Flash Flood Warning 42, NWS St. Louis, MO

951 
WGUS73 KLSX 271900
FFSLSX

Flash Flood Statement
National Weather Service St Louis MO
200 PM CDT Sat Jun 27 2026

ILC121-272045-
/O.CON.KLSX.FF.W.0042.000000T0000Z-260627T2045Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Marion IL-
200 PM CDT Sat Jun 27 2026

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 345 PM CDT THIS
AFTERNOON FOR SOUTHERN MARION COUNTY IN SOUTH CENTRAL ILLINOIS...

At 200 PM CDT, emergency management reported thunderstorms producing
heavy rain across the warned area. Between 2 and 5.5 inches of rain
have fallen. Additional rainfall amounts of 1 to 2 inches are
possible in the warned area. Flash flooding is ongoing or expected to
begin shortly.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Emergency management reported.

IMPACT...Flash flooding of small creeks and streams, urban areas,
         highways, streets and underpasses as well as other poor
         drainage and low-lying areas.

Some locations that will experience flash flooding include...
  Centralia, Salem, Sandoval, Wamac, Central City, Odin, Omega, Helm,
  Iuka, Junction City, Kell, Walnut Hill, Cartter and Selmaville.

This includes Interstate 57 in Illinois between exits 109 and 116.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.

Be aware of your surroundings and do not drive on flooded roads.

&&

LAT...LON 3873 8870 3848 8870 3848 8897 3847 8900
      3847 8914 3862 8914

FLASH FLOOD...OBSERVED

$$

GK

762 
WGUS53 KLSX 272015
FFWLSX
ILC121-272145-
/O.EXT.KLSX.FF.W.0042.000000T0000Z-260627T2145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service St Louis MO
315 PM CDT Sat Jun 27 2026

The National Weather Service in St Louis has extended the

* Flash Flood Warning for...
  Southern Marion County in south central Illinois...

* Until 445 PM CDT.

* At 315 PM CDT, emergency management reported flooding across the
  warned area. Between 3 and 6 inches of rain have fallen. Additional
  rainfall amounts up to 1 inch are possible in the warned area.
  Flash flooding is ongoing.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Emergency management reported.

  IMPACT...Flash flooding of small creeks and streams, urban areas,
           highways, streets and underpasses as well as other poor
           drainage and low-lying areas.

* Some locations that will experience flash flooding include...
  Centralia, Salem, Sandoval, Wamac, Central City, Odin, Omega, Helm,
  Iuka, Junction City, Kell, Walnut Hill, Cartter and Selmaville.

This includes Interstate 57 in Illinois between exits 109 and 116.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.

Be aware of your surroundings and do not drive on flooded roads.

&&

LAT...LON 3873 8870 3848 8870 3848 8897 3847 8900
      3847 8914 3862 8914

FLASH FLOOD...OBSERVED

$$

GK

916 
WGUS73 KLSX 272141
FFSLSX

Flash Flood Statement
National Weather Service St Louis MO
441 PM CDT Sat Jun 27 2026

ILC121-272151-
/O.EXP.KLSX.FF.W.0042.000000T0000Z-260627T2145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Marion IL-
441 PM CDT Sat Jun 27 2026

...FLASH FLOOD WARNING WILL EXPIRE AT 445 PM CDT THIS AFTERNOON FOR
SOUTHERN MARION COUNTY IN SOUTH CENTRAL ILLINOIS...

The heavy rain has ended. Flooding is no longer expected to pose a
threat. Please continue to heed remaining road closures.

&&

LAT...LON 3873 8870 3848 8870 3848 8897 3847 8900
      3847 8914 3862 8914

$$

GK

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1243 PM CDT Sat Jun 27 2026

.KEY MESSAGES...

- Scattered showers and thunderstorms continue across the region
  through tonight, though the threat for flash flooding or severe
  weather is low.

- The first heat wave of the summer begins on Sunday. Dangerous
  heat index values over 100 degrees are expected to last at
  least through Thursday.

&&

.SHORT TERM... (Through Tonight)
Issued at 210 AM CDT Sat Jun 27 2026

A weak and nearly stationary front remains draped west to east
across the center of our forecast area this morning. To the south of
the front, light southerly winds have brought very humid conditions
northward, with dewpoints rising well into the 70s. To the north,
ENE flow has brought low clouds and slightly cooler conditions. In
some places, particularly where the front has sagged southward
overnight in central Missouri, areas of fog have developed.
Convective activity has focused on a few thunderstorm clusters
stretching from the southern High Plains eastward to the Ohio River
Valley. Our area has thus far been spared the more widespread
thunderstorms and heavy rainfall. However, with the front in the
vicinity we do still expect scattered convection over the next few
hours in particular, with this likely decreasing in coverage through
the morning hours. High precipitable water values (near 2 inches)
remain in place, so any thunderstorms will be capable of intense
local downpours. However, storm motions are expected to be quick
enough to prevent a significant threat of flash flooding. Because of
this reduced threat, the Flood Watch has been canceled.

The front will begin to lift northward today and especially tonight.
So long as it remains in the area we cannot rule out scattered
showers and thunderstorms along it. Convective activity likely picks
up in coverage after sunset tonight as a southwesterly low level jet
begins to push the front further northeastward. Again, locally heavy
rainfall is possible with this considering the very moist
environment, but the synoptic situation favors steady storm motions
which prevents a widespread flash flood threat.

Kimble

&&

.LONG TERM... (Sunday through Friday)
Issued at 210 AM CDT Sat Jun 27 2026

The surface front lifts fully northeast of our forecast area by
early Sunday, ending the rain chances and initiating a substantial
warm up. Upper level ridging builds over the Mississippi River while
troughing develops over the Western US and Northeast states. This
nearly stationary ridge allows for building heat on top of the
already high humidity levels in place. Temperatures are expected to
soar into the mid 90s on Sunday, with temperatures even a bit higher
over the following few days. When combined with the humidity,
dewpoints well into the 70s, the heat index will reach or exceed 100
degrees area wide beginning Sunday afternoon. Even higher heat index
values, up to as high as 110 degrees, are possible in spots, though
this will depend on subtle daily variations in humidity.

This period of high heat and humidity will be with us for a while.
We continue to have strong confidence that it will last through at
least Thursday, though it may last in some areas right through the
Independence Day weekend. Most guidance has the ridge weakening a
bit by the end of the week, though still persisting in some form
through the weekend. As the ridge weakens, daily chances for
thunderstorms start to creep back into the forecast providing a
potential break in the heat. We have issued a Heat Advisory for
nearly the entire forecast area for Sunday through Thursday as this
is the period we have the strongest confidence in dangerous heat.
For metro St Louis we have issued an Excessive Heat Watch as local
heat island effects make reaching heat index values of 105 or 110
more likely in this area. However, there's still enough uncertainty
on those more extreme values to warrant only a Watch at this time.
The Advisory and any subsequent potential Warnings may eventually be
extended in time as confidence in the duration of the heat improves.

Kimble

&&

.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1229 PM CDT Sat Jun 27 2026

The front that has been responsible for showers and thunderstorms
the last couple of days remains in the area and is serving as the
focus for another round of convection. Greatest impacts are
expected early this afternoon at KSUS, KCPS, and possibly KSTL,
with a lower threat at KCOU and KJEF. While KUIN remains north of
the front and only has a very low chance of seeing rain this
afternoon, the site is expected to be beneath low ceilings through
much of the afternoon. While VFR conditions are forecast here by
22z, there is a low chance that MVFR ceilings are continuous
through the evening.

The front will lift northward tonight and serve as the focus for
another round of showers and thunderstorms, with a low chance for
impacts at KSUS, KSTL, KCPS, and KUIN. Depending on the timing of
the front, forecasted ceilings may not be low enough, and there is
a low chance for a brief period of IFR conditions at KUIN. Once
the front lifts northward and clear of the region early tomorrow,
VFR flight conditions are then expected area-wide.

Elmore

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Heat Advisory from noon Sunday to midnight CDT Thursday night
     for Audrain MO-Boone MO-Callaway MO-Cole MO-Crawford MO-
     Franklin MO-Gasconade MO-Iron MO-Knox MO-Lewis MO-Lincoln
     MO-Madison MO-Marion MO-Moniteau MO-Monroe MO-Montgomery MO-
     Osage MO-Pike MO-Ralls MO-Reynolds MO-Saint Francois MO-
     Sainte Genevieve MO-Shelby MO-Warren MO-Washington MO.

     Extreme Heat Warning from noon Sunday to midnight CDT Thursday
     night for Jefferson MO-Saint Charles MO-Saint Louis City MO-
     Saint Louis MO.

IL...Heat Advisory from noon Sunday to midnight CDT Thursday night
     for Adams IL-Bond IL-Brown IL-Calhoun IL-Clinton IL-Fayette
     IL-Greene IL-Jersey IL-Macoupin IL-Marion IL-Montgomery IL-
     Pike IL-Randolph IL-Washington IL.

     Extreme Heat Warning from noon Sunday to midnight CDT Thursday
     night for Madison IL-Monroe IL-Saint Clair IL.

&&

WFO LSX