So this all changed rapidly overnight for ETn and especially areas south of interstate 40. Supercells seem to be the dominant storm mode giving the wind dynamics with this system. I don’t see this being a major issue overall but localized areas that see more sunshine could destabilize more than other areas. The part that worries me the most is the warm front running from W to E across the valley. If supercells develop in the warm sector and intersect with the WF this is where you will see more ingredients that support tornadoes.
From the NWS in Knoxville....
“Moving into the afternoon and evening the focus will shift to the
potential for strong to severe storms with the challenge being on
how far north the warm front makes it. The latest HRRR and RAP
runs suggest that the warm front will easily make it into the
southern valley and plateau counties. The NAM and GFS suggests
that the warm front stays just to the south of the area with the
instability remaining elevated. The latest SWODY1 from the SPC
favors the warm front making it more northwards and tend to agree.
The aforementioned jet maximum is forecast to strengthen this
afternoon into the 120-130 kt range. The low-level jet will
increase in response to the divergence aloft. The forecast area
will be the right entrance region of this jet. Due to this, the
warm front should be able to advance northwards into south and
western portions of the forecast area. SBCAPE values will range
from around 500-1000 J/Kg with 0-1 SRH values of 150-250 m2/s2,
and deep layer 0-6 km shear of 45-55 kts. Taking individually,
none of these parameters are really off the charts but the
combination is definitely supportive for strong to severe storms.
The low-level shear is supportive for rotating updrafts and the
potential for an isolated tornado or two. However, expect the main
threat will be damaging winds. The dry air aloft will create a
favorable thermodynamic environment for damaging winds. The
combination of mid-level lapse rates and wet-bulb zero heights
will be favorable for severe sized hail. Overall, the area with
the highest threat will be across the Cumberland Plateau and
southern Valley. This is also where the tornado threat will be the
highest. The warm sector becomes pinched off later tonight as the
low tracks to the northeast and the tornado threat will be very
low across northeastern portions of the forecast area. Although,
still cannot rule out strong to severe storms further to the north
across northeast Tennessee and southwest Virginia”
From the NWS in Knoxville....
“Moving into the afternoon and evening the focus will shift to the
potential for strong to severe storms with the challenge being on
how far north the warm front makes it. The latest HRRR and RAP
runs suggest that the warm front will easily make it into the
southern valley and plateau counties. The NAM and GFS suggests
that the warm front stays just to the south of the area with the
instability remaining elevated. The latest SWODY1 from the SPC
favors the warm front making it more northwards and tend to agree.
The aforementioned jet maximum is forecast to strengthen this
afternoon into the 120-130 kt range. The low-level jet will
increase in response to the divergence aloft. The forecast area
will be the right entrance region of this jet. Due to this, the
warm front should be able to advance northwards into south and
western portions of the forecast area. SBCAPE values will range
from around 500-1000 J/Kg with 0-1 SRH values of 150-250 m2/s2,
and deep layer 0-6 km shear of 45-55 kts. Taking individually,
none of these parameters are really off the charts but the
combination is definitely supportive for strong to severe storms.
The low-level shear is supportive for rotating updrafts and the
potential for an isolated tornado or two. However, expect the main
threat will be damaging winds. The dry air aloft will create a
favorable thermodynamic environment for damaging winds. The
combination of mid-level lapse rates and wet-bulb zero heights
will be favorable for severe sized hail. Overall, the area with
the highest threat will be across the Cumberland Plateau and
southern Valley. This is also where the tornado threat will be the
highest. The warm sector becomes pinched off later tonight as the
low tracks to the northeast and the tornado threat will be very
low across northeastern portions of the forecast area. Although,
still cannot rule out strong to severe storms further to the north
across northeast Tennessee and southwest Virginia”
