229
FXUS64 KMEG 220451
AFDMEG

Area Forecast Discussion
National Weather Service Memphis TN
1151 PM CDT Tue May 21 2024

...New AVIATION...

.UPDATE...
Issued at 940 PM CDT Tue May 21 2024

A very mild night across the Mid-South at this hour. Temperatures
are in the upper 70s to lower 80s with mid 60s dewpoints along and
west of the Mississippi River. Immediately to our west, a tornado
watch was issued about 30 minutes ago. The latest KLZK radar sweep
reveals a line of several supercells to the north and west of
Little Rock. The environment there is well supportive of
all hazards with over 2000 J/kg of MLCAPE, 60 knots of bulk
shear, and 300 m2/s2 of SRH. Storm motion is pretty healthy at
around 40 mph and a couple of warnings are currently in effect in
LZK`s CWA.

Downstream, the latest mesoanalysis data over eastern Arkansas is
less robust. The majority of the region is capped with and MLCAPE
values around 1000 J/kg. The latest Hi-res model guidance
suggests that the storms will likely congeal into a line and
contain pose a large hail and damaging wind threat. Although LCLs
are around 1500 meters, a low-end tornado threat will also exist,
mainly in eastern Arkansas. Additionally, mid-level lapse rates
are exceptional coming in around 8.5 C/km.

Storms are progged to arrive in eastern Arkansas within the next
2 hours or so. The overall trend should be a weakening state, but
the discrete supercell north of Little Rock may continue to chug
east with only slight weakening into eastern Arkansas. The line or
storms will likely weaken and break apart as it approaches the
Mississippi River around midnight. Although there is no official
mesoscale discussion, the chance of a convective watch should
remain below 50 percent.

Increased PoPs in the short term to account for the faster storm
arrival. The rest of the forecast is in good shape with no further
edits needed at this time.

AC3

&&

.SYNOPSIS...
Issued at 327 PM CDT Tue May 21 2024

A ridge of high pressure will weaken tonight with a cold front
bringing a return of shower and thunderstorm chances back to the
Mid-South. A strong to severe thunderstorm is possible across
portions of northeast Arkansas and the Missouri Bootheel late
tonight, However, the greatest potential for severe thunderstorms
will be Wednesday afternoon into Wednesday night across the Mid-
South. Damaging winds will be the primary severe weather threat
with a secondary threat of large hail, heavy rainfall, and
possibly a tornado. A period of unsettled weather will persist
across the Mid-South beginning late tonight and continuing through
early next week.

&&

.DISCUSSION...
(This evening through next Monday)
Issued at 327 PM CDT Tue May 21 2024

GOES-16 Water Vapor Satellite trends this afternoon show a mid-
level trough moving into the Upper Midwest, an elongated
upper-level ridge present from the Great Lakes Region back through
the Southeast U.S. and portions of the Lower Mississippi Valley.
This has resulted in another warm and dry afternoon with
temperatures in the middle to upper 80s as of 2 PM CDT. Strong to
severe thunderstorm potential will remain the predominant concern
in this afternoon`s forecast issuance, especially for the next
two days.

Short-term models indicate the aforementioned upper-level ridge
will begin to break down tonight across the Lower Mississippi
Valley with 20-30 dm 500 mb height falls occurring north of I-40.
A mid-level shortwave trough and associated cold front will drop
into the Mid-South late tonight into Wednesday morning bringing a
return of showers and thunderstorms back to the area. Short-term
models, particularly the operational CAMs have struggled with the
overall evolution of convection across the Mid-South into
Wednesday night. Nonetheless, a broken convective line is
expected to gradually weaken north of I-40 overnight. Steep
700-500 mb mid-level lapse rates, surface-based CAPE values, and
0-6 km bulk shear values between 40-45 kts suggest a potential for
strong to severe thunderstorms initially with damaging winds and
large hail being the severe weather threats until the storms
become elevated late in the night.

This weakening convection is expected to leave behind outflow
boundaries which may interact with with an MCS/MCV to produce
redevelopment of showers and and thunderstorms across the Mid-
South Wednesday afternoon into Wednesday evening. Large hail and
damaging winds will continue to be the primary severe weather
threats, with a secondary threat of heavy rainfall as precipitable
water values will remain high. A tornado or two may be possible if
there is enough streamwise vorticity available in the pre-
convective environment as can be the case with MCVs.

Operational and ensemble model runs indicate an unsettled pattern
will persist for Thursday through early next week as the
aforementioned cold front washes out over the Lower Mississippi
Valley and another front drops into the region for Memorial Day.
Additional strong to severe thunderstorms are possible during this
period, especially for portions of the forecast area Thursday and
again on Sunday.

CJC

&&

.AVIATION...
(06Z TAFS)
Issued at 1141 PM CDT Tue May 21 2024

Only a few thunderstorms remain over portions of central and
eastern Arkansas late this evening. Left mention of thunderstorms
overnight for the KJBR and KMEM TAFs, but confidence is on the low
side. A period of MVFR ceilings are expected over much of the
Mid-South north of the Tennessee/Mississippi border from late
Wednesday morning into the early afternoon. A second round of
thunderstorms is expected Wednesday afternoon into early Wednesday
evening with VFR conditions returning by the end of the forecast
period. Winds will be mainly from the south around 10 knots. Some
low-level wind shear is possible over northern sections of the
Mid-South overnight.

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&

$$

PUBLIC FORECAST...CJC
AVIATION...ARS