420
FXUS64 KMRX 191726
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
126 PM EDT Thu Sep 19 2024

...New AVIATION...

.UPDATE...
Issued at 1023 AM EDT Thu Sep 19 2024

No major updates to the forecast today, only minor changes.
Biggest change was lowering dewpoints this afternoon. Current
dewpoints trending lower than forecast. Decided to use NBM10, in
addition to yesterday`s obs, to make forecast adjustments through
the rest of the day. Even with these changes, min RH values this
afternoon only drop down into the mid to upper 40s for a few
locations. Otherwise, forecast on track.

&&

.SHORT TERM...
(Today and tonight)
Issued at 216 AM EDT Thu Sep 19 2024

Key Messages:

1. Isolated to scattered showers and possibly a few thunderstorms,
will confine to northeast Tennessee, southwest Virginia, and parts
of southwest North Carolina this afternoon and evening. Clearing
overnight.

2. Much warmer temperatures with highs in the 80s to near 90 in
Chattanooga, for example.

Discussion:

We start today on the back side of troughing aloft, thus
northerly flow. With time through Friday, heights aloft will also
be rising, a precursor of warming to come as well as dry weather.
Before that takes over the weather pattern for the weekend,
showers with maybe some rumbles of thunder will stretch south and
west again over the far northeastern parts of our forecast area.
Rainfall amounts look rather light, but of course could see more
under a heavier cell.

Elsewhere for the day, weather will be dry with markedly warmer
temperatures; highs in the mid to upper 80s for Knoxville and
Chattanooga. For comparison climatologically speaking, Knoxville
and Chattanooga will be about 5 degrees warmer than this date in
September normally averages. After sunset, precipitation will
diminish, skies will clear, and once again will have the chance of
isolated pockets of dense fog development Friday morning,
especially locations that see rain today.

&&

.LONG TERM...
(Friday through Wednesday)
Issued at 216 AM EDT Thu Sep 19 2024

Key Messages:

1. Continued well above normal temperatures (4-6 degrees) through
Monday.

2. High uncertainty for next week but in general, expect moderating
temperatures with gradual increase in rain chances.

Discussion:

An upper ridge, anchored over south Texas, will expand to the
northeast Friday through Sunday resulting in continued warmer than
normal temperatures and dry conditions across the forecast area.
Forecast highs in the low to mid 90s appear likely on Sunday for
central and southern TN valley areas. These aren`t record highs, but
at those values they will be within 3-4 degrees of calendar day
records. Something to keep an eye on certainly.

For next week, guidance continues to struggle on exactly how a
complicated upper pattern will evolve. Most guidance agrees that by
Monday the upper ridge will begin to flatten out as a trough/upper
low ejects eastward from the Rockies. Dry and warm conditions
continue on Monday. But there`s considerable disagreement with what
happens in the upper levels Tue onward. For now it appears the
initial trough will likely lay out a front somewhere from the Ohio
valley southwest through the Arklatex region, which will remain in
that general area through late in the period. This would result in
increased cloud cover and generally increasing rain chances across
the forecast area Monday night through the end of the period as
moist southerly/southwesterly low level flow and weak jet support
aloft aid in the potential for shower development. That said, not
sold on the combination of this continued level of warmth (4-6
degrees above normal) and increasing rain chances due to the
proximity of a stalled boundary. Seems like we either remain dry and
warm, or that we would see a notable downward tick in temperatures
due to rain and cloud cover. NBM is advertising both which isn`t out
of the realm of possibilities I guess, but seems less likely to me.
Toned down forecast highs and rain chances a bit too, for the Tue
onward time frame.

&&

.AVIATION...
(18Z TAFS)
Issued at 113 PM EDT Thu Sep 19 2024

VFR conditions through the period at CHA and TYS. Mostly VFR at
TRI until fog develops overnight, with LIFR conditions forecast.
Also, a few isolated showers and storms expected this afternoon.
However, not enough confidence in coverage to include VCSH or
VCTS at any site.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             65  91  65  93 /   0   0   0   0
Knoxville McGhee Tyson Airport, TN  63  89  62  91 /   0   0   0   0
Oak Ridge, TN                       62  89  61  91 /   0   0   0   0
Tri Cities Airport, TN              60  84  59  85 /  10   0   0  10

&&

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

$$

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