035
FXUS63 KLOT 131909
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
209 PM CDT Mon Oct 13 2025

.KEY MESSAGES...

- A chance (30-50%) for showers Tuesday night, north of I-80.

- A more active weather pattern looks will bring increasing rain
  chances (35-55%) next weekend.

&&

.DISCUSSION...
Issued at 152 PM CDT Mon Oct 13 2025

Through Tuesday Night:

Light showers/sprinkles have now largely dissipated across
northern IL as they move east. This is due to forcing from a
northern stream upper trough shifting away, along with a
strengthening upper ridge extending from the southern Plains and
into the lower Great Lakes. Skies are mostly cloudy, and will
continue to fill in for areas where cloud breaks have allowed
temperatures to reach into the 70s.

A cold front across northwest IL and into WI will slowly move across
the area tonight and will shift winds to the northeast. This
front will bring cloudy skies but it will remain dry. High
pressure behind the front will maintain onshore flow through
Wednesday and will create for a larger temperature gradient
across the area with 70s well inland and 60s for areas closer to
the lake. The upper ridge will hold on Tuesday and maintain dry
conditions during the day and into the evening hours.

The next disturbance of interest is working its way in southwest
flow ahead of the deep trough in the west. Precipitation chances
increase later Tuesday night into early Wednesday as this
disturbance crests the upper ridge. There are some signals that
we will get some initial erosion of precipitation similar to
what has been occurring today. The highest chances appear to be
north of I-80 with perhaps some potential for any precip that
develops to be north into southern WI.

KMD

Wednesday through Monday:

Lingering shower activity across far northern Illinois (north of I-
80) will diminish late Wednesday morning or early afternoon, as
a ridge of high pressure helps to dry out the lower atmosphere.
Surface high pressure associated with this upper level system
will drop into the mid-Atlantic states from the northern Great
Lakes, allowing a strengthening low pressure system in the
Rockies to eject northeast through the upper Plains during the
second half of the week. These systems are modeled to begin
lifting moisture back into the mid and upper Mississippi River
Valley`s during the second half of the week into next weekend.

As the warm nose lifts through the upper Mississippi River Valley
Thursday morning, limited chances of precip (<20%) will be possible
across northwest IL, as the high pressure side remains in control.
Heading across the border in Wisconsin, chances of precipitation
increase the further north throughout Thursday. High pressure then
streams south along the Atlantic coast to end the week,
ushering slightly warmer temperatures (mid to upper 70s
areawide) and additional moisture into the Midwest and Ohio
River Valley. Some uncertainty exists with the overall coverage
of precipitation throughout the weekend; with some camps having
a frontal push and ending rain Saturday, while others have
chances of precip throughout much of the weekend. NBM remains
with the main frontal push Saturday which brings the majority of
widespread chances, before leaning on the ECMWF for lingering
activity further southwest on Sunday. Looking at some
probabilistic NBM 24-hour precip data: trends are at a 30-50%
exceedance of 0.5-inch north of I-80, while trending closer to
50% exceedance of 0.5-inch south of I-80. So while this system
does not appear to be a soaker at this time for our area, we
will continue to monitor trends over the next several days.

Seasonal temps will linger through mid-week climb and back
above normal to end the week, before a cool down back to
seasonal after the weekend system exits.

Baker/KMD

&&

.AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 1221 PM CDT Mon Oct 13 2025

Sprinkles, or a few passing light showers will move through the
airspace through early afternoon, with the highest likelihood
for these to persist along and west of ORD/MDW.  Low to mid
level VFR cloud cover with bases around 4-7kft will then
continue into tonight. Otherwise, expect light and variable
winds either side of S (more SW at ORD/MDW) to turn north-
northeasterly later in the day as a cold front drops into the
area. Thereafter, northeasterly winds will persist through the
remainder of the TAF period. With these NE winds comes the
chance for cloud bases to lower to MVFR closer to the lake
Tuesday morning, and including ORD and MDW. With the chance
currently at around 30# will hold VFR conditions in the TAF at
this point.

KMD

&&

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

&&

$$

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