829
FXUS64 KMRX 060526
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
126 AM EDT Sat Jul 6 2024

...New AVIATION...

.UPDATE...
Issued at 939 PM EDT Fri Jul 5 2024

Forecast is generally on track tonight with drier weather expected
tonight and Saturday. There will still be a 10 to 20 percent
chance of showers over the next 6 to 9 hours as the front moves
across the area, mainly across northern counties through southwest
Virginia.

&&

.SHORT TERM...
(This evening through Saturday)
Issued at 330 PM EDT Fri Jul 5 2024

Showers and thunderstorms have been moving across much of the
forecast area this afternoon. With the moist and unstable airmass
with mixed layer CAPE values 1500 to 2500 J/KG ahead of the
convection some strong storms have occurred. Precipitable water
values continue to be very high 1.9 to 2.2. Dew points ahead of
the convection were in the mid 70s and heat index values have
reached around 105 in a few locations. With the temperature drop
behind the storms heat index values have dropped.

The risk for more storms is now lower because of the cooling with
the remaining threat just the far eastern part of the forecast
area the rest of the afternoon. Highest rain chances will be this
afternoon, then decreasing this evening and overnight. For tonight
the front over middle TN will move across this evening and into
early Saturday. Slight chance to chance showers/storms extreme
east. Lows tonight will still be warm in the lower to mid 70s but
cooler than this morning. Also patchy fog will form in the areas
with significant rainfall. Saturday with upper ridge to the south
and upper trough moving in temperatures will be cooler in the
upper 80s to lower 90s. Lower dew points will be observed by all
with the numbers in the mid to upper 60s so heat index values will
only be in the lower to mid 90s. With the front close to the
mountains a few showers and storms my form but likely move quickly
east of the Appalachians.

&&

.LONG TERM...
(Saturday night through next Friday)
Issued at 330 PM EDT Fri Jul 5 2024

Key Messages:

1. Mostly dry conditions continue into Sunday.

2. First half of next week looks fairly active, so confidence is a
little higher for better afternoon thunderstorm coverage each day.

Discussion:

The Tennessee valley and southern Appalachian region will remain
situated beneath southwesterly flow aloft for much of the long term
period, with troughing over the mid-Mississippi and Ohio valleys and
ridging off the southeast coast. In general, this will mean chances
for diurnally driven showers and thunderstorms most everyday from
Monday onward, with the best chances over higher terrain as is usual
in the summer.

We`ll be in a dry air advection regime Sat night, but by Sun morning
low level flow will begin to turn out of the southeast and bring
some better moisture content back our direction from the Carolinas.
Upslope flow into the southern Appalachians will likely be enough
for at least some isolated convection in the mountains so will keep
some slight chance PoPs through the morning hours in TN mountains
zones. Coverage should increase Sun afternoon with steering flow
pushing storms off into the lower elevations...but the best chances
will remain in the mountains. Don`t drop rain chances Sunday night
as the pattern could support some nocturnal convection, but coverage
should be limited.

Monday through the midweek time frame should see notably higher rain
chances, with southeast/southerly boundary layer flow allowing for
moisture return with theta-e ridge axis pulling into east Tennessee.
Best chance of diurnal convection will remain in orographically
favored mountains and plateau zones on Monday and Tuesday, but
outflow boundary interactions and steering flow pushing storms off
the Appalachians should yield fairly decent rain chances most
everywhere. By Wednesday and Thursday, persistent southwest flow and
the possibility of moisture associated with Beryl being siphoned off
and shot this direction should lead to a steady increase in
afternoon convective coverage.

&&

.AVIATION...
(06Z TAFS)
Issued at 118 AM EDT Sat Jul 6 2024

Patchy fog is starting to develop across the region. TRI and TYS
will likely see fog and low CIGs in the early morning hours but
there is some uncertainty with how dense and widespread the fog
will be. Fog and low CIGs will lift shortly after sunrise.
Otherwise, VFR conditions will prevail this TAF cycle with very
low rain chances. Light winds will become more northerly this
morning as a cold front moves through the region.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             94  72  94  74 /   0  10  20  20
Knoxville McGhee Tyson Airport, TN  92  70  92  73 /  10  10  20  20
Oak Ridge, TN                       92  69  93  72 /   0   0  10  20
Tri Cities Airport, TN              89  67  90  69 /  10  10  20  20

&&

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

$$

SHORT TERM...TD
LONG TERM....CD
AVIATION...McD