Overnight Snow Could Drop 5-7 Inches

February 21, 2011

UPDATE 12:30 p.m.: The Winter Storm Watch is now a warning for Carroll; Central and Eastern Allegany; Extreme Western Allegany; Frederick; Harford; Northern Baltimore; Washington.

“WINTER STORM WARNING IN EFFECT FROM 7 PM THIS EVENING TO 7 AM EST TUESDAY…  PRECIPITATION TYPE…BRIEF PERIOD OF SLEET…THEN SNOW WHICH WILL BE HEAVY AT TIMES. * ACCUMULATIONS…5 TO 7 INCHES OF SNOW. * TIMING…WINTRY MIX WILL BEGIN EARLY THIS EVENING…THEN CHANGE OVER TO ALL SNOW BY LATE THIS EVENING… AND CONTINUE OVERNIGHT. THE HEAVIEST SNOWFALL IS EXPECTED BETWEEN MIDNIGHT AND 6AM.”

UPDATE, 10 a.m.: A Winter Storm Watch has been issued beginning at 9 p.m. for the northern counties, including Frederick, Carroll, northern Baltimore and Harford counties. Forecasters say 4 to 6 inches of snow are possible overnight in the Watch area.

A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT
SNOW AND SLEET ACCUMULATIONS THAT MAY IMPACT TRAVEL. CONTINUE TO
MONITOR THE LATEST FORECASTS.”

Earlier today, the National Weather Service had predicted 1 to 3 inches of snow overnight at BWI-Marshall Airport as a pair of low-pressure systems move through the region. The precipitation will start as rain, become mixed in the wee hours of Tuesday as temperatures drop behind the first low, then change to snow before ending during the rush hour.

Here’s how Eric the Red saw it last night:

Over the weekend, models did everything imaginable… no storm, all rain, all snow, and now back to a north to south changeover.  I think I’ll stick with 2 to 5″ on grassy surfaces for central and northern MD… and once you get down toward Annapolis and DC, the question of when (and if) the changeover occurs becomes fuzzier.  I would suspect that unless the cold air really pushes in fast, locales south of Baltimore will struggle to get more than an inch or two.”

“If it weren’t for the warm ground and time of year, I’d go higher on the totals… but I’m gonna scale back to account for recent warm weather and time of year.  In the northernn tier counties, I’m guessing 3-5″.  Farther south… say Baltimore and environs, 1 to 3″.  Down toward DC… trace to perhaps 2″ in the colder burbs.” 

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