No watches, warnings, advisories, or iPhone alerts have been issued, but all indications are that something quite extraordinary is about to happen.
After one of the stormier Julys in the period of record, for the first time in almost four months — that’s 118 days — by the weekend, the region will have experienced two straight days of clear skies.
Of course, this comes with a caveat.
“It’s our forecast, and it hasn’t happened yet,” said Joe Miketta, the warning coordination meteorologist at the National Weather Service office in Mount Holly, which has been issuing a whole lot of warnings these days.
Officially, Philadelphia this month has had 11 “thunderstorm days" — that’s days on which thunder was observed at Philadelphia International Airport. That would be the most for any July since the 11 days recorded in 2009, and that was the highest number since 1985. The lowest came in 1998, when there were none.
It is a decent metric of storminess, said Miketta’s colleague Jonathan O’Brien, and while “sometimes that can be misleading," that has not been the case this July.
“This month has been pretty robust, a lot of legitimate thunderstorms,” O’Brien said. Just over a half-foot of rain has fallen at the airport. Nowhere near a record, but nearly double normal.
Until last week, lower pressure or lighter air in the upper atmosphere had dominated in the eastern half of the country, meteorologists said, and that favors storminess.
Before another nasty front arrived earlier this week, setting off another round of floods, power outages, and transit trauma, high pressure centered offshore was in control.
But since winds circulate clockwise around high centers, all it did was draw up warm, moisture-laden subtropical air. Thus, the heat wave. At least one death in Philadelphia was attributed to the resultant extreme heat, according to the city Public Health Department.
Around here, a major pattern change is unfolding, with benign high pressure cresting over the East. “We’re getting a little break from all the extremes we’ve had recently,” said Paul Walker, senior meteorologist with AccuWeather Inc.
Perhaps more than a little.
The skies are due to become “clear” — defined as 30% or less cloud-covered — early Thursday and stay that way through Friday. The region hasn’t had two such consecutive clear days since March 26 and 27.
Philadelphia has had only five clear days since June 1; on average, it has about seven a month in June and July, according to weather service records.
Saturday afternoon technically would be “partly cloudy,” but still dry.
In fact, no rain is in the official forecast for the rest of the month.
“We’re all a little surprised,” said O’Brien, adding that the impending blue is long overdue. “We have some catching up to do."