Johnson City, Tennessee 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

983
FXUS64 KMRX 282255
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
655 PM EDT Sun Jun 28 2026

...New AVIATION...

.KEY MESSAGES...
Updated at 653 PM EDT Sun Jun 28 2026

- Additional isolated to scattered showers and storms are expected
  this evening across portions of the central east TN Valley.
  Although confidence is low, additional flooding is possible if
  these cells move across already saturated grounds.

- Hot temperatures well into the 90s are likely this coming work
  week. Heat indices will climb above 100 degrees in the Tennessee
  Valley. The central and southern valley will be right around to
  just below Heat Advisory criteria of 105 degrees. No Heat
  Advisory at this time but one may be needed in the following
  days.

&&

.DISCUSSION...
Issued at 242 PM EDT Sun Jun 28 2026

The bulk of the precipitation has moved off to our southeast.
Flooding remains on going across some areas. MRMS 24 hour QPF
estimates a swath of 3 to 4 inches of rainfall, with isolated
amounts over 5 inches, fell in a corridor from the northern
Cumberland Plateau, down through Knoxville, and then continuing down
through the Great Smoky Mountains National Park. Areas adjacent
to this heavier swatch picked up 1 to 3 inches. Our southern areas
saw very little to no rainfall, this includes the southern TN
Valley and southwest NC.

Something to watch this evening and overnight, a strong thermal
gradient is in place between the southern TN Valley and central TN
Valley, roughly 15 to 20 degree difference between CHA and TYS.
The gradient is due to clear skies and resultant heating to the
south and earlier clouds and rain cooled air to the north. The
CAMS suggest that this gradient will provide focus for additional,
isolated to scattered, showers and storms this evening and into
the overnight hours. Though the corridor of convection will be
small, areas that are already saturated and see any additional
heavier rain may flood quickly. This is due to 1 hour FFG values
as low as half an inch in some spots across the central TN Valley
and some 3 hour FFG values below 1 inch. With PW still elevated,
between 1.5 to 2 inches, any stronger convection has the potential
to produce high rain rates. Soundings still look sufficient for
heavy rain makers with tall skinny CAPE profiles and some weak
shear. The mean steering flow is out of the west northwest. Some
locally training of storms is likely with the evening round of
convection. Again, low confidence, but additional flooding is
certainly possible if storms occur and occur across areas already
saturated.

A few showers and storms are expected on Monday along the leading
edge of the advancing high and backside of the trough (central TN
Valley). Otherwise, Monday through Friday will be hot and mostly dry
as a strong ridge stays anchored over the Eastern U.S. Monday and
Tuesday highs will be mainly in the lower to mid 90s in the
Tennessee Valley. Wednesday through Friday will be even hotter with
highs in the mid to upper 90s. Heat index around 100 degrees is
likely in the Southern and Central Tennessee Valley Monday and
Tuesday. Heat index will be climbing into the 100 to 105 range on
Wednesday through Friday.

&&

.AVIATION...
(00Z TAFS)
Issued at 653 PM EDT Sun Jun 28 2026

A few showers or even an isolated storm are possible through the
evening around TYS, but these chances diminish towards midnight.
CHA and TRI are expected to stay dry. Overnight into the early
morning hours, fog is likely at TRI with lesser but still present
chances at TYS. TRI has a much higher chance of seeing IFR or
less, but this is still possible at TYS. Conditions should improve
by mid-morning with light and variable winds afterwards.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             74  95  76  97 /   0   0   0  10
Knoxville McGhee Tyson Airport, TN  72  91  73  93 /  50  30   0   0
Oak Ridge, TN                       72  92  74  94 /  40  30   0  10
Tri Cities Airport, TN              68  89  69  93 /  10  20  10  10

&&

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

$$

DISCUSSION...99
AVIATION...BW