Lafollette, Tennessee Weather Forecast Discussion

886
FXUS64 KMRX 221745
AFDMRX
Area Forecast Discussion
National Weather Service Morristown TN
145 PM EDT Mon Sep 22 2025
...New DISCUSSION, AVIATION...
.KEY MESSAGES...
Updated at 107 PM EDT Mon Sep 22 2025
-  Scattered showers and storms both today and Tuesday. A few
    storms may produce strong gusty winds.
-  Increasing chances of showers and storms are expected
    Wednesday and especially Thursday. A few strong to severe
    storms will be possible, and there will be potential for
    locally heavy rainfall capable of producing localized
    flooding.
-  The weekend into Monday will trend drier, with slightly below
    normal temperatures trending toward normal by Monday.
&&
.DISCUSSION...
Issued at 107 PM EDT Mon Sep 22 2025
We remain under quasi-zonal flow aloft today, with another weak
short wave approaching from the west. This short wave will move
over our area tonight. Models show an area of upper level jet
forced divergence that clips at least our northwestern counties
late today or early tonight. Convective energy this afternoon is
modest and midlevel lapse rates weak, while effective shear shows
a very slight uptick to around 15kts. The best chance for strong
to severe storms looks to be across and near our Plateau counties
as well as near the TN/KY/VA borders later today into this
evening associated with the area of better forcing, with damaging
winds the primary threat. We will see convection lingering during
the night as the short wave moves across.
Tuesday will see a similar environment to today overall although
forcing looks to be more lacking and effective shear a bit higher.
In addition, lingering cloud cover and morning precipitation
associated with the exiting short wave will likely limit convective
energy especially northern half of the area. We will see
scattered showers and storms again, and a few may become strong to
marginally severe with damaging winds again the primary threat.
The pattern will be shifting for Wednesday and Thursday as an upper
trough stretching from the Great Lakes to the central Plains pivots
southeast into the Ohio and Mississippi River valleys. The
associated cold front will push through our area Thursday into
Thursday night.  Increasing southwesterly flow will bring increasing
moisture ahead of this system, with the NAEFS data still showing
PWAT values around or exceeding the 90th percentile values for this
time of year for much of the Wednesday into Thursday time frame. We
will see an increase in showers and thunderstorm coverage for
Wednesday and especially Thursday, and localized flooding will
become more of a concern especially in areas that see repeated
rounds of heavy rainfall. In addition, bulk shear will be increasing
to around 30 to 40 kts, which suggests the chances for severe storms
will be enhanced assuming enough convective energy. The amount of
CAPE that the convection will have to work with is definitely a
question mark, especially given uncertainties in how much cloud
cover and precipitation will inhibit solar heating as well as the
timing of the better forcing. This will bear watching.
How quickly drier air will push in is still in question given the
poor consistency in the models, but right now it looks like Friday
will trend a bit drier as the trough and front shifts east. The
weekend and Monday look to be mostly dry, especially Sunday and
Monday. Temperatures Saturday will likely be slightly below seasonal
normals, trending closer to normal by Sunday and Monday.
&&
.AVIATION...
(18Z TAFS)
Issued at 107 PM EDT Mon Sep 22 2025
We will see scattered showers and storms around especially this
afternoon/early evening with another uptick in activity expected
early Tuesday. Will try to time best chances for thunder with
prob30 thunder groups and VCTS. Fog development later tonight is
possible and a source of significant uncertainty. Right now much
of the model data suggests a mid deck of clouds will be present
overnight, and it is also unknown at this time if any given site
will see rain later today or this evening. Given this, confidence
level for fog is too low to include right now, so will keep the
mainly VFR forecast all sites for the period.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             68  87  68  86 /  20  30  30  50
Knoxville McGhee Tyson Airport, TN  66  85  68  83 /  30  40  40  50
Oak Ridge, TN                       66  83  66  81 /  40  50  40  60
Tri Cities Airport, TN              63  80  63  80 /  40  50  40  60
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
DISCUSSION...99
AVIATION...99

NWS MRX Office Area Forecast Discussion