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February 11, 2007

"Heavy snow" coming

A "winter storm watch" was posted today for most of Maryland. That means there is a significant potential for heavy snow or ice that could affect travel. Here's how the meteorologists at the Sterling forecast center see it. Here's the official forecast. Notice the reference to "heavy" snow on Tuesday. That means 4 inches or more.

The storm that's threatening us, mostly on Tuesday, is just now coming ashore in California - as rain. But it is expected to shoot across the country in the next day or two and run into arctic air. That cold air has been entrenched here for a week, and is expected to be reinforced on Tuesday with another surge of polar weather.

The storm will begin to draw moisture from the Gulf of Mexico, and sweep it north and east into the mound of frigid air already in place, and make sleet, ice and snow. And once it reaches the Atlantic coast, the storm may well intensify and draw Atlantic moisture in from the northeast. And presto. We get an old-fashioned nor'easter and gobs of snow.

Just how much, of course, is still in debate. As always, it depends on the storm's precise track and speed, and where the rain/mix/snow lines fall. And nobody knows that for sure yet, even though the supercomputers have been cranking on this storm for a week.

Accumap

AccuWeather has us in a zone likely to see up to 6 inches, and there are hints, at least from their snow blogger Henry Margusity, of up to a foot of snow. Here's their take. The Weather Channel is hinting at "several inches" of snow for our area. For Margusity's giddy, worst-case scenario outlook for this storm ("a hum-dinger") click here and watch his video.

Here's a bit of the discussion this morning from Sterling (edited by me for clarity), where they are beginning to hint at 5 inches or more:

"CENTRAL VIRGINIA AND
LOWER SOUTHERN MARYLAND STILL MAY EXPERIENCE SOME MIXING (FREEZING
RAIN AND SLEET). (ONE COMPUTER MODEL) EVEN BRINGS SOME SLEET INTO DC/BWI.
THIS MAY BE THE CASE...BUT WILL NOT EXPAND MIXED PRECIP THAT FAR
NORTHWEST AT THE MOMENT. EVEN WITH MIXING THOUGH...OUR ENTIRE CWA (FORECAST AREA) HAS THE
POTENTIAL TO RECEIVE APPRECIABLE SNOWFALL ACCUMULATIONS THAT WOULD
REACH WARNING CRITERIA FROM THIS HIGH QPF (WET) STORM WITH HIGH IMPACT
POTENTIAL.

THEREFORE...WILL BE ISSUING A WINTER STORM WATCH FOR OUR
ENTIRE CWA FOR SNOW...WITH THE POSSIBILITY OF MIXED PRECIPITATION AS
WELL OVER THE POTOMAC HIGHLANDS...CENTRAL VIRGINIA AND LOWER
SOUTHERN MARYLAND. WHILE SOME WINTRY PRECIPITATION WILL OCCUR
THROUGH MONDAY NIGHT...THE WATCH WILL COVER A 24 HOUR PERIOD FROM
TUESDAY MORNING THROUGH WEDNESDAY MORNING WHEN THE WARNING CALIBER
HIGH IMPACT WINTER CRITERIA ARE EXPECTED (5 INCHES OF SNOW/SLEET IN
A 12 HOUR PERIOD AND/OR GLAZE OF ICE 1/4 INCH OR GREATER IN A 12
HOUR PERIOD).

(COMPUTER CONSENSUS) INDICATE A SLIGHTLY SLOWER EXIT WITH THE STORM AS
WELL...AND HAVE INCREASED POPS (PRECIPITATION PROBABILITIES) ON WEDNESDAY FOR LINGERING SNOW.
BEYOND WEDNESDAY...COLD NORTHWEST FLOW DEVELOPS AS SURFACE HIGH
PRESSURE DROPS INTO THE DEEP SOUTH OVER THE WEEKEND. WINDS WILL BE
GUSTY THROUGH MUCH OF THE PERIOD...AND TRAJECTORIES WILL BE
FAVORABLE FOR UPSLOPE SNOW SHOWERS OVER OUR WESTERN ZONES.
TEMPERATURES WILL BE BELOW CLIMATOLOGY (SEASONAL NORMS)  DUE TO THE COLD AIR MASS. IF
THERE IS A SNOWPACK...TEMPERATURES WILL NEED TO BE DROPPED EVEN MORE
DUE TO ALBEDO-PRODUCED RADIATIVE EFFECTS (WHITE SNOW COVER REFLECTS MORE SOLAR HEAT).

So, buckle up Baltimore. Something white this way comes.

Posted by Frank Roylance at 10:09 AM | | Comments (1)
Categories: Winter weather
        

Comments

I think you mis-labeled Margusity's comment as "worst-case", you probably meant to write "best-case"... just wanted to point that out so someone could go back and correct it. :O)

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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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