600
FXUS64 KMRX 230200
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
1000 PM EDT Sun Jun 22 2025

...New UPDATE...

.UPDATE...
Issued at 958 PM EDT Sun Jun 22 2025

Overall, limited changes were made with the evening update.
Temperatures were running slightly warmer, so they were raised.
Also, some limited shower coverage in southeast Tennessee to the
North Carolina border led to added PoPs. Otherwise, the forecast
was kept the same.

&&

.SHORT TERM...
(This evening through Monday)
Issued at 211 PM EDT Sun Jun 22 2025

Key messages:

1. Hot and dry most everywhere.

2. Isolated to scattered storms over the higher terrain both
today and Monday.

Discussion:

A strong upper ridge will remain situated to our northeast through
the short term. That will keep temperatures some 5 to 7 degrees
above normal, with highs in the low to mid 90s expected on Monday.
We`re not yet knocking on the door of heat advisory or warning
criteria but it will be warm nonetheless, with afternoon heat index
values near 100 this afternoon and likely reaching 100-103 in places
tomorrow. Have continued with the night shift`s thinking of the past
couple of days with regards to lowering dewpoints with respect to
the NBM output. It is simply too high. Mixed in some NBM 10th
percentile, but also some CAM guidance to keep dewpoints around or
even slightly below 70 degrees tomorrow.

Regarding rain chances, the ridge won`t be strong enough to
completely suppress convection and expect similar conditions to
what`s occurring this afternoon. Any showers and thunderstorms that
develop will initiate over the higher terrain of the plateau and
east TN mountains, primarily south of I-40. I do have some PoPs into
higher terrain of northeast TN and our VA counties tomorrow. But if
I`m honest, with those areas being closer to the ridge axis I would
be a bit surprised if they saw anything develop. However there`s
some signal in a few guidance sources so I left it in. Lack of
strong steering currents means that storms would be short lived and
nearly straight up and down. Thus, once they collapse any outflow
boundary interactions could result in some convection propagating
out into the valley. However, that should be very hit and miss so
PoPs will largely stay confined to the terrain both this afternoon
and on Monday.

&&

.LONG TERM...
(Monday night through next Sunday)
Issued at 211 PM EDT Sun Jun 22 2025

Key Messages:

1. Hot temperatures, with highs in the mid or even upper 90s at
times, for the week ahead.

2. Diurnal shower and thunderstorm activity will favor higher
terrain though the mid-week. Coverage and chances of afternoon
convection is expected to increase late week and into the weekend as
high pressure gradually weakens.

Discussion:

By mid-week the afternoon temperatures and associated heat indices
will be approaching the peak of this on-going heat wave as a ~598mb
H5 high centers over south-central Appalachia. This is around 2-3
standard deviations above normal according to NAEFS ensemble data.
Blended NBM/NBM10th together for afternoon dewpoints in effort to
account for the often wet bias in extended periods and the HI is
still generally encroaching Advisory criteria Tue/Wed afternoon,
thus, a product may need to be considered in the near future. The
big question is how effective afternoon mixing will be in
transporting lower dewpoints to the surface. As higher resolution
model runs become available we should start to get a better idea on
this process. Strong diurnal heating will continue to promote
afternoon & evening shower and storm development generally favoring
higher terrain locations through mid-week.

By the second half of the week the upper heights and surface high
pressure show signs of minor deamplification. While temperatures may
trend down a few degrees, the heat continues with indices in the
upper 90s to low 100s. The main implication will be increasing
coverage of diurnal convection as there will be less subsidence
opposing the strong thermodynamic profile. As with general
summertime thunderstorms brief heavy downpours and gusty winds are
possible always a possibility.

A shortwave propagating across the very northern CONUS will promote
continued weakening of ridging and high pressure as we head into the
weekend. This will result in slightly cooler temperatures(upr 80s
lwr 90s) and potential for enhanced coverage of diurnal convection
once more.

Daily Record High Maximum Temperatures

Date    Chattanooga    Knoxville      Tri-Cities     Oak Ridge
06-24   101(1988)      102(1988)      96(1988)       101(1988)
06-25   102(1952)      99(1988)       97(1952)       98(1988)
06-26   101(1988)      101(1988)      96(2024)       100(1988)

Daily Record High Minimum Temperatures

Date    Chattanooga    Knoxville      Tri-Cities     Oak Ridge
06-24   75(1896)       76(2015)       70(2015)       75(2015)
06-25   77(2022)       77(1952)       71(1949)       74(2022)

&&

.AVIATION...
(00Z TAFS)
Issued at 712 PM EDT Sun Jun 22 2025

Very quiet aviation conditions are expected with variable winds
and minimal cloud cover in the 5,000 to 10,000 foot range. Patchy
fog is possible (mainly at TRI), but it was still left out of the
TAF because of limited confidence.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             72  95  74  98 /   0  10   0  10
Knoxville McGhee Tyson Airport, TN  71  94  73  97 /   0  10   0  10
Oak Ridge, TN                       72  94  72  97 /   0  10   0  10
Tri Cities Airport, TN              68  92  69  94 /   0  10   0  10

&&

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

$$

SHORT TERM...CD
LONG TERM....KRS
AVIATION...BW