Heavy Rain Threat to Persist for Tennessee Valley/Southern Appalachians the Rest of This Week

Lead Forecaster Daniel Crawley

Good Tuesday evening, the synoptic weather pattern across the Eastern US is truly stuck in a rut. Which honestly for late July isn’t that big of an anomaly. The jet stream is at its furthest point north that you will see during the year. Of course as a result…. hot, humid, sultry air is in place and is just waiting on something to serve as a trigger to fire up storms.

We have a true atmospheric battle going aloft. A shortwave trough is moving across the northern tier of the country while the Bermuda High has placed its western extent into the Interior Southeast US. In between the two is a conveyor belt of deep moisture, embedded vorticity (upper level energy) and a surface boundary. The trio has resulted in a stripe of very heavy rainfall from Midwest into the Ohio Valley.

When you look at the forecasted 500 mb flow the rest of this week, there’s just not enough jet stream energy to break down the Bermuda High, so this pattern we are in will not budge anytime soon.

500mb height pattern (Through Sun Night)

Precipitable Water Values (Through Sun Night)

Daily thunderstorms are going to be a part of the forecast for the next seven days. The “lowest chances” look to be tomorrow and Thursday with an increase in coverage for the weekend. As a forecaster the concern for a flood threat grows as we get toward the weekend. Physics would suggest that the front and outflow boundaries along that front will tug the moisture axis south into the Tennessee Valley and I-40 Corridor ultimately. The WPC precipitation forecast is reflective of a slowly sagging boundary through the upcoming weekend. Widespread rainfall amounts of 1-3 inches is expected with 3-6 inches along and West of the Appalachians. Any mesoscale features should they develop has the chance to transport the moisture across the Southern Appalachians more efficiently than guidance is currently showing, that’s something to keep in mind.

WPC QPF (Through Aug 1st, 8 am)

With the pattern in place and the expectations the Weather Prediction Center has also highlighted the Tennessee Valley and SoApps for a heavy rain threat…

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