Downpours may return to the Philly region this weekend, with some flash flooding possible
Warm layers of clouds 2 miles above the ground might enhance the rainfall.
The atmosphere may be ready to engage in some regressive behavior, with August-like downpours in the weekend outlooks.
Don’t be surprised to see the National Weather Service post flash-flood watches on Saturday, with heavy showers possible at night and into early Sunday.
“We have plenty of moisture coming up front the south,” said Frank Pereira, meteorologist with the federal Weather Prediction Center, in College Park, Md.
The center has the I-95 urban corridor from central Virginia through Philadelphia with an enhanced probability of “excessive rainfall.”
Widespread heavy rain amounts aren’t likely, said Pereira, but hefty totals could occur in a short period of time.
The weather service office in Mount Holly said rainfall rates of two inches an hour would be possible.
Fortunately, after a week’s respite from the episodic rains that so characterized July and August, setting off record numbers of flood warnings, the weather service notes that levels are low in the region’s major waterways.
» READ MORE: The Philly region has been a national hot spot this year — for flood warnings
“The bigger concern with this event will be flash flooding,” the weather service said, the familiar likes of flooding along roads and near the smaller streams.
While the downpours may evoke August, these would be a shade different in that they wouldn’t be driven by daytime heating, said Paul Fitzsimmons, meteorologist in the Mount Holly office. The sun is getting weaker, the days shorter.
Setting off the rains would be an approaching cold front from the west and a warm front migrating northward.
The rains could get an extra kick from very warm decks of clouds about two miles above the surface, said Pereira.
“You have this very deep saturated warm layer,” he said. “This increases the efficiency of the rainfall,” along with producing larger raindrops.
In any event, Saturday should be dry during the day, as should most of the day Sunday. And further on the plus side, the drought conditions continue to recede.
Is the drought officially, absolutely over in the Philly region?
All of New Jersey remains under a state-declared drought warning; however, conditions throughout the Philadelphia region have improved immensely.
After 16 consecutive months of below-normal precipitation in Philadelphia heading into July, the totals at Philadelphia International Airport are above normal for the year.
In the latest interagency U.S. Drought Monitor update posted Thursday, most of the region was categorized as absolutely drought-free, a big change from just last week.
All of Philly was drought-free. Last week, the entire city designated as “abnormally dry” — the least-serious tier on the monitor’s scale.
In Chester County, which had been under a state drought “warning” last month, 90% of the county was considered to be in the clear, an increase of 37% from the previous week.
It might be time for a drought farewell party.
