve. Displacing the Arctic Air Mass southward will generally lessen the regionalized extreme cold, and instead it will spread it out over a much larger area. The result is a somewhat diluted and less concentrated potency, albeit at a level that is still frigid and strong.

Posted by: TheAnalyst | January 6, 2010 4:03 PM | Report abuse

CWG guys, when can we expect these winds to go away? I keep thinking my house will fly away any minutes, my windows will shatter any second. Almost want to board up the windows. Next house I buy will not have windows to the northwest side.

Posted by: RoseVA | January 6, 2010 4:19 PM | Report abuse

Ian,

I believe that calling 4"-8" a "bit ridiculous" is a bit harsh. His point has been the high snow ratios. He is forecasting (as this morning) from .25 liquid equivalent. The 12z runs has .1 to .15. Then again the 18z NAM has backed off. The point is that .1 to .25 is not huge error factor, especially given strength of the upper low.

Posted by: mciaram1 | January 6, 2010 4:49 PM | Report abuse

Wow, temps 12 deg. above in Anchorage, if colder than normal here means no GW, then by the same reasoning, 12 above in Anchorage should confirm GW. Just shows, that picking out an area where the temps r above or below average 4 a period time can neither prove nor disprove GW.
Any1 know if the Potomac is frozen on the MD side at the 301 Bridge? Don't want 2 drive 48 miles 2 put my boat in & find the ramp frozen over.

Posted by: VaTechBob | January 6, 2010 5:15 PM | Report abuse

I think I prefer 1 to 2 inches of snow at this point. It's nice to get those big snow falls once in a while, but they quickly become a nuisance (especially since MoCo has done a terrible job with plowing; one lane of Mass. Ave in Bethesda is still unplowed in sections). One to two inches, though, is just enough to cover the lawn while not being a hassle.

Posted by: nlcaldwell | January 6, 2010 5:21 PM | Report abuse

A 2 hour delay on Friday would be nice. I'd prefer not to have the day off. I don't want to be teaching in July.

Posted by: PoorTeacher | January 6, 2010 5:30 PM | Report abuse

Actually, Accuweather's most recent post on the potential storm puts us in the 1-2 inch range...with West Virginia mountains taking the 4-8 inches. http://www.accuweather.com/news-story.asp?article=0

Thoughts?

Posted by: jdtdc | January 6, 2010 5:56 PM | Report abuse

A couple of inches would be lovely, if only to cover (at least temporarily) the icky grey snow left around. When's schoolcast going up? I'd love a delay, too, PoorTeacher!

Posted by: dinergirl1 | January 6, 2010 6:12 PM | Report abuse

mciaram1, .25" liquid producing up to 8" is a bit of a stretch in my opinion. I think it's somewhat hard to say for a fact that you'd get much higher than 20:1-25:1 snowfall in a system like this east of the mountains. I would guess probably to the lower end or even lower in spots. Even ignoring that, the general "consensus" midday today was around .1-.15".. in a moisture-starved storm like this, even getting a few additional .01s is somewhat tricky. The afternoon package of American models trended downward with precipitation as well, though the intermediate runs are sometimes discounted. I don't read JB and only see what's posted about him, so I can't say for sure what he mentioned, but 4-8" on the east side of the apps seems a stretch.

Posted by: Ian-CapitalWeatherGang | January 6, 2010 6:14 PM | Report abuse

I heard Doug Hill earlier on WTOP and he downplayed the storm. Just watched Lou Scally on NBC25 (Hagerstown) and he also said just an inch or two.

Footsforecast is still higher (4" at BWI and 6" for the Blue Ridge).

This will be interesting.

Posted by: spgass1 | January 6, 2010 6:28 PM | Report abuse

I don't pay Accuweather any mind.

I have the ingredients for ginger/carrot/apple soup that, while delicious, would taste much better made on a snow day ;)

Posted by: Snowlover2 | January 6, 2010 6:30 PM | Report abuse

Isn't this the same system that came in off the Pacific over the Northwest that has slowly tracked east over the past week, or did I miss something? I don't recall any low pressure forming in Alberta, and therefore no reason to call it or compare it to an "Alberta Clipper." As for the cold stretch, despite all the headlines, this doesn't seem particularly severe - especially compared to winters in the late 70's when many portions of the Bay were freezing solid.

Posted by: manatt | January 6, 2010 6:46 PM | Report abuse

oh good, the blog is back. Was jonesing without it this a.m. and haven't got back onto the Internet until now. I'd settle for 4 inches, that'll get the kiddies out for a snowday but won't ruin the weekend .... if we only get an inch or so, these winds will blow it all away!

Posted by: weathergrrl | January 6, 2010 7:20 PM | Report abuse

The kids just had two weeks off. I don't think that a five-day week would kill them. PLEASE no snow day. They really need to get back on their routine.

Posted by: 1Reader | January 6, 2010 9:15 PM | Report abuse

it should be a delay

Posted by: samdman95 | January 6, 2010 9:22 PM | Report abuse

@manatt

If you look at where the upper level disturbance (at 500 mb) is originating, it's clearly from Alberta. In fact, the National Weather Service referred to this as an Alberta Clipper in one of its technical discussions.

Posted by: Jason-CapitalWeatherGang | January 6, 2010 10:36 PM | Report abuse

1-2 inches would be nice, like a couple of folks have said, to cover up the nasty dirty snow piles. We need a couple of January thaw 50 degree days to have those piles melt before I'm in the mood for another serious storm.

Maybe not a meterological question, but I'll ask anyway... I know the ground is saturated and also pretty well frozen right now - at least the top several inches. Does any of that evaporate while frozen (sublimation, I think is the process) or will the ground be just as wet when it thaws...? Just wondering if anyone knew.

Posted by: MKoehl | January 6, 2010 10:43 PM | Report abuse

I think it's "home in" not "hone in." Old military/artillery term. "Hone" is when you sharpen a knife.

Posted by: SnowLovr | January 6, 2010 11:48 PM | Report abuse

Silly question, maybe - why is the CWG forecast showing a 70% chance of measurable snow, while the graphic only shows 20% and doesn't even have any snowflakes? Is NWS really that dubious about the chances, or is this another glitch in the code or updating?

Posted by: fsd50 | January 6, 2010 11:56 PM | Report abuse

@fsd

The 20% is during the day Friday, whereas the bulk of the snow is Thursday night --and percentages aren't shown for overnight periods.

Posted by: Jason-CapitalWeatherGang | January 7, 2010 12:08 AM | Report abuse

Actually, hone in is correct - "To move or advance toward a target or goal"

Posted by: jjtwo | January 7, 2010 12:32 AM | Report abuse

Jason - NWS now refers to it as a "CLIPPER-LIKE SYSTEM..." - which explicitly wouldn't be "a clipper." Jan 6 NWS discussion at 2:50pm.

Prior to that NWS referred to it as a "shrtwv trof in the nrn plns" earlier in the week that has since produced fairly substantial snowfall, even if an upper level disturbance has since developed north. While a NWS discussion on Tuesday does refer to it as an "Alberta Clipper," that's inconsistent with what NWS says now.

I think if you're looking for a forecast analogy, calling anything out of the northern plains a "clipper" is the easy way out, but doesn't genuinely apply to this system.

Posted by: manatt | January 7, 2010 1:29 AM | Report abuse

@manatt:


As I said before, you identify a system like this by looking at where the upper level disturbance is coming from, and it's clearly traceable to alberta if you look at the upper level charts for the past couple days.

Posted by: Jason-CapitalWeatherGang | January 7, 2010 1:42 AM | Report abuse

Com'n guys, it's Thursday morning already...where's the updated forecast??

Posted by: hokiefan1992 | January 7, 2010 8:56 AM | Report abuse

Thanks for the clarification, Jason, and great site as always!

Posted by: fsd50 | January 7, 2010 9:00 AM | Report abuse

@hokiefan1992

We published a brand new forecast at 5 a.m. this morning. Maybe you didn't refresh your browser?

Posted by: Jason-CapitalWeatherGang | January 7, 2010 9:07 AM | Report abuse

The comments to this entry are closed.

 
 
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