Severe Thunderstorm Warning 407, NWS Memphis, TN

Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
632 PM CDT Tue Sep 23 2025

...New AVIATION...

.KEY MESSAGES...
Updated at 610 PM CDT Tue Sep 23 2025

- Strong to severe thunderstorms are expected this afternoon and
  evening, especially across northern and western portions of the
  Mid-South. Damaging winds and heavy rainfall are the primary
  threats.

- Another round of strong storms is forecast for Wednesday
  afternoon, mainly along and east of the Mississippi River, ahead
  of an approaching cold front.

- A cold front will bring drier and much cooler air for the end
  of the week, with pleasant conditions expected for the weekend.

&&

.DISCUSSION...
(This afternoon through next Monday)
Issued at 1240 PM CDT Tue Sep 23 2025

The latest surface analysis places a couple of weak surface lows
over the Plains with one over western Oklahoma and another over
northern Kansas. A warm front extends southeast from the Kansas
low through southeast Missouri and back into the Mid-South. The
front is currently stationary across the Mid-South and located
along a WNW to ESE line from Jonesboro, AR to Jackson, TN and back
into Huntsville, AL. North of the front, scattered showers and
thunderstorms continue to slowly stream across NE Arkansas, the
Missouri Bootheel, and NW Tennessee.

Aloft, the pattern remains rather messy, with a deep upper low
churning over Colorado with several weak perturbations
translating through mainly zonal flow across the Plains into the
Lower Mississippi Valley. A couple of MCSs are ongoing across
Missouri and have since merged and intensified into one back over
extreme SW Missouri. The current weather hazard remains instances
of flash flooding as storms continue to train across NE Arkansas,
the Missouri Bootheel, and NW Tennessee.

The evolution of the MCS over SW Missouri will dictate our severe
weather potential this afternoon and evening. The aforementioned
front will wobble north and south across the region and serve as
a focal point for renewed convection and potentially heavy
rainfall this afternoon and evening. Hi-res guidance continues to
show significant run-to-run variability on the evolution of
convection across the area this afternoon, likely due to the
somewhat diffuse upper level pattern. The highest confidence
resides across northern and western portions of the Mid-South,
which will see multi-clusters of strong to severe thunderstorms.
However, the extent of how far south the storms go still remains
uncertain. Nonetheless, areas south of the front have moved into a
humid airmass evidenced by lower 70s dewpoints. By this
afternoon, instability is forecast to max out around 2500 J/kg of
MLCAPE with bulk shear values up to 40 knots by late afternoon,
which will support organized multi-clusters. However, mid-level
and upper-level lapse rates and low-level helicity remain quite
poor. A 2% tornado risk was added to portions of eastern
Arkansas, but the threat seems highly conditional and dependent on
storms interacting favorably with the frontal boundary. The main
threats with any strong to severe storms will be damaging wind
gusts and heavy rainfall with a secondary threat of hail and a
spinup tornado or two.

Convective activity should weaken late this evening as the mid-
level 40 knot speed max lifts north of the area. The latest hi-
res guidance is now showing another round of storms moving into
the Mid-South after midnight. If this cluster of storms can
materialize and hold together, mainly outflow dominant activity
will occur due to weak shear and instability in place. The rest
of the overnight period will feature mainly scattered non-severe
showers and thunderstorms.

Wednesday's forecast continues to be a challenge. Scattered
ongoing thunderstorms and clouds will keep instability shunted
across the northern portions of the Mid-South. However, south of
I-40 and ahead of a cold front, HREF guidance continues to
advertise moderate instability developing by early to mid
afternoon across most of north Mississippi and portions of west
Tennessee near the TN River. Forecast soundings show only up to 20
knots of deep layer shear, which would limit overall storm
organization. Nonetheless, a Marginal Risk (1/5) for strong to
severe thunderstorms remains in effect for tomorrow afternoon with
damaging winds as the main threat. A higher threat could
materialize if deep shear strengthens across the region.

The cold front will sweep through the entire Mid-South by
Thursday morning with scattered post-frontal showers during most
of the day. Conditions will dry out Friday as the upper-level
trough pushes to our east. The weekend will feature dry
conditions and highs in the mid 80s and lows in the upper 50s and
lower 60s.

&&

.AVIATION...
(00Z TAFS)
Issued at 630 PM CDT Tue Sep 23 2025

An outflow boundary was noted on radar moving south through KNQA
at 2330Z. Scattered SHRA was developing behind the boundary, and
moving northeast toward a larger area of SHRA/TSRA over northeast
AR and northwest TN.

TSRA potential for MEM will edge up after 02Z, when TSRA over
central AR arrive. This convection will likely weaken as it
approaches MEM, but will continue to pose a threat of thunder.

Short term guidance remains varied with TSRA timing and coverage
on Wednesday. The 00Z TAFs relied on the 12Z HREF, which depict a
bump in post sunrise TS chances ahead of a surface trough and wind
shift. A secondary TSRA chances peak should arrive in the
afternoon, mainly southeast of JBR. TSRA timing confidence at MEM
and MKL is limited by the potential for stabilizing convective
outflow during the morning. To the south, TUP should have ample
convective instability in the afternoon and will have the
potential for strongest surface wind gusts.

PWB

&&

.FIRE WEATHER...
Issued at 1240 PM CDT Tue Sep 23 2025

Widespread wetting rainfall chances will maximize on Wednesday as
a cold front sweeps across the area. Lingering scattered rain
will occur on Thursday as an upper level low slowly lifts out of
the area. Dry and warm conditions will return this weekend with
minimum relative humidity above 40% each day.

&&

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

PUBLIC FORECAST...AC3
AVIATION...PWB

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