Joliet, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

876
FXUS63 KLOT 131730
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1130 AM CST Tue Jan 13 2026

.KEY MESSAGES...

- After unseasonably mild temperatures today through this
  evening, expect a return to generally much colder
  temperatures Wednesday through the upcoming weekend.

- Chance of wind whipped snow showers/flurries late tonight into
  Wednesday morning, greatest coverage from northeast Illinois
  and east central IL and points eastward into northwest Indiana.

- Wind-blown accumulating lake effect snow expected downwind of
  Lake Michigan Wednesday afternoon through Thursday morning.
  The highest amounts are expected to occur east of Porter
  County, but hazardous travel appears likely in particularly
  northeast Porter County due to a combination of light to
  moderate lake effect snow and strong northwesterly winds.

- Another round of accumulating wind-driven snow appears likely
  Thursday night into Friday. An unsettled weather pattern then
  continues through the weekend and into next week with periods
  of gusty winds and occasional chances for light
  snow/flurries.

&&

.DISCUSSION...
Issued at 345 AM CST Tue Jan 13 2026

Through Thursday:

The main concern is the anticipated lake effect snow event for
portions of northwest Indiana, north central Indiana, and far
southwest lower Michigan. Bottom line up front for this issuance
is that no winter weather headlines were issued yet for Porter
County, but expecting that we`ll need to hoist a Winter Weather
Advisory on the day shift.

Today will be breezy/windy and mild, especially in the afternoon
as some sunshine appears probable. Looking at highs in the upper
40s to lower 50s, which will be the last non-winter-like day
for a while. As noted in yesterday`s discussion, can`t rule out
some mid 50s in spots. West-southwest winds will gust up to
30-35 mph, and if mixing heights are deeper/maximized, sporadic
gusts to 40 mph are in the realm of plausibility.

The advertised abrupt (and unwelcome for some) change in our
weather is on track for prior to daybreak Wednesday as a strong
cold front rips through the area. A potent 500 mb vort lobe is
progged to pivot southeast across the area from the pre-dawn
hours through the mid morning. In the overnight guidance suite,
the corridor of maximized forcing over the eastern 1/3 to 1/2
or so of the area exhibited a slightly deeper convective layer
on forecast soundings than noted in the previous discussion.
For this reason, right behind the fro-pa, there could be
scattered more robust wind-whipped snow showers (outside chance
for a few snow squalls) for a short period (between ~4 and 10
AM CST). West of this area (northwest and north central IL),
expect primarily flurries and perhaps a few isolated snow
showers.

Temperatures will quickly cool into the 20s from north to south
behind the front and paired with strong north-northwest winds
gusting to 30-40 mph, daytime wind chills will range from +5 to
+15F. So after any morning snow showers/flurries, the main
story for the areas outside the lake effect threat zone (which
is most of the CWA), is that it will be decidedly back to
winter, so bring the winter clothes back out!

As the column dries out west of Lake Michigan by Wednesday
afternoon (ending lingering flurries/snow showers), the lake
effect machine will roar to life, with multi-banded snow showers
likely streaming into Porter County (and even portions of Lake
County). Fairly impressive lake effect parameters with top of
the synoptic frontal inversion up to around 7-8kft or more with
convective cloud layer well within the DGZ. By Wednesday
evening, LES should organize into a a strong single band with
the million dollar question being where will that band set up.
Synoptic flow continues to favor LaPorte County and points east,
but it still could be close for especially northeast Porter
County.

Even after the more intense single band develops during
the evening, recent CAM depictions favor light to moderate snow
showers still streaming into the northeast 1/2 or 1/3 of Porter
County, with some accumulations likely. Still can`t rule out a
trend to a bit more veered with the flow that would potentially
open the door to the intense single band and heavy snowfall
rates getting into northeast Porter County for a time Wednesday
evening. Our latest forecast update favors fairly continuous
periods of snow Wednesday through early Thursday over northern
and northeast Porter County gradually adding up to a few to
perhaps several inches of accumulation. Localized 4-6" amounts
appear plausible in the far northeast portion of the county.
Paired with strong northwest winds enhanced by lake-induced
convergence processes, falling and blowing and drifting snow
will likely cause hazardous travel. Feel confident we`ll need a
Winter Weather Advisory for Porter County, possibly needing to
start as early as Wednesday morning for the initial lake
enhanced wind-whipped snow showers.

Lows will fall into the teens area-wide on Wednesday night,
except perhaps right on the northwest Indiana shore, and with
northwesterly winds slowly easing, expect wind chills to bottom
out around 0 degrees (plus or minus a few degrees either side).
After a mostly sunny start to Thursday away from northwest
Indiana, clouds will increase in advance of the next system
expected to bring periods of snow Thursday night into Friday
(detailed below). Expect highs in the mid 20s, a few degrees
below normal for the date.

Castro

Thursday Night through Monday:

A deep long-wave upper level trough is forecast to take up
residence across eastern North America through the period,
reinforced by a series of short waves digging into the western
periphery of the trough from the Canadian prairies to the
Midwest. Global ensembles (EPS/GEFS and CMCE) continue to be in
good agreement with a potent wave rotating through the region
Thursday night into Friday, with an associated surface low of
around 995 mb tracking across the northern Lakes. This would
support a wind-driven accumulating snowfall developing across
the forecast area from Thursday evening into Friday morning as
the vort pivots overhead. Deep forcing eventually weakens behind
the initial vort Friday, though steepening lapse rates driven
by cold advection, the continued deepening of the upper trough
and lingering low-mid level saturation should support additional
light snow/snow showers through the day. Guidance is also in
good agreement in a reinforcing push of colder low-level air
Friday night.

Models then remain in good agreement in keeping the long-wave
trough axis near or just east of the area though the weekend and
into early next week. However, ensembles continue to show spread
in the timing of additional short waves rotating through the
trough in the Saturday through Monday time frame. While periods
of snow/snow showers will likely occur, confidence in timing the
impacts of individual short waves is quite low at this distance
and have made no changes to NBM pops. Of higher confidence is
that we`ll see a prolonged period of cold and occasionally
blustery weather into early next week with wind chills spending
considerable time in the single digits either side of zero.

Ratzer

&&

.AVIATION /18Z TAFS THROUGH 00Z THURSDAY/...
Issued at 1130 AM CST Tue Jan 13 2026

Key Aviation Messages for the current TAF period:

- Gusty west winds becoming north-northwest overnight. Gusts in
  excess of 30 knots at times this afternoon and tomorrow
  morning.

- MVFR ceilings develop late this evening and persist overnight.

- A period of snow showers possible early Wednesday morning.
  Brief IFR possible.

Winds have turned to the west with increased gusts over 25
knots. Gusts around 30 knots are possible this afternoon. After
a brief lull in wind gusts back down 20 to 25 this evening, a
cold frontal passage after midnight will veer the winds to the
north-northwest and increase once again tomorrow morning to
around 30 knots. Expect northerly winds to remain through the
end of the TAF and gradually diminish through tomorrow
afternoon.

Skies have cleared this afternoon. An MVFR cloud deck is
expected to descend over the area ahead of the cold front. With
ambient temperatures still above freezing and weak forcing,
there is a less than 20 percent chance for a few sprinkles/rain
drops that could occur before midnight. With low confidence and
little impact, it was left out of the TAF presently. Scattered
snow showers, capable of producing brief IFR conditions, are
possible for mainly the Chicago terminals. Flurries may
linger through the morning/early afternoon, though lake effect
snow will prevail east of KGYY.

DK

&&

.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 3 AM to 9 PM CST Wednesday for Winthrop
     Harbor IL to Gary IN.

     Gale Warning from 3 AM Wednesday to 3 AM CST Thursday for Gary
     to Burns Harbor IN-Burns Harbor to Michigan City IN.

&&

$$

Visit us at weather.gov/chicago