Loudon, Tennessee Weather Forecast Discussion

012
FXUS64 KMRX 241108
AFDMRX
Area Forecast Discussion
National Weather Service Morristown TN
708 AM EDT Wed Sep 24 2025
...New AVIATION...
.KEY MESSAGES...
Updated at 705 AM EDT Wed Sep 24 2025
-  Periods of rain and thunderstorms through this week,
    culminating on Thursday. Flash flood risk will increase later
    today and Thursday as the ground continues to saturate. Small
    streams and poor drainage areas most at risk of seeing rapid
    rises.
-  Today and Thursday more widespread storms will be likely. A
    few strong to severe storms will be possible today, primarily
    in a damaging wind threat, but the overall risk is low. There
    is about a 5% chance of damaging winds within 25 miles of any
    location on this afternoon and evening.
-  Saturday has shifted to a more rainy solution, but likely
    light precipitation. Low rain chances continue into next week.
&&
.DISCUSSION...
Issued at 208 AM EDT Wed Sep 24 2025
Radar right now has a couple blobs, a technical term, of convection
across Tennessee, with the easternmost one moving into East
Tennessee as the parent thunderstorms gradually weaken. Latest
hourly HRRR runs trek these showers across the northern third of
East Tennessee into southwest Virginia by daybreak. Locations north
of Knoxville are more likely to have a wet commute. Storm activity
may enter a lull as daylight arrives.
The next impulse should help fire convection across the area later
today, CAMs show a little variety in timing but should see
additional development by the afternoon. Rain showers and storms of
varying intensities will then continue into the night, before
becoming more scattered on Thursday. Risk of a damaging wind gust
either day looks very low, more likely any stronger storms will be
proficient and efficient at putting down heavy rain rates that have
the potential of bringing issues to small streams and poor drainage
areas. Interestingly the 00z HREF PMM keeps the bulk of the heavy
rain totals going forward over Middle Tennessee into Kentucky, with
lesser totals around or under 2 inches in the Tennessee Valley.
Exact placement of the heaviest rain isn`t a guarantee though, and
the atmosphere sporting anomalous PW profiles with MLCAPE of 1000J
is fueling the risk. Thursday the trough will be pushing into the
local region, but available CAPE and shear profiles would suggest a
nonzero wind risk, but the rainfall threat by then will be closer to
North Carolina or exiting east in response to the trough`s exact
position. Flash flood guidance (aka the amount of rain necessary
to produce flooding) is the lowest in the northern half of the
area, around 2 inches in 3 hours or 3 inches in 6 hours. These
values suggest we`ve still have some leeway before seeing
flooding, thankfully. South of Interstate 40 this gradually
increases to the Georgia state line of 3-4 inches and 4-5 inches,
in the same time periods.
As the week progresses into the weekend and beyond, the upper trough
digging into the Eastern US is expected to split, with the southern
lobe now likely to become a cutoff low. Predictability tends to go
down with cutoffs, as they meander slowly in a meadow of low
steering winds. So, for our local area heading into the weekend,
northeastern portions of Tennessee into southwestern Virginia have
seen their rain chances increase as the forecast position of the
upper low has shifted in the model consensus to be anchored over
East Tennessee, bringing light rainfall. Rain rates during this
period are less likely to overwhelm anything, with PWATs closer
to the 75th percentile, and no substantive convective development
currently expected.
With the shallow upper low struggling to move anywhere, low rain
chances are forecast to remain into next week now, at first closer
to North Carolina, then area wide during the work week as better
instability may return by then. Temperatures to remain near seasonal
averages, dependent a bit on when exactly rain falls and depth of
clouds each day versus the diurnal heating of the sun.
&&
.AVIATION...
(12Z TAFS)
Issued at 705 AM EDT Wed Sep 24 2025
Showers and isolated storms are moving across northern portions of
the area and will continue to affect TRI over the next couple of
hours. Periods of MVFR can be expected. Later today, off and on
showers and storms will continue across the region with the better
coverage being around CHA and TYS. Reductions to MVFR are possible
during the day with a much higher chance of these reductions
overnight. Winds will be generally from the southwest at about 10
kts or less. Overnight, the coverage of showers and storms is
uncertain, but chances for MVFR are increased.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             86  70  82  66 /  50  80  80  40
Knoxville McGhee Tyson Airport, TN  83  69  79  65 /  40  80  80  50
Oak Ridge, TN                       82  67  78  64 /  50  70  80  40
Tri Cities Airport, TN              81  66  77  63 /  40  70  80  50
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
DISCUSSION...Wellington
AVIATION...BW

NWS MRX Office Area Forecast Discussion