Special Marine Warning 13, NWS Chicago, IL

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
648 PM CDT Tue Jun 29 2021

.SHORT TERM...
300 PM CDT

Through Wednesday night...

Widely scattered storms will continue to be possible across areas
south of a line from Mendota to Waukegan. This is the area in
which we have seen more insolation early this afternoon due to
more breaks in the cloud cover. This has allowed temperatures to
warm into the mid 80s amidst 70+ degree dew points, thus
supporting ample MLCAPE values in excess of 1,500 J/KG across much
of the area east of I-39 and south of I-88. Effective deep layer
remains the strongest just north and west of this area, but with
values of shear still up near 30 kt in the areas of better
instability some organized storm clusters capable of producing
localized strong wind gusts and torrential downpours will be
possible. We have already seen this with some of the storm
clusters over parts of east central IL into parts of northwestern
IN. Local instances of flash flooding will be possible with these
storms, especially in areas in which the storms train over the
same areas.

The storms should be on diminishing trend this evening, so the
threat of strong storms and very heavy rainfall will wane. For
this reason, we have opted to allow the current flash flood watch
to expire this evening. While the chances for some showers and
storms will continue tonight, it appears the threat of widespread
areas of very heavy rainfall will wane quickly this evening.

A surface cold frontal boundary will began to shift southward
into northern IL on Wednesday. This should act to keep the primary
threat of thunderstorms with heavy rain on Wednesday south of
I-80.

KJB

&&

.LONG TERM...
300 PM CDT

Thursday through Monday...

The thinking for the extended period has not changed. See below
for more info.

In the wake of a cold front Wednesday night, Thursday will be
noticeably less humid. A secondary front off Lake Michigan by early
afternoon will usher in breezy northwest winds. Widely scattered
showers and thunderstorms may develop during the afternoon hours as
a sharp upper-level wave dives south over the western Great Lakes
cooling mid-level temperatures sufficiently for some 1000+ J/kg of
MLCAPE. Thursday does not look like a washout however, and most
areas will reach the 80 degree mark except along the lakeshore where
the low to mid 70s are expected.

Friday onward through the holiday weekend look splendid! Friday will
feature below normal highs in the lower 70s followed by highs in the
low to mid 80s Saturday and Sunday. Partly sunny skies and light
winds are expected with slim to no chances for precipitation each
day. Temperatures Sunday evening look to be in the neighborhood of
the mid to upper 70s--perfect for fireworks. An early glimpse at
next week reveals a trend toward warming temperatures and a return
of chances for shower and thunderstorm.

Borchardt

&&

.AVIATION...
For the 00Z TAFs...

648 PM...Forecast concerns include...

Chance of thunderstorms Wednesday afternoon.
Wind shift/lake breeze Wednesday afternoon.
Possible mvfr cigs and light fog Wednesday morning.

There is a chance for showers and a few thunderstorms this
evening, mainly south of the terminals. There may be a few light
showers this evening across the terminals. There will be another
chance for showers and thunderstorms Wednesday afternoon. The best
chance is again expected south of the terminals but a lake breeze
is expected Wednesday afternoon, shifting winds to the northeast.
This lake breeze may allow isolated thunderstorms to develop.
Confidence is fairly low but current prob mention is reasonable
from this distance.

There is a small chance for light fog to develop Wednesday
morning, especially in the usual more rural locations. Mvfr cigs
are also possible overnight into mid/late Wednesday morning but
confidence is low and opted for scattered mention with this
forecast. cms

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

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Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
359 PM CDT Tue Jun 29 2021

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-302100-
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-
359 PM CDT Tue Jun 29 2021 /459 PM EDT Tue Jun 29 2021/

This Hazardous Weather Outlook is for portions of North Central
Illinois...Northeast Illinois and Northwest Indiana.

.DAY ONE...Tonight.

Weather hazards expected...

  Elevated Thunderstorm Risk...with an associated:
    Limited damaging wind risk...up to 60 mph.
  Limited Flooding Risk.

DISCUSSION...

Scattered thunderstorm clusters will continue through early evening,
mainly southeast of the I-55 corridor. Torrential downpours and gusty
winds will accompany the strongest storms. The heavy rain will
lead to flooding of ditches, farm fields, and roadways, especially in
areas that already received heavy rainfall over the past several days.
A Flash Flood Watch remains in effect for northern Illinois and
northwestern Indiana through early this evening.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Wednesday...
  Limited Flooding Risk south of I-80.
  Limited Thunderstorm Risk.
Thursday...
  Limited Thunderstorm Risk.
  High Swim Risk.
Friday...
  High Swim Risk.
Monday...
  Limited Thunderstorm Risk.

.SPOTTER INFORMATION STATEMENT...

Spotters activation is not anticipated, though rainfall and
flooding reports would be appreciated.

GENERAL STORM MOTION OF THE DAY:

  Moving toward the north northeast at 30 to 35 mph.

LMZ740>745-302100-
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-
359 PM CDT Tue Jun 29 2021

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...with an associated:
     Limited thunderstorm wind gust risk...up to 40 knots.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Wednesday...
  Limited Thunderstorm Risk.
Thursday...
  Hazardous conditions for small craft are likely.
  Limited Thunderstorm Risk.
Monday...
  Limited Thunderstorm Risk.

KJB

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Special Weather Statement
National Weather Service Chicago/Romeoville
307 PM CDT Tue Jun 29 2021

ILZ033-INZ019-292100-
Iroquois IL-Benton IN-
307 PM CDT Tue Jun 29 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN IROQUOIS AND BENTON
COUNTIES UNTIL 400 PM CDT/500 PM EDT/...

At 306 PM CDT/406 PM EDT/, Doppler radar was tracking strong
thunderstorms along a line extending from near Cissna Park to 7 miles
southeast of Stockland to near Oxford. Movement was north at 20 mph.

Wind gusts up to 50 mph and pea size hail will be possible with
these storms.

Locations impacted include...
Fowler, Milford, Otterbein, Oxford, Boswell, Earl Park, Stockland,
Woodland, Wellington, Ambia, Dunnington, Wadena, Claytonville,
Swanington, Templeton and Raub.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4049 8790 4075 8779 4073 8710 4048 8710
TIME...MOT...LOC 2006Z 202DEG 18KT 4052 8783 4052 8754 4052 8718

Petr

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO IL
342 PM CDT TUE JUN 29 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0338 PM     TSTM WND GST     1 SE KENTLAND           40.76N 87.44W
06/29/2021  M62 MPH          NEWTON             IN   MESONET

            MEASURED GUST TO 62 MPH AT KENTLAND AIRPORT.

&&

Special Weather Statement
National Weather Service Chicago/Romeoville
411 PM CDT Tue Jun 29 2021

INZ010-011-292215-
Newton IN-Jasper IN-
411 PM CDT Tue Jun 29 2021

...SIGNIFICANT WEATHER ADVISORY FOR NEWTON AND JASPER COUNTIES UNTIL
515 PM CDT...

At 409 PM CDT, Doppler radar was tracking a strong thunderstorm near
Brook, or near Morocco, moving north at 25 mph.

Wind gusts in excess of 50 mph will be possible with this storm.

Locations impacted include...
Rensselaer, DeMotte, Kentland, Remington, Morocco, Wheatfield, Lake
Village, Roselawn, Brook, Collegeville, Mount Ayr, Sumava Resorts,
Thayer, Baileys Corner, Stoutsburg, Foresman, Fair Oaks and Parr.

Including the following interstate...
 Indiana I-65 between mile markers 201 and 262.

This includes...  US 41 Dragway.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4084 8706 4084 8710 4076 8710 4079 8750
      4117 8744 4116 8739 4118 8737 4118 8733
      4122 8729 4123 8725 4118 8693 4116 8693
TIME...MOT...LOC 2109Z 200DEG 20KT 4092 8733

Petr

Special Weather Statement
National Weather Service Chicago/Romeoville
444 PM CDT Tue Jun 29 2021

INZ002-011-292230-
Porter IN-Jasper IN-
444 PM CDT Tue Jun 29 2021

...SIGNIFICANT WEATHER ADVISORY FOR PORTER AND NORTHERN JASPER
COUNTIES UNTIL 530 PM CDT...

At 443 PM CDT, Doppler radar was tracking a strong thunderstorm near
Kouts, or near Hebron, moving north at 30 mph.

Penny size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations impacted include...
Valparaiso, DeMotte, Hebron, Wheatfield, Lakes of the Four Seasons,
Kouts, Wheeler, Dunns Bridge, Boone Grove, Malden and Stoutsburg.

This includes...  Valparaiso University and Porter County
Fairgrounds.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4118 8722 4154 8722 4152 8693 4115 8693
TIME...MOT...LOC 2143Z 195DEG 28KT 4129 8709

Petr

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