Special Weather Statement, NWS St. Louis, MO

Area Forecast Discussion
National Weather Service Saint Louis MO
359 PM CDT Tue Apr 23 2019

.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 359 PM CDT Tue Apr 23 2019

A cold front has stalled over Missouri and Illinois...stretching
from near Springfield Missouri up to near Matoon Illinois.  The
front is forecast to remain nearly stationary through this evening,
but then lift northward overnight as a weak low moves northeast from
Oklahoma into central and eastern Missouri late tonight and
Wednesday.  Models aren't really showing any strong signals for
organized convection through Wednesday...just a broad area of
generally weak low level moisture convergence.  For this reason,
it's tough to nail down timing and coverage of any showers and
storms.  Therefore have stuck with chance PoPs for the most part,
with a few spots of 60+ late tonight ahead of the low and then again
on Wednesday in the vicinity of the front over southeast Missouri
and southern Illinois during peak heating.  With extensive cloud
cover and showers in the vicinity, temperatures should continue to
be a little cooler tonight and Wednesday than they have in the past
few days.  Stuck pretty close to guidance with lows tonight in the
50s and highs Wednesday in the mid 60s to low 70s.

Carney

.LONG TERM...  (Wednesday Night through Next Tuesday)
Issued at 359 PM CDT Tue Apr 23 2019

A broad upper level trough will move from southwest Texas east into
the Mississippi Valley from Wednesday night through Friday morning.
This trough will help move the stalled cold front along to the
southeast by Thursday morning.  However, there will be a continuing
threat for showers and a few thunderstorms during the day Thursday
as the trough from the southwest syncs up with a northern stream
trough diving into the upper Mississippi Valley.  This merger will
briefly amplify the upper level pattern producing northwest flow
over the Mississippi Valley Thursday night and Friday.  This should
bring drier weather to our area for this period, but another fast-
moving short wave is forecast to move through the Midwest on
Saturday. Both the GFS and ECMWF show a fairly strong surface system
moving into northern Missouri or southern Iowa Saturday morning with
moderate to strong low level moisture convergence in the warm
sector.  This looks good enough for mid to high chance and likely
PoPs Saturday until the front goes through.

Medium range models diverge by Sunday with the GFS bringing a
sprawling 1020 mb high pressure system into the Mississippi Valley
while the ECMWF has a more zonal pattern aloft and the high stays
well to the northeast over the Great Lakes.  The EC is therefore
warmer and wetter for Sunday through Tuesday while the GFS is
relatively cool and dry at least until late Monday when the next low
developing over the Great Plains pushes a warm front back up from
the lower Mississippi Valley into Missouri and Illinois.

Carney

&&

.AVIATION...  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1229 PM CDT Tue Apr 23 2019

A cold front stretching from near KSGF to KSLO will remain nearly
stationary today and into tonight.  MVFR ceilings along and north
of the front are expected to lift this afternoon to above 3,500
ft. While timing is a little uncertain...most models agree that
the entire forecast area should be VFR by 22Z-00Z. Scattered
showers and thunderstorms are likely to move into the area from
the southwest and/or develop in the vicinity of the front this
afternoon. A broader area of showers with a few thunderstorms is
expected to develop tonight as low pressure moves from Oklahoma
northeast long the stalled front into the mid Mississippi Valley.
Low MVFR and IFR ceilings are likely to move into the area along
with the showers overnight ahead of the low and persist into
Wednesday morning.

SPECIFICS FOR KSTL:

Latest satellite imagery shows the MVFR ceiling at Lambert trying
to clear from the south. This process may take a little while
yet, but all guidance seems to agree that the low ceiling will
lift and scatter this afternoon. VFR flight conditions are
expected to prevail until late this evening or overnight with
scattered showers in the vicinity...possibly a thunderstorm or
two. More numerous showers are likely overnight ahead of a low
pressure system and the ceiling is expected to drop again to low
MVFR and then IFR by 10Z-12Z. Low ceilings and intermittent
showers are expected to prevail at least through 18Z.

Carney

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     54  68  55  73 /  60  40  30  20
Quincy          48  63  49  72 /  40  50  10  20
Columbia        52  67  53  74 /  50  40  20  20
Jefferson City  53  69  54  75 /  50  40  30  20
Salem           52  67  55  70 /  40  50  30  30
Farmington      55  71  55  70 /  40  70  50  30

&&

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

WFO LSX

Hazardous Weather Outlook
National Weather Service Saint Louis MO
407 PM CDT Tue Apr 23 2019

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-242115-
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-
407 PM CDT Tue Apr 23 2019

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

.DAY ONE...Tonight.

Tonight across portions of central, east central and southeast Missouri
and southwest Illinois.

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

There is a chance for thunderstorms across much of the area on
Wednesday.  Additional chances of thunderstorms exist on Saturday
and Monday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated tonight.

Carney

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