Severe Thunderstorm Warning 113, NWS Nashville, TN

Area Forecast Discussion
National Weather Service Nashville TN
1227 AM CDT Mon Jun 26 2023

...New AVIATION...

.UPDATE...
Issued at 838 PM CDT Sun Jun 25 2023

It's been a quiet evening so far across Middle TN. We should see
that change as head into the late evening and early overnight. A
surface boundary is starting to push into KY stretching southwest
into AR. An MCS developed over AR and has pushed into western TN.
This MCS overall will miss our area but should clip our far
southern counties of Wayne, Lawrence, and Giles Counties. This
will bring a strong wind threat. Thunderstorms are expected to
fill in along the surface boundary over western and northern KY.
These storms will be the main threat for our area. They look to
push into northern areas after 10 PM and continue to push south
and east through the area. Surface dew points are in the mid to
upper 70s, CAPE values are up to 2000+ j/kg, and effective shear
of 40+ knots. This will support the potential for strong storms
with wind and hail the main threat. The low level jet will also
increase after 03z and that will bring increased low level
helicity and a chance for an isolated tornado or two. The line of
storms should clear our area by 4 am with much quieter and less
humid weather tomorrow.

&&

.SHORT TERM...
(This afternoon through Monday Night)
Issued at 129 PM CDT Sun Jun 25 2023

The severe weather threat we have been talking about over the last
several days is being realized this afternoon. A severe
thunderstorm watch for counties mainly south of I-40 and east of
I-65 is in effect until 6 PM. Radar is lit up with robust, tall
strong to severe thunderstorms that have a history of producing
large hail and gusty winds with very frequent lightning. This is
no surprise considering the amount of moisture and instability
that is out there. On the topic of moisture, dew points are well
into the 70s across all of Middle Tennessee. Couple that with the
high surface temperatures caused by a mass of warm air advection
and voila...you have heat index values soaring past 100 degrees.
This sparked a heat advisory for our 2 western rows of counties
that will be in effect until 7 pm.

One interesting note to add for those of you that like to look at
models is that the HRRR forecasted afternoon dew points to drop
into the low 60s which definitely did not happen. Because of
this, we recognized that convection was possible a lot sooner
than what the HRRR was showing, i.e. the current storms on radar.

We are still monitoring the potential for another round of severe
thunderstorms late tonight into the overnight hours as troughing
aloft will help push a weak front across the area. Though we are
experiencing storms now, instability values at the surface and the
mid-levels will still be plentiful enough to fuel storms and
produce large hail provided there is enough lift. From the
beginning, this complex of storms has been the most difficult to
forecast given the large amount of model uncertainty. Timing and
coverage have been the hardest to communicate because those
parameters are different on just about every model you look at.
The best way to handle the evolution of this is to simply say
this: anticipate severe storms from now through the overnight
hours. Again, healthy lapse rates with plenty of 0-6km shear and
large MLCAPE values will lead to storms capable of producing
damaging wind with large hail. The tornado threat remains low as helicity
values are less than 150 m2/s2.

If the storms tonight do not form a line like some model solutions
are showing, the more likely outcome will be widely scattered hit-
or-miss strong to severe thunderstorms; the kind where some may
not get anything at all. After whatever front moves through
overnight, our weather should be calm and hot for the remainder of
the week.

Monday is looking dry and mostly clear with highs in the low 90s
and lows in the upper 60s.

&&

.LONG TERM...
(Tuesday through next Sunday)
Issued at 129 PM CDT Sun Jun 25 2023

A large ridge responsible for the record-breaking heat in Texas
will slowly shift east and influence our weather for the remainder
of the week. Highs will steadily increase each day with a forecast
high of 100 degrees in Nashville by Thursday. Models are showing a
shortwave developing across the Great Plains that will bring our
next chance of rain by the weekend.

&&

.AVIATION...
(06Z TAFS)
Issued at 1218 AM CDT Mon Jun 26 2023

A band of strong to severe thunderstorms will move southeast from
KY, across the Upper Cumberland area. The heaviest of the storms
will track north of SRB/CSV, but a few cells and some brief gusty
winds will likely impact SRB/CSV briefly between 06Z-09Z.
Otherwise, VFR through this taf cycle with mainly clear skies.
Winds will be mainly west. A few gusts around 18KT are expected
during the daytime hours.

&&

.PRELIMINARY POINT TEMPS/POPS...
Nashville      91  68  91  67 /   0   0   0   0
Clarksville    90  66  91  65 /   0   0   0   0
Crossville     83  61  81  58 /  10   0   0   0
Columbia       90  65  90  65 /  10   0   0   0
Cookeville     85  63  84  61 /  10   0   0   0
Jamestown      82  62  81  60 /  10   0  10   0
Lawrenceburg   89  64  89  63 /  10   0   0   0
Murfreesboro   90  65  90  63 /   0   0   0   0
Waverly        89  64  89  65 /   0   0   0   0

&&

.OHX WATCHES/WARNINGS/ADVISORIES...
None.
&&

UPDATE.......Mueller
SHORT TERM...Baggett
LONG TERM....Baggett
AVIATION.....13