258 

FXUS63 KLSX 060713

AFDLSX



Area Forecast Discussion

National Weather Service Saint Louis MO

213 AM CDT Sat Jun 6 2026



.KEY MESSAGES...



- Isolated to scattered showers and thunderstorms are forecast today 

  through Monday, mainly during the afternoon and evening. 



- The primary thunderstorm threat is locally heavy rainfall, 

  especially on Sunday and Monday. 



- Summer-like heat and humidity build into the region starting

  Tuesday next week, with a 30% chance of heat index values reaching

  and exceeding 100 degrees through the rest of the week.





&&



.SHORT TERM... (Through Sunday Night) 

Issued at 211 AM CDT Sat Jun 6 2026



Quasi-zonal flow extends across the Central Plains eastward through 

the Middle Mississippi Valley as a cutoff spins over the Southern 

Plains per water vapor imagery. A bifurcated low-level jet is 

fueling convection over the Middle Missouri Valley and Great Lakes. 

Of immediate concern, upwind propagation vectors favor the 

convection over the Middle Missouri Valley moving south-

southeastward toward the CWA through this morning. However, with the 

western prong of the low-level jet weakening through the morning and 

the air mass south of the convection being increasingly dry and 

stable, confidence remains high that this convection will struggle 

to reach the CWA. A reasonable worst-case scenario is that outflow 

helps force isolated to scattered weak showers and thunderstorms 

across Knox, Lewis, Adams, and Brown counties around sunrise. 



Our next round of convective potential comes this afternoon as the 

atmosphere ahead of the aforementioned cutoff drifting northeastward 

becomes increasingly unstable. The 00z HREF and REFS means have 

approximately 2,500-3,000 J/kg of SBCAPE across the CWA during peak 

heating today, with this instability and weak forcing from the 

cutoff inducing CI at roughly 3pm. Deep-layer shear of 10-20 kts 

favors disorganized single cells to multi-cells primarily west of 

the Mississippi River where lift will be greatest; though, there is 

at least a low threat (15-20% chance) for showers and thunderstorms 

area-wide. There is a low chance that residual outflow boundaries 

and/or a weak front just north of the CWA may provide a focus for CI 

in proximity to greater instability this afternoon and evening. The 

greater instability favors relatively stronger updrafts compared to 

elsewhere in the CWA, leading to a localized threat of hail up to 1" 

in diameter and damaging wind gusts. However, the weak shear 

suggests that updrafts will tend to be too short-lived to provide a 

severe threat; therefore, the SPC Day 1 Marginal Risk will not be 

publicly messaged. 



Diminishing instability with the loss of day-time heating will lead 

to decreasing convective coverage this evening. The exception will 

be areas west of the Mississippi River where forcing from the 

approaching cutoff will keep a low chance (30%) for showers and 

thunderstorms going through the overnight hours. As this shortwave 

continues to pass overhead during the day Sunday and instability 

builds once again, convective coverage will increase. Thanks to more 

widespread lift via the shortwave, the entire CWA has a 80-90% 

chance of seeing scattered showers and thunderstorms at times Sunday 

into Sunday evening. Deep layer shear is expected to be weak once 

again, with the greater storm coverage and PWAT just under 2" 

supporting a threat of locally heavy rainfall.



Elmore



&&



.LONG TERM... (Monday through Friday) 

Issued at 211 AM CDT Sat Jun 6 2026



With the aforementioned cutoff only slowly lifting northeastward 

through the Midwest, guidance consensus is that rain chances will 

linger across the Middle Mississippi Valley on Monday. Uninhibited 

Gulf flow will keep dew points in the low 70s, yielding SBCAPE 

around 2,000 J/kg to as much as 3,000 J/kg per the 90th percentile 

of ensemble guidance. While deep-layer shear of around 20 kts leads 

to low confidence in organized severe convection, when coupled with 

PWAT around the 99th percentile of climatology, there is concern 

for localized heavy rainfall. 



Confidence in the forecast decreases as we get into the middle of 

next week through the end of the week, with both deterministic 

guidance and ensemble clusters differing on the phasing of an upper-

level trough over the northwestern CONUS and expansive ridging over 

the southern CONUS. A deeper trough and one that encroaches more upon 

the Midwest will keep the ridge further south relative to the CWA, 

favoring temperatures topping out around 90 degrees Tuesday through 

Thursday (50-80% chance per global ensembles). If the ridge is able 

to build further northward into the CONUS, then portions of the CWA 

could see high temperatures warm into the mid 90s (30% chance). The 

current forecast (NBM) favors the warmer solutions and represents a 

realistic "worst-case" scenario. If this scenario comes to fruition, 

then the first heat headlines of the season will be needed for 

portions of the CWA.



Elmore



&&



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

Issued at 1027 PM CDT Fri Jun 5 2026



A large majority of the period will be VFR with light, diurnal

surface winds around 5-10 knots that become light and variable in

the overnight hours. Mid/upper level clouds continue to increase

out of the southwest ahead of a disturbance in the southern

Plains, which eject northeast later in the day. The system remains

departed to southwest until afternoon, when a isolated to widely 

scattered showers and perhaps an isolated thunderstorm are 

possible. The limited coverage makes it too difficult to 

pinpoint any one terminal that could be impacted, but 18z 

Saturday afternoon to 02z Sunday would be the best timeframe for 

convection. Once beyond sunset isolated activity fades as we await

better chances(30-60%) that arrive early Sunday morning.



Maples



&&



.LSX WATCHES/WARNINGS/ADVISORIES...

MO...None.

IL...None.

&&



$$



WFO LSX