A storm system that brought heavy rain to the Lehigh Valley on Thursday has moved out of the region, but not before dumping 1 to 2 inches of rain in some areas.
The National Weather Service has lifted all flood advisories and watches for the region.
The weather service had flagged the Lehigh Valley and Poconos as “the area of greatest concern” for a flash flooding threat Thursday, with rain amounts possibly exceeding three inches.
As of 6:30 p.m., 1.75 inches of rain had fallen at Lehigh Valley International Airport, according to National Weather Service measurements.
“A few gauges showed 2.2 inches toward Walnutport,” NWS meteorologist Nick Carr said at 5:45 p.m. “Some streams may have been a bit high and there was probably some minor flooding in poor drainage areas, but nothing rising above the nuisance level.”
“Impressive winds” associated with some of the stronger showers and thunderstorms were also expected, according to meteorologist Trent Davis.
“Peak wind gusts were between 30 and 35 mph in the Lehigh Valley,” Carr said. “All our reports of stronger winds causing damage were farther south of that region.”
There was even a risk for tornadoes, with atmospheric profiling suggesting some storms “will easily be able to rotate,” but no tornadic activity had been reported as of 6:30 p.m.
A round of storms moving through the area just after noon included rumbling thunder and multiple lightning strikes. Numerous downed trees and wires have been reported around the region.
One Thursday evening meeting canceled due to the forecast was that of the Allentown Youth Council, which is now rescheduled to 6 p.m. Wednesday in city council chambers. Some schools, including Emmaus High School, have canceled outdoor sporting events scheduled for Thursday evening.
A “large and occluded upper-level low” was responsible for both the severe and flash flooding threat, the weather service said on Twitter early Thursday.
In weather parlance, an occluded front is a developing cyclone that typically has a preceding warm front (the leading edge of a warm, moist air mass) and a faster moving cold front (the leading edge of a colder, drier air mass) that wraps around the storm. As the storm intensifies, the cold front rotates and catches the warm front, forming a boundary and creating changes in temperature and wind direction.
In this case, the occluded front included a quick intensification of a storm near Lake Erie on Wednesday. As the system started to bring ample moisture into our region, physical geography (mainly the mountains and sloping terrain) helped to enhance the rainfall.
Occasional showers are expected throughout the evening over portions of the region, mainly before 11 p.m., according to the weather service. New precipitation amounts should be no more than between a half inch and three quarters of an inch.
With clearing skies and plenty of sunshine on Friday, the weather service said it will feel quite fall-like as highs reach into the 60s to lower 70s across the region.
Here is the extended forecast:
This Afternoon
Showers. Steady temperature around 70. South wind 10 to 15 mph, with gusts as high as 25 mph. Chance of precipitation is 90%. New precipitation amounts between a quarter and half of an inch possible.
Tonight
Showers, mainly before 11pm. Low around 54. Southwest wind around 5 mph becoming northwest after midnight. Chance of precipitation is 80%. New precipitation amounts between a half and three quarters of an inch possible.
Friday
Sunny, with a high near 70. West wind around 5 mph.
Friday Night
Clear, with a low around 48. Calm wind.
Saturday
Sunny, with a high near 74. Calm wind becoming southwest around 5 mph.
Saturday Night
Partly cloudy, with a low around 53.
Sunday
Sunny, with a high near 69.
Sunday Night
Mostly clear, with a low around 52.
Monday
Sunny, with a high near 71.
