Weather Discussion: Thunderstorm and Flash Flooding Risks

Current Situation:

• Wind Patterns: Winds at lower levels have shifted to a more southerly direction across eastern Georgia and South Carolina. In North Carolina, winds are coming from the south-southeast, with speeds picking up due to an approaching jet streak and a subtle weather disturbance.
• Storm Development: A line of thunderstorms is forming over the central Appalachian Mountains and is moving towards a stalled surface front in southern Virginia. This has led to scattered storms with towering clouds from western North Carolina into the lower foothills of west-central North Carolina.
• Moisture and Instability: The merging of moist air from the Gulf of Mexico and the Atlantic Ocean is creating an area of enhanced convergence in central South Carolina. This is bringing in more moisture, pushing levels above 2 to 2.25 inches, and maintaining an unstable atmosphere with high energy for storm development (2000-2500 J/kg in MLCAPE).

Impacts:

• Thunderstorm Coverage: Increased convergence near the surface wave exiting the higher terrain will lead to more widespread thunderstorms. The strongest storms could produce rainfall rates of 2 to 2.5 inches per hour.
• Flash Flooding: Storms moving north along the convergence zone across the Piedmont and Fall-line may train over the same areas, meaning they could repeatedly hit the same locations. This, combined with the movement of storms from the foothills, could lead to significant rainfall accumulation. Given the lower flood guidance values in the Piedmont (as low as 1.5 to 2 inches), localized flash flooding is possible, with some areas potentially receiving 3 to 4 inches of rain within 1 to 3 hours.

Key Takeaways:

• Expect scattered thunderstorms with heavy rainfall.
• Be alert for possible flash flooding, especially in the Piedmont region.
• Stay informed about weather updates and be prepared to take action if flash flood warnings are issued.