084
FXUS64 KMRX 130522
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
122 AM EDT Sat Jul 13 2024

...New AVIATION...

.UPDATE...
Issued at 832 PM EDT Fri Jul 12 2024

Did wind up having a few isolated showers develop over the terrain
of the plateau late this afternoon and early evening. Those are on
the decline now and do not expect any further development.
Wouldn`t be surprised to have a similar scenario tomorrow as well.
Upper heights will rise tomorrow, but there`s a subtle shortwave
moving into western Kentucky this evening that will continue to
shift eastward tonight and through the day tomorrow. That could
hamper the effects of rising heights enough for there to be
another instance of some isolated showers over the higher terrain
of the plateau and certainly the Appalachians. That said, steering
flow, albeit weak, would likely keep any mountain convection on
mainly the NC side of things so the plateau may have relatively
speaking better odds. In any case, not enough confidence in this
low-impact aspect of the forecast (nearly all areas will be dry)
to consider making edits at this time.

Also made some slight adjustments to temperatures and dewpoints
through roughly midnight to account for current trends. Blended in
some of the latest HRRR which is slightly slower to cool temps
off and bring dewpoints up. Nothing significant though, and the
forecast seems to be in good shape otherwise.

&&

.SHORT TERM...
(This evening through Saturday)
Issued at 329 PM EDT Fri Jul 12 2024

Key Messages:

1. The area is likely to stay dry with even hotter temperatures on
Saturday in the mid to upper 90s across most of the area.

This Evening/Tonight

Currently this afternoon, weak upper troughing is centered to our
west with surface high pressure. Model sources indicate lower than
average PWAT values for mid July, around or even below 1 inch. Weak
flow from the N to NE has been around 5 to 10 kts and will continue
overnight. PoPs are low, however some scattered showers are possible
in our northeastern counties, due to fairly subtle surface troughing
to our east. Patchy fog is certainly possible in the northeast, but
continued dry air will limit development. With how dry conditions
are today, many places will likely drop into the 60s by the morning.

Tomorrow

Hot and dry conditions will continue as 500mb heights rise to around
5,940m. Dew points and PWATs are slightly higher, but much of the
region can still expect below average moisture. Winds become
northwesterly Saturday afternoon and evening. Model agreement
indicates MLCAPE values slightly higher than today with most areas
around 500 J/kg. Orographic lift from northwesterly flow could bring
isolated convection along the mountains, but this potential is very
limited due to continued dry air and subsidence. 850mb temperatures
will rise beyond 20 Celsius, which suggests that many areas will
rise well into the 90s. However, heat index values shouldn`t be too
much higher because of drier air due to the deep mixing and
subsidence.

&&

.LONG TERM...
(Saturday night through next Friday)
Issued at 329 PM EDT Fri Jul 12 2024

Key Messages:

1. Warming trend continues this weekend into early next week, with
the potential for record breaking daily high temperatures for the
start of the work week.

2. Outside of an isolated high elevation shower/storm, mostly dry
conditions are expected through the middle of next week.

3. Chances of precipitation begin to increase by late next week as a
weakness in the ridge develops.

Discussion:

Ridging will continue to dominate our weather through the weekend
and middle part of next week. This will result in continued dry
weather, sunshine, and warm 850mb temperatures around 22 to 25 deg C
across the Southern Appalachians and Tennessee Valley. Based on
these warm boundary layer temperatures, most model and statistical
guidance is placing max temperatures in the upper 90s to lower 100s
across the region which would be near record max high temperatures.
A few isolated showers or thunderstorms may be able to develop
across the higher elevations due to the differential heating along
the high terrain, but probabilities are less than 20 percent. Lack
of deep moisture and continued ridging will limit instability for
convection. This hot and dry pattern will likely exacerbate drought
conditions over the coming week.

By late next week, a weakness in the ridge is expected to develop
across the Mississippi Valley with increased convective coverage.
The question is how much convection will make it into our area with
continued ridging across the Southeast limiting the eastern
progression of precipitation. There are signals that perhaps we get
some relief with precipitation in the week two period, as seen in
the latest CPC 6 to 14 day outlooks, but confidence is low. At this
point, chances for meaningful rainfall coverage and amounts is not
very high over the next 7 days.

Daily Record High Maximum Temperatures

Date    Chattanooga    Knoxville      Tri-Cities     Oak Ridge
07-12   104(1930)      104(1930)      93(1993)       100(1980)
07-13   105(1980)      100(1936)      96(1993)       100(1980)
07-14   103(1954)      101(1954)      98(1954)       101(1954)
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...
(06Z TAFS)
Issued at 117 AM EDT Sat Jul 13 2024

VFR conditions through the period at all sites with light and VRB
winds.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             98  75  99  75 /  10   0  10   0
Knoxville McGhee Tyson Airport, TN  95  72  97  72 /   0   0  10   0
Oak Ridge, TN                       95  71  96  72 /  10   0  10   0
Tri Cities Airport, TN              92  67  93  68 /  10   0  10  10

&&

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

$$

SHORT TERM...CD
LONG TERM....JB
AVIATION...