Area Forecast Discussion

KEY MESSAGES

Issued at 633 PM CDT Tue Jul 21 2026

- Scattered showers and thunderstorms will be possible through mid-evening, in advance of a cold front approaching from the north. The strongest storms will be capable of producing damaging winds. These storms will primarily affect northeast Arkansas, the Missouri Bootheel and northern West Tennessee.

- Heat and humidity will moderate Wednesday through Friday, following tonight's 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

(00Z TAFS) Issued at 633 PM CDT Tue Jul 21 2026

The primary aviation weather challenge will be TSRA chances this evening. The primary large-scale forcing for sustained and organized TSRA will remain to the east, over central KY into northern middle TN. Further west, upstream convective trends over southeast MO and western KY thus far don't appear promising for sustained TSRA into the MEM TRACON after 03Z. In the interim, an isolated TSRA or two cannot be ruled out in the MKL and MEM vicinity, aided by remaining daytime heating. This isolated TSRA potential is best handled with a PROB30.

No significant aviation weather impacts are expected overnight and during the day Wednesday, as light northerly winds prevail behind a weak surface cold front.

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.