Severe thunderstorms are possible in Scott County and across East Tennessee and much of Middle Tennessee on Sunday.
The National Weather Service's Storm Prediction Center continues to include the northern Cumberland Plateau region in an "enhanced" risk area for severe weather on Sunday. It's the third stage in the agency's five-stage threat assessment for severe weather. Specifically, an "enhanced" threat means there is a 30 percent chance for severe weather.
There will be two lines of thunderstorms that forecasters will monitor for severe weather potential. The first is anticipated during the morning hours. That line of storms is not expected to intensify until it moves east of the region; the severe threat accompanying it will be quite low. Later in the afternoon, however, a second round of storms will arrive. With the heat of day, the second round will carry more of a risk for severe weather.
In a special weather statement published Saturday morning, the National Weather Service at Morristown said that damaging winds will be the primary concern with the second round of storms, "but isolated tornadoes and hail up to half dollar size will also be possible."
The timing of the second round of storms is expected to be late afternoon — around 4 p.m.
The Storm Prediction Center said Saturday morning that severe weather on Saturday will be largely storm mode-dependent. Supercell storm structures are possible just ahead of the main line of storms, which would carry a greater risk for tornadoes. Storms that develop in a cluster, or line, are more likely to contain damaging straight-line winds. Freezing levels will be low enough to warrant a concern for large hail, as well.
Independent of the storms, a tightening pressure gradient is likely to create gusty winds on Sunday, with gusts to 40 mph possible outside of the storms.
Another round of severe weather is possible later next week.
The original story follows . . .
Rain is in the forecast for East Tennessee both Friday and Saturday, but it is Sunday that has the eye of weather forecasters.
As the region continues through the heart of the severe weather season, the first episode of severe thunderstorms is possible across all of East Tennessee, and the National Weather Service's Storm Prediction Center has placed the region under an "enhanced" threat for severe weather.
An enhanced threat is the third level on a five-level risk assessment for severe weather under SPC guidelines. Statistically, an enhanced threat means there is a 30 percent chance of severe weather in any given area.
Forecasters said the primary risk is damaging thunderstorm winds, but did not rule out isolated tornadoes.
"(The) primary storm mode is progged to be banded/loosely linear, with embedded/complex bows and rotating updrafts," the SPC said in its technical assessment of the threat. "Damaging winds will likely be the primary threat, though tornadoes will also be possible across much of the area -- particularly near and west of the mountains."
The severe weather threat begins on Saturday to the southwest of Tennessee, across portions of Louisiana, Arkansas and Mississippi. There, strong tornadoes are possible to begin the weekend.
As the storm system shifts eastward, warm and moist air is expected to be pumped into East Tennessee ahead of an approaching cold front from the west. Meteorologists expect daytime heating to fuel instability within the atmosphere that would create an environment in which strong thunderstorms could develop.
The National Weather Service at Morristown said in a hazardous weather outlook published on Friday morning that the main concern for Sunday is "damaging winds, isolated tornadoes and hail up to quarter size." In a separate special weather statement, the NWS said that windy conditions can also be expected as the pressure gradient tightens around the storm system.
Changes to the forecast can be expected as Sunday draws nearer.