-- Discussion containing changed information from previous version are highlighted. --
722
FXUS64 KMRX 151454
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
1054 AM EDT Sat Jun 15 2024

...New UPDATE...

.UPDATE...
-- Changed Discussion --
Issued at 1031 AM EDT Sat Jun 15 2024

Surface high pressure is building into the area in the wake of a
very weak cold front, that is now working its way southward in MS,
AL, GA. Slightly drier air should be working its way southward as
well, as air from the Ohio Valley (where dewpoints are in the
50s) tries to make its way toward us. Dewpoints in the grids
needed to be lower a few degrees into the early afternoon to
account the drier air. This will also lower the Heat Index by a
few degrees into the early afternoon, but mid to late afternoon
grids did not need any adjusting. Temperatures will be hot for
sure this afternoon with Chattanooga to Knoxville corridor getting
to the mid 90s this afternoon, with the Heat Index getting in the
upper 90s in Chattanooga this afternoon. Farther north in the
forecast area, it won`t be as bad since some of the cooler drier
air has more success filling into those areas, with The Tri-cities
area only having Heat Index readings in the upper 80s. However,
tomorrow looks to be a step hotter everywhere.
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&&

.SHORT TERM...
(Today and tonight)
Issued at 338 AM EDT Sat Jun 15 2024

Key Messages:

1. Warmer today as upper ridge increases across the Tennessee
Valley.

2. Mostly dry with limited precip chances across the higher
elevations.

Discussion:

Warm again today, near or slightly warmer than Friday`s
temperatures, as a 590 dam 500mb ridge builds across the Tennessee
Valley and Southern Appalachians. Subsidence and dry air across
northeast Tennessee/southwest Virginia will result in some lower
RH values near 30 percent with more humid conditions across
southern portions of the forecast area where heat index values
will be in the mid to upper 90s. Ridging and subsidence will
limit rain chances to 10 percent or less, mainly across higher
elevations. Warm and clear tonight with patchy fog near area
lakes and rivers. With high pressure and upper ridging, dry
weather continues.

&&

.LONG TERM...
(Sunday through Saturday)
Issued at 338 AM EDT Sat Jun 15 2024

Key Messages:

1. Isolated to scattered storms are expected Sunday and Monday,
especially along the higher terrain. Highs will reach into the 90s
for most areas both days.

2. Drier conditions are expected Tuesday onward with temperatures
reaching into the 90s for most areas.

Sunday through Tuesday

At the start of the period, a 5,920m 500mb high will be centered
just to our east with surface high pressure over New England.
Surface flow will become more southerly with the recent frontal
boundary moving towards the north. This will allow for moisture
return and a continuation of hot and humid conditions. The increased
moisture, weak forcing aloft, and terrain considerations will
support diurnal convection, especially along the higher terrain and
further south closer to better moisture. This first run of the CAMs
does show pretty decent coverage throughout the day with MLCAPE of
1,000 to 1,500 J/kg. Storms could produce strong winds if they get
tall enough, but the coverage and intensity will also depend on the
influence of the surface high. On Monday, the 500mb high will
strengthen and move over the Mid Atlantic. With lingering moisture
and similar thermodynamics, diurnal convection is likely again,
especially along the higher terrain. Otherwise, hot and humid
conditions will continue with daytime highs certainly dependent on
the timing and coverage of convection both days.

By Tuesday, the 500mb high will become even more impressive, near
5,980m, as it moves up into New England. Locally, heights will reach
or exceed 5,940m, which are near record high values for the time of
year. Also, drier air will move in from our east, which will
diminish the potential for diurnal convection. This will lead to a
very hot day with highs likely reaching well into the 90s area-wide.

Wednesday through Friday

On Wednesday, 500mb heights will reach or exceed an even more
impressive 5,960m over our area. With continued surface high
pressure and drier air. Diurnal convection will remain unlikely.
This will also help to keep heat index values close to the air
temperature values in the 90s. Overall, similar conditions will
remain for Thursday and Friday with limited moisture keeping very
suppressed chances for diurnal convection.

&&

.AVIATION...
(12Z TAFS)
Issued at 602 AM EDT Sat Jun 15 2024

High pressure will result in prevailing VFR conditions with light
northeasterly winds. Patchy fog along Boone Lake is impacting TRI
this morning with tempo LIFR cigs, but impacts will fade by 14z.

&&

.PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN             96  72  95  75 /   0   0  20  10
Knoxville McGhee Tyson Airport, TN  92  69  93  72 /   0   0  30  10
Oak Ridge, TN                       94  67  93  71 /   0   0  30  10
Tri Cities Airport, TN              90  67  90  69 /   0   0  20  10
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&&

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

$$

SHORT TERM...GM
AVIATION...