Southern Appalachian Weather Events of 2012

Southern Appalachian Weather: Year in Review 
Top Five Weather Events of 2012

Like 2011, 2012 was another dramatic year for weather across the southern Appalachian region. In 2012, the area was impacted once again by a significant tornado outbreak in the spring, endured a record breaking summer-time heatwave, and experienced flash flooding, a severe thunderstorm damaging wind event across the Great Smoky Mountains, and a rare early season winter storm/blizzard across the mountains from the remnants of Hurricane Sandy. In the spirit of those year-end countdown shows, we've decided to take a look back at the year that was and rank the top 5 weather events that occurred in our county warning area (CWA) in 2012.  

#5 Extensive Flash Flooding in Johnson City, TN - 05 August 2012 

Several clusters of slow moving thunderstorms developed across northeast Tennessee on the afternoon and evening hours of August 5th. Though there was only one report of severe thunderstorm damage in the forecast area that day (downburst tree damage in Cocke County), the storms that formed still produced some significant hazardous weather in the form of flash flooding. The combination of some moderately high bulk (0-6 km) wind shear values of 30 kts and a moderate to highly unstable atmosphere resulted in the development of strong, semi-organized, sustained multicell clusters of thunderstorms across east Tennessee and southwest Virginia ahead of an advancing cold front from the west. Given the very, moist/warm environment, these storms were able to become very effective rain-producers.

Map of the radar estimated rainfall from the KMRX (Morristown, TN) on August 5, 2012. The bright purple and blue colors circled in black indicate storm-total rainfall across Johnson County, TN to have been between 3 to 6 inches that evening.

Flood waters rush by a home in Johnson City, Tenn., Sudnay Aug. 5, 2012.  Heavy rains pounded northeast Tennessee Sunday stranding vehicles and surrounding homes and apartments with flood waters.  (AP Photo/The Johnson City Press, Dave Boyd)

People wade in flash flood waters in Johnson City, Tenn., Sunday Aug. 5, 2012.   Heavy rains pounded northeast Tennessee Sunday stranding vehicles and surrounding homes and apartments with flood waters.  (AP Photo/The Johnson City Press, Dave Boyd)
Flash flood waters inundate homes and race through the streets of Johnson City, TN, on the evening of August 5, 2012. Flash flooding is an often forgotten, but significant hazard posed by thunderstorms.

#4 Severe Weather Hits the Great Smoky Mountains - 05 July 2012

A day after Independence Day, the southern Appalachians experienced some additional fireworks courtesy of Mother Nature. A cluster of strong thunderstorms developed along a residual outflow boundary (from earlier thunderstorm activity the previous evening) across Kentucky and West Virginia and dropped south into southwest Virginia and East Tennessee during the afternoon hours of July 5th. The combination of strong wind shear and a highly unstable atmosphere allowed these storms to morph into an intense squall line as it moved through southwest Virginia, northeast Tennessee and eventually the Knoxville metro area and the Great Smoky Mountains National Park. The strong straight-line winds associated with these thunderstorms produced a large swath of wind damage (over 40 separate reports) as it pushed across the forecast area. The most significant damage occurred in Sevier and Blount counties as thunderstorm winds in excess of 70-80 mph toppled numerous trees, power lines, and caused some structural damage to a few buildings in Sevierville. Tragically, these winds also knocked trees down onto trailers at a campground in Abram's Creek and Cades Cove in Great Smoky Mountains National Park, killing 2 and injuring 7 people. This event proved once again that a thunderstorm does not need to produce a tornado to cause significant damage and threaten life and property.
Map courtesy of the Storm Predicition Center, which shows the various reports of severe weather that occurred across the United States on July 5, 2012. Note the large cluster of blue dots over East Tennessee and southwest Virginia, each representing an individual report of thunderstorm wind damage. The National Weather Service in Morristown recieved over 40 such reports on July 5th, between 2:30-8:00 PM EDT. 
Radar image taken from KMRX (Morristown, TN)  at 6:05 PM EDT as a line of severe thunderstorms moved through the Knoxville metro area and Great Smoky Mountains National Park. The very bright red/pink colors on the image on the right indicate intense thunderstorm outflow winds in excess of 70-80 mph that produced the deadly winds in Sevier and Blount counties.