540
FXUS64 KOHX 071120
AFDOHX

Area Forecast Discussion
National Weather Service Nashville TN
620 AM CDT Tue May 7 2024

...New AVIATION...

.SHORT TERM...
(Today through Tonight)
Issued at 202 AM CDT Tue May 7 2024

Radar is clear at forecast time. Same goes for the satellite.
With small to almost zero dew point depressions, fog has already
started to develop in many areas across Middle TN. Right now, only
a couple of spots are showing anything dense, but this may change
over the next couple of hours. Winds at about 1kft are 20 kts off
the OHX VAD profiler and this may be enough to keep us from
getting widespread dense stuff, but an advisory may become
necessary in the next couple of hours.

Well, I`m glad I bumped PoPs from what the NBM gave me yesterday
morning. However, storms WAY overperformed yesterday afternoon from
what I was seeing in the models at this time yesterday morning. CAPE
was near 2000 J/Kg as expected, but even with meager shear, storms
were able to produce large hail, damaging wind and from the look of
it, possibly a couple tornadoes. That does not bode well for the
next couple of days because forecast soundings over the next 72
hours look much more severe than yesterday.

Let`s start with today. Remnants of yesterday`s High Risk area over
the Plains merged into a QLCS last night, which is now wreaking
havoc over western Missouri. This QLCS feature will continue pushing
eastward through the morning hours and while latest CAMs have it
falling apart upstream from us late this morning, the residual
outflows from this system may very well provide us with the lift I
thought we may be missing today. Forecast soundings are healthy.
2500+ CAPE values, lapse rates similar to yesterday and much better
shear values than I was seeing for yesterday`s storms. For these
reasons, while I think damaging wind gusts (60+ mph) and large hail
will be the main threats, any storms that develop will likely be
rotating, so while lower on the totem pole, I can`t rule out a
tornado threat. In addition, with the amount of rain we`ve received
over the last couple of days and PWs in the 90th percentile this
afternoon, localized flash flooding is also possible. Please don`t
sleep on the flash flood threat and heed any warnings that may be
issued. Ok. That`s just the afternoon. Almost across the board, CAMs
are showing additional development tonight as another wave passes
through the region. While we lose some of the heating of the day,
CAPE values only fall into the 1000-1500 J/Kg range. This means
we`ll hold onto plenty of instability during the overnight hours.
Deep layer shear holds steady around 40 kts and helicities are such
to sustain updrafts. This means we`ll hold an overnight severe
threat, as well, with any additional storms that develop. It also
means that we`re going to be dealing with overnight severe potential
two nights in a row.

&&

.LONG TERM...
(Wednesday through next Tuesday)
Issued at 202 AM CDT Tue May 7 2024

While today and tonight`s severe threat is healthy, that might make
Wednesday`s severe potential super human. In fact, with the forecast
soundings I`m seeing I am becoming a little worried. As tonight`s
storms wane towards daybreak, the boundary created by them is
actually being picked up in some of our models. This is unusual and
may serve as a quasi-warm front that is expected to slowly lift back
to the north during the late morning and early afternoon hours on
Wednesday. As it lifts, there is some signal of convection
developing along this boundary. With forecast soundings showing
3000+ CAPE south of the boundary, plenty of shear and mid-level
lapse rates closing in on 7.0 deg/km, there is some concern of
discrete supercell development Wednesday afternoon. Supercell
composites closing in on 10.0 and STP values nearing 2.0 suggest a
fairly decent chance of tornado development. In addition, lapse
rates only get worse through the afternoon. This means large hail
(1.5 inches or larger) is going to be possible. While the afternoon
potential for severe weather is more on the isolated to scattered
level, yet another round of much more widespread storms is still
expected Wednesday night. Again, this is an all-mode severe weather
threat overnight Wednesday into early Thursday morning, with
damaging wind gusts, large hail, tornadoes and flash flooding all
possible.

The next 48-60 hours is going to be VERY active across Middle TN.
This is not a time to fret, however. Take this morning and review
your safety plan for you and your family. Know where you need to go
for shelter if you go under a warning. Wherever that shelter may
be, have essential items in there waiting for you. Phone chargers,
NOAA Weather Radios, helmets for the kiddos, just to name a few.
If you need additional support for making a plan, please visit
ready.gov/plan to help you put one together. Don`t wait until you
go under a warning. Be prepared. Especially with overnight severe
threats for the next two nights. Don`t go to bed without having
your phone fully charged and the volume turned up so you can wake
up and get to shelter.

Once we get through early Thursday morning, I think the severe
threat is over. There is an outlier signal from the NAM that the
front may not get all the way through Middle TN on Thursday and we
could see additional storms Thursday night across our south, but
let`s deal with that once we get through the next two days. By
Friday, temperatures relax back into the 70s and while the GFS is
suggesting some showers and storms on Saturday, most models do not,
so hopefully we can remain dry for several days after Thursday
morning.

&&

.AVIATION...
(12Z TAFS)
Issued at 616 AM CDT Tue May 7 2024

Sites have slowly returned to VFR following some patchy to locally
dense fog. Multiple periods of TSRA through the current TAF
period, but confidence is low in location and when. Covered
morning/afternoon coverage with VCTS, but will likely see some
SHRA/TSRA again overnight. Winds will remain from the S/SW, with
gusts up to 25kts in the afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
Nashville      85  70  85  69 /  30  60  80 100
Clarksville    83  68  83  67 /  50  60  90  90
Crossville     80  64  80  63 /  30  70  70  90
Columbia       84  68  86  66 /  30  70  70 100
Cookeville     81  66  81  65 /  30  70  70 100
Jamestown      82  64  80  64 /  30  70  70  90
Lawrenceburg   83  68  85  66 /  40  70  70 100
Murfreesboro   85  68  85  66 /  40  60  70 100
Waverly        83  68  85  66 /  50  70  90 100

&&

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

$$

SHORT TERM...Unger
LONG TERM....Unger
AVIATION.....Adcock