FXUS63 KLSX 252303

AFDLSX



Area Forecast Discussion...Updated Aviation

National Weather Service Saint Louis MO

603 PM CDT Sat Apr 25 2026



.KEY MESSAGES...



- There is the potential for severe thunderstorms Monday afternoon 

  and evening. Large hail, damaging winds, and tornadoes are all 

  possible.



- Warm weather continues through at least Monday before a shift

  toward cooler weather for the rest of the week.





&&



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

Issued at 158 PM CDT Sat Apr 25 2026



Our recent cold front has brought us a dry, sunny day, but the front 

has stalled to the south and moisture is already beginning to return 

over the Plains. Looking aloft we see a large trough over the 

Canadian Prairies and another over the North Atlantic. In between, 

ridging has led to persistent warm temperatures even despite the 

recent surface cold frontal passage. Westerly flow across the 

Rockies has led to the establishment of a lee trough in the High 

Plains, triggering the moisture return east of there. This leads to 

another round of storms developing over the Plains of Oklahoma and 

Kansas today, but this activity will remain to our west and south, 

keeping us dry.



On Sunday, moisture pushes even further north in the Plains with the 

next round of storms Sunday afternoon focusing on Kansas and 

Nebraska. Surface based convection stays well west of our area 

Sunday afternoon as we remain in the dry air for one more day. But 

that moisture return finally gets redirected toward our area 

beginning Sunday night into Monday morning as a shortwave trough 

emerges out of the Rockies and drives a surface low northeast 

through the Midwest. We may see some elevated convection early 

Monday morning on that moisture return, particularly across 

northeast Missouri closer to the surface low and upper trough. Any 

threats with this activity should be limited to lightning and hail 

as they would not be surface based. But they will be the herald of 

the moisture arriving back into our region.



Kimble



&&



.LONG TERM...  (Monday through Next Saturday)

Issued at 158 PM CDT Sat Apr 25 2026



Monday is clearly the most impactful weather day of the week. Not 

only does it bring the greatest severe weather threat but it also 

initiates a shift in the weather pattern toward cooler conditions 

for the rest of the week. The shortwave trough drives a surface low 

northeast out of Kansas toward the Upper Mississippi River. Ahead of 

the low, we'll find our area solidly in the warm, moist sector ahead 

of a cold front arriving from the northwest late in the day. The 

moist sector will be characterized by moderate to very strong 

instability (1000 to 3000 CAPE) along with strong wind shear (45 to 

55KT 0 to 6 KM). Once storms form in this environment they will 

quickly organize into supercells with a primary threat of large to 

very large hail and tornadoes. As storm coverage grows, 

consolidation into one or more clusters is expected with damaging 

winds becoming a greater threat along with a continued tornado 

threat. Storm coverage is likely to be greater to the north closer 

to the surface low, while further south in the open warm sector 

ahead of the front coverage may be more isolated especially 

initially.



There remains some uncertainty on the track of the low, with some 

guidance taking this as far north as Minneapolis or as far south a 

Des Moines. A closer track would favor greater storm coverage and 

potentially more backed low level winds and a greater tornado 

threat. There's also some uncertainty on how unstable the warm 

sector becomes with clouds potentially being a limiting factor. 

However, greater low level moisture and cooling aloft with the 

arrival of the trough will help ensure access to instability 

sufficient for supercell thunderstorms. So while we may be able to 

further refine the timing and location of the greatest threat in the 

coming days, for now we remain confident in a broad severe weather 

threat across the warm sector Monday afternoon and evening 

encompassing our entire forecast area.



All guidance indicates that Monday night's cold front clears our 

area by early morning Tuesday, shifting us back to a cooler, drier 

air mass. However, the next shortwave trough moves east pretty 

quickly behind the departed one on Tuesday, this time tracking 

further south through the MidSouth. Most guidance keep the moist 

sector well south of our area at this point, though some do have the 

front wobbling back north briefly on Tuesday to the point where we 

could see surface based convection in the southern CWA Tuesday 

afternoon. The more likely scenario is that any convection will be 

elevated in association with synoptic forcing with this trough. In 

either case, the better chances for another round of rain will be in 

the southern half of the forecast area on Tuesday afternoon and 

evening.



Monday and Tuesday's shortwave troughs help to expand the broader 

Canadian trough to encompass much of the lower 48 states by Midweek. 

This shifts the storm track to the south and puts us solidly in a 

cooler and largely drier pattern to end the week with Gulf moisture 

trapped well to the south. There may be a few embedded shortwaves in 

the Thursday/Friday time period that bring some light rain chances, 

but the threat for thunderstorms, particularly severe thunderstorms, 

ends after the early week activity. As additional cool air spills 

south later in the week we'll see daily highs and lows some 10 or 

more degrees below normal as we head into the first part of May.



Kimble



&&



.AVIATION...  (For the 00z TAFs through 00z Sunday Evening)

Issued at 549 PM CDT Sat Apr 25 2026



Dry and VFR conditions will prevail through the TAF period.



Jaja



&&



.LSX WATCHES/WARNINGS/ADVISORIES...

MO...None.

IL...None.

&&



$$



WFO LSX