Nashville Illinois Weather Forecast Discussion

964
FXUS63 KLSX 121111
AFDLSX
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
611 AM CDT Sun Oct 12 2025
.KEY MESSAGES...
- Near to above normal temperatures are expected to continue through
  the upcoming week.
- Mostly dry conditions are expected until Saturday, when the best
  chances (40-50%) of appreciable rainfall arrive.
&&
.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 252 AM CDT Sun Oct 12 2025
An upper level ridge continues to amplify over the eastern Plains
with surface to mid-level ridging extending from the southeastern
Canadian Provinces into the western Gulf early this morning. IR
satellite shows mostly clear skies overhead with clouds well to the
west and east. A steep inversion has already begun to develop with
light surface winds around most areas and calm conditions in the low-
lying valleys and riverbeds. Nighttime microphysics products show
fog has already settled into some of the riverbeds and adjacent
land. KSUS and KJEF have been bouncing in/out of dense fog (1/4SM),
but fog of this magnitude should remain near rivers, aided by the
water/air temperature differential and added moisture via warmer
river water.
Fog is expected to burn off through mid-morning with another mild,
dry day to finish out the weekend. High temperatures will be nearly
uniform across the CWA, peaking near 80 degrees this afternoon.
Clouds begin to increase over sections of central and northeast
Missouri into west-central Illinois tonight with mainly clear
conditions south and east. Locations insulated by increasing cloud
cover (Quincy to Columbia/Jeff City) will be slightly warmer (near
60) tonight into Monday morning with upper 40s to mid-50s for the
remainder of the area.
The amplifying upper level ridge is expected to steer the active
track through the central and northern Plains into the Upper
Midwest. The first in a series of upper level disturbances crosses
the upper Midwest late Sunday into early Monday, pushing a cold
front into the northern sections of the forecast area. Southerly
flow being funneled between the eastern surface ridge and a weak
surface low over the central Plains is more than likely to wash the
front out with little support for anything more than isolated to
perhaps scattered showers over northeast Missouri and west-central
Illinois. The chances for measurable rainfall peak at 30-35% over
these locations with less than 20% of the members showing amounts
any higher. High temperatures will largely be in the 80s Monday,
where it remains dry. Rain-cooled areas under thicker cloud cover
will be a touch cooler (mid/upper 70s).
Maples
&&
.LONG TERM...  (Monday Night through Saturday)
Issued at 252 AM CDT Sun Oct 12 2025
The upper level ridge amplifies over the region and drives unsettled
weather through the Plains and Upper Midwest. The cold front that
stalls through the region Monday lifts back to the north as a
shortwave rounds the upper ridge Tuesday. NBM data shows some spread
beginning Tuesday, which is largely attributed to the surface
boundary position, along with the amplitude and orientation of the
upper ridge. LREF data shows the greatest spread in the vicinity of
the Missouri/Iowa border, where the front meanders at the southern
edge of a surface ridge and approaching disturbances having subtle
influence on the extent of its north/south position. Much of the
spread is in the temperature data with thicker cloud cover and
cooler 850 mb temperatures having a glancing impact on the region.
All-in-all, dry conditions are likely to hold through the end of the
week.
Long range guidance shows some consensus in a pattern change late
week into next weekend. The upper level ridge begins to break down
and/or the axis to the ridge moves east. A longwave upper level
trough moves out of the southwest CONUS into the central Plains late
Friday into early Saturday. This enables a cold front to move
southeast into the area as the upper ridge gives way to the east.
Though ensemble data remains spread at the end of the period, there
is a declining trend in temperatures through next weekend. Long
range guidance shows a surface low over the southern Plains
positioned at the southern end of an upper level trough and at the
trailing end of the cold front. This system would bring the best
potential for rain next weekend, though there are differences in the
timing/position of the system. It may be the first opportunity as
widespread rain in weeks. Exactly where and how much is uncertain at
this length in time, but will bear watching over the upcoming week.
Maples
&&
.AVIATION...  (For the 12z TAFs through 12z Monday Morning)
Issued at 610 AM CDT Sun Oct 12 2025
KJEF, KSUS and KCPS have spent much of the early morning in and
out of fog, some of which has been dense at KJEF and KSUS. Fog is
expected to dissipate just after sunset.
VFR conditions are expected through the remainder of the period
once fog mixes out. Light and variable surface winds increase and
turn out of the southeast this morning into this afternoon. Mid to
high clouds increase from the west later this evening into tonight,
but should remain VFR.
Maples
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX

NWS LSX Office Area Forecast Discussion