A dry and warm Tuesday is expected across East Tennessee due to a surface high pressure being in control of our weather. At the same time, a deep trough of low pressure will move out of the Rockies and into the Central United States. A strong surface low pressure system is expected to form in response to this trough and move towards the Midwest region on Tuesday and Wednesday. With a low pressure to the west and surface high pressure sliding to the east, the wind flow will be out of the south across the Tennessee Valley. This will allow for warm air to be transported into the region. Daytime highs on Tuesday should be in the mid 60’s in the Knoxville and Tri-Cities areas. Skies are expected to be partly cloudy.
Clouds will increase on Tuesday night as the low pressure system moves northeast through the Central U.S., and the associated cold front moves toward the Mississippi River. A warm front in advance of this system is expected to lift north of our region by Tuesday night. This will allow for good isentropic lift and will trigger showers and thunderstorms. The chance of rain for late Tuesday night and Wednesday morning is 60% across East Tennessee.
This region will be located within the warm sector of the approaching system by Wednesday afternoon. A warm and moist air mass will be in place as a fairly strong low level jet provides warm air advection. Temperatures are expected to climb into the upper 60’s to near 70 degrees. This will increase atmospheric instability during the afternoon hours before the cold front starts to affect the region. At this point, it looks like a line of thunderstorms will form to the west of East Tennessee and move into the region by late Wednesday afternoon and evening. The models are suggesting that high speed shear values will be in place as powerful mid and upper level winds move through aloft. For this reason, the Storm Prediction Center has placed most of Tennessee within the Slight Risk area of the Convective Outlook for Wednesday. The slight risk area includes most of East Tennessee with the exception of Northeast Tennessee. This map can be viewed at the top of this article.
Since the low pressure system will be so far to the north with this event and the wind profiles suggest a nearly unidirectional (lacking directional shear) wind field, the main threat with these storms should be straight lined winds and hail. A couple of isolated tornadoes cannot be ruled out within and near the risk area. While parts of Northeast Tennessee may not be in the actual risk area, strong to severe storms are still possible in that region as well. The chance of precipitation on Wednesday is 80%. In addition to the thunderstorms, breezy conditions are also expected across the region.
The rain should move out late Wednesday night. A brief period of nice weather is expected before another strong system brings more rain and thunderstorms back to the region by late week.