Johnson City, Tennessee 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

799
FXUS64 KMRX 240547 AAA
AFDMRX

Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
1247 AM EST Wed Dec 24 2025

...New AVIATION...

.KEY MESSAGES...
Updated at 1241 AM EST Wed Dec 24 2025

- Low rain chances this morning mainly north of I-40. Otherwise
  cloudy skies.

- Unseasonable warm weather through the weekend, especially Thursday
  through Saturday.  Near record temperatures possible across
  Chattanooga.

- Rain showers are expected off and on from Wednesday night through
  Friday night mainly north of I-40. Rain amounts will be light.

- The best chance for widespread rain will be Sunday with a cold
  front moving through the region in the evening.

- Much colder airmass moves into the Tennessee valley and southern Appalachians
  for late Sunday and especially early next week. Wind chills may
  drop below zero across the higher elevations Monday night.

&&

.DISCUSSION...
Issued at 1228 AM EST Wed Dec 24 2025

Currently light showers are noted across southern Kentucky moving
east southeast into southwest Virginia and northern half of east
Tennessee. Isentropic lift is the main forcing especially around
the 295 and 300K levels. This forcing is the strongest over the
area until around 12-15Z. QPF amounts will be very light and
average less than 0.05 inch mainly north of interstate 40.

Main weather story for much of the week will be a strong upper ridge
of high pressure over the southern half of the United States with
the storm track over the Ohio valley into the central
Appalachians. This ridge will produce unusual warmth for late
December with highs around 20 degrees above normal. Near Record
highs are possible Christmas Day, Friday and Saturday across
Chattanooga.

Christmas Day:

                 Forecast High     Normal High      Record High
Chattanooga:           73               52               75
Knoxville Airport:     68               49               76
Tri-Cities:            64               48               74

A series of jet streaks will move quickly with the fast flow from
the Ohio valley into the central Appalachians for Wednesday
night/Thursday and again late Friday and Friday night. A frontal
boundary will also approach the area Thursday. Due to increasing
isentropic lift with each wave and fronto-genetic forcing, rain
showers chances increase during those periods. LREF and
deterministic models show the great coverage of rain over southwest
Virginia and northeast Tennessee then decreasing south. Overall, QPF
amounts for the latter half of the week will vary from around 0.25
inch over southwest Virginia to 0.05 or less around Knoxville.

A major pattern change will occur late this weekend into early
next week. Ensemble cluster analysis and deterministic models
show a digging upper trough over the eastern third of the nation.
A strong 300mb jet of 160-165kts digs into the Ohio valley and
central Appalachians producing a good deal of jet dynamics as a
strong frontal boundary moves into the area Sunday afternoon and
evening.

Deterministic models show increasing fronto-genetic forcing along
this frontal boundary due to the strength of the jet dynamics.
Widespread showers is becoming more likely Sunday afternoon into
early Sunday night.

Much colder airmass quickly moves into the region for Monday and
Tuesday with highs 30+ degrees colder than this week.  Wind chills
may drop below zero across the higher elevations Monday night with
single digits and teens in the valley.

&&

.AVIATION...
(06Z TAFS)
Issued at 1241 AM EST Wed Dec 24 2025

Surface observations and satellite imagery show that MVFR CIGS
across the region are not as solid as they were a few hours ago,
as evident by SCT-BKN bases at KTYS and KCHA with OVC050-060 decks
above. Still think that all sites lower to MVFR levels after
midnight but in light of these trends, feel that any IFR
categories will be limited to KTRI. Otherwise, these BKN-OVC low
clouds will continue through midday before scattering out this
afternoon at KCHA. Further north they likely hold on through the
period. Light to near calm winds are expected at all sites through
the period.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             72  55  73  57 /  10   0  10  10
Knoxville McGhee Tyson Airport, TN  68  57  68  58 /  30  20  40  40
Oak Ridge, TN                       67  56  68  57 /  30  20  40  40
Tri Cities Airport, TN              63  52  64  55 /  10  50  80  60

&&

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

$$

DISCUSSION...DH
AVIATION...CD