Johnson City, Tennessee 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

944
FXUS64 KMRX 141729
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
129 PM EDT Wed May 14 2025

...New AVIATION...

.UPDATE...
Issued at 1015 AM EDT Wed May 14 2025

Currently a very weak boundary is pushing through the southern
Appalachians region which is allowing for a few showers to develop
along it. This boundary will continue to move east/northeast
throughout the day and as we get into the late afternoon and
evening hours will possibly act as a focus for additional shower
and thunderstorm development if the skies are able to clear out
and the sun makes it to the surface. Low level clouds are being
stubborn to evaporate and wherever they linger will see
temperatures kept in check from the sun. Have backed off a bit on
temperatures where the clouds are the thickest, but we should
start to see more pronounced breaks in the cloud deck as the
morning and afternoon wears on.

&&

.SHORT TERM...
(Today and tonight)
Issued at 323 AM EDT Wed May 14 2025

Key Messages:

1. Low-end marginal severe weather threat today primarily for
hail and damaging winds. Flooding is a possible threat as well.

2. Patchy dense fog possible this morning and tomorrow morning.

Discussion:

The closed low is currently undergoing phasing back into the mean
flow, which will allow some ridging to finally punch in for the
mid to late week. Before that happens, isolated to scattered
thunderstorms are possible this afternoon and evening. A weak low
pressure center and frontal system will position over the east
coast again today, similar to yesterday. Peak heating and just the
right conditions, may allow an environment for marginal severe
thunderstorms.

Grabbing a point forecast sounding for northeast TN for around 10
PM tonight, does depict a marginal severe weather set-up, with
>30kt effective shear, 6.7 C/km mid-level LR`s, CAPE just under
1000 J/kg, DCAPE approaching 900, and some CAPE within the hail
growth zone. SPC Day 1 does categorize the "threat" area for hail
and damaging winds. Tornadoes are not likely, as low level shear,
SRH, and the wind field in general are just not conducive. If
things follow what CAMs show, precipitation will increase in
coverage from the southwest to northeast this afternoon and into
the evening hours. Storms appear to look stronger as they pass the
I-40 corridor after 00z. Precipitation is forecast to exit the
area in the middle of the night tonight. Overall, it appears like
a low-end marginal threat, but should still be aware of the
strong to severe storm potential.

Afternoon highs today will trend warmer than they have been with
readings approaching or exceeding climatological norms. Due to
excessive moisture lately and more to come for some areas, late
night/early morning dense fog is possible in spots so be extra
cautious for the morning commute this morning and Thursday
morning.

&&

.LONG TERM...
(Thursday through Tuesday)
Issued at 323 AM EDT Wed May 14 2025

Key Messages:

1. Warmer and drier on Thursday.

2. Strong to severe thunderstorms possible sometime in the Friday to
Saturday morning time frame, potentially in multiple rounds.

3. An unsettled pattern continues next week with rain chances each
day and above normal temperatures.

Discussion:

Thursday will be one of our driest days for the past week and into
the next week too. Ridging will be building across the region
Thursday, and the notable weather for Thursday will be the very warm
temperatures climbing above seasonal normals, and afternoon highs
reaching into the 80s.

The warm, unstable air mass will prime the pump for strong to severe
thunderstorms on Friday as a strong system crossing the Great Lakes
drives through a front across the Tennessee and Ohio Valleys. The
timing of this front and the associated thunderstorms will play an
important factor in the type and coverage of the severe threat. If
the front holds up a bit and comes through in the overnight hours,
typically this leads to a wind driven event with possible strong
straight-line winds with thunderstorms. However if the front is able
to come in earlier in the afternoon/evening hours, the daytime
heating and tightening pressure gradient could spark off storms
ahead of the main line, leading to all modes of severe weather.
There remains much uncertainty regarding the timing as the
deterministic models are in disagreement, leading to lower
confidence in the probabilistic guidance. We could also see multiple
rounds of storms during the Friday to Saturday morning period.
However, at this time signs are pointing to the most likely scenario
being the Friday night timing, with upstream convection spreading
into the area, and damaging straight line winds as the highest
potential threat. Rain chances should be waning through Saturday
with the frontal passage likely to be in the morning.

The front stalls out near or just south of the Tennesee Valley,
lifting back to the north on Sunday. This could be a focus for
additional storms for the start of next week. Low chance PoPs and
above normal temperatures will be in the forecast for each day as
high pressure over the eastern Gulf and western Atlantic appears to
be the main feature that will drive our weather.

&&

.AVIATION...
(18Z TAFS)
Issued at 127 PM EDT Wed May 14 2025

Afternoon storms could develop at all sites, but coverage and
certainty of impacts is much higher in northeast TN and southwest
VA closer to the trough. Expect coverage and strength of storms to
peak in the afternoon/evening hours, but chances will linger
overnight near KTRI. Low certainty on fog overnight, but if mid
level clouds clear out KTRI will likely drop to IFR or lower
before sunrise.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             65  86  70  88 /  10   0   0  20
Knoxville McGhee Tyson Airport, TN  65  86  70  86 /  30  10  10  30
Oak Ridge, TN                       64  86  69  86 /  30  10  10  40
Tri Cities Airport, TN              60  83  66  84 /  30  20  20  40

&&

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

$$

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