River Flood Warning 110, NWS St. Louis, MO

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
638 AM CDT Wed Jul 3 2024

.KEY MESSAGES...

- The combination of heat and humidity will allow heat index
  values to climb to around 105 degrees over parts of southeast
  Missouri where a Heat Advisory is in effect this afternoon into
  early this evening.

- There will be additional rounds of thunderstorms through
  Thursday night. A few of the storms could be severe this
  afternoon and this evening and again on Thursday afternoon and
  evening.

- In addition to the severe weather potential, locally heavy
  rainfall is possible with these thunderstorms.

&&

.SHORT TERM...  (Through Late Thursday Afternoon)
Issued at 422 AM CDT Wed Jul 3 2024

Highs will reach the lower 90s over southeast Missouri and dewpoints
are forecast to be in the mid to upper 70s over much of the area.
Peak heat index readings will reach around 105 over parts of
southeast Missouri, so I have issued a Heat Advisory for Reynolds,
Iron, and Madison counties from 11 am through 8 pm today.

I have gone ahead and canceled the flood watch early as the heavy
rainfall threat has ended over the northern CWA.  We are continuing
to see showers and thunderstorms over the central part of the CWA
early this morning.  These were occurring on the nose of the LLJ and
they should gradually weaken and move east over the next few hours
as the LLJ veers and weakens.  The associated outflow boundary will
move south into the southern part of the CWA this afternoon.  The
most likely time for additional thunderstorm development today will
be this afternoon over southeast Missouri into southwest Illinois
along this effective front where MLCAPES will be 2500+ J/kg with
deep layer shear of 30+ knots.  This could is favorable for
producing a few organized multicell clusters that could produce
damaging winds through early this evening.

The coverage of showers and thunderstorms will increase across the
area late this evening and overnight as a shortwave trough
approaches the area and the low level jet kicks back warranting 60-
90% PoPs.  We are still looking at PWATS between 2-2.5" and very
high warm cloud depths, and the HREF LPMM has some small spots with
with totals exceeding 3" tonight into tomorrow morning.  Will
continue to look at the potential for locally heavy rainfall tonight
into early Thursday.

Then there will be another risk for severe thunderstorms Thursday
afternoon and evening as yet another shortwave trough move across
the area where the warm front will intersect the incoming cold
front.  The combination of CAPE/shear favors a few supercells/
organized multicells capable of producing damaging winds and large
hail.

Britt

&&

.LONG TERM...  (Thursday Night through Tuesday)
Issued at 422 AM CDT Wed Jul 3 2024

Available guidance is still favoring the front moving through the
area on Thursday night with showers and thunderstorms moving out of
the southeastern part of the CWA on Friday.  Friday night into
Saturday look dry as large surface high moves across the area.  The
next upper trough moves through the area early next week bringing a
chance of showers and thunderstorms as early as Sunday.

Britt

&&

.AVIATION...  (For the 12z TAFs through 12z Thursday Morning)
Issued at 633 AM CDT Wed Jul 3 2024

Complex of showers and thunderstorms currently affecting the St.
Louis area terminals is expected to move out of the terminals by
14Z. Low clouds with MVFR and IFR ceilings will affect UIN/COU/JEF
through 17Z. There will be the chance for additional showers and
thunderstorms through the day into the evening, but coverage will
be too low to include in the TAF. A better chance for
thunderstorms will occur later this evening and overnight with the
potential for MVFR and and IFR ceilings and visibilities in heavy
rain.

Britt

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Heat Advisory from 11 AM this morning to 8 PM CDT this evening
     for Iron MO-Madison MO-Reynolds MO.

IL...None.
&&

WFO LSX

Hazardous Weather Outlook
National Weather Service St Louis MO
502 AM CDT Wed Jul 3 2024

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-041015-
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-
502 AM CDT Wed Jul 3 2024

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

.DAY ONE...Today and tonight.

There is a chance of thunderstorms over the region through tonight. A
few of these storms could be severe mainly across southeast Missouri
into southwest Illinois this afternoon and early this evening.
Damaging winds will be the primary threat. Locally heavy rainfall
will also be possible this afternoon and tonight.

Heat index values today will climb to around 105 degrees over parts
of southeast Missouri where a Heat Advisory is in effect.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

There is a chance of thunderstorms Thursday through Friday and again
through Tuesday. A few of these storms could be severe on Thursday
afternoon and evening over parts of central, east central, and
southeast Missouri. Damaging winds and large hail will be the primary
threats.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon over parts of
southeast Missouri and southwest Illinois.

Britt

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Preliminary Local Storm Report
National Weather Service St Louis MO
1045 AM CDT Wed Jul 3 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0700 AM     Rain             2 N Saint Charles       38.82N 90.51W
07/03/2024  E1.65 Inch       St. Charles        MO   CO-OP Observer

            Corrects previous rain report from 2 N Saint
            Charles.

&&

CS

Preliminary Local Storm Report
National Weather Service St Louis MO
1046 AM CDT Wed Jul 3 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0715 AM     Rain             1 S Cottleville         38.74N 90.65W
07/03/2024  E2.51 Inch       St. Charles        MO   CO-OP Observer

            Corrects previous rain report from 1 S
            Cottleville.

&&

CS

Preliminary Local Storm Report
National Weather Service St Louis MO
1052 AM CDT Wed Jul 3 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0700 AM     Rain             2.4 E Labadie           38.52N 90.81W
07/03/2024  E3.62 Inch       Franklin           MO   Cocorahs

&&

CS

Preliminary Local Storm Report
National Weather Service St Louis MO
1054 AM CDT Wed Jul 3 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1053 AM     Rain             5 N Columbia            39.03N 92.33W
07/03/2024  E5.80 Inch       Boone              MO   Public

&&

CS

Preliminary Local Storm Report
National Weather Service St Louis MO
1113 AM CDT Wed Jul 3 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0700 AM     Rain             1 NNE Troy              38.99N 90.97W
07/03/2024  E2.72 Inch       Lincoln            MO   Cocorahs

&&

CS