Elgin, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

655
FXUS63 KLOT 200803
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
203 AM CST Sat Dec 20 2025

.KEY MESSAGES...

- After a see-saw in temperatures this weekend, a warming trend
  will take hold next week and peak on Christmas with high
  temperatures potentially in the 50s to locally lower 60s.

- The upcoming pattern will not be supportive of widespread
  soaking precipitation events in our region. With that said,
  there will be occasional opportunities for drizzle
  particularly Monday and again Wednesday night into Thursday
  morning.

&&

.DISCUSSION...
Issued at 203 AM CST Sat Dec 20 2025

Through Sunday:

A shortwave trough continues to traverse across Manitoba and
northern ND this morning. Just ahead of this trough a 994 mb
surface low has developed near the Manitoba-Ontario border with
a cold front stretching from the low across MN, northwest IA,
into eastern NE. At the present time, northern IL and northwest
IN are sandwiched between this low and a surface high over the
Appalachians which is resulting in breezy south-southeast winds.
While wind gusts should generally remain in the 20-25 mph range
today, a period of stronger gusts (around 30 mph) may develop
around daybreak as the atmosphere mixes into a departing low-
level jet. Otherwise, the main theme for today will be
increasing clouds ahead of the aforementioned cold front with
highs topping out in the upper 30s to lower 40s before the front
arrives this evening.

That said, there remains a signal for a few light snow
showers/flurries to develop near the IL-WI line towards midday.
With forecast soundings continuing to show a fairly stout dry
sub-layer suspect these snow showers/flurries will fail to
materialize into northern IL and remain in southern WI. Though
as a precaution have opted to maintain the ~15% POPs along the
stateline just in case an isolated flurry or two sneaks in.
Regardless, no accumulation or travel impacts are anticipated.

Tonight, temperatures will quickly cool behind the cold front
with readings bottoming out in the mid-teens to lower 20s by
Sunday morning. Since winds will remain breezy out of the
northwest tonight, wind chills in the single digits are once
again in store. A surface high will pivot overhead on Sunday
which will allow winds to finally diminish and gradually become
more southwesterly Sunday afternoon. Despite the stout cold
advection and light winds, temperatures on Sunday will rebound
into the lower 30s due to sunny skies and lack of snow cover.

Yack


Sunday Night through Friday:

A long-awaited pattern change will commence on Monday as
anomalous blocking south of Alaska generates aggregate troughing
across the Pacific Coast and broad quasi-zonal flow along the
US/Canadian border. With our area expected to be positioned
south of the energetic jet stream, we should largely escape
opportunities for widespread precipitation events and instead
have the opportunity to enjoy a period of above-average
temperatures.

On Monday, strong low-level warm air advection on the backside
of a departing high pressure system and ahead of an upper-level
wave propagating along the US/Canadian border will facilitate
850mb temperatures rising some 8 to 10C/24 hours to +2C or so
into the Lower Great Lakes. So, in spite of expected widespread
mid to upper-level cloud cover, do expect temperatures Monday
afternoon to warm into the upper 30s to lower 40sF across the
area. A wedge of dry low-level air left in the wake of the high
pressure system should prevent any widespread precipitation
falling from mid-level echoes that develop within the persistent
the warm air advection/isentropic ascent regime. With that
said, still cannot rule out a few snowflakes or ice pellets
surviving the trip toward the ground particularly near the
Wisconsin state line (will advertise 20% of such primarily from
midnight to midday Monday). Am also noting some guidance
depicting better moisture return by Monday night mainly east of
I-57 which may allow for the development of drizzle, though this
appears to be an outlier scenario at this point. Continued low-
level warm air advection Monday night into Tuesday will support
nearly steady overnight low temperatures in the low to mid 30s.

By Tuesday, 850mb temperatures of +10 to +12C will prove
dominant over a washing out cold front supporting afternoon
highs in the mid to even upper 40s. At least modest mid-level
subsidence tied to the right exit region of an embedded upper-
level jet streak passing to our north as well as column-wide dry
air advection should provide an opportunity to see the sun
(even if filtered thorugh high clouds).

Somewhat neutral upper-level height and low-level advection
tendencies as well as building upper-level cloud cover in
advance of the next storm system Wednesday morning suggest that
temperatures may be slow to warm after daybreak. In fact,
already am seeing a signal for a non-diurnal temperature curve
with daytime temperatures in the 30s and 40s and then
temperatures surging into the 50s after dark as low-level
moisture and warm air advection ramp up. So, will cautiously
undercut NBM hourly guidance during daylight hours in favor of
showing the high temperature occurring after dark. With
increasing low-level moisture beneath a residual dry pocket of
mid-level air left in the wake of the cold front on Tuesday,
forecast soundings exhibit a signal for pockets of drizzle and
low-intensity rain showers after dark supporting the NBM-
delivered 20 to 40% chances for rain. Should the signal remain
for drizzle and low-intensity rain showers, will have to
eventually increase PoPs. With that said, Christmas Eve does not
look like a complete washout, so a rain jacket should do the
trick of out and about for holiday festivities.

On Christmas, ensemble mean guidance hints at the ejection of
one or more shortwaves from aggregate troughing along the
Pacific Coast toward the central US. As a result, another push
of warm-air advection is expected in our region, leading to
surge in anomalously warm temperatures. Both ensemble mean and
NBM highs range from the low 50s to even lower 60s across the
region (warmest temperatures south), which seems reasonable
given a warm morning starting point and 850mb temps of +12C.
While it`s still too early have any real confidence in the exact
high temperature forecast, it does look like Christmas 2025
will have a shot of ending up as a top-5 warmest at both Chicago
and Rockford.

Even in the wake of another cold front Thursday night into
Friday, the positioning of the jet stream north of our area
supports a continuation of above average temperatures into the
weekend.

Borchardt

&&

.AVIATION /06Z TAFS THROUGH 12Z SUNDAY/...
Issued at 1120 PM CST Fri Dec 19 2025

Key Aviation Messages for the current TAF period:

- Low level wind shear (LLWS) is expected overnight

VFR conditions are expected through the TAF window. Winds
remain around or just under 10 knots this evening, but are
slowly becoming more southerly. A low level jet will continue to ramp
up and peak at almost 60 knots above 2000 AGL through mid
morning. So, will maintain the mention of LLWS even as periodic
surface gusts occur.

Surface winds will become more west-southwesterly in the
morning. While the low level jet is expected to subside and end
the risk for LLWS, better mixing should allow for surface gusts
to continue into the early afternoon. Winds should diminish by
late afternoon. Another low level jet increases tomorrow
evening. Wind gusts are expected to increase once again between
20 to 25 knots through the overnight.

DK

&&

.MARINE...
Issued at 215 AM CST Sat Dec 20 2025

A period of 35 kt south-southwest gales will materialize over
the next 1-2 hours and persist through mid-morning as the
unstable marine layer mixes into a strong low-level jet
overhead. As a result a Gale Warning remains in effect for the
Illinois and Indiana nearshore waters through 9 AM CST today.

While winds will diminish later today, northwest 25-30 kt winds
will linger through tonight behind yet another cold front. Since
another low-level jet will be present tonight cannot completely
rule out another period of gale force gusts this evening into
the early morning hours Sunday, especially along the Illinois
shore. However, with the frequency of gales expected to lower
have opted to handle this period with a Small Craft Advisory for
now.

Yack

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Gale Warning until 9 AM CST this morning for the IL and IN
     nearshore waters.

     Small Craft Advisory from 9 AM this morning to 4 AM CST Sunday
     for Winthrop Harbor IL to Gary IN.

     Small Craft Advisory from 9 AM this morning to noon CST Sunday
     for Gary to Burns Harbor IN-Burns Harbor to Michigan City
     IN.

&&

$$

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