852
FXUS64 KMRX 051920
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
320 PM EDT Thu Jun 5 2025

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

.SHORT TERM...
(This evening through Friday)
Issued at 229 PM EDT Thu Jun 5 2025

Key Messages:

1. Diurnal convection this afternoon and evening looks sub-severe.

2. Isolated to scattered severe storms possible on Friday.
Damaging winds and some large hail are the primary concerns.

Discussion:

Typical summertime diurnal convection will continue to be focused
primarily over higher ridge lines and the mountainous areas of
our CWA this afternoon and evening. A weak shortwave is moving
east through Kentucky this afternoon and has provided enough
weakness in the ridge aloft to allow for storms to develop over
more complicated terrain this afternoon. Instability and shear
values aren`t concerning with regards to severe storms, but with
1,000 to 1,500 J/kg of surface based CAPE a few stronger storms
with gusty winds and small hail could occur.

Notably better chances for severe storms exist tomorrow.
Convection will be active over the central and southern Plains
today, and again Friday. A remnant MCV associated with this
activity will spread east tonight with the nearly zonal flow
aloft, and arrive tomorrow afternoon in an environment ripe
for convective redevelopment. HREF probabilities show greater than
70-80 percent chances for CAPE to exceed 2,000 J/kg in the
southern valley late tomorrow afternoon and evening, and even
respectable odds (40 percent) further north into the central TN
valley. However, shear will be limited, with deep layer shear
peaking around 30 kt. The shear/CAPE threshold probabilities
overlap best in the western half of the area late Friday afternoon
and evening, with damaging winds being the main threat from
multicell storms.

Timing wise, there could be two distinct rounds, one in the early
to mid afternoon hours which would be more discrete cells in the
central part of the forecast area, and another in the evening
which would be a full on MCS moving in from the west. The former
would be both a hail and damaging wind threat, and the latter
primarily a wind threat. The hail threat looks conditional though
as freezing levels will be in the 13-14k ft AGL range, with
wetbulb zero heights up around 11k. Lack of shear and subsequent
low chances for rotating updrafts suggests that the hail threat is
limited, but with some guidance forecasting surface based CAPE
values upwards of 2,500 J/kg, severe sized hail wouldn`t be
surprising. Damaging winds appear to be the better bet as both the
afternoon and evening rounds would feature DCAPE values in the
700-1,000 J/kg not to mention an MCS and associated cold pool to
further enhance damaging wind potential.

&&

.LONG TERM...
(Friday night through next Thursday)
Issued at 229 PM EDT Thu Jun 5 2025

Key Messages:

1. Another round of severe weather is possible on Saturday, with
the ceiling actually being a bit higher in terms of hazard types.

2. Stormy afternoons continue Sunday through Tuesday.

3. Weak cold front passage expected by Tuesday for drier and
slightly cooler conditions midweek.

Discussion:

Another round of severe weather is possible Saturday. The setup
will be similar, with another MCV approaching from the west and
strong instability in place. However better synoptic support will
be in place on Saturday, with deep layer shear of around 40kt as
opposed to 20-30kt on Friday. As such, convective modes would
support some supercell activity on Saturday in addition to another
MCS. One unknown that would have significant impacts on hazard
types will be where Friday`s storms deposit any boundaries. If
those wind up in northern Alabama and northern Georgia, then the
tornado threat would be very low. However, with the shear and
instability we will have, if the boundary is in our southern CWA
then a threat for a tornado would be in play. Otherwise, damaging
winds will be the main concern on Saturday. Will also need to
watch for flash flooding potential on Saturday as well. High PWATs
and high freezing levels will mean the potential for more efficient
warm rain processes and resulting heavy rains. Friday`s activity
looks pretty progressive, but there`s potential for training
activity along a west to east boundary on Saturday that could
lead to flooding concerns.

Sunday through the end of the period, progressive upper flow and
multiple shortwaves moving through will mean continued chances for
mostly diurnally driven convection. A weak cold front is expected
to move through Monday night into Tuesday and give a break in the
heat and humidity, knocking temperatures back down to seasonal
norms and pushing diurnally driven rain chances mainly into the
southern TN mountains for Tue afternoon onwards.

&&

.AVIATION...
(18Z TAFS)
Issued at 131 PM EDT Thu Jun 5 2025

VFR conditions are expected through the period. Some ISOLD or even
SCT SHRA are likely to develop across far western Virginia and
along the east TN mountains this afternoon. The only terminal they
might affect I believe is KTRI but a PROB30 should continue to
cover that. More widespread convection is likely tomorrow but
should occur after 18z, so no mention of that with this TAF
package.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             69  90  70  86 /  10  60  60  80
Knoxville McGhee Tyson Airport, TN  68  86  68  83 /  10  70  80  80
Oak Ridge, TN                       67  86  68  83 /  10  70  80  80
Tri Cities Airport, TN              62  83  66  81 /  20  70  80  80

&&

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

$$

SHORT TERM...CD
LONG TERM....CD
AVIATION...CD