Elgin, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

467
FXUS63 KLOT 181551
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
951 AM CST Thu Dec 18 2025

.KEY MESSAGES...

- Strong southerly, then westerly winds are expected today as a
  multi-faceted weather system moves through the region.

- Thin line of showers may result in some sporadic wind gusts of
  50+ mph between about 11 AM and 3 PM (earliest west).

- Scattered wind-shipped snow showers with reduced visibilities
  and rapidly falling temperatures could lead to some slippery
  travel conditions this evening.

- Wind chills of 0 to 10 below expected early Friday morning.

- The blustery and briefly colder conditions tonight into
  Friday will be followed by variable, but generally above
  normal temperatures into next week.

&&

.UPDATE...
Issued at 951 AM CST Thu Dec 18 2025

Opted to issue a short-fused Dense Fog Advisory for portions of
interior northern Illinois. Webcams, reports, and observations
show that the worse conditions are primarily confined to the
western half of Kane County to eastern half of Lee and Ogle and
points north. In the affected area, wind blown thick dense fog
aided by the quickly melting snow cover is resulting in fairly
widespread coverage of visibility less than 1/4 mile (as low as
a couple hundred feet in spots per reports).

The dense fog threat should come to an end with the thin line of
strongly forced convective showers marching into far western and
northwestern IL at this time. We`ll be keeping a close eye on
observations for 50+ mph wind gust potential, as noted in the
full discussion below.

Castro

&&

.DISCUSSION...
Issued at 310 AM CST Thu Dec 18 2025

Through Tonight:

Moisture is surging northward across the region early this
morning with low stratus rapidly expanding overhead. Cloud
depths will increase beyond 5-6 kft through 5 AM, and this will
result in a rapid expansion of showers and drizzle through the
morning hours. Earlier this evening, we had noted a fair amount
of frost/ice development on untreated surfaces, even with above-
freezing air temperatures. This was likely tied to fairly deep
frost development coming out of the recent cold stretch.
Thankfully, road temperature sensors at this hour have
continually warmed, with all available data showing temperatures
now above freezing. With air temperatures continuing to warm,
we don`t have any concerns with icing threats this morning.

A robust--currently roughly 980 mb--surface low will shift east
across the Minnesota Arrowhead Region this morning and will
eventually drag not one, but two, cold fronts through the
region--one this afternoon, followed by the main cold push this
evening. The Omaha, NE radar is nicely picking up this first
front which is slicing into western Iowa at this hour. Expecting
the development of a thin, strongly-forced line of shallow
convection later this morning as the front begins to intercept
deeper moisture with dewpoints pushing into the mid and upper
40s. A very narrow axis of non-zero 0-3 km CAPE is forecast to
develop and push into parts of central Illinois along the front.
At this time, it looks like the bulk of this still meager low-
level instability will remain well to our south, but a very
narrow ribbon of reduced static stability may accompany the line
of convection through our forecast area. While the severe
threat remains relatively low, such strong forcing coincident
with an intensifying southerly LLJ overhead suggests some
potential for stronger wind gusts being transported to the
surface withing any taller cores. In fact, can`t rule out a few
gusts near 50-60 mph as this convective line marches eastward
(either side of 11 AM near I-39, Noon-2 PM through the Chicago
Metro, before clearing our NW Indiana counties around 3-4 PM).
In the wake of this activity/cold front, temperatures will fall
quickly into the 30s.

Out ahead of this line, a ripping low-level jet just off the
deck will result in increasing southerly synoptic winds. Low-
level inversion looks formidable, and likely will curtail the
more significant winds from mixing down to the surface, but a
few 40-45 mph gusts will be possible before the convective line
passes.

A secondary narrow corridor of low-level instability is forecast
to develop immediately ahead of the secondary cold front,
focused primarily across central Illinois. Could envision some
additional low-topped showers developing in this region towards
4-7 PM south of the Kankakee River, but this activity seems like
it`d be occurring with above-freezing wetbulb temperatures.

The secondary cold front with the main push of CAA will arrive
near I-39 towards 5-6 PM and will surge through the rest of the
forecast area through the late evening hours. Temperatures are
expected to fall quickly into the teens and 20s through
midnight. Snow squall parameter output remains pretty muted,
even on the previously-aggressive NAM. This seems to be tied to
fairly shallow low-level instability (0-2 km lapse rates
generally less than 5-6 C/km, with most of the steeper lapse
rates confined to the 0-1 km layer). This will still support the
development of some gustier, wind-whipped snow showers which
may knock visibilities down briefly under a mile this evening
with localized coatings of snow.

As the previous shift mentioned, we`ll likely see another "pop"
of winds as this front arrives, with strong westerly gusts
developing through the evening and overnight. While the peak
gusts map currently across the Dakotas shows quite a few 50+ kt
reports, guidance continues to suggest the strongest winds will
have a very difficult time pushing past the Mississippi River.
3-hr pressure rises are forecast to ease significantly with
eastward extent, and it looks like the main core of stronger
925-850 mb winds will end up passing off to our south and west.
As a result, while a few 45 mph gusts will be possible this
evening, not seeing enough of a signal that these will be
widespread and long enough duration to warrant a Wind Advisory
at this point.

Scattered snow showers/flurries will probably persist through
much of the night, at least until the main 700 mb vort lobe
passes overhead. Wind chills by daybreak Friday are forecast to
be in the 0 to 10 below range.

Carlaw


Friday through Wednesday:

Stratus with some flurries (cloud layer in the DGZ) trapped
under a strong subsidence inversion late tonight may linger
into Friday morning, but substantial low-level dry air advection
should erode clouds from west to east as a surface ridge
crosses the area Friday afternoon. Expect a much colder day on
Friday with highs in the mid 20s. Only a small drop in
temperatures is expected Friday evening as a 50 knot LLJ spreads
over the area and results in steady WAA through the night.

A low-amplitude wave will then cross far western Ontario on
Saturday. A brief warmup into the 40s is expected early in the
day before temps fall with the passage of a cold front during
the afternoon. Marginal moisture profiles may support a narrow
band of light mixed precip along and slightly behind the front
mainly north of I-80. Colder conditions with highs in the upper
20s and mostly sunny skies will follow on 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
on Tuesday. Guidance continues to favor the development of a
broad ridge across the central CONUS by early Christmas.
Expansive WAA with steady low-level moisture advection is
expected across the mid-Mississippi River Valley by Christmas
Eve, with a likely area of stratus and drizzle/light rain in the
region. Placement is still a bit far out to pin point, but a
mild and damp Christmas Eve into Christmas is possible.

Kluber

&&

.AVIATION /12Z TAFS THROUGH 18Z FRIDAY/...
Issued at 543 AM CST Thu Dec 18 2025

Conditions have rapidly deteriorated over the past couple hours
as a 60+ knot low-level jet advects abundant low-level moisture
over the area. Even with ongoing S gusts over 25 knots and
expected SSW gusts to 30 knots through the morning, have
maintained LLWS as KLOT VWP data indicates winds of 60-65 knots
are located as low as 1500kt. Meanwhile, areas of SHRADZ will
persist through the morning, but likely be more prevalent
through mid-morning.

Ceilings/visibilities range from VLIFR/LIFR west of the Fox
Valley to IFR closer to Lake Michigan. Existing snowpack at
DPA/RFD is likely contributing to the LIFR or lower conditions,
which should persist for at least a few more hours before slowly
improving late this morning. Ceilings and visibility should
remain in IFR levels at ORD/MDW/GYY through the morning.

A cold front will bring a thin line of strongly forced showers
(almost convective in nature) across the terminals early this
afternoon. Squall-like conditions from west gusts over 40 knots
and visibility as low as 1SM are possible for 30 min or less in
the 18- 20Z window for ORD/MDW.

Winds will turn west and gust up to 30 knots behind the front
while ceilings lift into VFR levels later this afternoon. A
secondary cold front will then bring a period of scattered SHSN,
westerly gusts over 30 knots, and a return of MVFR ceilings
early this evening and overnight. Brief periods of IFR
visibility are possible for the first few hours behind the
front (generally 03-06Z), with SHSN waning in intensity the
overnight.

Kluber

&&

.MARINE...
Issued at 435 AM CST Thu Dec 18 2025

A strong area of low pressure near 29.1 inches will move across
the Great Lakes region today and tonight. In advance of this
system, southerly winds will continue to gradually increase
this morning, with frequent gusts around 30 kts expected. A
strong low-level jet with winds near 50 kts is forecast to
develop later this morning and afternoon. Strong stability over
the colder lake waters is expected to limit the frequency of
stronger gusts, but some intermittent gales into the 35-40 kt
range will be possible during a brief window between about 10 AM
and 3 PM, mainly at elevated/higher-level platforms.
Thereafter, winds may briefly ease into the 25-30 kt range
through the rest of the afternoon.

A thin line of fast-moving showers is expected to push across
the lake, approximately during the 1 to 4 PM timeframe. Some
wind gusts near 45 kts will be possible with any stronger/deeper
showers. Special Marine Warnings may be needed for this
activity.

A second cold front will move across the southern portions of
Lake Michigan this evening. Westerly winds around 35 kt are
expected, and a Gale Warning remains in effect this evening and
tonight to cover this potential. Winds will diminish through
late Friday afternoon as an area of high pressure briefly builds
across the southern portion of Lake Michigan.

Carlaw

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Gale Warning from 6 PM this evening to 6 AM CST Friday for the
     IL and IN nearshore waters.

&&

$$

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