Johnson City, Tennessee 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

503
FXUS64 KMRX 070802
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
402 AM EDT Sat Jun 7 2025

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

.SHORT TERM...
(Today and tonight)
Issued at 340 AM EDT Sat Jun 7 2025

Key Messages:

1. A few lingering showers and storms this morning, primarily across
northern portions of East Tennessee.

2. Lower confidence than usual, but a line of strong to severe
thunderstorms is possible this afternoon into the evening. Wind
gusts up to 70 mph, lightning, and another round of torrential
rainfall are the expected hazards.

Discussion:

Yesterday morning I discussed the high resolution CAMs not really
showing the solutions I expected. 00z HRRR and 00z RRFS this morning
have delivered potential solutions more in line with my thinking.
Both feature a MCS type system with at least some bowing structure
racing across southern TN this afternoon into early evening. Having
said that, 18z runs of both models did not have these solutions, so
run-to-run consistency is poor and lower confidence exists for
today`s weather outcomes. As of this writing, the 06z HRRR splits
the difference between the two prior synoptic runs. Assuming we do
see thunderstorms later today though, we have a supportive
environment for severe storms and heavy rainfall. Effective shear is
40 knots, very moist atmospheric profiles in terms of PWATs, and
again high freezing heights. Yesterday some storms produced rain
rates of 2"/hr or greater while they progressed. With the atmosphere
once again moist, thunderstorms will have the capacity to produce
additional torrential rain today, and any location that experiences
round two, especially in the southern valley where the storms are
more likely, will be at a low risk for flash flooding.

There is a low tornado risk in the southern valley from the Storm
Prediction Center, this will be greatly dependent on the location
of the MCS - overall helicity is pretty low on model soundings so
a tornado isn`t something I`d necessarily expect today but weirder
things have happened. Straight line winds if we see a convective
complex will have more damage potential though.

Tonight rain chances will continue with potential redevelopment as
seen in the CAMs overnight. These later storms aren`t expected to be
severe, with a loss of potential energy by that point in the night.
Lighter rainfall amounts from those showers overnight into Sunday
morning.

&&

.LONG TERM...
(Sunday through Friday)
Issued at 340 AM EDT Sat Jun 7 2025

Key Messages:

1. Unsettled pattern with daily chances of showers and storms
continues Sunday through Tuesday. Chances for severe weather are
marginal at this point, with isolated flooding possible due to the
repeated rounds of activity over multiple days.

2. Drier weather mid to late next week following a frontal passage
Tuesday evening.

Discussion:

The active pattern continues 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. At the surface, a low will be centered over the Ohio Valley
by Sunday morning. A weak cold front will move through the region
Sunday afternoon with a slight dew point drop noted after passage
and brief, slight wind shift. CAMs do not look impressive for Sunday
afternoon with isolated to scattered showers and storms mainly north
of I-40. However, forecast soundings look pretty impressive with
1500-2000 J/kg CAPE and 35 to 40 knots effective shear. So SPC`s
marginal risk looks appropriate for that timeframe.

Drier weather is expected Sunday night through Monday morning. Rain
chances return Monday afternoon as a cut-off low moving through
MN/WI strengthens 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 northeast into Canada. A cold front
will move through the region around Tuesday evening bringing drier
weather for the following couple of days. Severe potential looks low
Monday and Tuesday with CAPE below 500 J/kg and effective shear
around 20 knots.

Forecast rain totals are fairly low during this period, less than
one inch from Sunday through Tuesday. Spotty flooding issues will be
possible with either round of wet weather mainly in places that have
already received heavy rain. 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 148 AM EDT Sat Jun 7 2025

Moisture laden atmosphere presents a complicated and uncertain
forecast. Scattered showers over the northern area are possible
overnight and near sunrise, and patchy dense fog seems likely
given the heavy rainfall a few hours ago though cloud cover will
also be flirting with MVFR. Conditions should generally improve to
VFR after daybreak. Another round of heavy TS is possible late
this afternoon. IFR VIS due to torrential rainfall, and gusty
winds are possible during storm passage. Confidence is higher at
KCHA for potential storms.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             88  70  85  66 /  60  70  60  10
Knoxville McGhee Tyson Airport, TN  85  69  81  64 /  40  70  50  10
Oak Ridge, TN                       85  68  81  64 /  50  70  50  10
Tri Cities Airport, TN              81  65  78  62 /  70  70  60  20

&&

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

$$

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