First measurable snow may come Thursday
BWI-Marshall Airport could see its first measurable snow of the season - barely an inch - Thursday as a weak low-pressure system begins to move out of the southern Plains states and heads our way. There's a chance for a bigger event this weekend, but forecasters and their computer models haven't quite figured that one out yet.
What seems most certain at this point is that our unusually cold December weather will continue to unfold well below the long-term average temperatures for Baltimore. The average high for this time of year is 46 degrees, and we'll have trouble breaking the freezing mark today.
In fact, we've broken 40 degrees on only six dates so far this month, with only two above-average days..
Baltimore City has declared another Code Blue for tonight, extending shelter hours and inviting anyone in from the cold who needs a place to warm up. Outreach workers will seek out the homeless and other vulnerable citizens.
"Extreme cold weather is a killer," said Dr. Oxiris Barbot, Health Commissioner. "While we are primarily concerned about individuals experiencing homelessness, the elderly and chronically ill also are at risk for developing hypothermia should they lose heat or venture out in the cold without adequate protection. Please check in frequently on those loved ones, friends and neighbors who might benefit from the extra attention."
Overnight temperatures reached 19 degrees out on the Weather Deck in Cockeysville, and 21 degrees here at The Sun's weather complex at Calvert and Centre streets. BWI recorded a low of 19 degrees. Strong winds have made being outdoors downright painful. Record lows at this time of year range from 5 to 11 degrees.
Thursday's storm will develop as warm air out of the southwest rides up and over the cold air at the surface we've been grappling with for days. That can mean snow, or at least mixed wintry precipitation. And it will be cold enough for either. Overnight lows will fall into the 20s, and the teens farther west.
Forecasters say the center of the clipper-type storm will pass to our south, and they're not entirely sure how far north the precipitation - which is expected to be light in any event - will reach.
They've settled, for now, on the theory that it will reach the Mason-Dixon Line, and fall as snow, with some chance for mixed precipitation to our southwest. It's likely to reach the Baltimore region in the afternoon, although the timing is still a little iffy. The official forecast calls for less than an inch of snow before it ends in Thursday evening.
Here's AccuWeather.com's take on the prospects. Foot's Forecast - the consortium of student forecasters that did so well with last winter's storms, is a bit more ominous about the prospects:
" ... [M]eteorologists, school officials and transportation managers are keeping close watch on a non-descript and fast-moving clipper system that has the potential to schedule a nightmare on Thursday from the Ohio Valley to the southern Mid-Atlantic.
"The unique alignment of suppressed northerly flow from central Canada, a squashed high pressure ridge off the southeast coast, and the 5,000 foot 0 degrees C line in North Carolina tomorrow morning means precip from Virginia and Kentucky northward should be snow. The Shenandoah and Blue Ridge mountains are likely to experience periods of sleet Thursday. For everyone else extending from Richmond to the PA line, prepare for a challenging day tomorrow."
Eric the Red, a professional meteorologist from Baltimore and frequent contributor here, says, "We're not talking major storm here. But the ground is frozen solid ... and with the snow likely to start after we're all at work/school, the afternoon trip could get a bit dicey. Or hellish. The dusting last Friday caused all sorts of issues, and this has repeat written all over it."
The next event out there begins Friday night as a new low forms off the coast and brings light snow to the counties to our south Friday night and Saturday.
Foot's Forecast is ringing the alarm bells on that one, too. Sort-of:
"It looks to come right on the exact day 365 days ago when on December 19,  Baltimore received its first Kahuna of the winter. The time frame for this storm, if impacted the area, would be Saturday evening through Sunday evening.
"Right now the team continues to analyze all the models, which shows both extremes. One extreme shows the potential for a repeat of last December's storm. Others show an out-to-sea situation which would leave us with no snow. We are fairly confident all precipitation with this storm will be snow, so the main thing to watch is how close to the coast this storm comes."
Eric the Red makes this observation: "Three of the [computer] ensembles have a major snow; four have a very close call, and the other five have nothing (too far offshore)."
(SUN PHOTOS: Top:, light snow in Baltimore, 2008, Amy Davis. Bottom: Baltimore, Dec. 19, 2009, Karl Merton Ferron)