Flash Flooding Possible Over Northern Parts Of The Area For Several More Hours

Latest Mesoscale Precipitation Discussion from the WPC…

Summary
Widespread rainfall this morning across areas with saturated soils could lead to flooding. Totals of 1 to locally 2″ will be possible through 8:00 am.

In-Depth Discussion
Ahead of a surface low tracking through portions of the Deep South, anomalous moisture for this time of year was being pulled north/northeastward toward the southern Appalachians. The latest blended TPW product showed values of 1.2 to 1.4″, which is 2-3 standard deviations above the mean. Regional radar depicts a large shield of moderate rainfall where recent mesonet observations indicate hourly totals of 0.25″ to occasionally near 0.50″.

With a 40 to near 50 kt low level jet nosing into the area, there will be a 3-6 hour period of increased moisture transport which should drive the shield of rain northeastward toward southeastern TN and southwestern NC. The main limiting factor against higher rain rates and greater risk for flash flooding is the lack of instability, and rain rates are likely to stay on the lighter side (less than 1″). However, recent heavy rainfall events have primed the soils (7-day precipitation anomalies 300-600 percent of normal) and as such, the latest FFG values are quite low. The National Water Model shows high streamflows and high soil moisture, so the expected additional rainfall this morning should route as mostly runoff and could initiate or worsen ongoing flooding in the area.

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