603
FXUS64 KMEG 211121
AFDMEG

Area Forecast Discussion
National Weather Service Memphis TN
621 AM CDT Tue Jul 21 2026

...New AVIATION...

.KEY MESSAGES...
Issued at 621 AM CDT Tue Jul 21 2026

- Dangerous heat reaches its peak Tuesday, with heat indices up to
  116F. An Extreme Heat Warning and Heat Advisory remain in
  effect through late Tuesday evening.

- An incoming cold front will trigger organized severe storms late
  Tuesday afternoon through midnight. Damaging wind is the primary
  threat with a secondary threat of heavy rainfall.

- The front exits Wednesday, providing a reprieve from heat and
  humidity for both Thursday and Friday. Uncertainty persists
  regarding the return of hot and humid weather next weekend.

&&

.DISCUSSION...
(Tonight through next Monday)
Issued at 1152 PM CDT Mon Jul 20 2026

It`s currently a muggy night across the Mid-South, with
temperatures ranging from the upper 70s to mid-80s and heat
indices holding steady near 90 degrees.

Attention is focused on newly-formed Tropical Storm Bertha in the
Gulf. This system helped relax heights across the region on
Monday, allowing for enough convective coverage to provide some
heat relief. We`re tracking Bertha on a nearly westerly path
near the Gulf Coast over the next 24 hours, which may impact
storm development across North Mississippi on Tuesday afternoon.

Meanwhile, prepare for our most dangerous and oppressive heat of
this event on Tuesday. NBM 50th percentile guidance indicates
widespread, dangerous heat indices reaching up to 116F. The
Extreme Heat Warning has been expanded eastward to include the
majority of west Tennessee and portions of northwest Mississippi.
The peak and cumulative effect of this current heatwave will
create dangerous health risks for our most vulnerable-check on
your neighbors, stay hydrated, and avoid being outdoors between
11 AM and 7 PM.

A cold front will begin tracking south into the area late Tuesday
afternoon. With an unstable airmass-MLCAPE values exceeding
3000 J/kg-and bulk shear around 30 knots, organized severe storms
are highly likely. While HREF guidance suggests we`ll be in the
right exit region of the mid-level jet (typically inhibiting
large-scale lift), the combination of extreme instability and the
incoming boundary should trigger strong to severe convection.
Storm mode will favor multi-cells that could grow upscale into
line clusters capable of producing severe wind gusts.

The current Slight Risk covers northeastern counties near the
Tennessee River, with a Marginal Risk across much of West
Tennessee, the Missouri Bootheel, and parts of Northeast
Arkansas. Based on the latest data, I anticipate the Slight Risk
expanding across West Tennessee and likely further west into
Northeast Arkansas. Expect the primary threat to be damaging
wind, supported by DCAPE values over 1000 J/kg, with the main
window from late afternoon through midnight.

The front will lose momentum overnight as the parent trough lifts
northeast, then slowly traverse the region on Wednesday. Our
southernmost counties may still see heat indices of 100-104F,
but heat products seem unlikely at this point. Significant relief
arrives Thursday; temperatures will feel "downright cool" by
comparison, with highs in the 80s and dewpoints dropping below
70.

The late-week outlook hinges on the dissipation rate of TS Bertha
as it tracks west. Current LREF and deterministic guidance
suggests dissipation by late Wednesday, which would allow the
subtropical ridge to nudge east, bringing back heat and humidity.
However, if the system persists longer near the Gulf Coast, we`ll
likely see a broad northwest flow, leading to near-normal highs
in the low 90s and continued convective activity. Long-range
guidance consistently shows the ridge amplifying across the
Plains while troughing persists over the Ohio Valley, likely
positioning us on the edge of the ridge under the main storm
track.

AC3

&&

.AVIATION...
(12Z TAFS)
Issued at 621 AM CDT Tue Jul 21 2026

VFR conditions are expected to prevail across the airspace this
issuance. Today`s overall thunderstorm coverage, placement, and
mode is tough to pinpoint as 1) storms could be driven by daytime
heating and 2) with a cold front dropping south after 23Z. For
now, confidence in the coverage and timing of thunderstorms
allows for PROB30s at MEM/MKL/TUP as well as a VCTS at MEM.
Confidence is slightly higher at JBR warranting a TEMPO and
vicinity for thunderstorms this afternoon into early evening.
CAMs are hinting at lingering showers at both MKL/TUP overnight
Wednesday, therefore, VCSH was added at these sites.
South/southwest winds will remain sub 10 kts over the next
30 hours.

AEH

&&

.FIRE WEATHER...
Issued at 1152 PM CDT Mon Jul 20 2026

Light 20-ft winds and minimum RH values remaining above 40% will
keep fire weather concerns minimal through the period.

&&


.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Extreme Heat Warning until 9 PM CDT this evening for ARZ009-018-
     026>028-035-036-048-049-058.

MO...Extreme Heat Warning until 9 PM CDT this evening for MOZ113-115.

MS...Extreme Heat Warning until 9 PM CDT this evening for MSZ001>003-
     007-008-010>012-020.

     Heat Advisory until 9 PM CDT this evening for MSZ004>006-009-
     013>017-021>024.

TN...Extreme Heat Warning until 9 PM CDT this evening for TNZ001>004-
     019>021-048>052-088>090.

     Heat Advisory until 9 PM CDT this evening for TNZ022-053>055-091-
     092.

&&

$$

PUBLIC FORECAST...AC3
AVIATION...AEH