If it seems like only yesterday that temperatures fell into the teens in much of the region over healthy layers of snow, it was.
But on Thursday, borne on increasing south-southwest winds expected to peak overnight, temperatures soared to an April-like 69 degrees at Philadelphia International Airport, a record for the date.
The warm surge pulsed ahead of an approaching front that was stirring the winds of change, and the National Weather Service has posted a wind advisory in effect from 11 p.m. Thursday until 10 a.m. Friday for gusts to 50 mph, with showers. With trees still bare, however, this was not expected to result in many power outages, and winds should back off some midmorning, said Amanda Lee, a meteorologist in the weather service’s Mount Holly office.
The front will restore a measure of temperature order, and highs during the weekend will be in the February-like low- and mid-40s, a good 25 degrees lower than Thursday’s.
The Feb. 17 record for Philadelphia, 68 degrees, notably was set in 1976 during a remarkable warm spell that was followed by a rather dramatic demonstration of late-winter caprice.
As is apt to happen this time of year, the atmosphere appears to be having a seasonal identity crisis. On Wednesday morning, temperature readings were in the teens on either side of the river outside Philadelphia and as low as 15 degrees in Pottstown.
» READ MORE: In Philly winters, anything is possible
That had a lot to do with the remains of Sunday’s snow cover. With clear skies, light winds, and a well-chilled surface, conditions were ideal for radiational cooling under that brilliant, almost-full moon. At the snowless airport site, it got no lower than 28, a micro clinic in how important snow cover is to the future of Earth’s climate.
“It’s amazing what a little snow will do,” said Dean Iovino, a lead meteorologist at the National Weather Service Office in Mount Holly.
Although the fallout here should be only mildly eventful, across much of the nation, winter and the approaching spring appear to be having quite a dustup this week, driven by the strongly contrasting temperatures.
On the cold side of the frontal boundary Thursday heavy snow and ice were in the forecast from the Great Lakes to Maine, and to the southeast of that line, flooding was possible in the Ohio Valley and the interior Northeast.
Around here, showers overnight should be done by daybreak Friday, and the winds back off during the afternoon.
High temperatures will return to the 40s during the weekend, close to averages, followed by another warmup early in the week, followed by a significant chance of further volatility.
The Climate Prediction Center’s outlook through March 3 sees the odds favoring below-normal temperatures and above-normal precipitation toward the end of the period.
Regarding 1976, the year the Feb. 17 record was set, temperatures that month finished a full 7 degrees above normal. The average high from the 16th to the 29th (it was a leap year)was 62. On March 5 it went all the way up to 79 officially in Philly.
On March 9, it snowed 6.9 inches, which was the biggest snowfall in nine years.