textproduct: Jackson

KEY MESSAGES

- Dangerous heat stress conditions are expected through at least the middle of this week.

- Chances for afternoon storms will increase, and the risk for dangerous heat will decrease late this week into the weekend.

MESOSCALE UPDATE

Issued at 902 AM CDT Tue Aug 18 2026

Following latest trends in guidance, there is now a Marginal Risk for isolated strong to severe thunderstorms across portions of east and central Mississippi this afternoon/evening. Afternoon heat and humidity will see MLCAPE values spike to around 4000+ J/kg in an axis extending from the northwest to southeast. A stalled frontal boundary in the region may help to provide some convergence for storm initiation, and then expect clusters of storms to spread southeast through the unstable air mass. Damaging wind gusts and locally heavy downpours are the primary hazards, but hail cannot be ruled out. Afternoon POPs were increased to at least a mentionable slight chance across the forecast area. /NF/

DISCUSSION

Issued at 320 AM CDT Tue Aug 18 2026

Through tonight: Heat and humidity will remain the main concern in the short term. With the exception of our northeast, another day of near record high temperatures is expected today. A large 596dam ridge will continue to span from the Four Corners region across the southern Plains and across the southwest portions of our CWA. At the surface a weak stalled frontal boundary was noted across our northern zones. Convection is expected to initiate along this stalled boundary this afternoon and spread to the southeast across our eastern zones into the evening. This may bring some relief to the heat today in the areas that receive rain but otherwise, temperatures in the upper 90s to lower 100s will combine with relatively high humidity to result in heat indices just above 110F along the Mississippi river and southern zones with 105-110F expected again elsewhere. Thus, the Heat Advisory will remain in effect for the whole CWA today. The convection will taper off this evening but the warm and humid conditions will continue tonight. /22/

Wednesday through next Tuesday

Another day of dangerous heat conditions is in the forecast for Wednesday. Model guidance continues to show an intense subtropical ridge axis that will maintain its positions over the southeast CONUS. A hot low level thermal ridge axis (e.g., H850 T up to 24 deg C) will support high temperatures approaching the 100 to 103 deg range across the area. This combined with dewpoints in the 70s and increased sunshine allow for peak heat index reading values in the 105-110 degree range. At the moment, no changes have been made to the heat graphic for Wednesday and the elevated to significant risks for dangerous heat will continue to be advertised. Likewise, a Heat Advisory will likely be needed for our entire CWA for Wednesday. There is a possibility that an Extreme Heat Warning could be introduced for portions of our forecast area on Wednesday as well. Additional heat related messaging/advisories will likely be needed beyond Wednesday. Remember to stay cool and hydrated and check on vulnerable populations and never leave children or pets unattended in hot vehicles as these can become lethal, as quickly as a matter of minutes.

Regarding the rain chances, strong westerlies will begin to increase over the northeast CONUS. Global models continue to show the strong subtropical ridge beginning to weaken. This combined with increased deeper moisture, increased convergence from frontal zone sagging southward may cause some better rain coverage across much of the area. The potential for marginal to slight organized severe weather threats will also need to be monitored especially per recent NCAR AI- NWP guidance in the Wed-Fri time frame.

It is also worth noting, the possibility for isolated strong storms over the next several days mainly during the afternoon into the evening as the combination of vertical totals 27+, lifted index of near -2C and dewpoints in the low 70s any storm that does manage to organize and break through the cap could overachieve previous forecasts warranting the issuance of future products.

Looking ahead into the weekend, scattered showers and storms will begin to decrease in coverage as the frontal boundary moves south across our CWA. By Monday, rain chances will start to slightly increase across our area (with PoPs around 15%). Afternoon highs for Monday will peak in the upper 90s to low 100s. /CR/

AVIATION

(12Z TAFS) Issued at 635 AM CDT Tue Aug 18 2026

Isolated to scattered TSRA wl affect the northern and eastern TAF sites this aftn but away from TSRA, VFR conditions wl prevail through the TAF period. /22/

PRELIMINARY POINT TEMPS/POPS

Jackson 101 77 100 76 / 20 30 30 10 Meridian 100 75 100 74 / 30 30 40 20 Vicksburg 100 78 99 77 / 20 20 10 10 Hattiesburg 101 77 99 75 / 50 60 60 30 Natchez 101 77 100 76 / 20 20 10 0 Greenville 101 78 102 78 / 30 20 10 20 Greenwood 99 76 101 77 / 30 20 10 10

JAN WATCHES/WARNINGS/ADVISORIES

MS...Heat Advisory until 8 PM CDT this evening for MSZ018-019-025>066- 072>074.

LA...Heat Advisory until 8 PM CDT this evening for LAZ007>009-015-016- 023>026.

AR...Heat Advisory until 8 PM CDT this evening for ARZ074-075.