KNOXVILLE, Tenn. (WVLT) – We were able to enjoy a most pleasant, Mother’s day weekend without an extended period of rainfall encompassing both days. While we finally did see a couple showers and a thunderstorm around Knoxville, it came very late in the afternoon, so as not to disrupt too many outdoor plans. Additionally, temperatures did not get uncomfortably warm which was a nice feature of our weekend weather. However, rain will be making a return to the region as we move into the overnight hours. An large area of showers, encapsulated within the broad circulation of an upper level low pressure system over Louisiana, will be expanding in coverage across Alabama and Georgia, with arrival in the Tennessee Valley after midnight. By that time, most of our afternoon showers and thunderstorms that formed over around interstate 40 and points south, will have faded away with the loss of daytime heating. The light rain showers may still be around toward sunrise Monday, as they continue to shift north across the Cumberland Plateau of Tennessee and southeast Kentucky. A light northeasterly wind around 5 mph will compete with the moist air from our light showers to bring temperatures down by daybreak. The humid air will win the battle, keeping lows from dropping into the 50s which is close to normal minimum temperatures for early May. Our lows will drop into the lower 60s.
MONDAY: As we watch the light rain shift north, away from the WVLT viewing area, we will start to see a more substantial area of rain build into the southern part of our viewing area, in the form of light to occasionally moderate rain showers. This area will increase in coverage across areas south of interstate 40 through mid morning, but should advance north across much of the remainder of the viewing area during the late morning hours. As temperatures slowly warm up, there may even be clap of thunder within this area of showers, and the rainfall should become a little heavier as surface heating adds to the relatively strong dynamic lift, from the upper level feature associated with our morning rainfall. Most of the higher resolution, mesoscale numerical models indicate that as we move into the middle and later afternoon hours, we may enjoy a break in the more widespread pattern of rain. During this mid to late afternoon period, we may even see a few rays of sunshine through scattered to broken cloud layers, as slightly drier air builds in behind the upper level feature rotating around the large upper low over the Lower Mississippi Valley. High temperatures should be able to rise into the lower and middle 70s during the afternoon. Winds will shift from a northeasterly direction to southeasterly at around 5 to 10 mph, during the afternoon. Rainfall will be lighter than during the day and more isolated in nature, but we should see a few more showers during the overnight hours, Monday night into early Tuesday morning. Twenty four hour rainfall totals Monday will be around a half inch to as much as one inch.
TUESDAY: The atmosphere will not be quite as moist on Tuesday as most of the deep moisture and stronger atmospheric rising motion will have pushed farther east away from the Appalachians. However, there will still be enough low to mid level moist air around for the development of scattered showers and even thunderstorms as the surface heats up around mid day into the afternoon hours. Therefore, the better chance for rain will be shifted into the afternoon and early evening hours. Once again, we should see breaks of sunshine across the area between the congested cumulus clouds, as the more pervasive, higher cloud levels around ten to twenty thousand feet slip away through the middle Atlantic coastal states. Because of the possibility of a few more rays of sunshine and a wind shift from an easterly direction to southerly during the afternoon, highs will reach the middle and upper 70s. Average rainfall amounts will be in the neighborhood of a quarter to half an inch, with locally higher amounts in areas that are impacted by thunderstorms…