602
FXUS63 KLOT 240519
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1119 PM CST Sun Nov 23 2025

.KEY MESSAGES...

- Increasing low-level cloud cover late tonight into Monday
  morning, with locally dense fog possible.

- Light rain or drizzle Monday night into early Tuesday.

- Turning cold and blustery Wednesday with wind gusts > 35 mph,
  potentially paired with a few flurries.

- Unseasonably cold temperatures (highs in the 30s) continue on
  Thanksgiving and through the end of the week, with wintry
  precip becoming increasing likely next weekend.

&&

.UPDATE...
Issued at 920 PM CST Sun Nov 23 2025

Clear skies, calm winds, and dewpoints in the 20s have allowed
temperatures to tank outside of the urban Chicago core this
evening. Have commensurately adjusted near term temperature
trends downwards. Later overnight, thickening cirrus cloud cover
and an incoming surge of moist air should help temperatures
level off or even rise a bit.

Have expanded the fog mention across the area late tonight and
through Monday morning, particularly for areas southwest of a
roughly Rockford to Watseka line. Dewpoints across downstate
Illinois and northeast Missouri are surging into the low to mid
40s as winds are turning southeast to south. This moist surge
is helping drive a northward-expanding region of very low
stratus and fog which will continue to slowly ooze northward
through the night. Earlier, had wondered if increasing flow in
the lowest 50 mb might help temper the fog threat in our area.
However, based on upstream observations across southern
Illinois, this does not appear to be the case, with numerous
sites reporting visibilities under 3/4 mile. Forecast soundings
depict a notable near-surface hydrolapse accompanying this moist
surge, with most of the flow immediately above this layer.

Based on ongoing trends, can`t rule out the potential for a
Dense Fog Advisory at some point across the southwest half of
the area towards daybreak Monday morning. Don`t have any plans
to tackle that right now given lingering uncertainties with the
near-surface flow`s impact on fog trends, however. Thankfully,
this moist layer appears too thin to result in any drizzle
potential at this time.

Finally, have adjusted temperatures in our west down a bit with
the thinking that this stratus layer will have some staying
power. Across our far south and northwest Indiana, filtered
sunshine may allow temperatures to push into the low to mid
50s, but will note there remains a significant bust potential on
the high temperature forecast tomorrow.

Carlaw

&&

.DISCUSSION...
Issued at 230 PM CST Sun Nov 23 2025

A broad surface high centered over southern Illinois has
yielded a sunny and seasonably mild day across the region, with
mostly clear skies remaining through the evening amid light SSW
winds.

A persistent band of thick stratus from central Missouri to
western Kentucky today will become a focus tonight and
especially Monday as low-level moisture advection takes hold
across the mid-Mississippi River Valley. Expectations are for
the stratus to expand NNE under a developing shallow inversion
from ongoing WAA. Added weak isentropic ascent within and below
this inversion should bring low stratus (possibly LIFR ceilings
and locally dense fog) into at least southwest portions of the
CWA prior to daybreak, and possibly across the entire CWA by
mid-morning. Where the northern edge of the stratus resides by
this time will dictate temp trends as diurnal erosion of the
clouds is likely given the expected shallow cloud depth. But
with thickening cirrus also spreading northward through the day,
erosion of any cloud cover will be notably slower than what was
observed farther south today. Have maintained a somewhat middle
ground with max temps in the upper 40s on Monday, but thick
stratus would support temps in the low to mid 40s and little
stratus would favor highs in the mid 50s.

Continued low-level WAA and some diurnal heating below
mid/upper-level diffluence will lift and weaken the low-level
inversion late in the day and especially Monday night into
Tuesday morning, which will support at least some areas of light
rain or drizzle for most locations. However, a disjointed
placement up the main upper-level trough crossing southern
Wisconsin and the mid-level wave crossing the south half of
Illinois may result in a minimum of precip coverage and QPF
across most of northern Illinois during this period.

A potent cold front will then sweep across the area Tuesday
evening, ushering in much colder and blustery conditions
overnight through Wednesday. A modest isallobaric component
mostly aligned with the gradient flow combined with added
diurnal mixing will support the potential for wind gusts nearing
wind advisory criteria (gusts of at least 45 mph) on Wednesday.
Additionally, the depth of expected stratocumulus should be
sufficient for isolated to scattered snow showers (or at least
flurries) in the morning and possibly into the afternoon. Cold
and somewhat blustery conditions will persist for Thanksgiving
Day, with the incoming cold airmass suggesting that max temps
both Thanksgiving and Friday will struggle to rise much above
freezing each afternoon.

Kluber


A much more active weather pattern will take hold across the
central CONUS this weekend and into the first week of December.
Overall, the larger scale pattern across North America continues
to favor upper troughing setting up across the western CONUS
and upper ridging across the southeastern CONUS during this
period. The presence of greatly enhanced southwesterly mid and
upper level flow into the lower Great Lakes in such a pattern is
notorious for steering numerous impulses across our region.
Accordingly, some periods of active weather, with rain and/or
snow is possible as we head into next weekend. Ensemble
solutions have steadily zoned in on a late Saturday into Sunday
period for potential wintry precip, including accumulating snow.
It is important to note that while the pattern looks
increasingly active, the finer scale details this far out remain
largely unclear and will need to be ironed out in the coming
days. For example, the potential wintry weather next weekend
will depend on phasing of a trough currently just east of the
Kamchatka Peninsula (that will also have to round the Aleutian
Low) and another trough halfway between Hawaii and California.
Nevertheless, this period will be monitored closely for
potentially impactful weather systems across the central CONUS
that could impact holiday travel. Stay tuned.

KJB/Kluber

&&

.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 1119 PM CST Sun Nov 23 2025

Forecast concerns include...

Ifr/lifr cigs Monday with mvfr/ifr vis/fog.
Chance of showers Monday afternoon/evening.
Light rain/drizzle/ifr/lifr cigs/vis Monday night.

A large area of lifr/vlifr cigs/vis continues to expand and lift
north across southeast IA and southern IL late this evening.
There is also fog developing across central IL, ahead of the
main area of cigs/lower vis. Guidance has slowed the progression
north and also shifted it just a bit west, possibly keeping it
west of ORD/MDW/GYY. Confidence is too low to make any
significant changes to the current forecast and maintained tempo
lifr cigs for ORD/MDW/GYY Monday morning. If it were to occur,
likely around and after sunrise. Its more likely there could be
some scattering/lifting of these cigs by afternoon as well.

Further west, especially RFD, there is increasing confidence
that at least ifr cigs may become prevailing through much of
Monday with a period of ifr vis around/after sunrise. There
could be vis under 1sm for some areas, especially southwest of
the terminals. These lower conditions may improve some by
midday/early afternoon. There may also be a few showers Monday
afternoon, mainly across northwest IL.

Cigs/vis are expected to expand east and lower through Monday
night with prevailing lifr/ifr cigs by early Tuesday morning
areawide. Periods of light rain and drizzle are also possible
late Monday evening into Tuesday morning.

Mainly southerly winds are expected through sunset Monday
evening, favoring south/southwest on Monday and then turning
south/southeast Monday evening. Directions may continue turning
more southeast Monday night and possibly easterly early Tuesday
morning. Speeds into the 10kt range by daybreak are still
expected and where clouds scatter on Monday, speeds 10-15kts
with a some higher gusts are possible. cms

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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