363
FXUS64 KMRX 160210 AAA
AFDMRX

Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
1010 PM EDT Wed May 15 2024

...New UPDATE...

.UPDATE...
Issued at 1007 PM EDT Wed May 15 2024

The forecast looks on track this evening, so no changes are
planned. Showers have been waning with the loss of heating after
sunset, as as the upper trough continues to move east of the area.
Drier midlevel air will build in behind the trough, but low level
moisture will likely result in low clouds and fog increasing as
the boundary layer cools. The forecast appears to cover this
situation well.

&&

.SHORT TERM...
(This evening through Thursday)
Issued at 213 PM EDT Wed May 15 2024

Key Messages:

1. Scattered showers and possibly a thunderstorm expected through
the evenings hours. A low-end chance of a strong storm with gusty
winds and small hail.

2. Patchy areas of fog will develop overnight/early Thursday
morning. Some of the fog may become locally dense.

3. Drier and warmer conditions return for Thursday afternoon.

Discussion:

Currently, an upper trough moving across the southern Appalachians
is producing scattered showers and possibly a thunderstorm.
Vertical profile shows a fairly saturated airmass with marginal
MLCAPE of 500-1000 J/Kg. Effective shear is limited at best with
values of 20-25 knots. Mid-level lapses rates are only around 6
degrees, but WBZ heights relatively low from 8500-9000, can not
rule out a strong storm producing small hail and gusty winds up to
35 mph.

The convection will diminish quickly by sunset as we loss
insolation.

For Tonight/Early Thursday morning, a saturated boundary layer
will allow for redevelopment of low-clouds and fog. NBM fog
probabilities show the potential of patchy dense fog.

For Thursday, upper trough builds across the region with the
airmass drying out. Much drier day is on tap with a gradual
clearing of low-clouds/fog during the morning becoming mostly
sunny/partly cloudy in the afternoon. A low-end chance of showers
exists across the terrain of southwest Virginia and northeast
Tennessee.

&&

.LONG TERM...
(Thursday night through next Wednesday)
Issued at 213 PM EDT Wed May 15 2024

Key Messages:

1. Showers, and some thunderstorms, likely Friday and Saturday, with
chances lingering into Sunday.

2. Severe weather risk appears low with the highest probabilities
remaining across the Lower Mississippi Valley.

3. Ridging builds in next week leading to temperatures climbing near
90 degrees by Tuesday.

4. Cold front brings increasing rain/thunderstorm chances next
Tuesday night and Wednesday.

Discussion:

As troughing amplifies across the Southern Plains through the Lower
Mississippi Valley, southwesterly flow aloft will increase across
our forecast area with isentropic lift bringing increasing clouds
and rain chances on Thursday night into Friday morning. A warm front
is expected to lift northward across the region Friday night with
rain showers ahead of this boundary.

There is still substantial disagreement in model solutions with two
potential outcomes: a quicker moving open wave trough or a
slower closed/semi-cutoff low? In either case, Saturday continues to
look wet across the region with the Tennessee Valley/Southern
Appalachians on the eastern side of the trough or closed low with
upper-level jet dynamics favoring more widespread synoptic ascent.

The severe weather risk appears low with better instability across
the Lower Mississippi Valley on Friday and limited instability on
Saturday. It`s not out of the question that some thunderstorms
become strong or severe across the forecast area during this time,
but the higher probabilities will be to our south. The CIPS analog
guidance reinforces this view with higher probabilities for 1+
severe weather reports across the Lower Tennessee Valley across
Alabama and southward through the Lower Mississippi Valley.

There is higher uncertainty on Sunday`s weather. With the quicker
moving solution, we should be clearing out with drier weather; but
in the slower solution, we will be wet with continued scattered rain
showers possible. Either way, Sunday`s precipitation chances will be
lower than Friday and Saturday with clearer weather expected on
Sunday night into early next week.

Ridging begins to build in early next week with temperatures warming
up above normal across the region. Temperatures near 90 degrees will
be possible by Tuesday with another cold front approaching from the
northwest with increasing shower and thunderstorm chances on Tuesday
night and Wednesday.

&&

.AVIATION...
(00Z TAFS)
Issued at 715 PM EDT Wed May 15 2024

Afternoon showers and abundant low level moisture will likely
result in fog and/or low cigs forming tonight at TYS and TRI.
Confidence is highest at TRI where rain is falling now and
temp/dewpoint spread is already low. Expect IFR to LIFR conditions
there. TYS may have some light wind overnight so low cigs are
expected to prevail, likely in the MVFR/IFR range. Conditions at
both sites will improve in the morning, with VFR prevailing by
noon. CHA is expected to maintain VFR conditions through the
period.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             78  60  85  64 /  60  10   0  10
Knoxville McGhee Tyson Airport, TN  74  60  80  60 /  70  40  10   0
Oak Ridge, TN                       75  59  81  60 /  70  30  10   0
Tri Cities Airport, TN              71  58  76  58 /  70  50  20   0

&&

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

$$

SHORT TERM...DH
LONG TERM....JB
AVIATION...DGS