410 

FXUS63 KLSX 290325

AFDLSX



Area Forecast Discussion...Updated Aviation

National Weather Service Saint Louis MO

1025 PM CDT Sun Jun 28 2026



.KEY MESSAGES...



- Dangerous levels of heat and humidity are expected through this

  week.





&&



.SHORT TERM...  (Through Late Monday Night)

Issued at 159 PM CDT Sun Jun 28 2026



Afternoon water vapor imagery shows an upper-level ridge quickly 

amplifying over the eastern CONUS, with surface obs showing last 

night's warm front having lifted well north-northeastward of the 

CWA. This has opened the door to robust warm air advection, pairing 

with ample insolation to push temperatures in to the upper 80s and 

low 90s across the CWA. With a few more hours of peak heating left, 

temperatures are expected to rise further into the mid 90s. When 

paired with the humidity across the region, heat index values are 

mostly in the 100-105 degree range and dangerous for those with 

prolonged exposure. The ridge only builds further northward on 

Monday, leading to high confidence in another day of dangerous heat. 

Temperatures will be a few degrees warmer thanks to lows only 

bottoming out in the mid to upper 70s tonight.



Elmore



&&



.LONG TERM...  (Tuesday through Next Sunday)

Issued at 159 PM CDT Sun Jun 28 2026



By the start of the long-range forecast period Tuesday morning, 

guidance consensus is that the upper-level ridge will have amplified 

to its northern-most latitude across the eastern CONUS. While a 

majority of global ensemble members have 850mb temperatures being at 

their warmest through this portion of the period on Tuesday, the 

gradual, subtle cooling through Saturday is expected to have an 

unnoticeable effect on surface temperatures thanks to the hot start to 

the week. The main impact of these slightly cooler 850 mb 

temperatures will be a more favorable thermal profile for air mass 

thunderstorms Thursday into Saturday. Given the brief, isolated 

nature of this potential convection, it is not expected to provide 

notable heat relief. There is at least a medium chance that heat 

headlines will be extended into Saturday, with the need for this 

being assessed with each forecast package. 



Ensemble clusters show the ridge retrograding westward for Sunday, 

with deterministic guidance showing a shortwave passing through the 

Midwest. Both factors favor at least some degree of cooling through 

height falls and/or a cold FROPA; however, specifics at this lead 

time are highly uncertain. While ensemble spread in surface 

temperatures increases on Sunday in response to this uncertainty, 

the 25th percentile of high temperatures is in the upper 80s, 

supporting a continuation of summer-like warmth.



Elmore



&&



.AVIATION...  (For the 06z TAFs through 06z Monday Night)

Issued at 1023 PM CDT Sun Jun 28 2026



VFR flight conditions will prevail through Monday evening. Expect

southerly winds to increase and become gusty during the late

morning or early afternoon. Gusts will diminish during the

evening.



Carney



&&



.LSX WATCHES/WARNINGS/ADVISORIES...

MO...Heat Advisory until midnight CDT Thursday night for Audrain MO-

     Boone MO-Callaway MO-Cole MO-Crawford MO-Gasconade MO-Iron 

     MO-Knox MO-Lewis MO-Lincoln MO-Madison MO-Marion MO-

     Moniteau MO-Monroe MO-Montgomery MO-Osage MO-Pike MO-Ralls 

     MO-Reynolds MO-Saint Francois MO-Shelby MO-Washington MO.



     Extreme Heat Warning until midnight CDT Thursday night for 

     Franklin MO-Jefferson MO-Saint Charles MO-Saint Louis City 

     MO-Saint Louis MO-Sainte Genevieve MO-Warren MO.



IL...Heat Advisory until midnight CDT Thursday night for Adams IL-

     Bond IL-Brown IL-Calhoun IL-Fayette IL-Greene IL-Jersey IL-

     Macoupin IL-Marion IL-Montgomery IL-Pike IL.



     Extreme Heat Warning until midnight CDT Thursday night for 

     Clinton IL-Madison IL-Monroe IL-Randolph IL-Saint Clair IL-

     Washington IL.



&&



$$



WFO LSX