Finney Cemetery Missouri Weather Forecast Discussion

454
FXUS63 KLSX 151037
AFDLSX
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
537 AM CDT Wed Oct 15 2025
.KEY MESSAGES...
- Above average temperatures and dry conditions will continue today
  through Friday afternoon.
- Widespread beneficial rain remains very likely (80-90+%) between
  Friday night and Saturday night, with a low and very conditional
  chance for strong/severe storms Saturday.
&&
.SHORT TERM... (Through Friday)
Issued at 321 AM CDT Wed Oct 15 2025
Very little has changed in the forecast between today and Friday, as
a persistent upper level ridge and high pressure will continue to
ensure warm and dry conditions area-wide.
While some high level cloud cover continues to pivot through the
area around the rim of the building upper ridge, there is much less
of this in the area than there was yesterday. Meanwhile, surface
high pressure remains in place, keeping winds very light. As
such, conditions are in place for efficient radiative cooling, and
as a result we may see a bit of valley fog development very close
to sunrise. On the other hand, surface dewpoints have slowly
dropped over the past couple of hours, and this appears to be the
result of advection rather than simply condensation. This is
likely to limit the coverage of fog to near main stem rivers and
other protected valleys, and may also delay its onset. This fog
should diminish shortly after sunrise, leading to a warm and quiet
afternoon.
Temperatures today are once again expected to climb into the low to
mid 80s, which is about 10 to 15 degrees above average for this time
of year. For the most part, these conditions will be relatively
unchanged tomorrow as well. We will likely start to see a slow
increase in wind speeds Thursday due to the influence of distant
pressure falls across the northern plains, and even moreso on
Friday. However, this is not expected to be particularly impactful,
aside from the implications this will have on this weekend`s rain
and thunderstorm chances.
BRC
&&
.LONG TERM... (Friday Night through Tuesday)
Issued at 321 AM CDT Wed Oct 15 2025
By Friday night, all attention turns to the potential for widespread
rain, along with a lower probability and highly conditional
threat of strong or severe thunderstorms.
Driving this potential will be a broad trough moving across the
northern half of the CONUS, along with an increasingly prominent
shortwave pivoting around its southern periphery in the
central/southern plains. This will drive a cold front southeastward
through the area sometime between Friday night and Saturday night,
although there remains considerable uncertainty regarding how
quickly this will occur. However, ignoring those timing details for
a moment, this feature is nearly certain to produce a relatively
brief period of much-needed widespread rainfall across the area.
Regardless of how quickly the boundary moves through, we will see
anomalously high moisture (60+ degree dewpoints, 1.3-1.6 in PWAT)
advected northward ahead of the boundary thanks to a robust
southwesterly low level jet. The combination of this moisture and
forcing from the surface front and shortwave will almost
certainly be enough to produce widespread rain, and this is
corroborated by widespread 90+% PoPs during this timeframe. Rain
amounts continue to be limited by the progressive nature of this
system, as 75th percentile amounts are only about 1". While this
isn`t going to be a drought buster, we should see some modest
short-term improvement.
While confidence in widespread rain remains high, our confidence in
the potential for strong or severe thunderstorms remains low at this
latitude. While ensemble agreement remains very low and that at
least keeps the door slightly ajar for stronger storms to
develop, there remain many negative factors that limit this
potential in our area specifically.
1. Ensemble spread remains very high, particularly regarding the
progression of the front.
For the past several days, ensemble members have struggled to
approach a consensus regarding the progression of the surface cold
front. Not only have LREF clusters maintained a huge discrepancy
in the timing of the front, with a difference of several hours and
as much as 200 miles, but this has been heavily weighted by what
appears to be model bias. As a general rule, the ENS (ECMWF) has
produced a high percentage of slower trough/cold front solutions,
while the GEFS (GFS) has been much more progressive. We have
noticed that in this forecast package there has been slightly more
overlap, but for the most part there has been little change. This
continues to limit our confidence in this aspect of the event,
and it has significant implications on our storm potential.
As has been discussed many times, the slower ECMWF solutions provide
a wider window for moisture advection and destabilization, leading
to a higher potential ceiling for severe storms as a result. This
will still depend heavily on the potential for widespread rain
during the day ahead of the front (discussed in depth later), but
these solutions at least open the door a little bit wider. On the
other hand, the GEFS consensus would significantly limit our
ability to destabilize before the front pushes through, which is
made even worse by the likelihood of widespread rain. So far,
there doesn`t seem to be a strong trend in one direction or
another.
Also complicating the speed of the front is the increasing
prominence of the previously mentioned shortwave moving through the
middle/lower Mississippi Valley Saturday. Pressure falls from such a
feature would undoubtedly alter the progression of any surface
front, and could either speed it up or slow it down depending on
both its strength and track. While this is showing up clearly in
a few deterministic model runs, including the operational GFS, it
is not well represented among ensemble members and clusters, and
its predictability is low as a result.
2) Widespread stratiform rain is likely to limit our instability,
possibly regardless of the surface front.
While there remains a lot of disagreement in the progression of the
surface front, this is less so when it comes to the potential for
warm-sector stratiform rain and cloud cover early in the day
Saturday. As such, this will likely limit the potential ceiling of
instability by peak heating, and makes some of the higher model
CAPE projections (750-1000 J/kg) somewhat unlikely. The latter is
still more likely to occur with a slower front, but it`s possible
that persistent rain wipes this out either way. It should also be
noted that morning rain and cloud cover is not always a death
sentence for severe weather in the afternoon, and this can be
overcome by strong low level flow and moisture advection, or
dynamic cooling aloft from a very strong shortwave. However,
neither of these things seem very likely in this case, unless the
aforementioned shortwave is stronger than most ensemble members
are currently forecasting.
3) The "worst-case" scenario seems unlikely, but is still possible.
At this point, several factors would need to work together to
realize the worst-case scenario in our area. A relatively slower
cold front, a stronger and slower shortwave, and less rain and cloud
cover early in the day could still lead to destabilization.
Should this occur, widespread moderate to strong wind shear will
be present, and likewise strong to severe storms would be
possible. Even then, many questions still remain about storm mode
and specific hazards, and much of this will depend on mesoscale
features (shear vector orientation, low level shear/helicity,
differential heating boundaries, etc.) that cannot be fully
resolved just yet...especially considering the larger scale
uncertainty we`re already contending with.
Considering all of these combined factors, while severe weather is
likely to occur somewhere in the south-central U.S. Saturday, the
path leading to severe weather in our local area still seems
relatively narrow. However, given the continued model spread and the
presence of ample wind shear, this lower-probability potential still
needs to be accounted for.
Beyond Saturday night, the cold front and trough will push through
the area, and a transient ridge is likely to quickly build and
replace them. While a quick cooldown is likely behind the cold
front Saturday, currently forecast temperatures do not appear to
be unusually cold, and we may only fall to near or slightly below
average before rebounding early in the week. Precipitation chances
also appear to be minimal Sunday and Monday, although we are
keeping an eye on the potential for an active pattern returning
during the mid-week period.
BRC
&&
.AVIATION...  (For the 12z TAFs through 12z Thursday Morning)
Issued at 534 AM CDT Wed Oct 15 2025
While fog has been a bit less prevalent early this morning due to
the arrival of slightly drier air, we may still see some brief
impacts for an hour or two near sunrise at SUS, CPS, and JEF.
Otherwise though, VFR conditions are expected for a majority of
the period.
Near the end of the period, another round of patchy river valley
fog will be possible at those same river valley sites, although
this will depend on the timing of increasing southeasterly winds.
As such, confidence remains too low at this time to include more
fog in the TAF.
BRC
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX

NWS LSX Office Area Forecast Discussion