Turtletown, Tennessee Weather Forecast Discussion

938
FXUS64 KMRX 231649
AFDMRX
Area Forecast Discussion
National Weather Service Morristown TN
1249 PM EDT Tue Sep 23 2025
...New DISCUSSION, AVIATION...
.KEY MESSAGES...
Updated at 1229 PM EDT Tue Sep 23 2025
-  Periods of rain and thunderstorms through this week,
    culminating on Wednesday night and Thursday. Flash flood risk
    will increase by Wednesday afternoon and Thursday as multiple
    days of rain steadily lead to higher accumulations and heavy
    rain rates.
-  Wednesday and Thursday more widespread storms will be likely.
    A few strong to severe storms will be possible on Wednesday,
    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 Wednesday afternoon and evening.
-  The extended forecast is highly uncertain. The weekend into
    Monday will trend drier, with slightly below normal
    temperatures. Still, questions exist on whether light
    scattered rain showers will continue across portions of the
    area.
&&
.DISCUSSION...
Issued at 1229 PM EDT Tue Sep 23 2025
An approaching shortwave trough will amplify the longwave pattern
and produce cyclogenesis across the mid-Mississippi Valley. This
low pressure system will move eastward across our region late
Wednesday and Thursday. Ahead of this low pressure system and cold
front, moist air will advect northward with PW values approaching
2.0 inches across the region Wednesday evening through Thursday
morning. MLCAPE will be between 500-1250 J/Kg, and this "skinny"
CAPE throughout the vertical depth of the atmosphere will support
efficient warm rain processes with deep vertical buoyancy for
convective updrafts favorable to heavy rain rates. This will
support localized flash flooding across the region late Wednesday
into Thursday morning. While the instability will support a low
risk of a strong to severe thunderstorm with damaging winds, the
primary risk will be for heavy rain rates and localized flash
flooding.
There is a growing probability that this upper-low becomes cutoff
and meanders across the Tennessee Valley and Southern
Appalachians on Friday through the weekend. In this scenario,
mostly diurnal showers, and perhaps a few thunderstorms, would be
possible each day (mainly in the afternoons). Confidence is still
not very high on this scenario, and the exact location of this
upper-level low will determine whether or not we see clouds and
continued scattered precipitation or clearing sky conditions.
With this uncertainty, low chances of precipitation will continue
into early next week with a general decrease in precipitation
chances late weekend into early next week as high pressure is
forecast to build in. However, much about our expected weather
will be the result of 1) if the upper-level low becomes cutoff and
2) what steering flow impacts the cutoff low. There`s still
significant uncertainty with these two variables.
&&
.AVIATION...
(18Z TAFS)
Issued at 1229 PM EDT Tue Sep 23 2025
VFR conditions prevail with brief/tempo MVFR vis and cig due to
scattered rain showers, and a low chance of thunderstorms,
throughout the TAF period. Chances for thunderstorms will decrease
this afternoon and tonight with an increase in coverage expected
again by late in the TAF period on Wednesday afternoon. Winds
remain light and prevailing from the S/SW.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             69  86  70  81 /  20  40  90  90
Knoxville McGhee Tyson Airport, TN  68  84  68  78 /  30  40  90  90
Oak Ridge, TN                       66  81  67  78 /  40  60  90  90
Tri Cities Airport, TN              63  80  66  76 /  40  50  80  90
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
SHORT TERM...JB
LONG TERM....JB
AVIATION...JB

NWS MRX Office Area Forecast Discussion