890
FXUS64 KMRX 220537
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
137 AM EDT Tue Jul 22 2025

...New AVIATION...

.UPDATE...
Issued at 757 PM EDT Mon Jul 21 2025

Just a small update this evening. Touched up PoP grids to better
align with latest radar trends. Best coverage of convection
remains along the southern plateau into central TN associated with
an outflow boundary. An additional band of showers continues to
train along eastern KY into southwestern VA in closer proximity to
a stationary front. Most notable adjustment was to extend the
Flash Flood Watch for southwest VA until 10pm, playing it on the
safe side with some of that training precip. Soils are just very
vulnerable in that area, with some 1hr FFGs less than an inch.
Convective activity will gradually wane into the night.

&&

.SHORT TERM...
(This evening through Tuesday)
Issued at 153 PM EDT Mon Jul 21 2025

Key Messages:

1. Numerous showers and storms continue this evening, with gusty
winds and localized flooding possible.

2. A Flash Flood Watch remains in effect for Southwest Virginia,
where recent heavy rains will raise the potential for flooding.

3. Decreased shower coverage tomorrow, mainly near the mountains.

Discussion:

Coverage of showers and storms so far today has been greater than
the past few days, thanks to weaker capping and an approaching
shortwave trough/MCV. While the environment does not look favorable
for severe storms, some strong wind gusts will be possible given
DCAPE values around 1000 K/kg and steep low level lapse rates. PW
values are lower today as drier air aloft has moved in, but training
cells will need to be monitored for heavy rainfall rates and
flooding, especially in SW VA where recent heavy rain has
occurred. The Flood Watch will remain unchanged for that area.
Convection will likely persist well into tonight, perhaps past
midnight, as we continue to have remnant upstream MCV spread
across the area in the NW flow aloft, and a backdoor front pushes
into the area from the northeast.

On Tuesday, the mid/upper ridge will be building across the region,
and the weak backdoor front appears to be to our south. A northerly
flow through the low and mid levels and slightly lower surface
dewpoints will mean less instability tomorrow afternoon. Convection
should mainly be focused along the mountains and SW NC, where models
show a weak inverted trough developing.

&&

.LONG TERM...
(Tuesday night through next Monday)
Issued at 153 PM EDT Mon Jul 21 2025

Key Messages:

1. High pressure aloft will lower rain chances through mid week.

2. Rain chances increase late in the week as the upper ridge
weakens.

Discussion:

The heat that was expected under the large high pressure ridge does
not appear to be quite as impactful as previously expected. NBM
high temperatures in the TN Valley reach the lower to mid 90s
Wednesday and Thursday, but thanks to a high pressure ridge over
New England extending toward the SW, we will get some lower
dewpoints that will make the humidity a bit more tolerable, at
least below Heat Advisory levels. NBM10 dewpoints will be used,
which seem more reasonable. A few spots may see a Heat Index near
100, but nothing out of the ordinary for this time of year. The
mention of Heat Index over 100 will be removed from the HWO. Some
scattered to isolated showers and storms will be possible
Wednesday and Thursday, but should favor the higher terrain areas
near the TN/NC border and Cumberland Plateau.

Late in the week, the high pressure ridge splits in two, with a
center off the Outer Banks, and another over TX/OK. This leaves a
weak trough across the TN Valley, and allows some Gulf moisture to
spread northward. Rain chances will be on the rise again Friday
through Sunday across the entire area.

&&

.AVIATION...
(06Z TAFS)
Issued at 128 AM EDT Tue Jul 22 2025

First 6 hours of the 06z TAF forecast may be a complex one, as
the stationary front sags further south, allowing drier air and
more stable conditions to filter in. Latest HREF and HRRR do hint
at possible VSBY and CIG restrictions at TYS and TRI this morning.
CHA most likely won`t be impacted as much, with maybe MVFR CIG
and VSBY. Introduced this TAF cycle is IFR VSBY and LIFR CIG
possibility at TYS and TRI approximately sometime after 09z.

By daybreak, things should scatter out. This afternoon poses a
lower chance than what usually has been the case for PM
thunderstorms. Closest to the mtns have the best chance, so only
have a PROB30 at TRI for now. Coverage seems a bit low at the
moment for TYS and CHA.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             93  75  94  73 /  50   0  30  10
Knoxville McGhee Tyson Airport, TN  92  72  93  72 /  30  10  20   0
Oak Ridge, TN                       92  72  93  72 /  30   0  30   0
Tri Cities Airport, TN              88  67  90  65 /  40  10  10   0

&&

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

$$

SHORT TERM...DGS
LONG TERM....DGS
AVIATION...KS