Wind Advisory 9, NWS Chicago, IL

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
125 PM CDT Sun Jun 28 2026

.KEY MESSAGES...

- Showers and a chance for thunderstorms this afternoon/early
  evening

- Dangerous heat is expected across the area this week with
  afternoon heat index values forecasted over 100 degrees.
  Little to no relief is expected at the lakeshore or at night.

&&

.DISCUSSION...
Issued at 125 PM CDT Sun Jun 28 2026

A complex of showers and thunderstorms is progressing eastward
through northeast Iowa at the time the discussion was published.
The current expectation is for it to follow a northwest to
southeast instability gradient across northern Illinois. But as
the upper level ridge pattern is amplifying and advecting in
warmer temperatures in the mid levels, there is lower confidence
in thunderstorms being able to maintain their strength. Perhaps
there is lower confidence in the eastward extent of the
lightning activity, but currently projecting the system to decay
as it approaches the Fox Valley with only isolated embedded
thunderstorms. Localized small hail is still possible, mainly
west of the Fox Valley, due to over 40 knots of effective shear
available. Otherwise, gusty winds are possible with any shower
or thunderstorm. However, as this complex of showers passes
east, an area of localized low pressure is expected to develop
in its wake. Southeast wind gusts unrelated to showers and
thunderstorms have the potential to increase late this
afternoon/early evening for an hour or two up to 40 mph.

As an anomalously deep low continues to sit over the
Intermountain West, another embedded impulse is expected to
move northeastward into Wisconsin. This may trigger some
scattered light showers or sprinkles around daybreak, mainly for
areas closer to the Wisconsin stateline and the Lake Michigan
shoreline. But any moisture is going to have to contend with the
growing dry air mass, preventing any formal mention of precip
in the PoPs forecast. More intriguing is that high-res guidance
is now suggesting an MCS could develop tomorrow off this impulse
in northern Wisconsin and head toward Michigan. If an MCS were
to occur, there is a chance that some outflow could race
southwestward toward are area, but the current guidance is that
the MCS tack would be far enough east to not impact our area.

Otherwise, the main story remains the heat wave. An amplified
upper level ridge over the area will set up prevailing southwest
winds, a drier air mass, and higher surface pressure. The
southwest flow will increase 850 mb temperatures north of 20C
and pull 70+ dewpoints across the forecast area. Hot and humid
conditions are forecast starting tomorrow through at least
Wednesday. Based on current guidance, heat indices are expected
up to around 105F. There's fairly good confidence that 110F (the
criteria for an Extreme Heat Warning) will not be reached.
Therefore, no changes were presently made to the Heat Advisory,
though cannot rule out upgrading it to a Warning IF the heat is
expected to continue through Thursday (more on that in a
minute). Otherwise, the Extreme Heat Watch for Cook County (with
its lower heat criteria) was converted to an Extreme Heat
Warning given the confidence in the heat for Monday through
Wednesday.

All the uncertainty on the duration of the heat wave focuses on
the strength and location of the ridge over the eastern CONUS.
Models have been bouncing around a lot over the last several
runs. The stronger the ridge late in the week, the better
chances for higher heat indices to remain in place and the
potential for that upgrade from the Advisory to a Warning.
However, a weaker ridge and/or a drift farther east would lead
open the door for convective systems to pass closer to the area
which could help give "some" heat relief. Given the uncertainty
and model disagreement, felt no need to change any of the chance
PoPs in the extended forecast though it is accompanied with
lower confidence. One last note, despite the model disagreement
on the ridge placement both the GEFS and Euro ensembles are
keeping 850 mb around 20C through the end of the week and
weekend. So even if heat index values were to fall at the end of
the week below an Advisory or Warning criteria, they could
still remain well into the 90s through the holiday weekend.
Welcome to summer, everyone!

DK

&&

.AVIATION /18Z TAFS THROUGH 00Z TUESDAY/...
Issued at 1256 PM CDT Sun Jun 28 2026

Key messages for the 18Z TAF period:

* A decaying system of showers and thunderstorms moving across
  northern IL this afternoon. Greatest thunder chances at RFD.

* A period of gusty SE winds expected behind the showers late
  this afternoon.

* MVFR cigs into this afternoon, possibly staying just outside
  of ORD. Low confidence on return to VFR.

A decaying system of showers and thunderstorms is working into
far northwest IL early this afternoon. It will continue weaken
on its way into Chicagoland, but could bring some scattered
showers for the mid-late afternoon period. Embedded
thunderstorms are more likely over RFD, but a storm cannot be
ruled out into Chicagoland. A brief period of gusty SE winds can
be expected behind these showers as a result of a wake low.

MVFR cigs over the terminals have managed to stay just outside
of ORD so far and appear to be lifting toward and above 3kft as
of late. MVFR may persist as late as mid-afternoon, although
exact timing on a return to VFR is uncertain.

Meanwhile, ESE winds will periodically gust to around 20 kt
this afternoon outside of the showers. They'll stay up near 10
kt overnight and veer to SSW by early Monday before increasing
to over 20 kt for the late morning and afternoon.

Doom

&&

.CLIMATE...
Issued at 252 AM CDT Sun Jun 28 2026

     .Daily Records for the Upcoming Week........

Chicago (KORD)
            Record High       Record Warm Minimum
June 29       97 (1954)            80 (1931)
June 30       99 (1953)            80 (2018)
July 1       103 (1956)            78 (1931)
July 2        99 (1970)            79 (1911)
July 3       102 (1949)            78 (1911)
July 4       102 (2012)            80 (1921)

Rockford (KRFD)
            Record High       Record Warm Minimum
June 29      103 (1931)            75 (1931)
June 30      102 (1931)            76 (2018)
July 1       101 (1931)            76 (1970)
July 2        99 (1910)            74 (1970)
July 3        99 (1925)            75 (2012)
July 4       102 (2012)            77 (1977)

NWS Chicago

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Heat Advisory from noon Monday to 10 PM CDT Wednesday for
     ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-
     ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-
     ILZ106-ILZ107-ILZ108.

     Extreme Heat Warning from noon Monday to 10 PM CDT Wednesday
     for ILZ103-ILZ104-ILZ105.

IN...Heat Advisory from noon CDT /1 PM EDT/ Monday to 10 PM CDT /11
     PM EDT/ Wednesday for INZ001-INZ002-INZ010-INZ011-INZ019.

LM...None.

&&

Visit us at weather.gov/chicago

Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
210 PM CDT Sun Jun 28 2026

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-291915-
Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-De Kalb-Kane-DuPage-
La Salle-Kendall-Grundy-Kankakee-Livingston-Iroquois-Ford-
Northern Cook-Central Cook-Southern Cook-Northern Will-
Southern Will-Eastern Will-Lake IN-Porter-Newton-Jasper-Benton-
210 PM CDT Sun Jun 28 2026 /310 PM EDT Sun Jun 28 2026/

This Hazardous Weather Outlook is for portions of north central
Illinois...northeast Illinois and northwest Indiana.

.DAY ONE...Tonight.

Weather hazards expected...

  Limited Thunderstorm Risk...with an associated:
     Level 1 of 5 Damaging Wind Risk...up to 60 mph.
     Level 1 of 5 Hail Risk...up to the size of a quarter.

DISCUSSION...

A cluster of thunderstorms may produce locally strong
wind gusts or small hail to to the size of a quarter,
primarily west of the Fox River Valley, this afternoon.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Monday through Wednesday...
  Elevated Excessive Heat Risk.
Thursday...
  Elevated Excessive Heat Risk.
  Limited Thunderstorm Risk.
Friday and Saturday...
  Limited Thunderstorm Risk.

DISCUSSION...

Dangerous heat with afternoon heat index values over 100 degrees
is expected tomorrow through at least Wednesday. Depending on
potential thunderstorm coverage late in the week, the dangerous
heat may persist into the weekend.

.SPOTTER INFORMATION STATEMENT...

  Spotter activation will not be necessary through tonight.

GENERAL STORM MOTION OF THE DAY:

  Moving toward the southeast at 35 mph.

LMZ740>745-291915-
Winthrop Harbor to Wilmette Harbor IL-
Wilmette Harbor to Northerly Island IL-
Northerly Island to Calumet Harbor IL-
Calumet Harbor IL to Gary IN-Gary to Burns Harbor IN-
Burns Harbor to Michigan City IN-
210 PM CDT Sun Jun 28 2026

This Hazardous Weather Outlook is for portions of the Illinois
nearshore waters of Lake Michigan and the Indiana nearshore
waters of Lake Michigan.

.DAY ONE...Tonight.

Weather hazards expected...

  Limited Thunderstorm Risk  this evening.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Monday and Tuesday...
  Hazardous conditions for small craft are likely.
Thursday through Saturday...
  Limited Thunderstorm Risk.

DK

Visit us at www.weather.gov/chicago

Special Weather Statement
National Weather Service Chicago/Romeoville IL
413 PM CDT Sun Jun 28 2026

ILZ003>006-008-011-012-103-290000-
Winnebago-Boone-McHenry-Lake IL-Ogle-De Kalb-Kane-Northern Cook-
Including the cities of Rockford, Belvidere, Crystal Lake,
Algonquin, McHenry, Woodstock, Waukegan, Buffalo Grove,
Mundelein, Gurnee, Rochelle, Oregon, Byron, DeKalb, Sycamore,
Aurora, Elgin, Evanston, Des Plaines, Schaumburg, Palatine,
and Northbrook
413 PM CDT Sun Jun 28 2026

...Locally damaging southeasterly winds this afternoon...

A period of gusty to locally damaging southeasterly winds is
expected this afternoon along the backside of a region of showers.
Peak wind gusts may approach 55 mph especially near the Wisconsin
State Line in McHenry and Lake counties. Such winds may be strong
enough to down tree limbs and cause localized power outages.

Secure loose outdoor objects and take care when driving on roads
with significant crosswinds.

Borchardt

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