textproduct: Memphis

KEY MESSAGES

Issued at 1208 PM CDT Tue Aug 18 2026

- A Heat Advisory remains in effect through today until 8 PM CDT for portions of eastern Arkansas and north Mississippi.

- Heat is expected to persist through Wednesday with additional Heat Advisories and Extreme Heat Warnings in effect.

- A Slight (level 2 out of 5) Risk for severe weather is in place for portions of northeastern Arkansas, the Missouri Bootheel, and West Tennessee. Expect storms to be capable of primarily damaging winds and heavy downpours.

DISCUSSION

(This evening through next Monday) Issued at 1208 PM CDT Tue Aug 18 2026

Compared to 24 hours ago, today is already markedly cooler late morning temperatures in the 80s compared to the mid 90s yesterday. Additionally, surface observations show dewpoints in the 60s due to the mixing of drier air aloft, which is visible in the 12z soundings from both BNA and LZK around 850 mb. The culmination of both of these effects will bring heat indices below Heat Advisory criteria (105 F) for the majority of the region. Portions of the MS River Delta and northern MS will still have enough moisture left in the tank to pump out sufficiently high heat index values to warrant a Heat Advisory through tonight at 8 PM CDT. A few showers and storms are also possible across northern MS where the higher moisture resides. By 21z, MLCAPE values are forecast to jump above 2000 J/kg in some areas, which alongside high DCAPE, a local damaging wind threat could materialize within stronger thunderstorms. Any convection is anticipated to end by midnight.

Looking to tomorrow, surface winds begin to recover following yesterday's frontal passage, turning to a more southerly direction. High temperatures increase amongst all short-term model guidance with highs approaching, if not exceeding, 100 F tomorrow afternoon. However, remnant outflow from storms that will develop tonight across MO may limit the amount of heating, introducing quite a bit of uncertainty into the precipitation and temperature forecast. As of this morning, the highest confidence in heat index values exceeding 105 F exists across southwestern West TN, eastern AR, and north MS with the expectation of 110+ F heat indices across the MS River Delta region. So, new Heat Advisories and Extreme Heat Warnings have been issued for these areas respectively.

Through the forecast period this far, the forecast will be dominated by the presence of strong ridging aloft which has kept us warm and relatively dry. When Wednesday night rolls around, this ridging will start to retreat south and west as a trough to our north gets tugged south while phasing with a shortwave. Enough moisture will remain across the region for MLCAPE values to climb into the 1500 - 2500 J/kg range throughout the day with similar values remaining overnight, albeit with an increase in MLCIN. However, models currently show a large amount of uncertainty regarding the coverage, timing, and intensity of any convection, likely due to the presence of strong capping below 850 mb. If storms are able to develop, such as in the case of the HRRR/REFS guidance, they would be capable of damaging winds, heavy downpours, and perhaps a tornado (although this seems fairly unlikely given the presence of a strong cap). The highest potential for rainfall will exist along and north of I-40 if precipitation does develop with around .5" expected across the northern 2 tiers of counties with locally higher amounts.

Thursday will then see the passage of the front associated with the precipitation chances from Wednesday along with the potential for more showers and thunderstorms throughout the day. Ensembles point to the parent upper trough amplifying with the trough axis from roughly northern GA towards the Great Lakes, placing the Mid- South in a decent fetch of northwesterly upper flow. In past forecasts, this has led to a decrease in both afternoon temperatures and dewpoints, dropping our heat indices below 100 in many areas. However, this is now changing in spite of a favorable synoptic environment for cooling. The main culprit appears to be a lack of appreciable decrease in the dewpoints, which some guidance has above 70 F into this weekend, keeping heat index values above 100 F. But the silver lining is that the temperatures should be cool enough from Thursday through the end of the forecast to limit the need for anything other than targeted Heat Advisories.

AVIATION

(18Z TAFS) Issued at 1208 PM CDT Tue Aug 18 2026

VFR conditions are expected at all sites. A remnant outflow boundary over north Mississippi will slowly lift north this evening and overnight resulting in variable wind, but prevailing direction should be from the south to southwest.

FIRE WEATHER

Issued at 1208 PM CDT Tue Aug 18 2026

Fire danger potential remains low as 20 ft winds remain light, but minimum relative humidity values could locally drop below 40% each afternoon through the period. Fog potential remains low (<10%) due to dry soils. Wetting rain chances increase Wednesday evening and into Thursday morning as a front moves south into the region across portions of northeastern Arkansas, the Missouri Bootheel, and West Tennessee. Some thunderstorms are possible during this time, which will be accompanied by a chance for damaging winds and heavy rainfall.

MEG WATCHES/WARNINGS/ADVISORIES

AR...Heat Advisory from 11 AM to 8 PM CDT Wednesday for ARZ026>028- 035-036-048.

Heat Advisory until 8 PM CDT this evening for ARZ049-058.

Extreme Heat Warning from 11 AM to 8 PM CDT Wednesday for ARZ049- 058.

MO...None. MS...Heat Advisory from 11 AM to 8 PM CDT Wednesday for MSZ001>005- 008-009-012>017-021>024.

Heat Advisory until 8 PM CDT this evening for MSZ007-010>012- 020>024.

Extreme Heat Warning from 11 AM to 8 PM CDT Wednesday for MSZ007- 010-011-020.

TN...Heat Advisory from 11 AM to 8 PM CDT Wednesday for TNZ048>053- 088>091.