Johnson City, Tennessee 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

260
FXUS64 KMRX 160712
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
312 AM EDT Fri May 16 2025

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

.SHORT TERM...
(Today and tonight)
Issued at 217 AM EDT Fri May 16 2025

Key Messages:

1. Isolated to scattered thunderstorms possible during the day.
Less confidence in coverage within a capped and weakly forced
environment.

2. Stronger forcing tonight and steep mid-level lapse rates will
increase instability and result in a likely line/complex of severe
thunderstorms across the area.

Discussion:

The main story of the forecast is today and tonight with the risk
of severe weather. We will have a very warm, unstable atmosphere
across the area this afternoon, and while coverage is uncertain,
isolated to scattered thunderstorms are possible mid-day through
the afternoon, mainly north of Interstate 40. HRRR/RAP forecasts
show MLCAPE this afternoon between 2000 and 2500 J/Kg with EBShear
of around 50 to 60 kt. This will be supportive of long-track
supercell structures and damaging wind complexes. With LCL heights
around 1000m and relatively weak low-level shear this afternoon,
the tornado risk will be very low with a risk of mostly large hail
or damaging winds from any supercells this afternoon.

As we get into the evening hours, loss of daytime heating will
result in less scattered convection. However, height falls
associated with the shortwave trough DPVA will steepen lapse rates
and result in rising instability to around 2500 J/Kg overnight
ahead of a line of strong to severe thunderstorms. This line will
be capable of all severe weather hazards. As the cold pool
intensifies and 850mb LLJ winds increase to around 50 kt, damaging
winds along the line of thunderstorms will be the primary risk.
Downed trees and power outages are probable. There will also be a
low (around 5 percent within 25 miles of a point) risk of
tornadoes associated with this line due to the strengthened low-
level shear and ESRH around 200 to 300 m2/s2. The main timing of
this line will be after 03z and before 08z. Additionally, RAP
forecast PW values of 1.6 to 1.8 will be near the climo max, and
NAEFS IVT values are forecast to be near climo max. This is a
strong signal for heavy rain rates which may result in localized
flooding for urban and poor drainage areas, and for any areas that
receive rainfall during the day today.

&&

.LONG TERM...
(Saturday through Friday)
Issued at 217 AM EDT Fri May 16 2025

Key Messages:

1. Mostly dry and warm over the weekend.

2. Precipitation chances increase early next week, especially
Tuesday into Wednesday.

3. Cooler late next week in the wake of a cold front.

Discussion:

Mostly dry and warm this weekend as shortwave ridging sets up
across the Tennessee Valley. By early next week, a stronger
shortwave trough will approach the Mississippi Valley with
increasing chances for thunderstorms on Tuesday into Tuesday night
across portions of the Tennessee Valley and Southern Appalachians.
Subtle vort maxima/MCVs will bring the potential of scattered rain
and thunderstorms on Monday through Tuesday night. By Wednesday, a
cold front moves east across the area with cooler temperatures,
and slight chance probabilities for primarily upslope light
precipitation across the higher elevations.

&&

.AVIATION...
(06Z TAFS)
Issued at 137 AM EDT Fri May 16 2025

Main aviation impacts through the forecast period are expected to
be thunderstorms. CHA should remain dry for most of the day with
thunderstorms possible mid-morning through the afternoon near TYS
and TRI. A line or complex of thunderstorms is expected to arrive
near the end of the forecast period.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             89  68  87  67 /  10  80  20  20
Knoxville McGhee Tyson Airport, TN  86  67  83  63 /  40  90  20  10
Oak Ridge, TN                       86  66  84  62 /  40  90  10  10
Tri Cities Airport, TN              84  64  80  58 /  60  90  20  10

&&

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

$$

SHORT TERM...JB
LONG TERM....JB
AVIATION...JB