NWS Weather Prediction Center
High Impact Weather Discussion
Date: July 21, 2024
Summary:
An increase in thunderstorms across the Cumberland Plateau and Central Appalachians is expected to bring heavy rainfall, with rates of up to 1.5 inches per hour and localized spots receiving 2-3 inches in the next few hours. This intense rainfall over steep and complex terrain could lead to scattered flash flooding.
Detailed Discussion:
A weather system over the Ohio Valley extending southwest to Arkansas is driving broad southwesterly winds across the southern regions and along the Appalachian Mountains. While a weather disturbance yesterday moved east and temporarily reduced moisture in the area, moisture is now returning due to upslope winds across North Carolina into southwestern Virginia. This area is experiencing dew points (a measure of moisture in the air) in the mid to upper 60s, with some spots reaching 70-71°F in the foothills.
Further west, the Cumberland Plateau is seeing moisture accumulation due to a stationary front near the Cumberland Gap, with similar dew points in the upper 60s to low 70s. A wave in the mid-level atmosphere is enhancing moisture over the area, contributing to the potential for heavy rainfall.
The current weather setup supports the development of thunderstorms with slow movement initially, which can result in localized rainfall amounts of 1.5-2.5 inches, potentially causing flash flooding in the rugged terrain. As these storms organize into larger clusters, they will likely move east off the terrain, where rain rates and totals could increase, supporting totals of 2-3 inches. Although these areas have a higher capacity to absorb rainfall (higher flash flood guidance), scattered incidents of flash flooding remain possible, especially in areas closer to the deeper moisture inflow from the south.
Key Points to Remember:
- Expect heavy rainfall rates of 1.5 inches per hour, with some spots receiving 2-3 inches in the next few hours.
- Flash flooding is possible in the steep and complex terrain of the Cumberland Plateau and Central Appalachians.
- Stay alert if you are in these areas, particularly in southwestern Virginia, eastern Tennessee, and western North Carolina.
- Monitor local weather updates and be prepared to take action if a flash flood warning is issued.
Stay safe and keep informed about the latest weather conditions.