Forecasting Flash Flood Events in Eastern Kentucky


Nature has both blessed and cursed Eastern Kentucky with the Appalachian Mountains. In fact, they have been called "lethal and lovely." The beauty is loved by all, especially tourists that only visit for a couple of days every once in a while. Those who live here enjoy all the beauty the mountains offer, too. However, there are a few times every year when the steep terrain along with ice and snow create treacherous travel challenges. That is very minor compared to the threat to life and property posed by flash flooding.

Flash flooding is defined as an area of local floods of great volume and short duration. These events are rising surges of water, and the most dangerous feature is that they usually occur with little advance warning. If that were not enough danger in itself, flash flooding happens primarily at night. This makes advance warning literally "life saving", because without it, lives are bound to be lost.

Shawn Harley is the Meteorologist in Charge with the National Weather Service at Jackson (Breathitt County), Kentucky, and says that the deadly flood of 1977 (April) in Eastern Kentucky was one of the main reasons the weather service office was opened here in the early 1980s. That large step taken by the federal government certainly backs up the fact that flash flooding is the top weather hazard in the area that local people simply call the "mountains."

The Buffalo, New York, area is a prime location for lake effect snow simply because of its geographic layout. The same can be said of Eastern Kentucky and its great potential for flash flooding. To give you an idea of just what kind of mountainous terrain I am writing about, Black Mountain is located in Harlan County at an elevation of 4,145 feet, which is the highest terrain in the entire state. With this type of steepness, the mountains sort of make up their own rules when it comes to weather. Flash flooding is not just a spring event like remembered in the devastating flood of '77. On occasion there are heavy snows, and the runoff from the melts can also trigger flash flooding. No matter how you size it up, alerting the public of the potential for flash flooding is paramount.

When I first moved here, my news director told me that I would have weekends off unless there was flooding. It did not take me long to understand what he meant by that as I covered a flash flooding event in August of 2003, just a few days after I started. Here in the mountains, most homes and some towns are located in hollows and valleys, and flash flooding can hit these areas quickly with very little advance warning. This scenario makes for large amounts of water washing most everything in its path down into the valleys. Included in that is everything from homes, cars, mud, and, sadly, humans.

Most of the flash flooding does take place in the spring and summer due to convective thunderstorms. In all fairness and safety, however you can never rule out the potential for flash flooding anytime of the year in Eastern Kentucky. Heavy rainfall in a small amount of time is one of the main culprits that can trigger flash flooding. It does not matter if a system is convective, frontal, tropical, or synoptic. It is these sort of conditions that put all the pieces for flash flooding together.

You can almost set your clock by it most days in the spring and summer when clouds increase in the late afternoon as warm moist air rises up the mountains along with cool air aloft forming clouds. It is that orographic lifting when the terrain provides uplift as air is forced up the mountains creating convective thunderstorms. These storms develop rather easily with an unstable atmosphere allowing air to rise. Most times the mountains just get a garden variety thunderstorm or simply the threat of such. Then there are those times when the clouds rise. Cloud particles grow inside the clouds, and moisture develops in the clouds. When this moisture becomes too heavy, the updrafts can no longer hold the particles in the air and allow them to fall toward the surface. Heavy rainfall is a result of the tilted structure of the updrafts. It becomes almost an assembly line of thunderstorms when there is sufficient instability. With these storms comes heavy rainfall that can literally dump quite a few inches of rain in a single hour creating an instant flash flooding event. Little, if any, wind in the mid-to-upper levels can keep a thunderstorm in place (training) for long periods of time fueling flash flooding. Again we get back to the importance of advance warning because these convective thunderstorms, intense rainmakers, can come together quickly and unleash heavy downpours of rain.

Convective thunderstorms may be at the front of everyone's mind in Eastern Kentucky when it comes to flash flooding, but other reasons for flash flooding loom. Dam or levee breaks and ice-jam floods are not quite the major threats as storms, but they must be considered dangerous. Heavy snowfall, which is rare, could eventually lead to flash flooding due to the quickly melting large amounts of snow. The main difference in these types of flash flooding events is warning time. Warning time is shortest with a convective storm.

Models do not deal well with convective thunderstorms which leads to challenges when attempting to forecast such events. For instance, should a model show any precipitation to indicate convective storms, the intensity and amount of precipitation could be greatly underestimated. Also there are those situations where a forecast simply does not come about, which means it is a smart and safe idea to check a few different sources when it comes to satellite imagery, forecast models and Doppler radar. People will be able then to have a better understanding of storm development, its path and the potential rainfall the storm may produce. Whatever the result, alerting the public in a timely manner continues to be the main priority when the potential for flash flooding exists.

Advance warning remains the key to saving lives, but education of the public about flash flooding and its dangers along with adjustments will also go a long way toward safety for all. A NOAA All-Hazards Weather Radio is the first step to saving lives. Secondly, one must have a game plan. What should one do when the alarm sounds and a flash flood warning is issued? If need be, the local emergency manager can help formulate a plan for safety. Third on the list is education about the hazards of flash flooding and what should be known when carrying out a plan of action. Adjustments is fourth on the list. Can the bed of the creek or stream near homes or places of business be deepened and widened so it can handle larger volumes of water and reduce the threat of flash flooding and also allow more time for execution of plans of action? Perhaps the most notable changes in the region as a direct result of the 1977 flood are the massive flood walls constructed in Pineville and Harlan, and the re-channeling of the Big Sandy River and moving of the railroad tracks in Pikeville.

Warning systems are better than ever before in helping give residents enough notice to save families and secure property. But as with anything else, there is always room for improvement, and when it comes to flash flooding, Eastern Kentuckians would welcome more advanced forms of notification. Continued research and regularly educating residents are musts. Flash flood potential storms need to be identified sooner so the public can be notified in a more timely and life saving manner.