Middle Grove, Missouri Weather Forecast Discussion

673
FXUS63 KLSX 130813
AFDLSX
Area Forecast Discussion
National Weather Service Saint Louis MO
313 AM CDT Sat Sep 13 2025
.KEY MESSAGES...
- The ongoing heat will continue through at least the middle of next
  week.
- There is a slight chance (15 - 25%) of showers and
  thunderstorms each afternoon from today through Wednesday.
&&
.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 311 AM CDT Sat Sep 13 2025
The temperature and precipitation forecast for today and Sunday are
essentially the same. Mid-level ridging, warm air advection, and
abundant sunshine will boost temperatures a few degrees from
yesterday`s, with widespread mid to upper 90s forecast. Warm air
advection will not be a factor tomorrow, so high temperatures will
be on par with those of today instead of warming further.
We are clipped by a Marginal Risk (1/5) for severe thunderstorms in
our far eastern counties in Illinois today, but any severe
thunderstorms should remain to our northeast where the better wind
shear will reside. In our CWA, HREF values of bulk shear this
afternoon top out at 25 kts near the Marginal Risk, which is well
southeast of where the best instability is expected (northeast
Missouri) and well northeast of where the bulk of convection is
forecast (southeast Missouri). With none of this overlapping, the
chances of us seeing strong to severe thunderstorms decreases. If a
thunderstorm is able to become strong, steep low-level lapse rates
will make gusty winds the primary threat.
Bulk shear values fall dramatically by tomorrow afternoon, so
despite increasing instability, the potential for strong
thunderstorms is much lower. Isolated pulse showers and
thunderstorms will be the nature of convection that develops.
Jaja
&&
.LONG TERM...  (Sunday Night through Friday)
Issued at 311 AM CDT Sat Sep 13 2025
Like this weekend, the forecast for Monday and Tuesday is nearly
copy and paste. With the mid-level ridge still influencing our
weather, high temperatures will remain in the 90s for the entire
area. The daily slight chance of isolated showers and thunderstorms
will maintain itself as well. The pattern begins to shift on
Wednesday as the ridge breaks down and a trough enters the Midwest.
Cluster analysis shows pretty good consistency regarding the
location and amplitude of the trough on Wednesday, and ensembles are
in consensus that portions of northeast Missouri will see increased
cloud cover and a high chance (70 - 90%) of light rain. Because of
this, there is high confidence that northeast Missouri and west-
central Illinois will drop to or likely below 90 degrees on
Wednesday, as corroborated by tight interquartile spreads at KIRK
and KUIN. The 75th percentile at these sites consistently cool
thereafter.
Confidence in the speed of the cooldown decreases with southern and
eastern extent as variability in the mid-level trough increases.
KSTL may fall below 90 degrees by Thursday or Friday whereas KSAR
may see a break as early as Friday or as late as early next week.
Uncertainty just becomes too high to draw any conclusions outside of
northeast Missouri/west-central Illinois at that timeframe.
Jaja
&&
.AVIATION...  (For the 06z TAFs through 06z Saturday Night)
Issued at 1042 PM CDT Fri Sep 12 2025
Mainly dry and VFR conditions are expected through the period. The
only exception will be a low (

NWS LSX Office Area Forecast Discussion