Flood Risk through Weekend
A moist tropical atmosphere has settled into the Ohio, Big Sandy and Kanawha Valleys for the Independence Day weekend. Weather-wise that spells an occasional shower or downpour in a thunderstorm. For that reason, the National Weather will have Flood Watches in effect periodically through Sunday.
Good rule of thumb through Sunday…if a downpour lasts longer than an hour, it has the capability of spawning a flash flood.
On Tuesday evening a sudden squall passed through far Western Kanawha County WV armed with a microburst (small scale high wind storm) and a deluge of rain (Doppler radar estimated an inch of rain fell in the St. Albans-Cross Lanes region).
The wind felled several trees as it passed Big Tyler road. These thunderstorm wind episodes are known as “wet” microbursts for their short term, short distance (hence the nickname “micro”) effects and since they occur in the midst of a downpour.
In fact the rains that accompanied the microburst gushed down hard enough to overflow the storm sewers in spots. The “flashy” nature of the flood in St. Albans was likely a convergence of two separate entities. First, the ambient soil conditions were extremely wet after a soggy June (Yeager airport registering more than 7”of rain, making for a top 10 wettest June on record in Charleston). That soaked soil was a sitting duck for the new downpour that arrived on Tuesday evening.
But an inch of rain should not cause such a violent flood. As Cathleen Moxley reported the storm sewers around Monmouth Street in St. Albans are notorious for backing up during heavy rains.
Of course street flooding is one thing, but when small streams flood the ante is raised for potential property and road damage. That leaves us waiting for what is likely an inevitable flash flood this weekend as well as possible mud/rockslides.