textproduct: Memphis

KEY MESSAGES

Issued at 637 AM CDT Thu Aug 20 2026

- A Marginal to Slight Risk for severe thunderstorms this afternoon and evening mainly south of I-40. Damaging winds and large hail are the main threats.

- A Heat Advisory remains in effect from 11 AM through 8 PM CDT today, with heat index values expected to range between 105 to 109 degrees.

- A transition to a zonal/northwest flow regime late this week will bring drier air and cooler temperatures for the weekend, providing relief from the oppressive heat.

DISCUSSION

(Tonight through next Wednesday) Issued at 1159 PM CDT Wed Aug 19 2026

GOES Water Vapor satellite trends finally show convective initiation occurring over portions of southern Missouri and north central Arkansas late this evening as a mid-level shortwave moves across the Middle Mississippi Valley. Latest short-term model soundings and mesoanalysis indicates this upstream activity is elevated with a low-level inversion in place and convective inhibition. The convective parameter space shows strong instability with MLCAPE values between 2000-4000 J/kg, and DCAPE values around 1000 J/kg. Additionally, effective shear in excess of 40 kts, moderately steep mid-level lapse rates above 6.5 C/km, 0-3 km storm relative helicity values between 150-200 m2/s2, and precipitable water values approaching 2 inches is located across northern portions of the Mid-South.

Short-term models have struggled to resolve the development and propagation of this activity overnight across the area. Short- term trends and upward propagation vectors suggest this mixed mode activity of multicell clusters and perhaps some supercellular-like structures will eventually propagate southeast towards the Tennessee River overnight. Damaging winds and large hail are the primary severe weather threats with low confidence in tornado development occurring across this area due to the elevated nature of the convection. Localized heavy rainfall is also possible with the high precipitable water values. Further south, confidence is much lower with any convective activity occurring closer to the TN/MS border.

Very hot temperatures are expected again across the Mid-South Thursday southwest of the nearly stalled surface boundary over portions of east Arkansas and north Mississippi where temperatures will rise to the upper 90s once again. These very hot temperatures combined with dewpoints in the 70s will translate to heat index values between 105 to 109 degrees with a Heat Advisory remaining in effect across these areas. Heat index values may approach advisory criteria in the Memphis metro area. However, confidence is limited as outflow boundaries from upstream convection may lower surface dewpoints below advisory criteria.

Additional showers and thunderstorms are possible south of I- 40 on Thursday as the boundary moves through as a weak cold front. Strong instability and weak shear may result in a few severe thunderstorms over north Mississippi during peak heating with damaging winds as the main threat.

Long-term models indicate slightly cooler air will gradually arrive later this weekend into early next week as a mid-level trough settles in across the eastern U.S. Heat advisory potential will remain limited to the southwest portion of the forecast area.

AVIATION

(12Z TAFS) Issued at 637 AM CDT Thu Aug 20 2026

Thunderstorms that have persisted across West TN and eastern AR have since diminished in coverage and intensity or have moved east over the TN River. Only a few weak showers remain across far West TN that are expected to bring VCSH to MKL for a couple hours this morning. Regardless, expect VFR conditions through this morning with a frontal passage gradually veering winds to a more northerly direction through the end of the period. Another round of convection is expected along the front as it moves south with PROB30s at MEM and TUP for -SHRA and -TSRA respectively. Expect precipitation chances to diminish quickly after sunset at both terminals.

FIRE WEATHER

Issued at 1159 PM CDT Wed Aug 19 2026

An overall low fire weather risk will hold over the next three days. While temperatures remain hot, light winds and adequate moisture levels will keep critical fire weather conditions under control. Rainfall through Thursday will result in the development of fog late Thursday night east of the Mississippi river.

MEG WATCHES/WARNINGS/ADVISORIES

AR...Heat Advisory from 11 AM this morning to 8 PM CDT this evening for ARZ048-049-058.

MO...None. MS...Heat Advisory from 11 AM this morning to 8 PM CDT this evening for MSZ007-008-010>017-020>024.

TN...None.