058
FXUS64 KMRX 141502
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
1102 AM EDT Wed Aug 14 2024

...New UPDATE...

.UPDATE...
Issued at 1048 AM EDT Wed Aug 14 2024

The cloud cover we saw for northern parts of the forecast area
this morning has dissipated with the increasing sunshine and
warmth. The rest of our forecast area currently is mostly sunny
with some cumulus development over the mountains and parts of SW
Virginia. Some weak shortwave energy paired with NWly flow may
support an isolated shower/storm over the higher terrain this
afternoon. As far as the immediate forecast, no big changes to
make note of; things seem to be on track.

KS

&&

.SHORT TERM...
(Today and tonight)
Issued at 308 AM EDT Wed Aug 14 2024

Key Messages:

1. Early morning patchy fog to quickly dissipate, dry weather to
continue outside of an errant shower in the high terrain. Patchy fog
again possible overnight.

Discussion:

Well not much different about today versus the weather yesterday,
upper level setup is still the same with the upper trough slowly
sliding eastwards now. What`s new is we have some patchy fog across
the Tennessee valley this morning according to area observations. So
despite low level flow not being overly supportive of increasing
moisture, the dewpoints have slowly trickled upwards the last couple
of days. Still, the suppression aloft will once again cap the
atmosphere, putting a halt on any air parcel`s dream of climbing the
atmospheric ladder and becoming a towering cumulus or more. That`s
not to say a shower isn`t possible, there were a handful in
northeastern TN into VA yesterday, but activity (and associated
rainfall) will be incredibly muted once more.

Heading into the nighttime hours, HREF and NBM sky cover depict
mostly clear skies, which should allow temperatures to once more
cool off to near dewpoint temperatures. If this morning is any
indication thus far, then patchy fog is again possible early
Thursday morning.

&&

.LONG TERM...
(Thursday through Tuesday)
Issued at 308 AM EDT Wed Aug 14 2024

Key Messages:

1. Mostly dry weather Thursday.

2. Scattered to numerous showers and storms Friday into Saturday,
with some strong to severe storms possible Friday into Friday night.

3. Drier for the remainder of the period but there still may be a
few showers/storms around at times.

Discussion:

Short wave ridging will be moving across our area aloft on Thursday,
providing one more mostly dry day. A few showers may pop up mainly
eastern mountains during the afternoon, but convective energy looks
very limited so thunder is unlikely. Temperatures will be near
seasonal normals.

The short wave ridge will move off to our east Friday night as an
upper trough over the western Great Lakes and Mississippi Valley
moves east and then over our area Friday/Friday night. A few showers
and thunderstorms may make it into our northwest counties late
Friday night, then scattered to numerous showers and storms can be
expected Friday into Friday night as the upper trough moves in.
Models are in decent agreement overall in showing increasing shear,
with effective bulk shear values in the 20 to 30 kt range generally
agreed upon for Friday.  Models disagree more on how much convective
energy will be available, with the NAM more aggressive than most
other model sources as is often the case. A look at the SREF mean
MLCAPES shows values generally in the 1000 to 1500 J/kg range, which
appears to be a reasonable compromise between the higher NAM
sounding values and the much less aggressive GFS (although it is
closer to the NAM). This would be supportive of more organized
convection and the possibility of some strong to severe storms.
Damaging winds and very heavy rainfall with the possibility of
localized flooding currently look like the main threats for Friday
into Friday night.

The cold front associated with this system is forecast to move
through Saturday with additional showers/storms, then slightly
cooler and drier air will move in as the front moves off to our
southeast and the upper trough axis shifts east of our area. Models
are not in good agreement for these later periods, but some weak
short wave energy may move through the northwest flow aloft on the
back side of the upper trough in the Sunday through Monday time
frame, with the possibility of additional convection. However, right
now convective coverage overall looks limited, and Tuesday looks
mainly dry. Temperatures should be near to a bit below seasonal
normals for the Sunday through Tuesday time frame.

&&

.AVIATION...
(12Z TAFS)
Issued at 720 AM EDT Wed Aug 14 2024

VFR and dry weather conditions expected to prevail through the TAF
period today. Winds will be light, generally northerly during the
day before weakening to calm or variable late. Uncertain about any
patchy fog impacts to KTRI late in the period. Notwithstanding the
current deck, clouds should be fairly scattered through the
period.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             92  71  91  72 /   0   0  10  10
Knoxville McGhee Tyson Airport, TN  89  67  90  70 /   0   0  10  10
Oak Ridge, TN                       89  66  89  70 /   0   0  10  10
Tri Cities Airport, TN              86  63  86  66 /  10   0  10  10

&&

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

$$

SHORT TERM...Wellington
AVIATION...Wellington