590
FXUS63 KLSX 110344
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1044 PM CDT Fri Apr 10 2026

.KEY MESSAGES...

- Above average temperatures return for most of the area on
  Saturday lasting for the entire area into late next week.

- Scattered showers are possible on Saturday with the best chance
  (40-60%) across central/northeast MO. A low chance (20-30%) for
  an isolated weak thunderstorm also exists.

- Several chances for showers and thunderstorms will impact the
  region Sunday evening through Thursday, with potential for
  severe thunderstorms. Once again, plenty of dry time is expected
  for this period as well.


&&

.SHORT TERM...  (Through Late Saturday Night)
Issued at 212 PM CDT Fri Apr 10 2026

Scattered showers along and south of I-70 have continued to slowly
decrease in coverage as they push eastward along/behind the cold
front, which is now stretched across southern MO/IL. North of this
frontal boundary, low-level CAA and post-frontal stratus have led to
temperatures remaining mostly in the 50s this afternoon with areas
along I-70 in the 60s. Locations that were south of the front at
sunrise experienced their warmest temperatures (70s) earlier today
before the southward moving front lowered temperatures into the 60s.
Rain chances (20-30%) linger near the cold front which is forecast
to stall across southern MO/IL until Saturday morning. With the area
under the influence of continued weak low-level CAA tonight, the
coldest night for the next 7 days is forecast with mid/upper 40s for
lows north of I-70 and lower 50s south.

Low-level flow veers southerly early on Saturday as a surface high
to our north slides east into the Ohio River Valley, which helps to
lift the front poleward as a warm front across the area on Saturday.
Rain chances increase as the front lifts northward with enhanced
moisture convergence along the front and warm air advection ramping
up south/behind the boundary. High-res guidance reveals scattered
showers lifting northeast along a WAA wing entering
central/southeast MO Saturday morning, potentially crossing over
into IL by the early afternoon. Precipitation coverage should be
more limited given the WAA nature which typically lends to more
scattered nebulous precipitation, resulting in prevailing dry time
for most locations. Coverage is forecast to be greater across
central/northern MO and west-central IL, where the HREF 6hr
probabilities for measurable rainfall max out around 60% late
Saturday morning into the afternoon. The reason for this is due to a
mid-level ridge that will be advancing across the area on Saturday
leading to height rises aloft that will be greatest with eastward
extent. This will have a tendency to suppress the WAA driven showers
for locations across southern MO and much of IL, where chances for
rain are less than 30-40%. An isolated weak pop-up thunderstorm
cannot be ruled out, particularly across central/southern Missouri
where the latest HREF has mean SBCAPE reaching up to 500 J/kg
Saturday afternoon into the evening. Temperatures will be slightly
warmer for most locations tomorrow, as southerly flow returns, with
highs in the upper 60s across northern MO/west-central IL and upper
70s/low 80s across central and southern MO.

Peine/Elmore

&&

.LONG TERM...  (Sunday through Next Friday)
Issued at 212 PM CDT Fri Apr 10 2026

An amplified, slow moving mid-level longwave trough will be sliding
into the West Coast on Sunday with ridging across the Ohio River
Valley, placing our region in southwesterly flow. Within this
regime, long-range guidance is resolving one distinct shortwave
propagating northeastward into the Midwest Sunday afternoon into
Monday. Continued southerly flow advects abundant moisture into the
region, with the highest LREF mean PWAT values across
central/northeast MO of 1.3-1.5" (near 99th percentiles) Sunday
afternoon into Monday morning. This, coupled with mid-level forcing
for ascent thanks to the passing shortwave, will lead to increasing
chances for showers and scattered thunderstorms from west to east
beginning Sunday afternoon. Where moisture is more plentiful and
forcing is stronger across central/northeast MO, the greatest rain
chances are forecast. Here, LREF probabilities for QPF >0.01" reach
70-90% Sunday evening into the overnight hours. For remaining parts
of the area, where the ingredients mentioned above are less
favorable, chances for rain are lower and generally in the 30-60%
range late Sunday night into Monday morning. As the mid-level
shortwave progresses eastward, model guidance reveals brief mid-
level ridging embedded within the the southwesterly flow allowing
for subtle mid-level height rises. As a result, dry conditions are
forecast to prevail for a majority of the area Monday into early
Tuesday, with the exception of lower chances (20-30%) for lingering
showers into Monday afternoon.

By Tuesday, long-range deterministic guidance positions the
amplified longwave trough over the Desert Southwest with a few subtle
shortwaves within the continued southwesterly flow. With smaller-
scale features at play, like nebulous forcing out ahead of the main
trough out west, widespread chances (20-40%) for showers and
scattered thunderstorms are indicated by both the LREF and NBM
Tuesday afternoon into Wednesday. Instability will steadily be on
the increase early next week, with LREF probabilities for SBCAPE
>1,000 J/kg peaking near 80% across northeast MO/west-central IL
Tuesday afternoon and evening. The best chance for severe
thunderstorms is expected to be when the main longwave trough ejects
into the Plains/Midwest, which is progged by guidance to occur
sometime between late Tuesday and Wednesday night. This is also near
the time when LREF joint probabilities for SBCAPE >1,000 J/kg and 0-
500mb Bulk Wind Shear >30kts maxes out near 70% for most of the
area. Conceptually, this makes sense as this is when the greatest
mid-level forcing and deep-layer wind shear associated with the mid-
level trough will be nearby. However, uncertainty remains with the
extent of severe weather potential our area has, as the exact
timing/placement/strength of the trough ejection still varies within
model guidance and will continue to be fine tuned as we near closer
to Tuesday/Wednesday.

In the wake of the departing longwave trough, the general large-
scale consensus is that troughing continues to our west with ridging
to the east, keeping the area under a southwesterly regime. Analysis
of deterministic guidance reveals that there would be subtle
shortwaves within this regime, bringing continued chances for
showers and thunderstorms much of next week. As a result, between
Thursday and next weekend, both the LREF and NBM have widespread
chances (20-50%) for precipitation for the region. It is important
to note that plenty of dry time can be expected for the area, even
with the consistent chances for rain in the forecast. Guidance is in
good consensus that warmer than average temperatures will continue
all of next week with a narrow LREF temperature IQR spread centered
on 5-15 degrees above average.

Peine/Elmore

&&

.AVIATION...  (For the 06z TAFs through 06z Saturday Night)
Issued at 1038 PM CDT Fri Apr 10 2026

Showers and low ceilings continue to be the main focus of this TAF
period. While VFR ceilings have developed at all terminals as of
03Z, low VFR to MVFR ceilings are likely to return to COU/JEF
tomorrow morning, and possibly UIN/STL/SUS/CPS but with a lower
probability. These low ceilings will likely persist through
at least early afternoon before transitioning to a
scattered/broken VFR cumulus field through the rest of the day.

Meanwhile, showers have largely ended for the time being, but may
return at various times throughout the day and into the early
evening tomorrow, mainly at COU/JEF/UIN. Confidence is low that
any of these terminals will see direct impacts from these showers,
thus the use of PROB30 groups, and lightning probabilities remain
too low to include in the TAF at this time.

BRC

&&

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

$$

WFO LSX