Forecasters weren't sure late yesterday where the rain/snow line will form, or how much snow the Baltimore and Washington metropolitan areas should expect.
"Some places will almost certainly get double-digits of snow totals. It's just a question of exactly where," said meteorologist Jeff Warner of Penn State Weather Communications Group in University Park, Pa.
But for Baltimore, he said, the computer models yesterday seemed to be pointing toward a changeover to sleet or rain - in some places, at some point - which would keep snow totals down.
If the snow forecasts prove even partly accurate, this would still be the first substantial snow of the season for Baltimore. There was only a trace of snow in December, and January managed just 0.9 inches.
Another 1.5 inches of fluff fell Wednesday as a weak "Alberta Clipper" storm raced in from the Northwest. It wasn't much, but it triggered a flurry of school closings in Baltimore and several counties.
Bright sunshine over the weekend might have kept Marylanders from focusing on the wintry forecast. Hardware store managers yesterday reported little evidence of snow panic in their store traffic.
"Just a little pickup, not much," said Chris Romeo, assistant manager at the Home Depot in Glen Burnie. "We sold one snow thrower and some pellets, for pellet stoves," but there was little snow-related business beyond that.
"Call tomorrow," she said. "I betcha it starts blowing out of here."
Greg Olin, operations manager at the Home Depot in Cockeysville, said he's ready. "To be honest, it's been such a late year [for snow] we have all the reserves from earlier in the year still ready," he said.
The Giant supermarket at Chatham Mall in Ellicott City was similarly calm. "It's our normal Sunday," said assistant manager Shaler Johnson. "We don't expect anything to hit till tomorrow."
Forecasters have said for several weeks that a colder, stormier pattern was developing that would end the mild, snow-free weather that characterized most of the winter.
Temperatures in Baltimore fell below freezing Feb. 3, as frigid arctic air tumbled out of Canada into the Midwest and Northeast. The mercury at BWI Marshall Airport fell as low as 8 degrees last week, and didn't rise above 32 again until Friday afternoon.
It's warmed up a bit since then, but the arctic air hasn't gone away. Highs this weekend at BWI remained about 10 degrees below normal for this time of year.
The only missing ingredient has been a storm with sufficient strength and moisture to mix it up with the entrenched cold air and produce substantial snow. Now that element appears to be on its way.
There will be updated forecasts at MarylandWeather.com this morning. Forecasters late yesterday were saying the approaching storm was shaping up on the Southern Plains.
It was expected to move toward the Ohio Valley today, with snow beginning in Maryland tonight. A second low was likely to form off the coast of North Carolina and Virginia and intensify there tomorrow before heading toward New England.
"This is a fairly classic track for one of these winter storms," Warner said.
At the same time, another surge of arctic air was expected to drift south today, and that is one of the keys to how snowy this storm gets for Baltimore.
"It may even slip south [of Baltimore], but you're not going to get very deep into this cold air," Warner said. When the storm center arrives off the coast, "you're going to get overwhelmed by mild air" from the ocean, changing the snow to freezing rain or rain.
Snow lovers will want the storm to stay farther out at sea, allowing the cold air to dominate, Warner said. Snow haters will root for a more landward track and milder temperatures.
The trend on the supercomputers pointed toward a warmer storm, Warner said. "But trends can certainly change."
With this storm, the winter of 2006-2007 in Baltimore looks even more like last winter.
December 2005 hit bottom at 18 degrees on Dec. 7 and 8, followed by a milder finish. This past December also ended mildly after touching 18 degrees on the 9th.
Similarly, January of last year was mild, with only a trace of snow. January 2007, too, was mild, especially for the first two weeks, with less than an inch of snow in a single storm.
February of last year turned colder, with a solitary snowstorm that dropped 13 inches at the airport Feb. 11-12 - and substantially more in other locations north and west of Baltimore. This month, too, has been a cold contrast to January, and now threatens us with snow on the 13th and 14th.
The middle of February seems to be a sweet spot for big snowstorms in Maryland.
Of the 10 deepest snows recorded in Baltimore since 1891, five fell between the 11th and 19th of February, according to the National Weather Service.
Those five include:
The deepest on record, 28.2 inches on Feb. 15-18, 2003.
The third-deepest, 22.8 inches on Feb. 11, 1983.
The sixth-ranked storm, 21.4 inches on Feb. 11-14, 1899
The seventh-deepest, 20 inches on Feb. 18-19, 1979.
The ninth-biggest storm on record, 15.5 inches on Feb. 15, 1958.
Warner said average temperatures begin to rise again by mid-February, and the jet stream is moving farther north. That brings warm, moist air from the south into more frequent conflict with lingering pools of arctic air from the north, increasing the potential for heavy snow.
"We're coming out of the depths of winter and into a really active [weather] season," he said.