-- Discussion containing changed information from previous version are highlighted. --
546
FXUS64 KMRX 071110
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
710 AM EDT Tue May 7 2024

...New AVIATION...

.SHORT TERM...
(Today through Thursday)
Issued at 334 AM EDT Tue May 7 2024

Key Messages:

1. Multiple rounds of thunderstorms are possible today into tonight,
some of which could be strong to severe with damaging winds and
large hail as the main threats. A low-end tornado threat exists in
northern portions of the area.

2. A much higher severe weather risk exists from late Wednesday
afternoon through Wednesday night. Damaging winds and hail are the
main concerns, but the there is also a fairly notable tornado risk
in comparison to most events in our area, especially north and west
of Knoxville.

3. Repeated showers and storms could lead to flash flooding anytime
from today through Thursday.

Today and Tonight

Currently early this morning, a negatively tilted trough is located
over the Great Plains with a >120-kt upper jet at its base. An
increasingly broad warm sector is noted at the surface with a cold
front extending through eastern Nebraska/Kansas to Oklahoma and a
warm front along the Ohio River Valley. Recent showers and storms
have continued to move off to the east with some additional showers
possible in northeastern portions of the area by late morning per
the CAMs. Heading through the day, the aforementioned northern jet
will gradually shift further east with an increasingly strong
southern jet extending into the southern Mississippi River Valley.
Depending on how quickly early activity clears out, significant
instability of >1,500 J/kg MLCAPE will be achieved with with the
wind profile strengthening and becoming increasingly veered with
height. Much of the lower level winds will remain fairly weak with
higher values further to the north. In any case, deep-
layer/effective shear is likely to reach or exceed 40 kts, more than
enough for robust and organized convection. The CAMs still differ on
the coverage and intensity of convection, but the focus for
potential development will be during the afternoon and evening
hours, possibly continuing overnight. Generally, the main concerns
are damaging winds and hail based on the thermodynamic profiles and
ingredients for organization. However, places further north will be
placed in slightly stronger flow, including in the lower levels. As
such, a low-end tornado threat can`t be ruled out, mainly north of
Interstate 40/81. The overall threat level has remained the same
with continued uncertainty in the coverage and general timing of
convection.

Wednesday and Wednesday Night

By Wednesday, the upper-level dynamics and flow will become even
stronger with our region being placed in the left-exit region of the
southern jet that will exceed 100 kts. Most high-res models are
suggesting scattered to numerous convection to be ongoing during the
morning hours. During this time, the intensity will likely be
limited based on persistence from the previous night. However, most
solutions are suggesting activity to clear by the early afternoon
with development and progression from places north and west later in
the afternoon. Due to strong dynamics and overall clearing, the
environment will likely destabilize even more than on Tuesday with
even greater shear throughout the column. This is especially true
with 850mb flow reaching to near 40 kts and 0-1km shear of around 25
kts. As this is the first run of several CAMs to at least the
evening hours, these outputs have revealed a solution suggestive of
scattered supercells and/or a large QLCS reaching the area by the
evening and overnight hours. Based on the overall wind profile,
instability, storm organization, and very impressive mid-levels (7.0
C/km lapse rates and 700+ J/kg of -10 to -30 C CAPE), there is a
threat for all severe weather hazards across the area. The tornado
threat is certainly elevated further to the north and west, but
there is elevated potential of a notable (and possibly nocturnal)
severe weather event. The threat for hail is especially elevated due
to the very organized nature of convection and very impressive
instability in the hail growth region. Hail occurrences to golf ball
sized or larger are certainly possible. Additionally, the repeated
rainfall will continue the concern for flash flooding, especially
after what has already occurred in the past few days. However, there
is still some uncertainty as to how far east the strongest storms
will progress and maintain strength.

Thursday

By Thursday, the frontal boundary will be moving into the area from
the northwest with upper divergence remaining due to the northern
jet continuing to approach from the west. By this time, the better
shear and instability will have shifted off to our west with values
still sufficient for continued convection during the day. At this
point, additional rainfall and flash flooding will be the only
concerns, especially within any thunderstorms.

&&

.LONG TERM...
(Thursday Night through Monday)
Issued at 334 AM EDT Tue May 7 2024

Key Message:

1. Off and on chances for lighter rain will continue with notably
cooler conditions.

Thursday Night through Monday

By Thursday night, the aforementioned front will have moved through
the area, shifting the flow to be from a more northwesterly
direction. It is also expected that moisture will clear out fairly
quickly during this time, leading to lessened rain chances. By
Friday, deeper troughing will move over the area and create cooler
conditions with only light rain chances focused further south.
Through the weekend, additional shortwaves will be sufficient for
light rain chances with continued cooler temperatures. By Monday,
high pressure will dry the region out with fairly mild conditions
under repeated troughing.

&&

.AVIATION...
-- Changed Discussion --
(12Z TAFS)
Issued at 704 AM EDT Tue May 7 2024

Showers are ongoing near TYS and TRI and will likely continue over
the next couple of hours. Current MVFR at TRI is also expected to
lift by late morning with a break in showers before storms begin
to develop again across the area during the afternoon. This
activity is more likely to occur around TYS and TRI with CHA
possibly seeing the activity more towards the evening hours. As of
right now, it is unclear if the terminals will be directly
impacted. However, if they are, reductions to MVFR are likely and
possibly lower. Additional activity is possible overnight, but the
timing and placement is less certain. Throughout the period,
persistent southwesterly winds are expected with some gusts at
TYS.
-- End Changed Discussion --

&&

.PRELIMINARY POINT TEMPS/POPS...
-- Changed Discussion --
Chattanooga Airport, TN             87  69  87  69 /  40  60  70  90
Knoxville McGhee Tyson Airport, TN  84  68  83  66 /  40  70  80  90
Oak Ridge, TN                       84  67  83  66 /  50  70  80  90
Tri Cities Airport, TN              81  65  80  64 /  50  50  70  70
-- End Changed Discussion --

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&

$$

SHORT TERM...BW
LONG TERM....BW
AVIATION...BW