843
FXUS64 KMEG 211811
AFDMEG

Area Forecast Discussion
National Weather Service Memphis TN
111 PM CDT Tue Jul 21 2026

...New DISCUSSION, AVIATION, FIRE WEATHER...

.KEY MESSAGES...
Issued at 110 PM CDT Tue Jul 21 2026

- Dangerous heat reaches its peak this afternoon, with heat
  indices up to 117 degrees. An Extreme Heat Warning and Heat
  Advisory remain in effect through 9 PM this evening.

- Scattered to numerous thunderstorms will develop from
  mid-afternoon through this evening, in advance of a cold front
  approaching from the north. Damaging wind is the primary threat
  with secondary threats of heavy rainfall and large hail.

- The heat and humidity will moderate Wednesday through Friday,
  following a cold frontal passage. Heat indices in excess of 100
  degrees will likely return for the weekend.

&&

.DISCUSSION...
(This evening through next Monday)
Issued at 110 PM CDT Tue Jul 21 2026

The primary concern remains dangerous heat through early this
evening. The Midsouth will remain under the eastern periphery of
a 597dam 500mb ridge, centered over western KS. As we move
through this evening, the ridge axis will drop into northern MS,
exposing the Midsouth to 30-35kt of deep layer (surface-6km)
shear. The combination of modest midlevel height falls and the
approach of a surface cold front will sufficiently erode CINH for
storms to develop over the lower OH River Valley. These storms
will move southward into the Midsouth, mainly after 21Z / 4 PM
CDT.  Surface temps in the mid/upper 90s and dewpoints in the
upper 70s will support impressive mixed-layer CAPE and PWAT
values of 3500 J/kg and 2.3 inches, respectively.

Despite the parameters mentioned above, 12Z CAMs continued to
show relatively wide variation in favored corridors for storms
this afternoon and evening. 700mb temps are depicted by the RAP
to remain near 13C into early evening, which is quite warm, even
by July standards.  In addition, RAP soundings depict relatively
dry air in the midlevels, above the base of an elevated mixed
layer. Potential dry air entrainment by storm updrafts may serve
to limit storm coverage. Where more persistent and organized
storms develop, inverted-V low level sounding profiles and DCAPE
nearing 1200 J/kg will support a damaging wind threat.

Beyond tonight, drier post-frontal air will settle into the
Midsouth, with 60s dewpoints moving through all but northeast MS
Wednesday afternoon. As such, heat indices will prevail below
105 over all but perhaps Monroe County MS. No extension to the
current heat headlines are planned at this time.

A few storms will be possible over northeast MS, near the stalled
front Wednesday night and Thursday. Rain chances may be aided by
midlevel moisture left from Tropical Storm Bertha`s remnants. For
the remainder of the Mid-South, northwest flow aloft will bring a
chance of thunderstorms on Friday. Thereafter, a southern plains
upper ridge will expand east, likely necessitating a return of
heat headlines for the weekend.

PWB

&&

.AVIATION...
(18Z TAFS)
Issued at 110 PM CDT Tue Jul 21 2026

Guidance continues to vary in timing and placement of TS
development this afternoon. Given this uncertainty, opted to push
back convective initiation a few hours. There is potential for
earlier pop-up storms to fire near all sites, but confidence is
too low to place in TAFs at this time. Overnight, a cold front
will allow winds to become northerly at all sites except for TUP.
Outside of thunderstorms, VFR conditions will prevail.

ANS

&&

.FIRE WEATHER...
Issued at 110 PM CDT Tue Jul 21 2026

Minimum RH values will remain above 40 percent through the next
several days. 20 foot winds will switch to north late tonight
into early Wednesday, following the passage of a cold front.
Scattered thunderstorms are expected ahead of the front this
evening, mainly over northeast Arkansas, the Missouri bootheel
and West Tennessee.

&&


.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...PWB
AVIATION...ANS