A late-season freeze is forecast for Philly Wednesday morning
Wind chills are forecast to be in the 20s and 30s Tuesday. Meanwhile, the drought appears to be easing.
Wednesday morning isn’t likely to be the best of times for all those fully bloomed daffodils and spectacular magnolia blossoms that have been animating the region in the last two weeks.
After a blustery day Tuesday that may feel like it wandered in from February with below-freezing wind chills driven by winds that could gust to 40 mph or higher, temperatures are forecast to fall into the 20s in much of the region by Wednesday morning.
It’s been awhile. “We’ve had some mornings that have been on the colder side, but not quite that cold,” said Paul Fitzsimmons, a lead meteorologist at the National Weather Service Office in Mount Holly.
Assuming it goes below freezing at Philadelphia International Airport — what would likely be the official “last freeze” of the season in the city — it would be the first time since March 4.
This freeze would be later than most in recent years
The growing seasons, the intervals between the last spring and first autumn freezes, have been growing as the planet has warmed, and this would be the latest official spring freeze in seven years, according to the weather service.
In the 150-year-period of record, the median last-freeze date is April 5, but that last freeze has occurred after that date only seven times in this century.
What’s behind the cold
A strong cold front was due to cross the region Monday night, drying out the region, at least temporarily, and stirring up gusts from the northwest expected to kick in before daybreak and continue through the day.
“In January and February we’d be calling that an Arctic-style cold front,” said Dave Dombek, senior meteorologist with AccuWeather Inc. The forecast highs Tuesday in the mid- and upper 40s, similar to Monday’s, would be about 15 degrees below normal.
Dombek added that it may well be a “carryover” from a dramatic warming in the upper atmosphere over the Arctic last month — a so-called sudden stratospheric warming event.
That often results in cold outbreaks in North American and elsewhere weeks later.
Remember the drought?
A stage crew couldn’t have done a better job of prepping the atmosphere for a classic, dreary Monday on which measurable rain fell for an eighth consecutive day.
The 2.5-plus inches that have fallen in that period at PHL are more than triple the total rainfall of September and October combined.
New Jersey and Pennsylvania remain under drought advisories, and given that accumulated deficit in the fall, they are likely to continue for a while.
More rain is in the forecast Thursday into Friday night, and if a potential coastal storm pops, Dombek said, the rains could continue into Saturday.
“Slowly, but surely, you’re chipping away at that deficit,” he said.
The rains have been a bonanza for the rapidly greening vegetation — and certainly more beneficial to the grasses than a freeze would be for the blooms on the magnolias.
As for how to protect all those spectacular tree blossoms, said William Cullina, executive director of the Morris Arboretum in Chestnut Hill: “Really not much we do except cross our fingers.”