073 
FXUS64 KMRX 211811
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
211 PM EDT Tue Jul 21 2026

...New DISCUSSION...

.KEY MESSAGES...
Updated at 210 PM EDT Tue Jul 21 2026

- Showers and storms will affect the area tonight into at least 
  Wednesday night. Some of the storms this evening into the first 
  part of tonight may be strong to severe with damaging winds the 
  primary threat along with a low end possibility of a tornado 
  mainly across the northern portions of the area. 

- Very heavy rainfall will be possible with a threat of flash 
  flooding tonight through Wednesday night, with the primary 
  threat mainly northern half or two thirds of the area tonight 
  into Wednesday with the threat then shifting southward by 
  Wednesday night. 

- Below normal high temperatures can be expected Thursday through
  Saturday, then temperatures will not be far from normal for the
  remainder of the period.

&&

.DISCUSSION...
Issued at 210 PM EDT Tue Jul 21 2026

There is still uncertainty in the details for the tonight through
Wednesday night time frame although the envelope of model 
solutions is narrowing a bit overall as we get closer. Weak short 
wave energy will be moving through the northeast CONUS upper 
trough and a summertime cold front will sag southeast toward our 
area tonight. With the core of the upper jet staying well to our 
north, the upper support over our area looks weak overall. This 
leaves us with a less certain scenario more dependent on the 
timing/location of the summertime front (which is as usual quite 
difficult to pinpoint in advance) as well as the evolution and 
movement of upstream convection and related outflow 
boundaries/cold pool dynamics. That being said, the main two 
concerns in the short term continue to be the potential for severe
storms and also flash flooding. 

The potential for severe storms still looks to be highest across our 
northern areas this evening into tonight.  Most of the CAMS show a 
broken line of convection dropping out of KY this evening but 
weakening as it moves into our area, with some showing a westward 
development of the stronger cells following the gradient of higher 
CAPE which is a plausible scenario. How well convection maintains 
itself will be critical for our severe threat and is still unclear. 
The more significant effective bulk shear (around 30 to 40 kts and 
possibly even briefly higher north) will be across the northern half 
of our area , and low level hodographs show enough of a clockwise 
curve to keep the low end threat of a tornado in place providing the 
convection maintains enough strength. The primary severe threat 
still looks to be damaging winds. Our northern counties will be the 
first to be impacted and given the expected weakening trend, would 
thus be facing the higher severe threat.  Also, with the potential 
for a pivot to the west for the stronger storms our northern Plateau 
counties would be another location that may see a higher threat. 
However, strong to severe storms may push well into our area 
overnight if the weakening trend is slower than most CAMS currently 
depict.  

As for the flooding threat tonight through Wednesday night, models 
continue to indicate moisture will be plentiful with PWAT values 
either side of 2 inches for much of the period and CAPE generally 
exhibiting a tall skinny profile which would favor warm rain 
processes and high rainfall rates. Placement of convective 
boundaries and eventually the frontal boundary that will move in but 
be slow to exit will play a large part in location and timing of the 
heavy rain threat.  Hi-res ensemble data is pointing toward a threat 
of heavy rain across northern half or two thirds of our area tonight 
into Wednesday as the northern convection pushes in and likely 
leaves a residual boundary, and then the front itself pushes in 
Wednesday. Both the HREF and REFS show bands of very heavy rainfall 
somewhere across our northern half, with potential for 3 to 5+ 
inches in some spots tonight through Wednesday. The precipitation 
focus then shifts further south by Wednesday night as the front 
slowly sags southward. Given the expected slow boundary movement, 
training cells will be a concern and this combined with the fact 
that the ground is still on the wet side across portions of the area 
from recent rains and flooding, will issue a flash flood watch for 
roughly the northern two thirds of our area for tonight and 
Wednesday.  Will let later shifts look at whether or not an 
additional watch is needed for southern areas as the threat shifts 
south. It is possible that the flooding threat will linger into 
Thursday across the south as the front struggles to push south of 
our area although northern areas will likely be mainly dry.


The remainder of the forecast has the basic pattern of upper ridging 
to our west and troughing over the eastern CONUS continuing.  We 
will see short wave energy moving southeast on the back side of the 
trough at times that will bring additional showers an storms to our 
area for the Friday through Tuesday period.  Timing of these 
features and the resulting convection is of course unclear this far 
out. Temperatures for Thursday into Saturday look to be a bit below 
normal, then the remainder of the period through Tuesday will likely 
see temperatures not far from normal for this time of year.

&&

.AVIATION...
(18Z TAFS)
Issued at 1257 PM EDT Tue Jul 21 2026

Showers and thunderstorms will be more isolated this afternoon 
and mainly north, then coverage will increase especially around 
the TRI and TYS areas tonight into Wednesday. Will carry prob30 
thunder groups when the better chance of storms is expected at TYS
and TRI. VFR conditions expected at CHA and VFR conditions are 
likely at TYS outside of any heavier shower or storm, but 
prevailing MVFR conditions look likely later tonight into 
Wednesday at TRI. Lower conditions will be at least briefly 
possible especially in heavier precipitation. 

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             76  89  71  86 /  20  60  60  50 
Knoxville McGhee Tyson Airport, TN  74  86  68  84 /  60  80  70  40 
Oak Ridge, TN                       73  86  66  84 /  70  70  50  20 
Tri Cities Airport, TN              70  82  64  82 / 100  90  50  30 

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...Flood Watch from midnight EDT tonight through Wednesday evening 
     for Anderson-Blount Smoky Mountains-Campbell-Claiborne-
     Cocke Smoky Mountains-Grainger-Hamblen-Hancock-Hawkins-
     Jefferson-Johnson-Knox-Loudon-Morgan-North Sevier-Northwest 
     Blount-Northwest Carter-Northwest Cocke-Northwest Greene-
     Roane-Scott TN-Sevier Smoky Mountains-Southeast Carter-
     Southeast Greene-Sullivan-Unicoi-Union-Washington TN.

VA...Flood Watch from midnight EDT tonight through Wednesday evening 
     for Lee-Russell-Scott VA-Washington VA-Wise.

&&

$$

DISCUSSION...99
AVIATION...99


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