Johnson City, Tennessee 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

307
FXUS64 KMRX 261757
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
157 PM EDT Thu Jun 26 2025

...New SHORT TERM, LONG TERM...

.SHORT TERM...
(This evening through Friday)
Issued at 154 PM EDT Thu Jun 26 2025

Key Messages:

1. Scattered showers and storms mainly this afternoon/early evening
and again tomorrow afternoon. A few strong to severe storms possible
as well as localized flooding.

2. Still hot tomorrow, although should be below heat advisory levels.


Discussion:

The large ridge of high pressure continues over the region, although
its grip will begin to slowly weaken. We have seen convection firing
across the northeastern part of the area this afternoon near the
remains of an outflow boundary that pushed north from the early
morning southern convection. Areas further south behind the outflow
boundary had stabilized, but have been slowly destabilizing and
additional isolated to scattered convection is likely to develop
across southern and central areas later this afternoon into early
evening. With plenty of CAPE and DCAPES generally around or
exceeding 1000 J/kg along with steep low level lapse rates, any
stronger storms this afternoon will have the potential to produce
damaging wind gusts. In addition, given the week flow resulting in
slow storm movement, very heavy rainfall will be possible along with
localized flooding.

Tomorrow will see another hot day. Heat index values are forecast
to top out in the mid 90s to around 100 range in most valley
locations, and the HeatRisk values tomorrow are currently no
higher than moderate, so the heat advisory will be allowed to
expire this evening on schedule. Convective energy and moisture
tomorrow are not forecast to be much different than this
afternoon and flow will still be weak, so scattered to numerous
showers and thunderstorms are expected again with damaging wind
and localized flooding threats similar to this afternoon.

&&

.LONG TERM...
(Friday night through next Thursday)
Issued at 154 PM EDT Thu Jun 26 2025

Key Messages:

1. Higher rain chances and slightly lower daytime temperatures
through the weekend into the early part of the week. Isolated strong
or severe storms and localized flash flooding are possible each day.

2. A cold front approaches the area Tuesday, with the possibility of
less precipitation coverage Wednesday and Thursday if the front
makes it to our south/east.

Discussion:

Ensemble data continues to show a very moist airmass over the region
for Saturday through Tuesday, with mean PW values generally in the
range of 1.7 to 2 inches. Meanwhile, the upper ridge will be
gradually loosening its grip on the Southeast. We will see a high
CAPE/low shear environment with numerous showers and thunderstorms
around each day Saturday through Monday. The strongest of these
pulse type storms will be capable of producing damaging wind gusts
at times especially during peak heating.  Also, given the very moist
environment, any storms will be capable of producing very heavy
rainfall that causes localized flooding.  This threat of localized
flooding will continue Tuesday as well as a weak cold front
approaches.  High temperatures during the Saturday through Monday
period are expected to be near to just a few degrees above seasonal
normals.

As is often the case with summertime cold fronts, there is a
question about whether or not it will make it through our area
before stalling.  Right now, much of the model data suggests it will
make it to our south and southeast by early Wednesday, allowing for
slightly cooler and drier air to move in. Given the uncertainty
about where the front will stall, we will still have some showers
and thunderstorms in the forecast for Wednesday and Thursday, but
PoPs are currently lower.

&&

.AVIATION...
(18Z TAFS)
Issued at 1233 PM EDT Thu Jun 26 2025

Thunderstorms around TRI to start, and additional scattered storms
are expected around further south later this afternoon/early
evening. Will carry prob30 thunder groups all sites during the
period of highest probability. Brief gusty winds can be expected
with any thunderstorms.  Fog development later tonight will be
possible especially TRI (given the rainfall there this afternoon),
so will include MVFR vsby in fog at TRI for now and lower vsby values
may occur. Outside any convection and the aforementioned fog at
TRI, will have a VFR forecast all sites.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             72  93  72  90 /  20  60  30  60
Knoxville McGhee Tyson Airport, TN  71  92  71  89 /  30  60  40  70
Oak Ridge, TN                       71  91  71  88 /  20  60  40  70
Tri Cities Airport, TN              68  89  68  85 /  30  70  40  70

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...Heat Advisory until 8 PM EDT /7 PM CDT/ this evening for
     Anderson-Bledsoe-Bradley-Hamilton-Knox-Loudon-Marion-McMinn-
     Meigs-North Sevier-Northwest Blount-Northwest Monroe-Rhea-
     Roane-Sequatchie-West Polk.

VA...NONE.
&&

$$

SHORT TERM...
AVIATION...