Lombard, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

939
FXUS63 KLOT 132036
AFDLOT

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

.KEY MESSAGES...

- Chance of wind-whipped snow showers Wednesday morning across
  far eastern IL into northwest Indiana.

- Unseasonably mild temperatures will continue until a strong
  cold front sends temperatures tumbling starting late tonight;
  seasonably cold temperatures expected Wednesday through
  Thursday.

- Winter weather advisory issued for northern and eastern Porter
  County for lake effect snow showers Wednesday and Wednesday
  night, localized accumulations of 2-5 inches expected,
  especially northeast Porter County.

- A "Clipper Express" pattern may materialize from the end of
  this week into early next week with periodic opportunities
  for snow, reinforcing shots of cold air, and blustery
  northwest winds.


&&

.DISCUSSION...
Issued at 236 PM CST Tue Jan 13 2026

Through Thursday:

Water vapor imagery early this afternoon shows an amplifying
trough digging south into the Upper Mississippi Valley and
western Great Lakes. Fascinating to see all of the smaller
embedded vorticity maximums embedded within the larger
developing trough, the most significant being the one over
extreme southwest Ontario. This Ontario vort max is progged to
dive south-southeastward into southern WI by 12z Wednesday and
could bring some precipitation to the area very late tonight
into Wednesday morning, but there are some pretty big
uncertainties...

Guidance is pretty split with GFS and NAM dry, while ECMWF and
GEM do squeeze out some light QPF over mainly eastern portions
of the CWA, including the Chicago Metro area, Wednesday morning.
While vort max of interest will be quite strong, the associated
ascent is mostly progged to occur in dry air above a strong low
level frontal inversion. The difference between the guidance
that produces QPF and those that don`t seem to lie in the height
of the progged frontal inversion and depth of the subsequent
convective cloud depth under the inversion. Guidance with lower
inversion heights are dry while those with slightly higher
inversion heights do have some QPF. Hard to say with high degree
of confidence which scenario is more likely at this point, so
opted to hang onto the chance pops late tonight and especially
Wed morning. The low probability, worst case scenario seems to
be some more robust wind driven snow showers, leading to a
coating to a half inch of snow and potentially hazardous travel.
The chances of that occurring appear quite low, so not planning
to hit the messaging any harder at this time. Worth noting the
HRRR does break out some light rain showers ahead of the front
overnight, but forecast soundings from the HRRR look
suspiciously moist and not realistic. Just kept some slight
chance pops in the grids as a nod to the HRRR, but this scenario
seems unlikely.

Regarding the lake effect snow...

Strong cold air advection over a fairly warm lake (SSTs in the
lower 40s over most of the open waters) should result in
moderately strong lake induced instability Wednesday into
Wednesday night. Inversion heights are progged to be extreme,
topping out 6-8kft, but plenty high to support some heavy lake
effect snow showers, particularly given the DGZ embedded within
the convective clouds.

Expecting mostly multi-banded lake effect set-up during the
daytime hours Wednesday, effecting northern and perhaps eastern
Porter County. Wednesday night, land breeze convergence could
lead to a more dominant, strong lake effect band, which would
likely take aim on areas east of Porter County. Some CAM
guidance suggests the there could be a weaker secondary band
to the west over Porter County or even just some weaker
multi-band structure snow showers. Lake effect chances for
Porter County look to decrease early Thursday morning as winds
back and push the band east into WFO IWX`s area. Given the
strong winds and the potential for at least a couple/few inches
of snow, opted to issue a winter wx advisory for northern and
eastern Porter County. As is typically the case with lake
effect, totals could vary significantly over a short distance.

- Izzi

Thursday Night through Tuesday:

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
snow showers (if not snow squalls) 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 placing our area in the "cone of
uncertainty" for additional short waves/clipper systems to swing
into the area. While forecast confidence is naturally low on
the exact cadence and track of each clipper, confidence remains
high that we will experience 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. This includes during the upcoming weekend.

Ratzer/Borchardt

&&

.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...Winter Weather Advisory from 8 AM Wednesday to 4 AM CST
     Thursday for INZ002.

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.

&&

$$

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