Johnson City, Tennessee 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

400
FXUS64 KMRX 060817
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
417 AM EDT Fri Jun 6 2025

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

.SHORT TERM...
(Today and tonight)
Issued at 340 AM EDT Fri Jun 6 2025

Key Messages:

1. Scattered showers and thunderstorms periodically today and
tomorrow. Main window for the strongest storms are the PM hours.

2. A few storms today and tomorrow may be severe, with wind gusts up
to 60 mph the primary hazard expected, along with potentially
torrential rainfall and lightning.

Discussion:

Not much has changed with the forecast expectations for later today
and also Saturday. Today we`ll be lacking the shear needed to
sustain updrafts until the evening hours when shear begins to
increase to 30 knots or so. Showers and thunderstorms are expected
to flourish later this afternoon and evening, with a very moist
atmosphere to work with. Moisture-laden downdrafts will accompany
the thunderstorms, and will be helped along with the freezing
level near record heights of 13-14k feet and PWATs at 90th
percentiles. For those reasons, hail is a lesser risk, since the
hail has to fall 13,000 feet in >0C temperatures before reaching
the ground. CAPE before storms initiate will build to 1500 -
2000J, so plenty of initial juice for cells to work with. Some
guidance, such as the 00z HRRR, has some indications of multiple
rounds of thunderstorms, so where the storms set up today will
determine where the highest flash flooding risk exists, should
that materialize as soon as today.

On paper Saturday`s environment is more primed for
consistently severe thunderstorms, with effective shear 30 to 40
knots during the prime diurnal hours as a shortwave makes its way
across the southern Midwest. Biggest uncertainty is where the storms
will be on Saturday, with a lot of the 00z CAM suite depicting
storms missing to the south of Tennessee during much of the
afternoon hours, and uncertainty regarding evening development. This
goes against my mental model for how Saturday should play out, and
also the more coarse ensemble predictions feeding the NBM`s likely
probabilities of rain during the PM hours on Saturday. Given the
differences, hedged PoPs slightly lower, but my expectations are
still for robust thunderstorms Saturday afternoon and evening, with
severe straight line winds the main hazard, and a secondary hazard
of flash flooding depending on how many rounds of storms any one
location receives both on Friday and Saturday.

&&

.LONG TERM...
(Saturday through Thursday)
Issued at 340 AM EDT Fri Jun 6 2025

Key Messages:

1. The wet pattern continues through Sunday afternoon. Some flooding
issues will be possible in areas that already received heavy rain.

2. Another round of wet weather is expected Monday afternoon through
Tuesday evening.

3. Drier weather middle of next week in the wake of the cold front
passage around Tuesday evening.

Discussion:

The active pattern continues Saturday night and Sunday as a broad
trough sits over the Central and Eastern U.S. reaching all the way
to the Gulf Coast. A shortwave will slowly move through the Ohio and
Tennessee Valleys Sunday morning. At the surface, a low will be
centered over the Ohio Valley by Sunday morning. A weak cold front
seems to wash out as it moves into the region with a slight dew
point drop noted after passage but no wind shift. The best chance
for severe storms appears to be Saturday night with 0-6km shear
around 40 knots in the Cumberland Plateau. With decreasing
instability, storms will likely weaken as the night progresses.
Sunday, severe chances look marginal with CAPE getting up to 1200 to
1800 J/Kg in the afternoon. Shear will be weak around 20 knots but
the weak cold front moving into the region may help develop a few
strong to severe storms.

Drier weather is expected Sunday night through Monday morning. Rain
chances return Monday afternoon as a cut-off low moving through
MN/WI moves southeast, strengthening the trough over the Midwest and
Ohio Valley. This round of wet weather will continue through Tuesday
evening when the trough passes as the low moves east through the
Great lakes. A cold front will move through the region around
Tuesday evening bringing drier weather for the following couple of
days. Severe potential looks marginal with decent instability in the
afternoon/evening Monday and Tuesday. 0-6 shear will be decent in
the 30 to 40 knot range.

Spotty flooding issues will be possible with either round of wet
weather but will likely be minor unless training storms develop. The
biggest threat with any severe storms that develop will be straight-
line winds. Large hail will be more difficult with freezing levels
around 13k-14k feet.

&&

.AVIATION...
(06Z TAFS)
Issued at 147 AM EDT Fri Jun 6 2025

Brief MVFR with only a low probability of IFR conditions between
09z and 12z at TRI this morning. Otherwise VFR conditions are
highly likely through around 16z or so. Thereafter scattered
showers and TS become increasingly likely through the afternoon
and evening hours, but exact placement & coverage are highly
uncertain. Any TS will bring risk of strong gusty winds and MVFR
VIS. Activity should lessen by or after 03z. Outside of storms,
winds are light.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             89  70  86  70 /  60  40  70  80
Knoxville McGhee Tyson Airport, TN  85  68  83  68 /  60  50  70  90
Oak Ridge, TN                       85  68  83  68 /  60  50  70  90
Tri Cities Airport, TN              83  65  80  65 /  50  40  70  80

&&

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

$$

SHORT TERM...Wellington
LONG TERM....McD
AVIATION...Wellington