Flash Flood Warning 33, NWS St. Louis, MO

382 
WGUS73 KLSX 041008
FFSLSX

Flash Flood Statement
National Weather Service St Louis MO
508 AM CDT Fri Aug 4 2023

MOC151-041230-
/O.CON.KLSX.FF.W.0033.000000T0000Z-230804T1230Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Osage MO-
508 AM CDT Fri Aug 4 2023

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 730 AM CDT THIS 
MORNING FOR OSAGE COUNTY...

At 508 AM CDT, local law enforcement reported flash flooding from 
heavy rainfall. Highway U near Linn was impassable due to flooding. 
Although the heaviest rainfall has ended, flash flooding may still 
be ongoing through the warned area.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Law enforcement 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...
  Linn, Wardsville, Bland, Freeburg, Chamois, Westphalia, Rich 
  Fountain, Meta, Argyle, Morrison, Loose Creek, Frankenstein, 
  Bonnots Mill and Koeltztown.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

&&

LAT...LON 3870 9164 3829 9164 3829 9220 3837 9219
      3839 9213 3840 9211 3844 9216 3847 9217
      3847 9215 3846 9211 3847 9202 3850 9201
      3853 9203 3856 9202 3856 9200 3859 9198
      3860 9194 3866 9187 3868 9176 3871 9173

FLASH FLOOD...OBSERVED

$$

Kimble

087 
WGUS73 KLSX 041227
FFSLSX

Flash Flood Statement
National Weather Service St Louis MO
727 AM CDT Fri Aug 4 2023

MOC151-041237-
/O.EXP.KLSX.FF.W.0033.000000T0000Z-230804T1230Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Osage MO-
727 AM CDT Fri Aug 4 2023

...FLASH FLOOD WARNING AT 730 AM CDT THIS MORNING FOR OSAGE COUNTY 
HAS BEEN REPLACED WITH A FLOOD WARNING...

LAT...LON 3870 9164 3829 9164 3829 9220 3837 9219
      3839 9213 3840 9211 3844 9216 3847 9217
      3847 9215 3846 9211 3847 9202 3850 9201
      3853 9203 3856 9202 3856 9200 3859 9198
      3860 9194 3866 9187 3868 9176 3871 9173

$$

Elmore

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1052 PM CDT Thu Aug 3 2023

.UPDATE...
Issued at 724 PM CDT Thu Aug 3 2023

...Increasing heavy rain and flash flood threat tonight, as well
as increasing severe weather potential...

A flash flood watch has been issued from portions of central MO
across all of southeast MO into southern IL from 03-14z. The
latest surface analysis shows a well-defined quasi-stationary
front draped from southern KS across southern MO. The air mass
along and south of this front is very unstable at this time with
SBCAPE of 5000+ J/KG. Thunderstorms are expected to develop across
portions of central MO later this evening as an increasing west-
southwesterly LLJ provides strong lift of this unstable air mass
to the north of the frontal zone, and lift associated with a
migratory MCV in NW MO impacts the area. While the overall set- up
is not as prolific as the previous few nights, widespread
thunderstorms are expected to evolve from central into southeast
MO resulting in an elongated MCS with regions of training storms.
High rainfall rates with the stronger storms are expected due to
deep warm cloud depths of 4+ km and PWs of 2.2 inches or greater.
The latest LPPM guidance from the 12z HREF supports localized
rainfall totals of 4+ inches. The heavy rain last night and early
this morning has produced a broad region of saturated soils in
swath from central into southeast MO with MRMS CREST Soil moisture
of 60-80+ percent, which has suppressed the FFG values to 1.5
inches or less in 3 hours. As a result, locally heavy rainfall
resulting in flash flooding will be easier to develop, and given
this threat, the flash flood watch has been issued. There is also
a greater severe weather threat tonight than previously
anticipated. The very unstable air along with deep layer shear of
around 30 kts will support potential for organized severe storms,
possibly a short-lived supercell or two, but more likely multicell
storms possibly evolving into short bowing clusters capable of
damaging winds and large hail.

Glass

&&

.SHORT TERM...  (Through Late Friday Night)
Issued at 327 PM CDT Thu Aug 3 2023

1) A few showers, perhaps an isolated thunderstorm, are possible
this afternoon. Thunderstorm potential will increase later this
evening into the overnight period. A few of these thunderstorms may
be strong to severe with large hail, damaging wind and locally heavy
rainfall.

2) Active weather continues into Friday with yet another round of
thunderstorms possible with a few strong thunderstorms possible.

Clouds have lingered across the region longer than expected, helping
to temper any surface destablization this afternoon with SPC
mesoanalysis showing 25-50 J/kg of CIN extending from central MO
through southeast MO. A notable separation extists between thicker
cloud cover in these areas and much greater surface instability over
south-central and southwest MO, where 3000+ J/kg of SBCAPE exists.
Fortunately, the remnant MCV tracking over southwest sections of the
CWA hasn't had much to work with, producing scattered showers from
central MO to east-central and southeast MO. Thought much of the
actitity have remained lightning-free, a rumble of thunder cannot be
ruled out over far southwest sections of the forecast area.

Another MCV is expected to push out of Kansas and into northwest MO
late this afternoon. CAMs have varied on their handling of this
feature, ranging from next to nothing to loosely clustered
thunderstorms. The latest 18z run of the HRRR has truly backed off
development over northwest MO with development favored over central
sections of the state. This make better sense given the remnant
surface boundary extending across central sections of MO. South of
the boundary and within the warm sector, a corridor of MUCAPE values
are expected to range from 2000-3000 J/kg along a wind of 30-35
knots of 0-6km shear. However, the LLJ is more compact and focused
over southwest MO late tonight with the nose of the jet directed at
south-central and southeast MO. Furthermore, mid-level lapse rates
of 7-7.5C decrease to 6C from southwest MO through east-central MO.
A loosely clustered area of thunderstorms may produce a few strong
to severe thunderstorms with large hail and damaging winds with the
window likely limited to the 04z-08z. Despite PWATs of 2-2.5 inches,
thunderstorms will have movement and a bit less training potential
as the boundary is shifted slightly further southwest. Flood
potential looks localized, largely to areas that have seen rounds of
heavy rain in recent days. PMM/LPMM show localized striations of
2-4 inch amounts are possible where this system tracks, so we will
need to monitor this should it shift over areas that were
impacted last night.

The boundary continues to linger over the region in the same manner
it has today, though a bit further southwest. A few showers and an
isolated thunderstorm linger into early Friday. Yet another MCV
ejects out of eastern Kansas with additional chances for showers and
thunderstorms Friday evening over central MO, pushing southeast
through the late evening. CAMs have a variety of scenarios once
again, but the general theme is for the system to take a similar
track around the mid-level ridge Friday evening into Friday night
with a few strong thunderstorms possible once again.

Maples

.LONG TERM...  (Saturday through Next Thursday)
Issued at 327 PM CDT Thu Aug 3 2023

(Saturday - Next Thursday)

A broad upper ridge continues to encompass the southern U.S. with
quasi-zonal flow through the central portions of the country. Near
normal temperatures extend into the weekend with episodic chances
for showers and thunderstorms. The brunt of the activity looks to
arrive late Sunday into early Monday along a cold front the will
push from north to south

Ensembles show a fairly limited spread through the long range period
with a general trend toward cooler and drier conditions. Monday
afternoon through early Wednesday. However, I am hesitant to call it
a completely dry forecast. There are some indications that the
southward progress of the boundary may slow a bit as an upper level
shortwave moves across the region. Some semblance of shower
potential may linger through the day Monday. If there is a
completely dry day next week, it would favor Tuesday with surface
high pressure building into the mid-Mississippi Valley from the
Plains.

The active pattern returns by midweek as the boundary begins to
shift back northward as a warm front and additional disturbance
track through the Midwest late Wednesday into Thursday.

Maples

&&

.AVIATION...  (For the 06z TAFs through 06z Friday Night)
Issued at 1046 PM CDT Thu Aug 3 2023

Patchy light rain showers and patchy MVFR stratus was located from
central MO into the St. Louis area at 0330z. Some of this patchy
stratus may persist a bit after 06z, otherwise we are still
anticipating a big uptick in showers and storms during the
overnight hours. Things look like they will get started a little
later than earlier thinking. Sometime between 06-07z a complex of
thunderstorms is expected to develop across central MO, elongate
and shift southeastward through the overnight hours. KJEF and KCOU
have the highest potential for thunderstorm impacts, while
thunderstorms may stay just southwest of the St. Louis terminals
and they will just have showers. In the wake of this activity,
around 10z, MVFR flight conditions due to stratus/fog will develop
and persist into mid-late morning with conditions improving to
VFR by 18z.

Glass

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Flood Watch until 9 AM CDT Friday for Boone MO-Callaway MO-Cole
     MO-Crawford MO-Franklin MO-Gasconade MO-Iron MO-Jefferson
     MO-Madison MO-Moniteau MO-Osage MO-Reynolds MO-Saint
     Francois MO-Sainte Genevieve MO-Washington MO.

IL...Flood Watch until 9 AM CDT Friday for Monroe IL-Randolph IL.

&&

WFO LSX

Hazardous Weather Outlook
National Weather Service St Louis MO
816 PM CDT Thu Aug 3 2023

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-050130-
Greene IL-Macoupin IL-Montgomery IL-Bond IL-Fayette IL-Clinton IL-
Marion IL-Washington IL-Randolph IL-Adams IL-Brown IL-Pike IL-
Calhoun IL-Jersey IL-Madison IL-Saint Clair IL-Monroe IL-Knox MO-
Lewis MO-Shelby MO-Marion MO-Monroe MO-Ralls MO-Pike MO-Boone MO-
Audrain MO-Moniteau MO-Cole MO-Osage MO-Callaway MO-Montgomery MO-
Lincoln MO-Gasconade MO-Warren MO-Saint Charles MO-Franklin MO-
Saint Louis MO-Saint Louis City MO-Jefferson MO-Crawford MO-
Washington MO-Saint Francois MO-Sainte Genevieve MO-Iron MO-
Madison MO-Reynolds MO-
816 PM CDT Thu Aug 3 2023

This Hazardous Weather Outlook is for portions of eastern and
central Missouri as well as west central and southwest Illinois.

.DAY ONE...Tonight.

Thunderstorms are expected across portions of central and southeast
Missouri and southwest Illinois into early Friday morning. Locally
heavy rainfall with the storms could produce flash flooding. A few
storms could also be severe with damaging winds and large hail as the
main threats.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Thunderstorms are possible each day through Monday. There is another
chance of thunderstorms on Wednesday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed. Spotters are asked to relay
any severe weather or flooding reports, and rainfall amounts of 2
inches or greater.

Glass