006
FXUS64 KMRX 151802
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
202 PM EDT Thu Aug 15 2024

...New AVIATION...

.UPDATE...
Issued at 1030 AM EDT Thu Aug 15 2024

A couple of light showers have developed over Greene County within
the past hour or so. Expect this trend to continue through the
afternoon and early evening where light showers and maybe a
thunderstorm possible over and adjacent to the Appalachians. A
couple hundredths to a couple tenths of an inch did fall over
isolated parts of the higher terrain yesterday. Inherited forecast
check out okay, only minor tweaks to some PoP and cloud cover,
mostly.

KS

&&

.SHORT TERM...
(Today and tonight)
Issued at 314 AM EDT Thu Aug 15 2024

Key Messages:

1. Dry weather to continue, humidity a little higher today.

Discussion:

Narrow upper ridge axis will be sliding overhead today, with sinking
air over the wider region. 00z CAMs are quiet with most forming
light returns over the mountains, whereas the most recent HREF
had at least some activity dotting both the mountains and the rim
of the Plateau. Left a slight chance for a shower in over the
East Tennessee Mountains, where the better low level CAPE might
allow for a brief shower during peak heating. Very unlikely for
anyone in the valleys to see rainfall once again today.

Otherwise low level winds will finally pivot to a more southerly to
southwesterly flow, and while they`ll remain weak, it marks the
beginning of low level moisture flowing northwards once more.
Depending on cloud coverage tonight, it might also allow for another
round of patchy fog, especially with guidance keeping rain at bay
through sunrise on Friday.

&&

.LONG TERM...
(Friday through Wednesday)
Issued at 314 AM EDT Thu Aug 15 2024

Key Messages:

1. Scattered to numerous showers and storms Friday and Saturday,
with some strong to severe storms possible.

2. More scattered showers/storms possible Sunday and Monday, with
better coverage across the north.

3. Dry Tuesday and Wednesday.

Discussion:

Models are in general agreement that an upper low over the western
Great Lakes region early Friday will move east/southeast with
multiple short waves dropping southeast around the back side,
carving out a significant upper trough over the eastern CONUS by
early in the week. However, the models differ significantly in the
details and have been rather inconsistent. Timing and strength of
the individual short waves is uncertain as is the timing of a cold
front that will drop southeast across our area sometime in the
Saturday/Saturday night time frame, which leads to uncertainties in
how the convection will unfold. The overall environment continues to
show significant effective bulk shear for this time of year although
latest runs have generally trended a bit lower for Friday with
values more in the 15 to 25 kt range, and show the higher values of
20 to 30+ kt for Saturday. Models vary widely on how much convective
energy will be available as well, but perusing the HREF and SREF
ensemble means would suggest SBCAPES will be in the 500-1500 J/kg
range Friday and more like 1000-2000 J/kg Saturday. Overall the
atmosphere looks supportive of more organized convection with some
strong to severe storms possible both Friday into Friday evening and
again Saturday. Damaging winds will be the primary severe threat
with these storms. In addition, any areas that see repeated and/or
prolonged rounds of heavy rainfall may experience localized
flooding.  Poor agreement in the CAMS does not lend high confidence
to timing of convection Friday, but current thinking is it will be
focused more late morning into the evening hours and this will
likely be the case for Saturday as well.

Additional upper short wave features are expected to be moving
through the upper trough and are expected to bring additional
showers/storms Sunday and to a lesser extent Monday with the better
coverage across the north. Cooler air will also be moving in behind
the front, with temperatures likely below normal both days.

Surface high pressure will build in from the north Tuesday as the
trough axis shifts further east, providing dry weather both Tuesday
and Wednesday along with a slight warming trend.

&&

.AVIATION...
(18Z TAFS)
Issued at 135 PM EDT Thu Aug 15 2024

VFR will prevail for much of the period. Calm conditions expected
overnight with possible patches of fog around TRI with the
continued influx of warm moist air. Winds will increase out of the
southwest once day time begins Friday. For the last couple hours
of the 18Z TAF period, showers and thunderstorms enter the picture
from the west. Timing is still not all that certain, even between
convective allowing models. PROB30s introduced starting at either
14 or 15Z to indicate the possibility of MVFR conditions due to
storms.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             72  93  73  91 /  10  40  50  70
Knoxville McGhee Tyson Airport, TN  71  90  71  88 /  10  50  70  70
Oak Ridge, TN                       70  89  70  88 /  10  50  70  60
Tri Cities Airport, TN              66  85  69  84 /  10  50  70  60

&&

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

$$

SHORT TERM...Wellington
AVIATION...KS