A surge of warm southern air and some sunshine brought Baltimore's first 70-degree December day in six years Monday, two degrees shy of setting a record.
The mild weather is expected to continue until a cold front moves through early Wednesday, eventually bringing a return to normal temperatures. Beyond that, some weather watchers are eyeing even colder weather ahead.
Southerly winds coming from the Gulf of Mexico began warming the air Sunday, and sunshine helped raise temperatures further Monday, said Jared Klein, meteorologist with the National Weather Service's Baltimore/Washington forecast office in Sterling, Va. Similar weather is forecast for the region Tuesday, with highs around 70 degrees.
"It's been over us the past day or so, but because we had the fog and low clouds we weren't able to fully realize all this warm air," Klein said Monday.
The temperatures were about 20 degrees above normal for this time of year, when a typical range is between about freezing and 50 degrees, according to the weather service.
The last time 70-degree temperatures were recorded at Baltimore/Washington International Thurgood Marshall Airport was 2006, when BWI reached 72 degrees on Dec. 18 and 75 degrees on Dec. 1, Klein said.
The warmth isn't necessarily a harbinger of weather to come, forecasters said.
December 2010 started with a 62-degree high, but things quickly turned frigid. All but one day out of the month dipped below freezing at BWI Marshall Airport, and the average temperature of 32.4 degrees was 4.3 degrees below normal.
December 2009 started with three days in the 50s and 60s but ended with an average temperature of 34.8 degrees, 1.9 degrees below normal.
Seven days last December reached 60 or above, building up to an average temperature of 42.2 degrees, 5.5 degrees above normal.
Forecasters don't expect a repeat of that, given larger snowpack and more frigid air building across Canada relative to last December. Both Foot's Forecast and AccuWeather.com's Henry Margusity expect colder air to come south later this month, with a threat of a winter storm in the middle of December.
The warmth also comes despite a cool trend throughout November, which ended with an average temperature of 42.8 degrees, 3.7 degrees below normal. The month snapped a string of 21 consecutive months with above-average temperatures at BWI.
"We have seen the colder air come through, but we haven't seen an Arctic blast yet," Klein said.
twitter.com/mdweatherCopyright © 2015, The Baltimore Sun