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December 21, 2010

NWS: Chance of Christmas snow here - 50/50

Well, we sure can't say we haven't had a white Christmas in ages. Our Dec. 18-19 blizzard last year left plenty of snow on the ground to make the place look like Santa's North Pole workshop. But there weren't any flakes in the air. And that's what all the ads have taught us to expect. Right?

(Actually, we had rain, more than and inch-and-three-quarters on the 25th and 26th.)

So that's what makes the current forecast so encouraging. The NWS forecast office in Sterling, Va. has posted chances for snow right through the weekend - 30 percent Christmas Eve, and 50 percent AccuWeather.comChristmas Day and Christmas night, and 40 percent on Sunday.

That's no guarantee, of course. Although the storm that they're watching is already making landfall on the West Coast with a ton of rain and snow for those people, its precise track remains up for debate amongst the computer models. Some runs bring us a major storm. Others bring us ... well, sunshine.

Here's the NWS discussion:

"MEDIUM-RANGE GUIDANCE STILL IN GENERAL AGREEMENT WITH A COASTAL LOW
PRESSURE MOVING UP THE EASTERN SEABOARD FOR THE CHRISTMAS WEEKEND.
HOWEVER...EXACT EVOLUTION INCLUDING TIMING AND TRACK DETAILS OF THE
STORM SYSTEM ARE UNCERTAIN AT THIS TIME.

"LATEST MODELS ARE TRENDING TOWARD AN OVERALL SLOWER SOLUTION. HAVE ACCORDINGLY TRENDED SLOWER WITH ONSET OF [PRECIPITATION] FRIDAY NIGHT. THE FASTER GFS AND ENSEMBLE SOLUTIONS HAVE THE MAIN IMPACTS FROM THE COASTAL LOW ON CHRISTMAS DAY WHILE THE SLOWER ECMWF/CANADIAN HOLD THE BULK OF THE SNOW OFF UNTIL SAT
NGT INTO SUN.

"ALSO...ANY SHIFTS IN THE TRACK OF THE COASTAL LOW WILL PRODUCE SIGNIFICANT CHANGES TO POTENTIAL SNOWFALL AMOUNTS. AT THE MOMENT,  IT APPEARS THAT THE LOW WILL TRACK CLOSE ENOUGH TO THE REGION THAT PEOPLE SHOULD CONTINUE TO MONITOR THE LATESTS. Dallas St., Baltimore FORECASTS AS DETAILS BECOME MORE CLEAR CLOSER TO THE EVENT...ESPECIALLY BECAUSE THIS COULD IMPACT THE HOLIDAY WEEKEND TRAVEL."

Eric the Red has checked in this morning. The Baltimore meteorologist sees the uncertainty in the model runs, and persistence in our cold, dry pattern. So he's being cautious:

"Until I see a high building over New England, I'm gonna lean away from a Christmas snow storm... but obviously, it is still several days away.  If there's one thing the snow camp has going for it, it is that the storm more or less already exists off the US west coast... so it's not like we're waiting for something to form.  It will be very trackable, which in turn should help me get a clue as the week unfolds."

Eric Update, 2 p.m.: With new model runs this afternoon, Eric is still siding with an outcome that  takes the storm away to our south and offshore. Little or no snow here. But he notes three models that slow the storm down, with snowier results for us. One, he says, "brings a monster Nor'easter up the coast Sunday night into Monday. Like a crippling snowstorm. Not making this up. Christmas itself would be sunny and cold, but we'd all be tapping into our stockpiles of milk and toilet paper early next week."

AccuWeather.com says:

"The roadblock from last weekend's storm in the Northeast may still be in place. If the block holds, snow could be avoided in Detroit, Scranton and New York City.  Meaning that Pittsburgh, Philadelphia, Wilmington, Baltimore and New York City may be on the "bubble" for this snowstorm right out of the box.

"The storm is forecast to be over the Rockies and Intermountain West Wednesday, the Plains Thursday, the Midwest Friday, and along the mid-Atlantic coast on Christmas Day. For portions of the Ohio Valley and central and southern Appalachians, this could transpire to deliver an old-fashioned classic Christmas Eve snowfall."

And here's Foot's Forecast's Forecaster Ryan: "The stage is beginning to be set folks. The chips are beginning to fall more and more, and the likelihood of a Christmas snowstorm is getting higher with each passing day (as I said on MPT last night.) The things we can tell at the moment are that it is highly likely that Baltimore will ...receive some snow, and as for the potentially for a significant storm (4"+), odds are around 60%."

(PHOTO: Lindsay Rothstein, Baltimore Feb. 6, 2010)

Posted by Frank Roylance at 9:01 AM | | Comments (5)
Categories: Forecasts
        

Comments

AccuWeather is hedging its bets for NYC, huh? They're going to avoid snow, but at the same time will be on the bubble for a storm!

"The roadblock from last weekend's storm in the Northeast may still be in place. If the block holds, snow could be avoided in Detroit, Scranton and New York City. Meaning that Pittsburgh, Philadelphia, Wilmington, Baltimore and New York City may be on the "bubble" for this snowstorm right out of the box."

FR: I noticed that, too. Then again, "on the bubble" means finely balanced between one outcome and another. That would make sense for NYC. Not sure what it would mean for us. AccuWeather was not very clear on this one.

Frank, why is it everytime there's even a slight mention of a snowstorm forecasters debate the tracking of the storm but with rain there's no such tracking debate?

FR: It's not really the forecasters debating the track at this point. It's the computer models. They're all constructed differently, and their predictions change as new data comes in. The forecasters then add their interpretation, experience and instincts to the forecast, and they can have different conclusions. The same things happen with rain storms, but I suspect we pay less attention because rain is generally less disruptive. We do pay attention when the models disagree on hurricane tracks.

Frank, When was the last time snow fell in the Baltimore area on Christmas Day? I remember a light snow late in the day on the 25th in the early 1990's. Thanks!

FR: A Christmas Day storm in 2002 shut down the airport for a time. That's the most recent I could find.

For the past 3 winters I had a job that was incredibly complicated by winter weather, so I used dread it. My new gig is not impeded as much, so bring on the Snowpocalypse 2.0!!!

Frank,

What models did Eric mention that showed the monster Nor'easter? Everything I've seen so far shows the storm going to our south and out to sea.

FR: The ECMWF. And UKMET

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About Frank Roylance
This site is the Maryland Weather archive. The current Maryland Weather blog can be found here.
Frank Roylance is a reporter for The Baltimore Sun. He came to Baltimore from New Bedford, Mass. in 1980 to join the old Evening Sun. He moved to the morning Sun when the papers merged in 1992, and has spent most of his time since covering science, including astronomy and the weather. One of The Baltimore Sun's first online Web logs, the Weather Blog debuted in October 2004. In June 2006 Frank also began writing comments on local weather and stargazing for The Baltimore Sun's print Weather Page. Frank also answers readers’ weather queries for the newspaper and the blog. Frank Roylance retired in October 2011. Maryland Weather is now being updated by members of The Baltimore Sun staff
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