720
FXUS63 KLSX 102001
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
301 PM CDT Tue Mar 10 2026

.KEY MESSAGES...

- Severe thunderstorms are possible, mainly late this afternoon
  and evening across northeastern MO/west-central IL. The threat
  for severe storms continues overnight across much of the area,
  however it is not as likely.

- Locally heavy rainfall is also possible overnight tonight into
  Wednesday morning.


&&

.SHORT TERM...  (Through Late Wednesday Night)
Issued at 152 PM CDT Tue Mar 10 2026

The main forecast concern remains to be the threat for severe
weather this afternoon through early Wednesday morning. Latest
surface analysis shows low pressure located across northwestern
Missouri with a stalled boundary extending northeast over Illinois
into Indiana. A dry line also currently exists southwest from the
low pressure towards south/ central Kansas. At 250 mb, the
northern jet streak is located across the Dakotas with a southern
stream closed low starting to shear out with fragments of PV
ejecting northeast. Some southern jet stream enhancement is
forecast, with weak coupling of the RRQ/ LFQ possible near Iowa/
Illinois.

Convective initiation is forecast to occur between 4 PM and 7 PM
over Illinois, or just northeast of the CWA. This convection will
then likely move northeast through the afternoon into evening. Latest
visible satellite trends shows most of the agitated CU field
remaining northeast of the region with the surface boundary just
south of Chicago. There is currently widespread 1500 to 2500 J/kg
of ML CAPE across the region (supported by the 18z Missouri
sounding), but strong capping remains in place. Bulk shear values
are around 50 kt as well with steep lapse rates and amble
instability in the hail growth region. If storms are able to
develop, supercells with large to very large hail remain possible.

A second round of convection is also forecast to develop over
south/ central Kansas along the dry line. Mean layer wind and bulk
shear vectors are southwest to west or oblique to the dry line.
However, a cold front will start to sag south tonight with the
mean wind and bulk shear vectors being boundary parallel. This
would favor upscale growth of convection into a potential MCS.
This convection will then move northeast along the frontal
boundary. A strong southwest LLJ will also favor training or back
building convection as new cells propagate into the LLJ. This
means heavy rainfall with isolated flash flooding are possible.
Another concern with these storms will be damaging wind gusts and
a tornado or two. Further south, or away from the boundary,
discrete cells with all hazards possible. The main limiting factor
further south will be the capping with little in the way of
forcing for ascent.

BAH

&&

.LONG TERM...  (Thursday through Next Tuesday)
Issued at 152 PM CDT Tue Mar 10 2026

Surface high pressure will be located across southeast Texas
Thursday morning with near seasonable temperatures forecast for
Thursday and Friday. Another shortwave will then dive southeast
out of Canada Thursday evening with surface low pressure tracking
from Minnesota to Wisconsin with a cold front approaching from
the northwest. Global ensembles are in fairly good with the cold
front crossing the area late Friday morning into afternoon with no
precipitation expected. The IQR in temperature spread is around 8
degrees for Friday which is rather impressive this far out. No
precipitation is expected with the Friday frontal passage.

Saturday into Sunday, the long wave pattern will modulate with the
trough axis centering over the central plains of the United States
with surface cyclogenesis occurring near the Kansas/ Oklahoma
region and then ejecting northeast. A surface cold front will then
sweep across the region Sunday afternoon into evening with much
colder temperatures for the beginning of next work week. Global
ensemble guidance is in very good agreement of below temperatures
forecast for Monday and Tuesday, but confidence is low on the
timing of the frontal passage on Sunday. The IQR for KSTL high
temperatures on Sunday is 20 degrees. This frontal passage will
bring a chance of precipitation and even the potential for some
snow as the region will be on the divergent side of a highly
amplified trough axis and PWATs near 1". Confidence on
precipitation amounts and type is low. The GEFS continues to
advertise the wettest and coldest set of solutions with
accumulating snowfall possible Sunday into Monday. However, the
EPS and CMC remains much drier and slightly warmer. Guidance
continues to advertise teens and 20s Monday morning and highs
struggling to reach the mid to upper 30s Monday afternoon.

BAH

&&
.AVIATION...  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1221 PM CDT Tue Mar 10 2026

Almost all TAF sites are VFR this afternoon with the only
exception being Quincy (KUIN) which has observed some transient
MVFR cigs. A stationary cold front remains around the Missouri/
Iowa border this afternoon with surface low pressure located
across eastern Kansas. A dry line is also extending south across
central Kansas. The general timeline and thinking for the TAFs can
be found below:

This afternoon: No precipitation and VFR conditions at all TAF
sites. Southwest winds could be gusty at times with peak gusts of
30 to 35 kt.

This evening/ early Wednesday morning: Showers and thunderstorms
will start northeast of Quincy between 7 PM and 9 PM with another
separate round of thunderstorms forming across south/central
Kansas this afternoon. Both areas of thunderstorms will be moving
to the northeast with a surface cold front slowly heading
southeast this evening. As this occurs, the area of thunderstorms
that was over south/ central Kansas this afternoon will be located
near the Kansas/ Missouri border late this evening. Showers and
thunderstorms could then ignite along the cold front (mainly north
of the TAF sites with the exception potentially being KUIN), with
the area of thunderstorms over the Kansas/ Missouri border
accelerating northeast. The TAFs were based on the primary threat
of thunderstorms coming from the complex that develops over
Kansas. Thunderstorms will first affect the KCOU/ KJEF terminals
(between 4z and 7z) and then progress towards KSTL/ KSUS and KCPS
(between 6z and 9z). There is uncertainty on how far east and
south these complex of storms will be able to make it. Gusty
winds along with reductions in visibilites are likely during any
thunderstorms that affect the terminals.

Wednesday morning: A cold front will sag southeast with post-
frontal showers continuing. The main threat behind the cold front
will be widespread IFR conditions. Model soundings show widespread
IFR conditions with 20 to 30 kt wind gusts possible due to the
cold air advection. A slow to recovery to VFR will occur mainly
after 18z.

BAH

&&

.CLIMATE...
Issued at 350 AM CDT Tue Mar 10 2026

Near record high temperatures are possible today.

            Today 3/10
KSTL        86F (1955)
KCOU        82F (1955)
KUIN        79F (1955)


&&

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

$$

WFO LSX