619
FXUS64 KOHX 241443
AFDOHX

Area Forecast Discussion
National Weather Service Nashville TN
943 AM CDT Tue Sep 24 2024

...New UPDATE...

.UPDATE...
Issued at 926 AM CDT Tue Sep 24 2024

At mid morning, scattered showers were occurring mostly in a band
from Lafayette and Gallatin, southwest across Nashville Metro,
with a few stragglers around Columbia and Lawrenceburg. There have
been some local downpours and lightning strikes this morning, but
nothing major so far. We continue to be under a marginal risk
today (level 1 out of 5) for severe storms with gusty winds.

Outside the noted shower areas, there were a lot of breaks in the
clouds. These breaks will allow recovery and heating, so
conditions will destabilize as we go into the afternoon.
1500-2000 J/kg ML cape still looks on target today. The biggest
differences from previous days will be more forcing and much more shear.
A couple of impulses will precede an approaching surface front.
Also, shear will strengthen with 40KT deep layer shear and 500mb
winds reaching 50KT. These factors will boost storm coverage and
potential for embedded damaging wind gusts.

Short range models seem to depict the general scenario well,
although placement of main bands may be off somewhat. Generally,
bands of showers and storms will fire up this afternoon with the
main focus over our northwest counties just after lunchtime. Then
the focus will shift to Nashville Metro southwest to Lawrenceburg
area mainly 2 PM to 8 PM, then gradually shifting east of I-65
into the evening from 6 PM to midnight.

&&

.SHORT TERM...
(Today through Tonight)
Issued at 109 AM CDT Tue Sep 24 2024

Water vapor imagery this morning shows an upper-level trough digging
into the Great Plains while surface obs reveal a cold front to our
west over Missouri & Arkansas. As this front pushes into the area
today, storm coverage will increase across Middle TN. With SBCAPE of
1500 to 2000 J/kg and bulk shear increasing to 30 to 40 knots, a few
of these storms may become strong to severe this afternoon. Main
risk will be gusty to damaging winds. Hail looks to be unlikely as
lapse rates will be poor at less than 6 C/km. Main time frame for
severe thunderstorm potential is between 1pm and 8pm. Meanwhile,
temperatures will start to cool thanks to increased cloud cover and
the rain. A few showers may linger overnight, especially across the
Plateau where the cold front looks to stall.

&&

.LONG TERM...
(Wednesday through next Tuesday)
Issued at 109 AM CDT Tue Sep 24 2024

A more active week is still on tap. Starting Wednesday, another
upper-level low dives southward into northern Arkansas and stalls in
this area through the weekend. Meanwhile, eyes are also on the
tropics as PTC9 is forecast to strengthen over the eastern Gulf this
week, eventually becoming Hurricane Helene. It`s expected to make
landfall on the Florida Panhandle Thursday, and then gradually
weaken as it tracks northward into eastern TN Friday. Once the
remnants of the tropical system move out the area, the low over AR
will finally eject towards the northeast, clearing Middle TN by
Monday or Tuesday.

These two systems will bring rounds of rain to Middle TN through the
remainder of this forecast period. Best chance for heaviest rainfall
will be on Thursday & Friday thanks to the tropical moisture moving
into the area, and with the track of future Helene to our east,
it`ll be eastern Middle TN that will be favored for the highest
rainfall amounts this time. The latest rainfall forecast is still
showing a general 2 to 4 inches through this upcoming weekend with
higher amounts possible across the Plateau. Minor flooding could be
a concern by week`s end, but widespread flooding is currently not
expected as the current drought status means that our rivers and
creeks will have room for the welcome rain. But of course this
forecast will continue to be refined as the future tropical system
takes shape over the next few days so stay tuned.

&&

.AVIATION...
(12Z TAFS)
Issued at 618 AM CDT Tue Sep 24 2024

A band of showers is marching across Middle Tennessee this
morning, so we`ve got TEMPO -SHRA in for a couple of hours while
the cells make their way through. We expect additional convection
this afternoon, as the atmosphere is already showing some
instability in place. As the surface boundary that is instigating
this activity makes its way eastward overnight, look for
additional showers and maybe some fog and low ceilings, especially
after 06Z.

&&

.PRELIMINARY POINT TEMPS/POPS...
Nashville      86  67  79  65 /  70  50  50  50
Clarksville    82  62  78  61 /  70  40  30  40
Crossville     83  61  74  59 /  60  80  80  70
Columbia       86  64  78  61 /  80  60  60  50
Cookeville     83  63  75  62 /  80  70  70  70
Jamestown      82  62  74  61 /  80  70  70  70
Lawrenceburg   87  64  76  61 /  70  70  60  50
Murfreesboro   87  66  78  63 /  80  60  60  60
Waverly        82  62  77  60 /  80  40  30  40

&&

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

$$

UPDATE.......13
SHORT TERM...Clements
LONG TERM....Clements
AVIATION.....Rose