Aurora, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

974
FXUS63 KLOT 170921
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
321 AM CST Wed Dec 17 2025

.KEY MESSAGES...

- Mild temperatures through Thursday should melt much of the
  remaining snow cover.

- Rain showers and drizzle will develop late tonight with a
  period of steady rain ahead with a strong cold front on
  Thursday.

- Blustery and briefly colder conditions Thursday night into
  Friday will be followed by variable but generally above normal
  temperatures into next week.

&&

.DISCUSSION...
Issued at 321 AM CST Wed Dec 17 2025

Through Thursday night:

A shortwave trough is in the process of swinging through the
region early this morning. We managed to wring out some spotty
sprinkles/light showers at the office a bit earlier from a 15
kft cloud deck. Given modeled ascent increasing through
daybreak, have added some sprinkle wording to the grids roughly
south of I-80. Thankfully, temperatures remain much warmer than
previously thought, and are currently solidly above freezing.
Seeing a few road temperature sensors still hovering around the
32 F mark, but given the light nature of things and warmer
ambient conditions, don`t have significant icing concerns before
the column rapidly dries out through 5-6 AM.

Upstream satellite trends reveal post-frontal stratus is thinning
across central Wisconsin. As a result, it looks like we`ll
probably clear out here this morning towards midday. Forecast
soundings suggests we`ll probably attempt to mix into at least
some spotty lower stratus/stratocu this afternoon, but it
remains a bit unclear just how widespread this will become.
Continue to advertise general partly cloudy/partly sunny wording
this afternoon as a result.

Dry conditions will continue through this evening, but cloud cover
will thicken up ahead of our next robust storm system. Model
guidance continues to indicate rapid saturation taking place under
700 mb during the 3 to 6 AM timeframe. This will likely manifest
as a quick blossoming of showers and drizzle across much of the
area, and PoPs commensurately increase during this time frame.
Wetbulb temperatures will be solidly above freezing, and even
pushing above 40 degrees, as precipitation develops, so no
concerns with slick spots at this point. Widespread rain/showers
will continue to expand across the region Thursday morning.
Given the dynamics at play, wouldn`t be totally surprised to see
a lightning flash approach our southern CWA mid-morning towards
midday. Any low-level instability of note appears like it`ll
remain decidedly south of the area.

An initial front/pre-frontal trough will push through the area
Thursday afternoon sending temperatures falling quickly into the
mid to upper 30s. Have worked to sharpen up this non-diurnal
trend a bit with the NBM-delivered grids not quite capturing
this sharp gradient. While we can`t totally rule out some snow
mixing in, the sharp nature of this boundary suggests that
precipitation will come to an end prior to the column cooling
enough to support a widespread changeover to snow.

The true push of deep cold advection will lag this initial
boundary a bit, but will arrive decidedly early Thursday
evening and overnight with temperatures plunging through the
teens. As the main blast of cold air arrives, saturation through
a thickening DGZ is forecast to occur. This setup looks
favorable for continued intermittent gusty snow showers and
widespread flurries through Thursday night. Continuing to keep
an eye on the Thursday evening timeframe as some guidance
(mainly the NAM) suggests a brief window for a potentially more
squall-like snow showers with notably steeper low-level lapse
rates compared to the rest of the guidance suite, but note that
this remains an outlier solution. Regardless, localized dustings
of snow will be possible before activity diminishes late
overnight into Friday morning. Wind chills by early Friday AM
will fall into the +5 to -5 range.

Carlaw


Friday through Tuesday:

A weakening mid-level ridge and associated surface ridge will
cross the forecast area through the day on Friday. Stratus with
some flurries (cloud layer in the DGZ) trapped under a strong
subsidence inversion late Thursday night may linger into Friday
morning, but substantial low-level dry air advection on gusty
northwest winds in the morning should erode remaining clouds
from west to east before the ridge arrives late in the
afternoon. After highs in the mid to possibly upper 20s Friday
afternoon, increasing WAA amid weak low-level stability and a
40+ knot LLJ spreading over the area will likely result in
steady or even rising temps Friday night.

A low-amplitude wave will then cross far western Ontario on
Saturday while keeping any appreciable forcing well north of the
area. A brief warmup into the 40s and a ribbon of very light
rain may precede a passing cold front Saturday afternoon and
evening. Colder conditions with highs in the upper 20s and
mostly sunny skies are expected Sunday as another high pressure
crosses the region.

Moisture return ahead of the next storm system passing well to
the north Monday into Tuesday appears to be insufficient for
widespread precip over the area before a weak cold front passes
through on Tuesday. Looking ahead to Christmas Eve and
Christmas, a rapid return of WAA over the central CONUS is on
track to bring unseasonably warm conditions over the area. With
a long trajectory of moisture from the Atlantic and Gulf,
abundant moisture surging over the region will likely bring
periods of showers/drizzle and plenty of stratus.

Kluber

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 1126 PM CST Tue Dec 16 2025

Low-level southwesterly flow will gradually weaken in magnitude
as directions turn northwesterly through the pre-dawn hours of
Wednesday as a weak cold front moves through the area. Recent
satellite imagery depicts a solid bank of MVFR stratus (based
just above 1000ft) racing southward across Wisconsin behind the
front. With the southern edge of the stratus deck struggling to
maintain intregity, confidence in whether the terminals will
actually experience stratus is somewhat low (30 to 50% chance).
All things considered, will go ahead and advertise a few hours
of MVFR in TEMPO groups, timed at around daybreak in line with
RAP guidance.

After daybreak, any remaining clouds should clear. As a surface
pressure ridge slides over the terminals, winds will back from
northwesterly to westerly, southwesterly, southerly, and
eventually southerly. With wind magnitudes remaining fairly
light (near 5kt or so), opted to forgo new lines for every 30
degree direction change and simply add a line at 23Z for when
the direction should settle on southeasterly.

Toward the end of the TAF period (and in the latter 6 hours of
the 30-hour TAF windows at ORD/MDW), intensifying warm-air and
low-level moisture advection in advance of an approaching storm
system will facilitate a rapid development and downward
expansion of low-level stratus, with medium to high (50 to 70%
chances) for high-end IFR to low-end MVFR conditions. With time,
drizzle and showers should develop as well, leading to drops in
visibility (3 to 6 miles). Will go ahead and introduce IFR to
MVFR aviation conditions at ORD/MDW, and allow for the same for
the remaining terminals in the upcoming 12Z set of TAFs.
Finally, the tightening low-level pressure gradient should
facilitate a transition back to southwesterly winds with gusts
increasing to the 20 to 25kt range through the overnight hours.
With the expectation that gusts occur, will hold off on
introducing LLWS in spite of strong low-level flow (50 to 60kt
at 2kft).

Borchardt

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory from 9 PM this evening to 6 PM CST
     Thursday for the IL and IN nearshore waters.

     Gale Watch from Thursday evening through late Thursday night
     for the IL and IN nearshore waters.

&&

$$

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