258
FXUS63 KLSX 010855
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
355 AM CDT Thu Oct 1 2026

.KEY MESSAGES...
- Widespread showers and a few thunderstorms will overspread the area
  today into tonight. One to two inches of rain is likely
  across the area with locally higher amounts.

- There is a chance for flooding on the Mississippi and Missouri Rivers,
  as well as smaller rivers in the northeast Missouri due to
  heavy rainfall upstream.

- Above normal temperatures will continue today, however
  temperatures will fall back to normal or below normal Friday
  into the weekend.&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 354 AM CDT Thu Oct 1 2026

Little change to the forecast this morning as a cold front
drifts southeast through Missouri and Illinois today and
tonight. Low level moisture convergence is producing widely
scattered showers over Missouri, and this activity should
increase in coverage through the day as the front approaches and
broad scale forcing increases with the approaching upper
trough. NBM QPF has been pretty consistent over the past few
runs showing widespread 1-2 inches of rainfall through Friday
across the area with some locally higher amounts. 1 hour flash
flood guidance is 1.75 to 3+ inches across the area, and 3-6
hour guidance is at least 2-5+ inches. Soils and streams should
therefore be able to handle 1-2 inches of rainfall with little
issue. However, short-range LPMM forecasts from the HREF and
REFS show a few streaks of higher QPF in excess of 2 inches
tonight. The streaks in both models are oriented very similarly
from southwest to northeast along and to the west of I-44. The
HREF is the wetter of the two with a few spots of 4+ inches
between Jefferson City and the St. Louis Metro Area. If these
higher rainfall amounts materialize there could be some
flooding, particularly in the St. Louis Metro area with all of
the impermeable surfaces which maximize runoff. With this in
mind, most of the CAMs which compose the HREF show a fairly
progressive area of rain, so those streaks of 4+ inches are
likely the worst-case scenario. Will therefore continue the
"wait and see" approach and not issue any new flood watches at
this time. Longer-term mainstem river flooding from upstream
rain will also be a possibility, and latest guidance from RFCs
puts a few points along the Missouri and Mississippi into flood.
However most of the precip has yet to fall and these flood
forecasts are mostly based on QPF. Will continue to monitor
river forecasts as more rain gets onto the ground and issue
flood products as needed.

Expect one more day of above normal temperatures across most of the
area today.  Persistent southerly flow ahead of the cold front will
push highs back into the 80s across east central and southeast
Missouri into southwest Illinois.  Temperatures farther west and
north will only reach the low to mid 70s due to denser cloud cover
and occasional precipitation.  Clouds and cold advection behind the
cold front will keep temperatures as much as 20 degrees cooler on
Friday in the mid 60s to around 70.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 354 AM CDT Thu Oct 1 2026

The remainder of the forecast continues to look seasonably cool
and dry into the middle of next week. A broad high pressure
system builds into the Midwest late Friday and then moves east
through the Great Lakes Saturday. Another upper level short wave
then moves through the Midwest Saturday night into Sunday. This
pushes a reinforcing cold front through Missouri and Illinois
late Sunday which will lower temperatures again. The GFS is
printing out a few specks of QPF Sunday along the front, however
moisture return ahead will be minimal at best so I don`t think
there will be much if any precip. Temperatures will be a little
warmer in the low to mid 70s on both Saturday and Sunday with
full or nearly full sunshine. Then temperatures drop into the
mid 60s to around 70 again Monday and Tuesday behind the
reinforcing front. The wind swings back around to the southwest
on Wednesday as the high moves over the East Coast and
temperatures rise back into the mid and upper 70s.

&&

.AVIATION /06Z TAFS THROUGH 12Z FRIDAY/...
Issued at 1221 AM CDT Thu Oct 1 2026

Areas of rain with a few embedded thunderstorms will overspread
northeast Missouri and west central Illinois ahead of a cold
front Thursday morning, along with MVFR and IFR ceilings. This
rain and lower ceilings will continue to spread southeast
through Thursday as the front moves into and through the region.
Rain will begin moving out early Friday morning along with
improving flight conditions across parts of central and
northeast Missouri into west central Illinois. Low flight
conditions and occasional showers will likely continue for the
remainder of the area through 12Z Friday.

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.

&&

$$

SHORT TERM...Carney
LONG TERM...Carney
AVIATION...Carney