749 
FXUS63 KLSX 281925
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
225 PM CDT Tue Jul 28 2026

.KEY MESSAGES...

- Near to slightly below normal temperatures (and humidity) are 
  forecast Wednesday through Thursday.

- The next chance (60-80%) of showers and a few thunderstorms is
  from late Thursday night - Friday night.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 221 PM CDT Tue Jul 28 2026

A midlevel shortwave trough is currently evident on GOES-19 
satellite imagery over west-central Missouri. This feature is 
slightly faster than anticipated 24 hours ago, and as a result, 
has led to thicker clouds farther east into our area. This has 
helped keep temperatures a bit cooler than forecast, 
particularly in/near central Missouri. Clouds have been thickest
and most persistent in those locations where temperatures are 
only in the low to mid 80s in some spots as of 2 PM. The heat 
advisory has been trimmed back from the northwest due to these 
cooler temperatures. Farther east/southeast, there have been 
enough breaks in the clouds to allow temperatures to climb to 
near or above the 90 degree mark. With anomalously high 
dewpoints still lingering back behind the surface cold front, 
this has led to heat index values in the 100-105 degree range 
with a few isolated spots above 105 degrees. No changes to heat 
headlines for the remainder of the area and they are on track to
expire at 7 PM.

Dry conditions are expected to continue across much of the area, 
though some light rain may continue to just clip parts of 
central/southeast Missouri. Cannot completely rule out a 
thunderstorm or two, but better chances for thunderstorms appear to 
be closer to the Missouri-Arkansas border closer to the synoptic 
cold front. Overnight, look for winds to veer more to the northeast, 
bringing in cooler and less humid air into the bi-state area. Near 
to slightly below normal temperatures are forecast day and night 
Wednesday through Thursday with dewpoints (relative humidity) values 
also closer to the 25th percentile. Dry weather is also expected 
areawide as a ridge of surface high pressure builds into the mid-
Mississippi Valley.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 221 PM CDT Tue Jul 28 2026

(Thursday Night - Sunday)

Increasing chances of rain and a few storms are forecast beginning 
late Thursday night as a midlevel shortwave trough moves into the 
mid-Missouri Valley/Upper Midwest. This feature has trended a bit 
more to the north over the past 36-48 hours, and has consequently 
shifted the best threat for widespread (and potentially 
more significant) rainfall totals northward as well. It still 
looks like our area will likely see at least some rainfall 
though with a slow-moving cold frontal passage, but the higher 
totals are likely to stay to the north where the stronger 
mid/upper level forcing is expected to reside. Probabilities for
at least 1" of rain through Sunday on the LREF are in the 
20-40% range, and even the 95th percentile is at or below 2.5".
Therefore, it does not appear that heavy rainfall/flash 
flooding is likely at this time. There also does not appear to 
be any severe threat with limited instability most likely. GEFS 
chances for 1000+ J/kg of SBCAPE stay below 50% on Friday 
afternoon/evening, and drop further this weekend.

Temperature wise, below normal daytime readings with values closer 
to normal overnight are expected with plenty of cloud cover through 
the period along with rain chances. Spread in the NBM IQR is pretty 
low even out through Sunday, generally at or below 5 degrees. Even 
the 75th percentile of the NBM shows below normal high temperatures, 
further increasing confidence in the forecast below normal highs.

(Sunday Night - Next Tuesday)

Forecast uncertainty increases heading into early next week with 
respect to how the midlevel shortwave trough evolves. More members 
from the grand ensemble show it cutting off (~80%) looking at the 
500-hPa height clusters, but exactly where is uncertain. A majority 
of members from the cutoff cluster show it near the lower Ohio 
Valley, though a smaller percentage are farther to the west. 
Assuming the low is to our southeast, continued cool 
temperatures would be expected along with dry weather. However, 
if the low is cutoff farther west, increased rain chances would 
exist. Either scenario though would continue the below normal 
temperatures, particularly during the day.

&&

.AVIATION /18Z TAFS THROUGH 00Z THURSDAY/...
Issued at 1205 PM CDT Tue Jul 28 2026

Some light rain may skirt KCOU/KJEF over the next few hours, but
visibilities should stay VFR even if any rain does reach either
terminal. Otherwise, dry conditions are expected to continue
with northerly winds veering more to the northeast tonight into
Wednesday morning.

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Heat Advisory until 7 PM CDT this evening for MOZ049-059-
     061>064.
     Extreme Heat Warning until 7 PM CDT this evening for MOZ065-
     072>075-084-085-099.
IL...Heat Advisory until 7 PM CDT this evening for ILZ064-069-070-
     100.
     Extreme Heat Warning until 7 PM CDT this evening for ILZ074-
     079-101-102.

&&

$$

SHORT TERM...Gosselin
LONG TERM...Gosselin
AVIATION...Gosselin