286
FXUS64 KMRX 050727
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
327 AM EDT Sun May 5 2024

...New SHORT TERM, LONG TERM...

.SHORT TERM...
(Today and tonight)
Issued at 322 AM EDT Sun May 5 2024

Key Messages:

1. Warm today with isolated diurnal convection mainly across
higher terrain.

2. Increasing rain chances tonight as more potent shortwave
transits eastward across the Tennessee Valley and into the
Southern Appalachians.

Discussion:

Subtle shortwave this morning is resulting in some isolated to
scattered convection across the area. This disturbance will move
east of the region this morning with drier conditions through
mid-day. Increasing chances of convection across the higher
elevations is expected this afternoon once again, but overall,
rain chances will be limited to slight chance/chance (<50
percent) for most areas. Shortwave ridging and southerly flow will
result in warm temperatures across the area.

By tonight, a stronger shortwave and associated longwave troughing
will shift eastward into the Tennessee Valley. Upper level
diffluence will overspread the region as we approach Monday
morning with increasing chance for widespread rain showers and
some embedded thunderstorms.

&&

.LONG TERM...
(Monday through Sunday)
Issued at 322 AM EDT Sun May 5 2024

Key Messages:

1. Scattered to numerous showers and storms are likely through much
of the week.

2. Strong to severe storms are increasingly possible Tuesday to
Thursday. Localized flooding is also possible as places receive
repeated, locally heavy rainfall.

3. Temperatures will remain near to above normal through Thursday
with notably cooler conditions Friday into the weekend.

Monday through Wednesday

At the start of the period, a shortwave will be moving into the area
from the west with broad moisture and instability in place across
most of the eastern United States. This initial setup will continue
showers and thunderstorms with coverage above and beyond that of
Sunday. At this point, shear will still be pretty weak with
thermodynamic means (MLCAPE around 1,000 J/kg) being the continued
support for the storms. With PWAT values back up above the 90th
percentile (near 1.5 inches), heavy downpours are likely again
within any storms. Isolated flooding will remain of concern,
especially in places that see repeated storms.

By Tuesday, a more organized synoptic pattern is expected with the
upper jet strengthening to over 100 kts north of the Ohio River
Valley. 850mb flow will also be strengthening to >30 kts with
similar moisture and potentially even better instability in place.
Current model data suggests repeated rounds of convection in our
area with a potential MCS arriving in the evening hours. Winds will
be veered through the profile with a broad consensus of near 40 kts
of deep-layer shear. While instability and timing will be more
favorable to our west, strong/severe convection is certainly
possible, especially in western portions of the area.

By Wednesday, the synoptic pattern will become even more favorable
with another near 100 kt jet extending through the lower Mississippi
River Valley, promoting additional upper divergence. Both deep-layer
shear and instability are indicated to be even higher than on
Tuesday. Multiple rounds of convection are indicated again with a
possibly more robust MCS arriving in the evening to overnight hours.
Uncertainty still remains, but the general pattern continues to
increase confidence in the potential for strong to severe storms mid-
week with damaging winds as the primary concern. This timeframe
continues to bear watching for flooding, in addition to the
aforementioned severe threat.

Thursday through Saturday

On Thursday, a frontal boundary will move into the area from the
west, which will provide continued chances for showers and storms.
Depending on how much cloud cover is lingering from overnight
activity, instability may be more limited than on Tuesday and
Wednesday. Also, as the upper-level pattern becomes more zonal,
winds will be more uni-directional through the column. In any case,
Thursday will be a time of additional rainfall on top of the several
days prior. By Friday, the front will likely have moved through the
area with deepening mid/upper troughing. This will usher in cooler
temperatures with additional showers and/or isolated thunderstorms,
depending on how far the front and antecedent moisture progresses.
On Saturday, deep troughing will keep cooler conditions with
expansion of high pressure to our west leading to a reduction in
rain chances.

&&

.AVIATION...
(06Z TAFS)
Issued at 105 AM EDT Sun May 5 2024

Sct showers and thunderstorms are moving eastward across the
region early this morning associated with a subtle upper level
feature. This convection is currently impacting CHA and may impact
TYS and TRI over the next few hours. Drier weather is expected by
10z across the region with shortwave ridging limiting convective
coverage. Winds will be generally light with a diurnal trend in
convective probabilities as low chances of showers and
thunderstorms increase on Sunday afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             86  65  83  65 /  30  50  80  40
Knoxville McGhee Tyson Airport, TN  82  63  80  63 /  40  30  70  50
Oak Ridge, TN                       83  62  80  63 /  40  30  70  40
Tri Cities Airport, TN              80  60  78  61 /  50  30  70  40

&&

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

$$

SHORT TERM...JB
LONG TERM....BW
AVIATION...JB