Heat Advisory 21, NWS Jackson, MS

Ashley County, AR, Chicot County, AR, Catahoula Parish, LA, Concordia Parish, LA, East Carroll Parish, LA, Franklin Parish, LA, Madison Parish, LA, Morehouse Parish, LA, Richland Parish, LA, Tensas Parish, LA, West Carroll Parish, LA, Adams County, MS, Attala County, MS, Bolivar County, MS, Carroll County, MS, Choctaw County, MS, Claiborne County, MS, Clarke County, MS, Clay County, MS, Copiah County, MS, Covington County, MS, Forrest County, MS, Franklin County, MS, Grenada County, MS, Hinds County, MS, Holmes County, MS, Humphreys County, MS, Issaquena County, MS, Jasper County, MS, Jefferson County, MS, Jefferson Davis County, MS, Jones County, MS, Kemper County, MS, Lamar County, MS, Lauderdale County, MS, Lawrence County, MS, Leake County, MS, Leflore County, MS, Lincoln County, MS, Lowndes County, MS, Madison County, MS, Marion County, MS, Montgomery County, MS, Neshoba County, MS, Newton County, MS, Noxubee County, MS, Oktibbeha County, MS, Rankin County, MS, Scott County, MS, Sharkey County, MS, Simpson County, MS, Smith County, MS, Sunflower County, MS, Warren County, MS, Washington County, MS, Webster County, MS, Winston County, MS, Yazoo County, MS

655 
WWUS74 KJAN 182131
NPWJAN

URGENT - WEATHER MESSAGE
National Weather Service Jackson MS
431 PM CDT Tue Aug 18 2026

ARZ074-075-LAZ007>009-015-016-023>026-MSZ018-019-025>066-072>074-
190900-
/O.CAN.KJAN.HT.Y.0021.260819T1600Z-260820T0200Z/
/O.EXT.KJAN.HT.Y.0020.000000T0000Z-260820T0200Z/
Ashley-Chicot-Morehouse-West Carroll-East Carroll-Richland-
Madison LA-Franklin LA-Catahoula-Tensas-Concordia-Bolivar-
Sunflower-Leflore-Grenada-Carroll-Montgomery-Webster-Clay-Lowndes-
Choctaw-Oktibbeha-Washington-Humphreys-Holmes-Attala-Winston-Noxubee-
Issaquena-Sharkey-Yazoo-Madison MS-Leake-Neshoba-Kemper-Warren-Hinds-
Rankin-Scott-Newton-Lauderdale-Claiborne-Copiah-Simpson-Smith-Jasper-
Clarke-Jefferson-Adams-Franklin MS-Lincoln-Lawrence-Jefferson Davis-
Covington-Jones-Marion-Lamar-Forrest-
Including the cities of Newton, Hattiesburg, Canton, Cleveland,
Pickens, Tchula, Taylorsville, Union, North Carrollton, Anguilla,
Columbus, Lake Village, Mendenhall, Madison, Purvis, Delhi,
Indianola, Natchez, Macon, New Hebron, Eudora, Epps, Brookhaven,
Prentiss, Yazoo City, Richland, Wesson, Laurel, West Crossett, Roxie,
Carthage, Bassfield, Lake Providence, Ackerman, Philadelphia,
Conehatta, Ruleville, Crystal Springs, Dermott, Mathiston,
Heidelberg, Rolling Fork, Brandon, West Ferriday, Greenville,
Fayette, Durant, Isola, Quitman, Forest, Columbia, Vicksburg,
Meadville, Stonewall, Winona, Grenada, Carrollton, Pearl, Scooba,
Monticello, Lexington, Jackson, Shubuta, Kosciusko, Goodman, Morton,
Lumberton, Eupora, West Hattiesburg, North Crossett, Weir,
Hazlehurst, Crossett, Newellton, Ferriday,
St. Joseph, Ridgeland, Brooksville, De Kalb, Meridian,
Louisville, Oak Grove, Hamburg, Winnsboro, Greenwood, Vaiden, Port
Gibson, Bude, Magee, Belzoni, Collins, Raleigh, Harrisonburg,
Starkville, Decatur, Bastrop, Mayersville, Jonesville, Vidalia,
Tallulah, Rayville, Waterproof, Pearl River, Bay Springs, Mount
Olive, and West Point
431 PM CDT Tue Aug 18 2026

...HEAT ADVISORY NOW IN EFFECT UNTIL 9 PM CDT WEDNESDAY...

* WHAT...Heat index values up to 110 degrees.

* WHERE...Portions of central and south Mississippi, southeast
  Arkansas, and northeast Louisiana.

* WHEN...Until 9 PM CDT Wednesday.

* IMPACTS...Hot temperatures and high humidity may cause heat
  illnesses.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Drink plenty of fluids, stay in an air-conditioned room, stay out of
the sun, and check up on relatives and neighbors.

Take extra precautions when outside. Wear lightweight and loose
fitting clothing. Try to limit strenuous activities to early morning
or evening. Take action when you see symptoms of heat exhaustion and
heat stroke.

Monitor the latest forecasts and warnings for updates.

&&

$$

DL

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
908 AM CDT Tue Aug 18 2026

...New MESOSCALE UPDATE...

.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.

&&

NF/CR/22