Johnson City, Tennessee 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

993
FXUS64 KMRX 201732
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
132 PM EDT Sun Jul 20 2025

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

.SHORT TERM...
(This evening through Monday night)
Issued at 130 PM EDT Sun Jul 20 2025

Key Messages:

1. Scattered showers and storms will mainly affect areas north of I-
40 through the evening, and will need to be monitored for gusty
winds and heavy rainfall rates leading to localized flooding.

2. Numerous showers/storms expected area-wide on Monday, with a
continued potential for flooding and strong/severe wind gusts.

Discussion:

Not much has changed with the weather pattern over the region in the
past few days, and the moisture-rich air mass in place will continue
to feed diurnal convection through this evening. The northern
portions of the area, mainly north of I-40, will see scattered
showers and storms that will produce brief heavy downpours and gusty
winds up to 40 mph. Severe-level winds are unlikely but storms will
need to be monitored for training and localized flooding. Coverage
will be more isolated south of I-40.

On Monday the ridge over the Gulf starts to build northward, and a
trough off the East Coast will deepen, leading to a NW flow through
the mid and upper levels across the Appalachians. The remnants of
upstream convection over the upper MS Valley and OH Valley will be
steered in our direction in this pattern, as well as a surface front
pushing through northern IL/IN/OH today. The front and a MCV will
lead to numerous showers and storms on Monday, starting in northern
sections in the morning and early afternoon, transitioning to
southern sections in the evening. Model soundings show some
drying/cooling aloft and steep low level lapse rates that could
produce a better chance of strong/severe winds from storms than we
have had the past few days.

&&

.LONG TERM...
(Tuesday through next Sunday)
Issued at 130 PM EDT Sun Jul 20 2025

Key Messages:

1. Building high pressure aloft will lower rain chances through mid
week.

2. Hot and humid conditions persist through the period with heat
index values of 100-105 degrees across the Valley next week.

The large ridge to our west begins to build eastward on Tuesday.
This will reduce our rain chances and increase our temperatures. The
boundary that will push through on Monday night will bring some
lower dewpoints on Tuesday and Wednesday, and help keep the
afternoon Heat Index below Heat Advisory criteria. Still, peak Heat
Index values of 100-105 degrees can be expected next week for the
central and southern TN Valley. The ridge will likely suppress
convective activity, with only slight to low chances of rain,
favoring the higher terrain. The NBM Pops appear too high for this
pattern, and will be cut back. By late in the week, the ridge may
begin to loosen its grip on the region, allowing for slightly lower
temperatures and increasing rain chances area-wide next weekend.

&&

.AVIATION...
(18Z TAFS)
Issued at 130 PM EDT Sun Jul 20 2025

With little change in the weather pattern and air mass over the next
24 hours, the TAFs will follow a persistence forecast. Afternoon and
evening showers/storms will affect the area through the rest of the
afternoon , with the best chance of TSRA at TRI. MVFR cigs can be
expected again at all sites late tonight and tomorrow morning,
especially if rain occurs at the terminals this afternoon/evening.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             74  96  74  95 /  10  40  10  60
Knoxville McGhee Tyson Airport, TN  74  94  73  93 /  30  60  30  60
Oak Ridge, TN                       73  93  73  93 /  20  60  30  60
Tri Cities Airport, TN              70  87  69  86 /  50  80  40  60

&&

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

$$

SHORT TERM...DGS
LONG TERM....DGS
AVIATION...DGS