Gary, Indiana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

594
FXUS63 KLOT 180910
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
310 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.

&&

.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 /06Z TAFS THROUGH 12Z FRIDAY/...
Issued at 1121 PM CST Wed Dec 17 2025

* Strong southerly winds develop early this morning, shifting
  to westerly and remaining strong and gusty through the rest of
  the TAF cycle.

* MVFR CIGS will developing prior to sunrise this morning
  morning, likely lowering to IFR shortly after sunrise.

Winds:

Southerly winds will gradually during the predawn hours this
morning, particularly after lower CIGS arrive. Strong and gusty
southerly winds are expected to continue through the morning
with gusts to 30kt possible. Winds will shift to westerly
behind a strong cold front midday, remaining strong and gusty. A
secondary cold front will move across the terminals early-mid
evening, with winds/gusts probably increasing a bit behind that
front, with gusts over 35kt possible at times tonight.

A strong low level jet with winds increasing to 50-55kt within
1500ft of the ground supports a continued mention of LLWS, even
with some modest mixing and strong winds at the sfc.

CIGS/VSBY:

Stratus deck will rapidly develop and move north tonight
overspreading the terminals prior between 07-09z this morning.
Initially, CIGS may come in low VFR, but should lower to MVFR
and eventually IFR by or shortly after sunrise. Once IFR CIGS
arrive, DZ/BR will likely result in MVFR/IFR VSBY. For now, kept
VSBY MVFR, but later updates may need to introduce IFR VSBY if
confidence increases.

Precipitation:

ISOLD SHRA will likely develop prior to sunrise with ISOLD-SCT
SHRA expected to continue this morning. Drizzle and some light
fog will also develop after sunrise. A more organized, stronger
line of showers with tops potentially up to around 20kft will
accompany the cold front across the terminals midday. In
addition to a period of heavier rain, these showers could
produce some gusts briefly up to around 40kt.

- Izzi

&&

.MARINE...
Issued at 417 PM CST Wed Dec 17 2025

A strong area of low pressure near 29.1 inches will move across
the Great Lakes region on Thursday. In advance of this system,
southerly winds will increase this evening over the Illinois
and Indiana nearshore waters. While winds are forecast to
increase to near 50 kts at 1500 ft very late tonight and into
Thursday morning, strong stability over the lake is expected to
limit much of this flow from reaching the surface, curtailing
the frequency of 35 kt gales. A Small Craft Advisory is in
effect from 9 PM this evening through 6 PM Thursday.

As the surface low moves across Lake Superior, a cold front
move across southern portions of the lake resulting in abrupt
shift to west gales to 35 kt. As a result, the Gale Watch has
been upgraded to a gale warning and is in effect from 6 PM
Thursday through 6 AM Friday. Given latest guidance it is
possible that the start time of the gales may need to be shifted
a few hours earlier into the late afternoon Thursday.

Winds will diminish through late Friday afternoon as an area of
high pressure briefly builds across the southern portion of
Lake Michigan.

Carlaw/Izzi

&&

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

     Gale Warning from 6 PM this evening to 6 AM CST Friday for the
     IL and IN nearshore waters.

&&

$$

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