Flash Flood Warning 26, NWS St. Louis, MO

619 
WGUS73 KLSX 021458
FFSLSX

Flash Flood Statement
National Weather Service St Louis MO
958 AM CDT Tue Aug 2 2022

ILC051-021508-
/O.CAN.KLSX.FF.W.0026.000000T0000Z-220802T1630Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Fayette IL-
958 AM CDT Tue Aug 2 2022

...FLASH FLOOD WARNING FOR NORTHEASTERN FAYETTE COUNTY HAS BEEN 
REPLACED WITH A FLOOD WARNING...

LAT...LON 3882 8880 3922 8903 3922 8881 3891 8881
      3891 8869 3883 8870

$$

19

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
634 AM CDT Tue Aug 2 2022

.SHORT TERM...  (Through Wednesday Night)
Issued at 438 AM CDT Tue Aug 2 2022

A warm and humid airmass remains over the Mid Mississippi Valley
this morning.  The weak front which moved into northern Missouri and
central Illinois yesterday stalled last night and is beginning to
drift back to the north as a warm front this morning.  The southeast
end of the front has been the slowest to move as it's being
continually reinforced by ongoing convection, but I expect it will
begin moving later this morning as the convection finally
dissipates. This will put the entire area into warm south-southwest
flow today.  There is some convection over southern Iowa this
morning which will likely spread some mid/high level clouds
southeast across our forecast area, but I expect these clouds will
thin and dissipate this morning, leaving us with a partly to mostly
sunny sky.  Between the warm airmass already in place, and strong
insolation and southerly flow, I expect temperatures will be at
least as warm today as they were on Monday, if not a degree or two
warmer in spots.  Heat index values across the majority of the area
were 105+ on Monday (with the exception of some of northeast
Missouri and west central Illinois).  Dew point temperatures may be
a bit lower in spots today, particularly over the eastern Ozarks
where drought conditions linger, and downstream into east central
Missouri, but the slightly warmer temperatures will likely balance
the less humid air to produce heat index values in excess of 105
degrees again today.  Additionally, with the warm southwest flow
over the entire area, temperatures should be warm enough in
northeast Missouri and west central Illinois to push the the heat
index to around 105 today, so we've extended the heat advisory to
include these areas today.

Most deterministic guidance is showing some isolated QPF this
afternoon across parts of the area, mainly along and south of I-44.
Interestingly, only a couple of the CAMs develop convection in this
area today, and they're usually the most bullish with respect to
developing storms.  Forecast soundings show little if any cap over
central/south central Missouri this afternoon...though I'm uncertain
what the trigger will be.  That said, differential heating due to
orography across the Ozarks has often been a trigger for isolated
storms when there was nothing else, so slight chance PoPs down there
look appropriate. Any convection that forms over the Ozarks late this
afternoon should dissipate by early evening.

The next upstream short wave will dip into the Mississippi Valley on
Wednesday.  Deterministic guidance continues to hint that this wave
will be somewhat sharper than the last one, and it should push a
stronger cold front further south into Missouri and Illinois.
Guidance is in pretty good agreement that the front will not make it
into northern Missouri and west central Illinois until after 00Z
Thursday, therefore Wednesday should be another hot and humid day
ahead of it.  Dew points will pool ahead of the front Wednesday
afternoon, which could push heat index values higher than either
today's or Monday's.  There is some uncertainty with respect to the
heat though: several models develop convection well out ahead of the
front on Wednesday afternoon.  The triggering mechanism may be the
short wave, which starts outrunning the surface boundary Wednesday
afternoon.  However, forecast soundings show a fairly stout capping
inversion ahead of the front during the afternoon.  The potential
public health impacts of 105+ heat index values outweigh the
uncertainty that it won't get that hot due to afternoon storms in my
opinion, so the Heat Advisory will continue for all areas through
Wednesday afternoon.

Strong instability ahead of the front during the afternoon and
evening should weaken by 03-06Z Thursday.  Until then, 3000+ J/Kg
MLCAPE is being forecast by the GFS, and forecast soundings show a
good inverted V signature.  Therefore strong downdraft winds could
produce wind gusts of 50-60 mph for a few hours once storms develop.
 The synoptic front will slow Wednesday night into early Thursday
morning.  GEFS/NAEFS and ECENS continue to show 95th+ percentile p-
wats and elevated moisture transport ahead of front. Deterministic
guidance is printing out 1-2 inches of total QPF for parts of the
area as well between 00-12Z Thursday, so there is some potential for
locally heavy rain as well.

Carney

.LONG TERM...  (Thursday through Monday)
Issued at 458 AM CDT Tue Aug 2 2022

Briefly in the long term...the short wave will outrun the surface
cold front overnight Wednesday into Thursday morning, causing the
front to stall over Missouri and Illinois.  Latest guidance shows the
front stalling farther north than previously forecast...generally
along or just south of I-70.  The stalled front will provide a
continued focus for convective development across much of the area
on Thursday, though with little upper level support, organized
storms don't look very likely.  The clouds and scattered convection
should keep cooler temperatures mainly in the 80s over the area for
Thursday, but guidance suggests that the front will wash out and/or
lift back to the north Friday.  This will begin a warm up back into
the 90s for central Missouri, and the 90s will spread eastward
through the weekend.  Another short wave is forecast to dip into the
northern Plains and Upper Midwest Saturday or Sunday, and this could
push another cold front into Iowa or northern Missouri.  However,
the deterministic GFS and ECMWF do not agree on the amplitude of
this wave, and both models have a relatively strong closed upper
level high pressure system centered over the east central Plains to
block the wave from digging too far south.  Therefore have only
slight chance PoPs with this potential front in the forecast for
now, and will keep the 90+ temps going through Sunday into early
next week.

Carney

&&

.AVIATION...  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 620 AM CDT Tue Aug 2 2022

A complex of thunderstorms continues to affect parts of south
central Illinois this morning. These storms are expected to
gradually weaken and dissipate over the next 2-3 hours.
Additionally, isolated showers over parts of the eastern Ozarks
and central Missouri should also weaken and dissipate over the
next 2-3 hours. There is also a small area of low ceilings and
visibilities in west central Illinois in the vicinity of a stalled
front which should lift and dissipate as the front begins moving
northeast this morning. VFR conditions are expected prevail
outside of these isolated portions of the area. Isolated
thunderstorms are possible again this afternoon, mainly across the
eastern Ozarks along and south of I-44. Any storms that do develop
should dissipate within a few hours after sunset.

Carney

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     95  78  96  74 /  10  10  20  80
Quincy          92  76  90  71 /  20   5  40  70
Columbia        97  77  96  72 /  10   5  30  80
Jefferson City  99  77  97  73 /  10   5  20  80
Salem           92  74  92  73 /  30  10  10  70
Farmington      95  74  94  71 /  20  20  10  60

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Heat Advisory until 8 PM CDT Wednesday for Audrain MO-Boone MO-
     Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
     Iron MO-Jefferson MO-Lincoln MO-Madison MO-Moniteau MO-
     Montgomery MO-Osage MO-Pike MO-Reynolds MO-Saint Charles MO-
     Saint Francois MO-Saint Louis City MO-Saint Louis MO-Sainte
     Genevieve MO-Warren MO-Washington MO.

     Heat Advisory from 1 PM this afternoon to 8 PM CDT Wednesday for
     Knox MO-Lewis MO-Marion MO-Monroe MO-Ralls MO-Shelby MO.

IL...Heat Advisory until 8 PM CDT Wednesday for Bond IL-Calhoun IL-
     Clinton IL-Fayette IL-Greene IL-Jersey IL-Macoupin IL-
     Madison IL-Marion IL-Monroe IL-Montgomery IL-Randolph IL-
     Saint Clair-Washington IL.

     Heat Advisory from 1 PM this afternoon to 8 PM CDT Wednesday for
     Adams IL-Brown IL-Pike IL.

&&

WFO LSX

Hazardous Weather Outlook
National Weather Service St Louis MO
417 AM CDT Tue Aug 2 2022

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-031200-
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-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-
417 AM CDT Tue Aug 2 2022

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 for thunderstorms across parts of northeast
Missouri as well as west central and south central Illinois this
morning. There is another chance for thunderstorms across parts of southeast
Missouri this afternoon and this evening...mainly along and south of
Interstate 44.

Hot and humid conditions will continue to produce heat index values
around 105 degrees this afternoon. A Heat Advisory is now in effect
for the entire area.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Hot and humid conditions will continue to produce heat index values
around 105 degrees on Wednesday afternoon. A heat advisory continues
for the entire area Wednesday afternoon.

Thunderstorms continue to be possible Wednesday afternoon through
Friday. A storm or two may be strong to severe late Wednesday
afternoon into Wednesday evening. The storms Wednesday night may
produce locally heavy rain.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

Carney