As the region cleaned up from Irene’s soggy tantrum, the weather luckily has been dry and tranquil. Unfortunately, this week’s weather looks like more of our August norm: rain, and some more rain.
A cool front will slowly cross the region on Monday and Tuesday while tapping into moisture from Tropical Storm Lee, which is spinning across Louisiana. Lee’s rains will push northeast along the front and enhance the front’s rainfall potential locally for Monday night into Tuesday morning across the region.
Odds are favoring one to two inches of rain north and west of Interstate 295, including Philadelphia, with lesser amounts towards the Shore.
This cool front will push south and stall out Tuesday afternoon and evening, leaving us with a break in the rains that could potentially last 24 hours.
There’s a good bit of forecast uncertainty for Wednesday into Thursday as Lee’s lingering low pressure may track close enough to the region to bring more rainfall, specifically around Lee’s track and how much rainfall this second punch could bring.
All told, the potential does exist for parts of the region to pick up four or more inches of rain by the time we get to Thursday night, especially if the brunt of round two focuses itself to the west of Philadelphia.
If that second round focuses to the south, everyone’s forecasts generally average out in the two or three inches of rain department
Neither scenario is ideal given that the ground is still saturated and flood guidance from the National Weather Service suggests that some local streams could flood with less than two inches of rain over a 12-hour period.
With the first round bringing potentially two inches of rain in that timeframe, some flooding potential does exist in the coming days but it should not be on the level of what was experienced on streams and creeks to the north of Philadelphia last weekend with Irene.
Tom Thunstrom is the founder, editor, and primary forecaster at Phillyweather.net, a site devoted to discussing weather and climate in the Delaware Valley.