Gary, Indiana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

436
FXUS63 KLOT 180521
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1121 PM CST Wed Dec 17 2025

.KEY MESSAGES...

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

- Rain showers and drizzle are expected late tonight into
  tomorrow before a transition to snow showers is expected
  tomorrow evening.

- The wind-whipped snow showers and rapidly plummeting
  temperatures could lead to hazardous travel conditions
  tomorrow evening with sharp visibility reductions and slick
  roadways in some locations.

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

&&

.UPDATE...
Issued at 916 PM CST Wed Dec 17 2025

Forecast looks to be on track with no significant changes
planned this evening. Only minor tweak was to slow the arrival
of drizzle chances by about 3-6 hours. As is often the case in
these WAA stratus setups, guidance was too quick in bringing the
lowest ceilings northward. Initially, stratus is likely to come
in as VFR and take a couple/few hours to build down to IFR (less
than 1000ft). Drizzle threat should increase as ceilings drop to
IFR, which should be after sunrise into the Chicago area and
probably not until 09z across our far southern CWA.

- Izzi

&&

.DISCUSSION...
Issued at 402 PM CST Wed Dec 17 2025

Through Thursday Night:

A powerhouse sub-980 mb surface low responsible for bringing
wide-ranging weather impacts to the Pacific Northwest, Rocky
Mountains, and Great Plains was analyzed over southern
Saskatchewan this afternoon. This low pressure system, in tandem
with a potent upper-level trough, will barrel into the Great
Lakes late tonight into tomorrow, bringing both strong winds and
precipitation to the area.

First, the incoming system will draw a healthy slug of low-
level moisture poleward into the region tonight. After midnight
tonight, stratus depths should grow deep enough to support
precipitation, which would initially come in the form of drizzle
given that temperatures in the saturated layer will be solidly
warmer than -10C. Droplet sizes will continue to skew more
towards drizzle until the stronger mid- and upper-level forcing
associated with incoming trough arrives after sunrise to help
saturate the dry mid-levels and introduce ice nuclei into the
deepening overhead cloud deck. Strengthening southerly winds
tonight into tomorrow morning will facilitate warm air advection
that will push temperatures well into the 40s and possibly even
into the low 50s in some locations during the morning hours, so
there aren`t any real concerns for water droplets freezing on
any surfaces. While the rain should suppress mixing heights and
thus limit the magnitude and frequency of wind gusts, low-level
wind fields look to be quite robust (40+ kts just a few hundred
feet above ground level), so it`s not difficult to envision some
40+ mph gusts being observed tomorrow morning.

The system`s leading cold front will plow through the area from
west to east from mid-morning through the early afternoon,
shifting surface winds to a westerly direction behind it. A
strongly-forced band of rain will be present along and just
behind the front as it chugs on eastward. If even just a sliver
of scant surface-based instability is realized, then that could
be enough for some of that stronger flow just off the deck to
more easily get brought down to ground level within any
convective elements of the rain band along the front. Would not
be surprised to see some 50+ mph gusts observed along the front
if that ends up being the case, but model guidance generally
favors this instability remaining pinched off to our south. Also
couldn`t completely rule out a rogue lightning strike or two in
or near our southern CWA given the strong dynamics that will be
in play, but the likelihood of this occurring does not appear
to be high enough to warrant introducing any formal thunder
chances into the forecast grids.

In the wake of the leading cold front, precipitation should
temporarily cease, temperatures will fall a bit, and blustery
westerly gusts will be observed. However, the more substantial
drop in temperatures and the onset of the strongest westerly
gusts will be delayed until a secondary reinforcing cold front
arrives during the late afternoon/early evening. Robust pressure
rises and steepening low-level lapse rates behind this front
should result in a period of more persistent ~40-45 mph westerly
gusts as temperatures rapidly plummet into the 20s and
eventually the teens. Couldn`t rule out a Wind Advisory
eventually being needed for this period, but did not have enough
confidence in 45+ mph gusts prevailing for a long enough period
of time to justify the issuance of one with this forecast
package.

Some high-resolution model guidance is also suggesting that a
narrow band of precipitation will be present along this
reinforcing front. This could be of some concern as strong
winds, steepening low-level lapse rates, and the presence of a
robust low-level frontogenetical circulation point towards any
precipitation along the front having at least some squall-like
characteristics. However, model progged moisture profiles along
this front range from somewhat questionable to not favorable at
all for supporting precipitation, so the presence/coverage of
any shower activity along the front remains in question. It also
appears that air temperatures may be a bit too warm initially
to support bona fide snow squalls along the front, and if
moisture profiles were to be sufficient for precipitation
there, then a mix of both rain and snow showers looks to be
favored instead. However, trends in forecast guidance will need
to be monitored closely.

Behind the reinforcing cold front, an upper-level vorticity
maximum will swing over the area and likely induce another round
of precipitation. By this point, air temperatures should be
solidly below freezing, so any precipitation will fall in form
of snow showers. The rapidly falling temperatures will allow for
localized coatings of snow to accumulate on roadways and may
also cause any lingering moisture to freeze up on untreated
paved surfaces. Between that and the wind-whipped nature of the
snow likely causing sharp visibility reductions, travel
conditions tomorrow evening could become hazardous in some
locations, so have issued a Special Weather Statement to
highlight this.

Ogorek


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 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 Thursday for the IL and IN
     nearshore waters.

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

&&

$$

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