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February 1, 2011

More freezing rain tonight; more snow Friday

Keeping up with the forecasts, the watches and advisories today is like playing Whack-a-Mole. The landscape has changed again. Here's how it looks for now:

A Winter Storm Watch remains in effect for the northern tier of counties, from Washington County in the west, to Harford in the east. That means there remains a chance for a quarter-inch of new ice accumulations today through Wednesday morning. Precipitation which may slow or end this afternoon, is forecast to resume, intensify and change to rain tonight. A quarter- to a half-inch of rain is possible by noon Wednesday. UPDATE: The watch was cancelled Tuesday afternoon.

Baltimore Sun Weather StationA Freezing Rain Advisory has been posted from Washington to Harford county and as far south as Howard and Montgomery, effective from 9 p.m. Tuesday evening until 11 a.m. Wednesday. It means these locations could see several tenths of an inch of accumulating ice before the precipitation changes to rain sometime during the night. Highest icing amounts would be near the Mason-Dixon Line. Baltimore City, Anne Arundel and PG counties could see a tenth of an inch.

A Winter Storm Warning is in effect just north of the Mason-Dixon Line in Pennsylvania. Here's the bad news for the Keystone State:

"ACCUMULATIONS...3 TO 6 INCHES OF SNOW AND SLEET NORTH OF
  INTERSTATE 80. 1 TO 2 INCHES OF SNOW AND SLEET SOUTH OF
  INTERSTATE 80 BETWEEN ROUTE 22. LITTLE TO NO SNOW OR SLEET
  ACCUMULATION FROM THE PENNSYLVANIA TURNPIKE SOUTH TO THE
  MARYLAND BORDER. SIGNIFICANT ICE ACCUMULATION BETWEEN ONE
  QUARTER AND ONE HALF INCH ALONG AND SOUTH OF INTERSTATE 80."

UPDATE, 1:25 p.m.: Here's Eric the Red's take on tonight: "Tonight (Tues. night) will be a very close call, with ice possible until 4 a.m. close to I-95, but lasting a bit longer in northern and western Maryland before changing to cold rain shortly after sunrise thanks to an east wind. This does not look like a crippling ice storm, but will be worse in northern and western Maryland for sure."

Here's Prof. Jeff Halverson, at UMBC. He has been watching relatively warm air gradually erode the cold air at the surface, and he sent this weather map, showing the (purple) freezing line, and the big precipitation hanging to our west:

"Consistent with the steady erosion of the cold air dam (CAD), the 32 F isotherm has notwpushed north of Montgomery Co., and now straddles Baltimore. I see this trend continuing. We could well be into 40 degree air by sundown. Note the very heavy rain well to the west - this line won't blast through until around dawn. I expect it will be all liquid, everywhere around Maryland."

And here's the big picture from AccuWeather.com

Oh yes. The forecast also includes mention of a new coastal low that's predicted to form off the Southeast coast Friday and move northeast. So far, the 7-day forecast for BWI-Marshall sets a 40 percent chance for snow Saturday and Saturday night, with highs near 40, falling to the mid-20s.

Whatever falls won't last long. The rest of the weekend looks sunny, with temperatures rising to 50 degrees by Monday.

Posted by Frank Roylance at 12:26 PM | | Comments (4)
Categories: Forecasts
        

Comments

Sterling has a new ice forecast map out, looks to be down to 0.1" even for northern MD. Some details about this in their discussion:

* JUST A QUICK THOT UPDATE - MDLS CONT TO TREND WARMER FOR TEH
OVRNGT HRS...EVEN UP TO THE MASON DIXON LN. THE AREA OF THE 2
SEGMENT FZRA ADVSRY WL RMN UNCHGD...BUT WL LKLY BE TRIMMING A FEW HRS OFF THE END TIMES OF BOTH W/ THE MID AFTN FCST PCKG.

Wanted to take a quick moment to let you know how valuable this weather blog has been for my family since we discovered it recently. The info written & collected here helps far more than the typical quick weather reports. Thank you for your hard work.

FR: Thanks!

Freezing rain advisory has been scaled back so that it ends at 4:00 a.m. Wed. morning.

Trivia question:

Is there a record for the coldest surface air temperature at which freezing rain (that fell as a liquid before freezing) has fallen? The coldest I can recall is around 23 or 24 degrees, but I'd imagine in the right conditions it could be colder.

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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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