Severe Thunderstorm Warning 207, NWS Nashville, TN

Area Forecast Discussion
National Weather Service Nashville TN
213 PM CDT Wed Aug 9 2023

...New SHORT TERM, LONG TERM...

.SHORT TERM...
(This afternoon through Tonight)
Issued at 126 PM CDT Wed Aug 9 2023

Key messages for today and tonight's severe weather threat:

1. Still two rounds of severe weather possible. The first round is
now through about 6PM with the second round in the 9PM to 3AM
time frame.

2. Lots of uncertainty in regards to the severity of these storms
still exists. For this afternoon, the highest severe weather
threat favors the southwest while the entire area has a chance for
severe weather overnight.

3. Damaging straight-line winds of 60-70 mph are the primary
threat. A tornado or two can't be ruled out overnight. Large hail
and localized flooding are also possible.

4. This is an overnight event. That means have multiple, reliable
ways to receive warnings that will wake you up in the event a
warning is issued for your area!

Now for the details:

Satellite imagery this afternoon shows a shortwave moving across
our area at this time with a deeper trough forming over the
central Great Plains. A line of thunderstorms developed a couple
of hours earlier than CAMs originally depicted which bumped up
our own timing for this first round. Unfortunately, radar trends
haven't lent any confidence to the evolving severe weather
threat. The thunderstorms have been steadily weakening as they
marched towards the TN River with the strongest thunderstorms
becoming focused towards the south where mesoanalysis indicates
greater instability along a warm front to our south. Given this,
this afternoon's severe weather threat has become more focused to
our south. A Severe Weather Watch was issued for our southern
counties which is in effect through 8 PM. Damaging winds and large
hail will be the primary threat with this first round.

Elsewhere, a lot of rain is moving into the area with even more
on the way as seen by radar to our west. With this and the given
cloud cover, the biggest question is still if our atmosphere can
recover in time for tonight's MCS. As the previously mentioned
deeper trough moves into Arkansas/Missouri, a line of
thunderstorms will develop late this evening and quickly move into
Middle TN through early morning. The best time frame for this
second round of severe weather may start as early as 9PM across
our western counties and continue through about 3AM as it marches
eastward towards the Plateau. An unseasonable amount of wind shear
will be present tonight as a LLJ strengthens to about 40-50 knots
and mid-level winds increase as well. Forecast soundings and
hodographs show curved hodographs and 0-1km SRH values exceeding
300 m2/s2. So while there is the question of whether or not the
atmosphere can recover, this shear may be more than enough to
keep our severe weather threat ongoing overnight. Damaging
straight- line winds will remain the primary threat, but a tornado
threat will also exist along this line before things come to end
during the early morning hours.

&&

.LONG TERM...
(Thursday through next Wednesday)
Issued at 126 PM CDT Wed Aug 9 2023

While our severe weather threat tapers off by the early morning
hours of Thursday, lingering showers and thunderstorms will
continue until drier air moves in behind a front during the
afternoon. Lesser storm chances are in the forecast for Friday as
dry air remains, but storm chances trend back up this weekend as
southerly surface flow returns and a couple of shortwaves track
through the area. An additional round of thunderstorms is expected
on Monday as a stronger system passes to our north, but once it
sends a cold front through the area, the mid-week period looks
pleasant with drier conditions and cooler temperatures.

&&

.AVIATION...
(18Z TAFS)
Issued at 1236 PM CDT Wed Aug 9 2023

At the moment a MCS is crossing the Tennessee River. This system
will begin entering CKV/BNA/MQY's taf site between 18Z-19Z and for
CSV/MQY after 23Z . There may be periods of heavy precip and
frequent lightning bringing conditions down to IFR. A second round
of storms is expected after 05Z which will bring gustier winds up
to 40KTS possible in the heaviest portions of the system. The
second system should clear out in the morning, but ceilings may
remain low with a few scattered showers. Winds will be mostly
southwesterly around and below 10KTs.

&&

.PRELIMINARY POINT TEMPS/POPS...
Nashville      70  84  71  89 /  90  50  10  10
Clarksville    70  84  68  89 /  90  40  10  10
Crossville     65  76  64  82 /  90  70  20  30
Columbia       69  83  69  88 /  80  50  30  20
Cookeville     67  79  67  83 /  90  80  20  20
Jamestown      65  76  66  82 /  90  70  30  20
Lawrenceburg   68  81  69  87 /  80  60  40  20
Murfreesboro   69  84  69  89 /  90  60  20  20
Waverly        68  83  67  87 /  90  40  10  10

&&

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

SHORT TERM...Clements
LONG TERM....Clements
AVIATION.....Shamburger