June 5, 2019

Tropical Downpours Could Lead To Flash Flooding In Parts Of The Southeast This Week

Heavy downpours could lead to localized flash flooding across parts of the southeastern United States this week as a deep plume of tropical moisture spreads over the region. Forecasts on Tuesday night called for a widespread drenching across the southeast through early next week, with some areas potentially seeing more than five inches of rain by the end of the period.

Last week, we started watching a tropical disturbance in the Bay of Campeche for signs of tropical development. The National Hurricane Center had given the system a 60 percent chance of developing into a tropical system at its beefiest, but the disturbance was never able to take root and grow. The disturbance ran out of room to develop on Tuesday as it approached eastern Mexico.

Source: Tropical Tidbits

Nothing ever really goes away in the weather, of course. Even though the soon-to-be-erstwhile disturbance is no longer a thing of interest on weather maps, the remnant moisture from the system will continue spreading across the southeast. The above chart from Tuesday night's run of the GFS model shows precipitable water (PWAT) values through the weekend.

Precipitable water is a great way to visualize how much moisture shower and thunderstorms can work with. PWAT tells us how much rain would fall if you could wring all the moisture out of that part of the atmosphere. Higher PWAT values indicate a greater potential for showers and thunderstorms to produce heavy downpours that could lead to flooding. A PWAT value over 2.00" is considered delightfully soupy and tropical, a ripe environment for drenching rains.

As a result of all that evaporated paradise moving over land, it won't be hard for a hefty thunderstorm to put down a quick inch or two of rain if it sits over one spot for too long. It's important to note that not everybody covered under, say, the five-inch rainfall contour in the Weather Prediction Center's forecast will definitely see five inches of rain. Storms are hit-or-miss during the summer. Most everyone will see rain, but some could see a whole lot more than others.

Stay alert for flash flood watches and warnings over the next couple of days. It's always wise to memorize or program multiple safe routes to get home, to work, or wherever you need to go, just in case your normal route is covered in water and you need to turn around. It only takes a few inches of moving water to pick up a vehicle and carry it away, and it's impossible to tell how much water is covering a roadway—or if the road is even still there under the water.

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I graduated from the University of South Alabama in 2014 with a degree in political science and a minor in meteorology. I contribute to The Weather Network as a digital writer, and I've written for Forbes, the Washington Post's Capital Weather Gang, Popular Science, Mental Floss, and Gawker's The Vane. My latest book, The Skies Above, is now available. My first book, The Extreme Weather Survival Manual, arrived in October 2015.