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6:40 update

Storms are now approaching the very western edge of the plateau. There is a very pronounced outflow boundary ahead of these storms, and I wouldn’t be a bit surprised if that boundary kicks off some storms as it approaches.

You can see it as that solid green line stretching across Middle TN in the image below. It is moving southeast, as are all the storms. That is a very pronounced outflow boundary. Those are quite common with remnants of big storm complexes.


It shows up really good in motion, if you can animate through the blog.


Outflow boundaries are like little cold fronts. The air behind them is rain-cooled from storm activity. As they push through, they force the air to rise, which can lead to shower and storm development. The reason they show up on radar as thin green lines is because radar is bouncing off all the humidity, dust, etc that these boundaries force upward into the atmosphere. It’s not necessarily raining when they pass through, even though radar looks like it is. As the gust front passes,  winds will become gusty and the temperature will drop a few degrees.

If the rain-cooled air is also cooled by hail, a huge temperature difference can result between the air ahead of behind the gust front. This can lead to destructive straight-line winds. Such is not the case today.

The severe threat continues to look low. We remain in the marginal risk for severe weather. I just noticed that the Storm Prediction Center has placed our entire region in the marginal risk for severe storms again tomorrow.

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