After weeks of relative tranquility with hardly a rumor of drama, the atmosphere is demonstrating its capacity for volatility.
The government’s Storm Prediction Center has the entire region, all of Eastern Pennsylvania, New Jersey, and Delaware under a severe-thunderstorm watch until 10 p.m., with the biggest risk being damaging winds.
Along with several reports of downed trees, and a wind gust of up to 65 mph, Peco reported about 2,800 power outages early Wednesday evening.
The storminess is a sequel to Wednesday’s quick pulse of heat and humidity that has been more like a flash fever than a hot spell — highs and heat indices around 90 — and it appears that one of the longer May dry spells in the period of record is due to end.
And widespread general rainfall is looking near certain for Friday, perhaps an inch or more, which would be the most since April 11.
As for the Memorial Day weekend, it should be ideal — at least for people in the beach towns who are in the arcade business.
» READ MORE: A ‘normal’ summer at the Shore
“That will be the place to be at the Shore this weekend,” said Jonathan O’Brien, meteorologist at the National Weather Service office in Mount Holly.
Rip-current advisories are likely through the weekend, he added, and on Saturday onshore winds of up to 30 mph are expected. “It could be a northeasterly gale situation.”
Highs Saturday might not get out of the low 60s throughout the region. That would be about 30 degrees cooler than Wednesday. And temperatures likely won’t get out of the 60s on Sunday, with continued strong breezes continuing at the Shore, but the sun will reappear.
Why the roller-coaster?
This weekend might be the official start of summer, but the atmosphere is quite a ways away from settling into summer mode.
Temperatures Wednesday were 15 to 20 degrees higher than Tuesday’s, and more significant, the atmosphere was swollen with more sweat-inhibiting moisture, which, in turn, served as thunderstorm fuel.
After a cold front sweeps through the region, Thursday should be far more comfortable with highs in the 80s. Then something resembling a cool-season storm with more-organized precipitation could generate the first significant rains in three weeks.
“It’s going to be a cool, steady rain,” said Dave Bowers, senior meteorologist with AccuWeather Inc., but he noted that the American and European computer models were very much at odds over how deeply the rain would intrude into Saturday.
End of a dry run?
No measurable rain has fallen officially in Philadelphia since May 9, making this the third-longest May dry spell in the last 70 years.
Through Monday, rainfall for the previous 30 days was about a third of normal in South Jersey and under a half or normal on the other side of the Delaware River. If the forecasts hold, those deficits should improve by the weekend.
And if one can believe the long-term outlooks — and the universe doesn’t hold many greater caveats — the odds favor normal precipitation for the next two weeks, and above normal for the June 1-Aug. 31 period, according to the government’s Climate Prediction Center.
Meanwhile, the shorter-term forecast does have a bright side: Monday should be a splendid day with sun and temperatures back in the 70s. Perfect for the drive home.