Flash Flood Watch 6, NWS St. Louis, MO

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
657 PM CDT Sat May 25 2019

.SHORT TERM... (Through Late Monday Night)
Issued at 321 PM CDT Sat May 25 2019

CAMs are indicating another round of strong to severe storms
developing, especially over northern portions of forecast area
early this evening through the overnight hours along an old
outflow boundary. With 0-6km shear 40+ kts, ML CAPES around 3000
J/kg, SCP values over 10, expect scattered supercell development
with main threats being large hail and damaging winds. In the
meantime, as an upper level shortwave lifts out of a trof to our
west with decent moisture convergence on nose of LLJ, will see
another thunderstorm complex develop and track east, mainly along
and north of I-70 corridor, moving into the forecast area after
09z Sunday. This complex will gradually weaken as it tracks to the
east, laying out numerous boundaries. These boundaries will be
the focus of activity that could fire up during the afternoon
hours on Sunday.

Once again activity will then shift back to the north as upper ridge
builds back into region. So for Sunday night through Memorial Day,
the best chances of showers and storms will be across portions of
northeast MO and west central IL.

Lows tonight will be at least 10 degrees above normal, in the mid
60s to low 70s. Highs on Sunday will be a bit lower than today due
to cloud cover and precipitation, in the upper 70s to mid 80s. Lows
Sunday night will be in the mid to upper 60s. Then hot and humid
conditions expected on Memorial Day with highs in the 80s. Dry and
mild weather expected Monday night with lows between 65 and 70
degrees.

Byrd

.LONG TERM... (Tuesday through Next Saturday)
Issued at 321 PM CDT Sat May 25 2019

Unsettled weather will persist into the middle of next week. Models
are still indicating that the upper level ridge will break down once
again allowing a developing system over the Central Plains to slide
through region. However, the models are a bit slower with this
system as it deepens over the Central Plains and is slowly ejected
out towards the Great Lakes. Beginning Tuesday afternoon decent
instability, low level moisture and convergence increase over region
ahead of pre-frontal trof, so will see strong to severe storms
develop by late afternoon and through the overnight hours Tuesday
night. Another round of showers and storms are expected Wednesday
night through Thursday morning as main cold front slides through.

Beyond Thursday morning, dry and mild weather expected through
Friday before next system moves in for the first part of next
weekend.

Temperatures will remain rather mild through the extended period.
Tuesday will be the warmest day with highs in the 80s, then a bit
cooler in the mid 70s to low 80s for the rest of the extended period.

Byrd

&&

.AVIATION...  (For the 00z TAFs through 00z Sunday Evening)
Issued at 541 PM CDT Sat May 25 2019

Thunderstorms will continue to develop in northwestern MO this
evening just south of an approaching cold front and on the nose of
a south-southwesterly low level jet. These thunderstorms will
eventually move into UIN by late tonight and likely into COU by
early Sunday morning. The weakening thunderstorm complex may make
it into the St Louis metro area early Sunday morning. New
thunderstorm development is possible Sunday afternoon along the
thunderstorm outflow boundary left behind as the atmosphere
destabilizes again with daytime heating.

SPECIFICS FOR KSTL: Diurnal cumulus clouds will dissipate this
evening with loss of daytime heating. A weakening complex of
thunderstorms may move into STL early Sunday morning. New
thunderstorm development is possible Sunday afternoon along the
thunderstorm outflow boundary left behind as the atmosphere
destabilizes again with daytime heating.

GKS

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     71  84  68  89 /  40  40  20  20
Quincy          65  79  65  84 / 100  70  30  40
Columbia        66  81  66  86 /  60  70  20  20
Jefferson City  67  82  66  87 /  60  60  10  10
Salem           69  84  65  87 /  30  40  20  10
Farmington      67  84  65  87 /  10  30  10  10

&&

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

WFO LSX

Hazardous Weather Outlook...CORRECTED
National Weather Service Saint Louis MO
408 PM CDT Sat May 25 2019

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-261200-
Adams IL-Audrain MO-Bond IL-Boone MO-Brown IL-Calhoun IL-Callaway MO-
Clinton IL-Cole MO-Crawford MO-Fayette IL-Franklin MO-Gasconade MO-
Greene IL-Iron MO-Jefferson MO-Jersey IL-Knox MO-Lewis MO-Lincoln MO-
Macoupin IL-Madison IL-Madison MO-Marion IL-Marion MO-Moniteau MO-
Monroe IL-Monroe MO-Montgomery IL-Montgomery MO-Osage MO-Pike IL-
Pike MO-Ralls MO-Randolph IL-Reynolds MO-Saint Charles MO-
Saint Clair IL-Saint Francois MO-Saint Louis City MO-Saint Louis MO-
Sainte Genevieve MO-Shelby MO-Warren MO-Washington IL-Washington MO-
408 PM CDT Sat May 25 2019

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

.DAY ONE...Tonight.

There is a chance for thunderstorms, especially across portions of
central and northeast Missouri and west-central Illinois.
Scattered severe storms are possible, mainly in northeast Missouri
and west-central Illinois. The primary severe weather threats are
large hail and damaging wind gusts.

Major river flooding is ongoing along parts of the Missouri,
Mississippi, and Illinois Rivers.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Major river flooding is expected to continue along the Mississippi,
Missouri, and Illinois Rivers.

The chance for thunderstorms will continue across portions of the
area each day. A few strong to severe storms are possible on
Sunday afternoon and early evening, with a more organized severe
weather threat for late Tuesday afternoon and Tuesday night.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed tonight, especially for portions
of northeast Missouri and west-central Illinois.

Byrd/TES