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Wednesday's rain in Roanoke a 200-500 year event

Published On: Jul 11 2013 04:22:22 PM EDT   Updated On: Jul 11 2013 05:04:31 PM EDT
Wednesday rainfall a 200-500 year event

Roanoke witnessed a historic weather event Wednesday when multiple rainfall records were shattered during the afternoon. A total of 3.35 inches of rain fell between 2:50 and 3:50 PM launching the total rainfall amount for the day to a record setting 3.88 inches.

After an already saturated beginning to the summer, much of Southwest Virginia finally got a break from the daily barrage of rain events early in the week.  This period ended up being very short-lived as a cold front began to trek east from the Ohio Valley yesterday afternoon. Ahead of the front, much of Virginia started out warm and muggy. Roanoke hit the 90 degree mark by 1 PM as a few scattered storms began to form over the eastern ridges of the mountains. By 2 PM, the storms began to encroach upon the Roanoke Valley from the south and west.  

As storms moved in, conditions were prime for the rapid development of intense rainfall.  These conditions led to the formation of a developing storm that dumped 3-4 inches of rain over much of Roanoke City and the northern parts of Roanoke County.  This amount of rain in such a small time period led to immediate flash flooding throughout much of the city. 

According to the National Weather Service in Blacksburg, VA. Roanoke Airport recorded 3.35 inches of rainfall between 2:50 and 3:50 PM, which set a hourly rainfall record for this date.  Extreme rainfall events of this magnitude are thought to only occur every 200 - 500 years.  By the end of the day, 3.88 inches of rain fell at the airport breaking a daily rainfall record set in 1931. 

The Roanoke area has already seen 10.32 inches of rain in the month of July. This is more than 6 inches above normal for the entire month already.  In perspective, this area has received nearly 20 more inches of precipitation than we had this time last year (2012).  With grounds so saturated and more rain in the immediate forecast, flooding will remain a major concern as long as the wet streak continues.