Thursday, August 11, 2011

8/11 - 10pm - Cooler Weather Comes at a Price

SE Louisville Webcam
How about that cool down going on around the Ohio Valley? Great, isn't it? We topped out at 83 degrees just before 3pm this afternoon in Louisville. The sky was very blue today due to dry air present both aloft and here at the surface. Tomorrow should feature more of the same with slightly warmer temperatures in the upper 80's and pleasant sunshine. That's where the good news ends.

Trough position by Sunday AM
On Saturday a gargantuan trough of low pressure is going to punch its way into the Eastern US. This will disrupt our tranquil weather pattern quite a bit as conditions become favorable for a couple areas of severe storms to form. The first line of storms will likely come through during the early to mid morning hours as the trough begins to dig in and southerly surface winds bring in the initial Gulf moisture. These probably won't be too bad, but frequent lightning, heavy rain, and a few wind gusts appear to be in the cards. Depending on how long these morning storms and their clouds stick around during the later morning and afternoon hours, we could be dealing with a considerable severe weather threat later Saturday afternoon or evening as a the associated surface cold front moves through the region. If dew points do indeed recover into the mid to upper 60's during the day on Saturday and we're able to get a good helping of sunlight, Saturday night will be rough. The storms that could roll through will pack damaging winds and a flash flood risk. I cannot rule out a tornado or two embedded in some of these storms in the evening because of the wind shear that this sharp trough will be ushering in. The biggest risk for severe weather will cover Louisville and points eastward according to the National Weather Service. (Below: Saturday morning storms on the left, Saturday evening severe storms on the right.)

The Storm Prediction Center says the severe risk around the Ohio Valley is conditional at this point due to uncertainty with cloud cover and moisture return to the area (both very valid points), but these factors likely won't be known until Saturday's morning storms clear out. Nevertheless, they've issued a Slight Risk for severe weather for areas just southeast of Louisville and mention that more areas might be added.

After Saturday, I'm off to Mississippi State University for another semester of classes, most of which will be weather-related this time around (yes!). I'm returning to WBBJ-TV in Jackson, TN on August 20th to begin again my Saturday morning weather shift on Good Morning West Tennessee. I've missed my job at ABC 7 like crazy over the summer break, so going back there will be very exciting!

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