289
FXUS64 KMRX 150231
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
1031 PM EDT Sun Jul 14 2024

...New UPDATE...

.UPDATE...
Issued at 1008 PM EDT Sun Jul 14 2024

Though they appear to be fading from radar since making changes,
did populate some showers for parts of the central plateau for the
next couple of hours. From about central plateau, to Knoxville, to
GSMNP and southward, mostly under two tenths of an inch was
recorded today from showers, that is if measuring equipment
captured it accurately. Highs today from mid-day climate verified
well against forecast. Everything else in the nearest term checks
fine besides some most recent obs being blended into the future
hourlies.

KS

&&

.SHORT TERM...
(This evening through Monday)
Issued at 306 PM EDT Sun Jul 14 2024

Key Messages:

1. Hot again on Monday with increasing moisture across the
southern valley and plateau.

2. Higher risk of diurnal convection on Monday afternoon, mainly
across the plateau and southern valley.

Discussion:

General persistence pattern continues with synoptic conditions
potentially resulting in slightly higher chances for diurnal convection
on Monday afternoon. Temperatures will be within a degree or two
of the past couple days with increasing moisture resulting in
higher heat index values between 100 and 105F for the southern
valley near Chattanooga.

While the 850mb ridge remains across the Southeast CONUS, a
weakness or col at 500mb will shift slightly eastward and will be
across Middle and West TN. These slightly lower heights aloft, and
increased moisture to our west, will result in some higher
convective coverage across the Midsouth and portions of the Lower
Tennessee River Valley. This is evident in RAP soundings which
show increasing moisture across the Cumberland Plateau and
portions of the southern valley near Chattanooga on Monday
afternoon. While LFC heights are around 3km this afternoon, they
lower to around 2km on Monday afternoon due to increased moisture.
Instability is also forecast to go from around 500 J/Kg this
afternoon to 1500 to 2500 J/Kg on Monday afternoon. This
thermodynamic environment will increase DCAPE to around 1000 J/Kg
across the plateau and southern valley on Monday afternoon with a
low risk for stronger, potentially severe thunderstorms capable of
damaging downburst wind gusts. Further north across the central
valley through northeast TN and southwest VA, drier air remains
with more limited rain and thunderstorm chances.

Daily Record High Maximum Temperatures

Date    Chattanooga    Knoxville      Tri-Cities     Oak Ridge
07-14   103(1954)      101(1954)      98(1954)       101(1954)

&&

.LONG TERM...
(Monday night through next Sunday)
Issued at 306 PM EDT Sun Jul 14 2024

.LONG TERM...

Key Messages:

1. Extreme heat will continue on Tuesday with highs in the mid to
upper 90s and heat index values into the 100s across much of the
area.

2. Scattered storms are expected on Tuesday with more numerous
coverage Wednesday and Thursday. Lower chances continue into this
weekend with temperatures dropping to below normal.

Monday Night through Thursday

At the start of the period, quasi-zonal flow will be in place aloft
with weak embedded shortwaves and surface high pressure receding to
the south. During this time, 500mb heights will still be above
5,900m with near record 850mb temperatures reaching to 21 Celsius by
the day on Tuesday. A shift to weak southerly flow will advect some
moisture into the area, which will increase humidity in comparison
to recent days. Accordingly, temperatures will not reach quite as
high as the days prior, but heat index values will still rise into
the 100s. The increase in moisture will also bring chances for more
scattered convection, mainly along the higher terrain due to weak
forcing overall.

On Wednesday, troughing from the north will deepen, leading to
height falls and further suppression of high pressure. A frontal
boundary will be noted north of the Ohio River Valley. As this front
approaches from the north, additional, more widespread chances of
convection exist on top of terrain-based development. By Thursday,
the front will likely reach near the area, providing additional lift
and further reduction in temperatures. It is still unclear how much
coverage there will be because of the significant drought and recent
trends. But the pattern does look promising for more substantial
rain chances, which are very much needed due to worsening drought.

Friday through Sunday

Late in the week and into the weekend, the main question will be how
far south the frontal boundary reaches, which will affect the
available moisture and overall forcing. Much of this timeframe will
see more of a troughing pattern, keeping temperatures more moderated
and even slightly below normal. Based on these indications, daily
rain chances were maintained, but confidence is still limited based
on the persistent dryness recent model biases.

Daily Record High Maximum Temperatures

Date    Chattanooga    Knoxville      Tri-Cities     Oak Ridge
07-15   103(1977)      98(1995)       96(1995)       100(1980)
07-16   105(1980)      100(1980)      100(1988)      103(1980)
07-17   103(1980)      101(1980)      94(1980)       103(1980)

&&

.AVIATION...
(00Z TAFS)
Issued at 739 PM EDT Sun Jul 14 2024

VFR expected for most of the period at all sites except an increasing
chance of showers and thunderstorms Monday afternoon at CHA.
PROB30 added to reflect that chance. Cloud cover expected to
increase at all levels into Monday afternoon as moisture is
advected into southern parts of the CWA. Otherwise, winds expected
to be light from the south to westerly direction.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             75  98  74  96 /  10  30  20  50
Knoxville McGhee Tyson Airport, TN  73  97  74  95 /   0  20  10  40
Oak Ridge, TN                       72  98  73  95 /   0  20  10  40
Tri Cities Airport, TN              68  95  69  93 /   0  10  10  40

&&

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

$$

SHORT TERM...JB
LONG TERM....BW
AVIATION...KS