Heavy Rain in Martinsville (c) County, Virginia

The NWS Cooperative station at Martinsville (MARV2) had its 3rd wettest May day on record with 3.10 inches for the 24-hour period ending 700 AM EST on May 21st. The existing May record is 3.85 inches on May 19, 2018. A May record for 2-day rainfall was set with 4.95 inches ending 700 AM on May 21st and a 3-day record of 6.63 inches ending 700 AM on the 22nd. The 4-day record for May was also established at 7.73 inches. Nearly complete data extends back to 1931 at this site.

An upper-level low became cut-off over the southern Appalachian region for several days leading to persistent rainfall and eventually some flooding. Four-day (96-hour) rainfall amounts ending at 800 AM EDT on May 22nd ranged from 3 to over 12 inches in the most favored locations. Some of the 11-inch+, 4-day rain totals in Roanoke County were within the 200-year recurrence interval (9.78 to 11.8 inches) per NOAA Atlas 14. The flooding that ensued was almost all in the form of river flooding that took several days to develop. Nearly every major river basin saw some flooding, but the most notable occurred in the New River basin where crests ranged from the 4th to 8th highest on record at the Virginia gaging stations along the river. Stages on the upper New were higher than in October 2018 when the remains of Hurricane Michael transited the region. The incredible rainfall, runoff and numerous debris flows produced widespread damage to roads in the region with VDOT reporting over $5 million in damages.