While the words “midwest” and “tropical” may not seem similar, the rainfall forecast through Saturday may say otherwise. In particular, the Ohio and Tennessee Valleys will see tropical moisture pushed into the region. The moisture will create widespread and heavy rainfall, with the potential for flash flooding. With forecasted dew points over 70 degrees for the region, what kind of feature could move that much moisture? The answer, Tropical Storm Cindy.
The Setup
Tropical Storm Cindy is currently making its onshore voyage on the Gulf Coast. The system will begin to track northeast , picked up by the outer edges of the jet stream. Because of this, the system will begin to substantially weaken, but still contain plenty of moisture. While this would typically spell for a rainy day across the eastern US, two other features are working in tandem to create the flash flood threat.
The forecasted track of Tropical Storm from the National Hurricane Center, with its northeast track after coming onshore Wednesday night.
Shifting our view further north to the Midwest, a stationary front is draped across the region. This boundary between two air masses is ideal for creating lift, but needs enough moisture and upper level support to create a flash flood threat. With Cindy bringing the moisture, the last piece needed is aloft with the jet stream.
An upper level jet will move over the front Friday and Saturday, creating what is called a “Kata Front” where the precipitation forms ahead of the front due to the injection of moisture parallel to the front. The kata front will also allow for sustained updrafts and longer lived storms. When all three are combined, the setup favors higher rainfall amounts.
The Forecast
Widespread showers and storms will form ahead of front Friday, and track northeast parallel to the edge of the front. Storms may also have a “training” effect, where a line of storms moves over the same location, similar to a train moving over the same set of tracks. With this being said, the orientation of the front and jet stream will not be able to maximize the effect the kata front. This has put some the of the modeled rainfall amounts into question, with the lower end of the spectrum being more favorable.
“NEAR THE WARM FRONT SOME BRIEF TRAINING COULD LEAD TO A LOCALIZED FLASH FLOOD THREAT AS WELL…ALTHOUGH COVERAGE AND MAGNITUDE OF THE THREAT IS LOW.” -NOAA Weather Prediction Center
Even with the less than ideal setup, rainfall amounts between 3-5 inches are possible across the lower Ohio and Tennessee Valleys. Localized flooding will also be possible in Northern Alabama, Kentucky, Tennessee, and West Virginia.
The Takeaway
In short, make sure to stay aware of rainfall amounts Friday and Saturday across the region, along with creeks and rivers that are prone to flooding. And as always, when you come across a flooded area…
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