textproduct: Memphis

KEY MESSAGES

Issued at 118 PM CDT Mon Aug 17 2026

- An Extreme Heat Warning is in effect today across north Mississippi, much of eastern Arkansas, and southwest Tennessee with a Heat Advisory in effect for the rest of the Mid-South.

- A Marginal (level 1 out of 5) Risk for severe thunderstorms capable isolated damaging wind is in place for areas along and south of I-40 for this evening.

- Another Heat Advisory is in place for portions of eastern Arkansas and northern Mississippi Tuesday.

DISCUSSION

(This evening through next Sunday) Issued at 118 PM CDT Mon Aug 17 2026

Another day of dangerous heat is upon us as the tropical air mass that has dominated the last week of our weather continues to stubbornly lounge across the Mid-South. This is expected to lead to heat index values between 105 F - 115 F through this afternoon in most areas. However, surface and satellite observations show a pronounced convectively-enhanced boundary moving across the region, currently (18z) analyzed across portions of north- central MS and West TN. Moisture behind the front has pooled, yielding dewpoints in the middle to upper 70s, which may offset any cooling brought by the boundary through the day. Therefore, no changes to the heat headlines were made, but heat indices could drop below 105 F over northern portions of the region much quicker than previous evenings.

Another aspect to today's forecast is the potential for convection through this afternoon and evening. Diurnally driven MLCAPE values are expected to exceed 2500 J/kg with isolated convection developing along the cool boundary across the region by late this evening. Cells from this mode of convection will likely be small, which will limit the amount of lightning and impacts to heating from outflow. However, a second area of convective potential exists with ongoing thunderstorms upstream in AR. A relatively organized line of thunderstorms has been producing severe wind through this morning, traveling east with time and producing an area of strong outflow. Current CAMs struggle to bring these storms into our region, but also have been struggling to maintain the line at its current intensity for several runs this morning, hence the new day 1 Marginal Risk from SPC. Therefore, it is not out of the question that remnant convection could last long enough to make it into the region this evening. The only real road block will be some weak 850-700 mb subsidence behind the preceding boundary across our area this morning, which would decrease the available instability to the line. So, isolated thunderstorms and an additional line from the west are possible this afternoon, offering local heat relief and the chance for isolated damaging winds.

More heat and humidity is expected tomorrow, but with the passage of today's front and increasing low-level subsidence, moisture will begin to decrease. Mid-level dewpoints drop into the low 60s, which will help mix surface dewpoints in the afternoon down towards the low 70s across much of the area. The only region that is expected to remain hot enough to warrant heat headlines will be the MS River Delta where a new Heat Advisory is now in effect for Tuesday through 8 PM CDT. Wednesday will see the resurgence of moisture as surface flow backs towards a southerly direction. So, expect the expansion of heat headlines Wednesday with the potential return of Extreme Heat Warnings to portions of the area, especially in the MS River Delta. Some models depict the troughing to our north nosing south with an increasing potential for convection, but variance between models remains high on the coverage and intensity of the convection.

By Thursday, high pressure to our north begins to strengthen in earnest, gradually pushing the humidity south out of the region. In turn, afternoon heat index values decrease to at or below 100 F for the first time in over a week for some areas. This forecast is expected to continue through the end of the period with relatively cooler, drier conditions through this weekend.

AVIATION

(18Z TAFS) Issued at 118 PM CDT Mon Aug 17 2026

TSRA potential will remain the primary aviation weather concern through early evening. A well-organized TSRA cluster moved from northeast OK into western AR this morning. This storm cluster continued well into AR and spawned additional TSRA to the southeast, toward LIT around midday.

KNQA and TMEM VWP products indicate winds have veered to the NNW from the surface up through FL010. Given the trajectory of the ongoing TSRA over AR, the favored downstream convective corridor will likely set up south of MEM, toward UTA and points eastward across north MS. TSRA may be in the dissipation phase if/when it makes it to TUP around 00Z or later.

FIRE WEATHER

Issued at 118 PM CDT Mon Aug 17 2026

Fire danger is expected to remain low through the period due to light 20 ft winds, although minimum relative humidity values may drop below 40% in some areas. Isolated showers are expected across northern Mississippi this afternoon along a weak front, which will shift winds to a more northwesterly direction after passage. Fog potential remains low due to dry soils.

MEG WATCHES/WARNINGS/ADVISORIES

AR...Heat Advisory until 8 PM CDT this evening for ARZ009-018.

Extreme Heat Warning until 8 PM CDT this evening for ARZ026>028- 035-036-048-049-058.

Heat Advisory from 9 PM this evening to 8 PM CDT Tuesday for ARZ049-058.

MO...Heat Advisory until 8 PM CDT this evening for MOZ113-115.

MS...Extreme Heat Warning until 8 PM CDT this evening for MSZ001>017- 020>024.

Heat Advisory from 9 PM this evening to 8 PM CDT Tuesday for MSZ007-010>012-020>022.

TN...Heat Advisory until 8 PM CDT this evening for TNZ001>004-019>022- 050>055-090>092.

Extreme Heat Warning until 8 PM CDT this evening for TNZ048-049- 088-089.