Portage Des Sioux Missouri Weather Forecast Discussion

881
FXUS63 KLSX 111106
AFDLSX
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
606 AM CDT Sat Oct 11 2025
.KEY MESSAGES...
- Areas of dense fog are likely in parts of central/northeast
  Missouri and west-central Illinois early this morning.
- A short warming trend is expected today and tomorrow, followed
  by a weak cold front Monday and another slow warming trend late
  in the week. Overall, above normal temperatures are favored for
  the next week.
- While some light rain is possible Monday (10-20% chance), dry
  conditions are expected overall for the next week.
&&
.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 240 AM CDT Sat Oct 11 2025
The primary issue in the immediate term is the development of dense
fog in parts of the area overnight and early this morning. While low
stratus cover is preventing fog from forming in parts of the Ozarks
and southwest Illinois, areas north of these low clouds have seen
quick fog development thanks to yesterday`s rain, light winds, and
clearing skies. Several ASOS/AWOS observation sites have reported
visibilities as low as 1/4 mile as of 2 AM, and this is likely to
expand over the next few hours. Eventually this fog may lift into
primarily a stratus deck, but not before we see at least some dense
fog that could impact visibilities and hinder driving. As such,
we`ve opted to go ahead and hoist a Dense Fog Advisory for parts of
central/northeast Missouri and west-central Illinois until 9 AM.
Fog is expected to dissipate shortly after sunrise, although low
clouds may take a few more hours to either dissipate or transition
from stratus to a scattered/broken cumulus field as mixing
commences. Otherwise, temperatures are expected to warm into the mid
70s to low 80s, with light easterly winds and no additional
precipitation expected.
Between tonight and tomorrow, an upper level ridge will gradually
move overhead from the west, and southerly return flow will increase
in response to a strong low pressure system across the northern
plains. This will drive slightly increasing temperatures area-wide,
and we can expect temperatures Sunday afternoon to reach the upper
70s to low 80s, and possibly slightly higher in a few places.
Meanwhile, moisture will remain meager, and precipitation is once
again not expected. South-southeast winds will also be a bit
breezier than in recent days across central and northeast Missouri,
with afternoon gusts in the 20-25 mph range possible.
19
&&
.LONG TERM...  (Sunday Night through Friday)
Issued at 240 AM CDT Sat Oct 11 2025
Much of the extended forecast period continues to favor a warm and
dry pattern overall, thanks to the persistence of an upper level
ridge across the central U.S. and Mississippi Valley region.
However, there are a few items to note, and perhaps some signs of
a shifting pattern in the 7+ day time range.
By Monday, persistent southerly flow is expected to result in
continued above-average temperatures, likely with similar afternoon
values as Sunday (upper 70s to low 80s). While the upper level flow
pattern will continue to feature a nearly stationary ridge, the low
pressure system alluded to in the short term forecast period is
likely to drive a weakening cold front into our region sometime on
Monday, likely late in the day or even overnight. Much like the last
cold front, this has the potential to produce some precipitation
during the day Monday as it approaches, although NBM probabilities
remain quite modest (10-20%) and restricted to northeast and central
Missouri. The most recently available LREF ensemble members are a
bit more bullish in terms of rain probabilities, but total amounts
remain very light, and the overall lack of moisture and weakening
nature of the front does not inspire much confidence that this
front will bring meaningful amounts. Still, it should be noted
that the footprint of NBM rain probabilities has expanded
slightly from previous forecasts, and it may be slightly
underestimating the chance for at least some rain...even if the
ceiling for rain amounts is likely very low and not enough to
meaningfully impact ongoing drought conditions.
Otherwise, this front may act as another speed-bump in our ongoing
warming trend, helping to cool some areas off slightly Tuesday and
Wednesday before resuming a slow upward climb into the weekend.
Forecast temperature spreads do increase a bit during the mid to
late-week period owing to differences in the timing and strength of
Monday`s cold front, but overall temperatures are favored to remain
slightly above seasonal averages.
By next weekend, long-range ensembles have begun to hint that the
upper ridge may finally weaken just enough to allow for a more
southerly low track, potentially opening the door for more
meaningful rain chances. Latest 24 hour rain probabilities in the
operational NBM have jumped to between 40-60% over the weekend,
although as one can expect there remains considerable spread among
ensemble members and clusters. Still, it is a step in the right
direction, and represents the next reasonable chance for meaningful
rain. This is also corroborated by increasing chances for above
normal rainfall in the 6-10 and 8-14 day periods in the latest CPC
outlooks.
19
&&
.AVIATION...  (For the 12z TAFs through 12z Sunday Morning)
Issued at 601 AM CDT Sat Oct 11 2025
The primary concern for the 12Z TAF period is the persistence of
fog and low clouds during the first few hours of the TAF period.
Widespread fog is being observed throughout the region, impacting
all local terminals except STL. In addition to fog, patchy low
stratus is also being observed at various places, and the end
result is that categories are fluctuating from LIFR to MVFR at
area terminals. The most prolonged LIFR conditions have been
observed at JEF and UIN, where 1/4 mile visibilities have been
common. These conditions are likely to last through roughly 13-14
Z before improving shortly after sunrise. Visibilities will
improve first, but low ceilings may persist for another couple of
hours in some areas.
However, once low clouds diminish later in the morning, VFR
conditions are likely for the remainder of the period.
19
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Dense Fog Advisory until 9 AM CDT this morning for Audrain MO-
     Boone MO-Callaway MO-Cole MO-Franklin MO-Gasconade MO-Knox
     MO-Lewis MO-Lincoln MO-Marion MO-Moniteau MO-Monroe MO-
     Montgomery MO-Osage MO-Pike MO-Ralls MO-Saint Charles MO-
     Saint Louis MO-Shelby MO-Warren MO.
IL...Dense Fog Advisory until 9 AM CDT this morning for Adams IL-
     Brown IL-Calhoun IL-Greene IL-Jersey IL-Pike IL.
&&
$$
WFO LSX

NWS LSX Office Area Forecast Discussion