Alert archive / Illinois / Severe Thunderstorm Warnings in 2017

Severe Thunderstorm Warning 84, NWS Chicago, IL

June 17, 2017Lee County, Illinois

NWS Chicago, IL issued this severe thunderstorm warning at Jun 17, 2017, 6:31 PM CDT for Lee County, Illinois. It was in force for 44 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Jun 17, 2017, 6:31 PM CDT (23:31 UTC)
Expired: Jun 17, 2017, 7:15 PM CDT
In force: 44 min
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Tornado: Possible
Hail: 1.25 in
Wind: 60.0 mph

County Lee County, IL

The radar

The Chicago radar (KLOT), 102 km from the middle of the area, began a volume at 23:32 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Jun 17, 5:39 PM CDT	Severe Thunderstorm Watch	SPC	7 hr

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 11.5 hours before the alert went out and 101 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 613 J/kg
Mixed-layer CIN: -75 J/kg
Mixed-layer LCL: 726 m above ground
0-6 km bulk shear: 26 kt
0-1 km storm-relative helicity: 122 m²/s²
0-3 km storm-relative helicity: 159 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 2.2

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Chicago, IL wrote its last area forecast discussion before this severe thunderstorm warning went out at Jun 17, 5:01 PM CDT, 1 hour 30 minutes earlier.

Area forecast discussion, Jun 17, 5:01 PM CDT, 1 hour 30 minutes before

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Hazardous weather outlook, Jun 17, 4:20 PM CDT, 2 hours 11 minutes before

Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
420 PM CDT Sat Jun 17 2017

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
182130-
Winnebago-Boone-McHenry-Lake Illinois-Ogle-Lee-De Kalb-Kane-
DuPage-Cook-La Salle-Kendall-Grundy-Will-Kankakee-Livingston-
Iroquois-Ford-Lake Indiana-Porter-Newton-Jasper-Benton-
420 PM CDT Sat Jun 17 2017 /520 PM EDT Sat Jun 17 2017/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL ILLINOIS...
NORTHEAST ILLINOIS AND NORTHWEST INDIANA.

.DAY ONE...Tonight.

WEATHER HAZARDS EXPECTED:
  Significant Thunderstorm Risk...with an associated:
      Limited Tornado Risk.
      Significant Hail Risk...up to half dollar size.
      Significant Thunderstorm Wind Damage Risk...up to 70 MPH.
  Elevated Flooding Risk.

DISCUSSION:

Scattered thunderstorms are likely late this afternoon into the
early evening across the entire outlook area. Severe threats of
hail, damaging winds, and heavy rainfall will be possible with any
storm. More widespread thunderstorms are expected later this
evening into the overnight hours, once again, across all of
northern Illinois and northwest Indiana. Damaging winds and heavy
rainfall will be the main threats, along with possible flash
flooding.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Sunday through Tuesday...
  Limited Thunderstorm Risk.
Wednesday through Friday...
  Elevated Thunderstorm Risk.

.SPOTTER INFORMATION STATEMENT...

Spotters will likely be needed late this afternoon into this
evening across the entire outlook area.

GENERAL STORM MOTION OF THE DAY:

East northeast at around 30 MPH.

&&

LMZ740>745-182130-
Winthrop Harbor to Wilmette Harbor-
Wilmette Harbor to Northerly Island-
Northerly Island to Calumet Harbor-Calumet Harbor to Gary-
Gary to Burns Harbor-Burns Harbor to Michigan City-
420 PM CDT Sat Jun 17 2017

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE ILLINOIS NEARSHORE
WATERS OF LAKE MICHIGAN AND THE INDIANA NEARSHORE WATERS OF LAKE
MICHIGAN.

.DAY ONE...Tonight.

  Significant Thunderstorm Risk...which includes possible wind
  gusts in excess of 33 knots and hail.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Monday and Tuesday...
  Limited Thunderstorm Risk.
Wednesday...
  Elevated Thunderstorm Risk.
Thursday and Friday...
  Limited Thunderstorm Risk.

&&

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-182130-
Lake Michigan from Michigan City IN to St. Joseph MI 5 NM
offshore to Mid Lake-
Lake Michigan from Seul Choix Point to Rock Island Passage 5 NM
offshore to Mid Lake-
Lake Michigan South of a line from Seul Choix Point to the
Mackinac Bridge and north of a line from Charlevoix MI to South
Fox Island 5 NM offshore-
Lake Michigan from Charlevoix to Point Betsie MI 5 NM offshore to
Mid Lake-
Lake Michigan from Point Betsie to Manistee MI 5 NM offshore to
Mid Lake-
Lake Michigan from Rock Island Passage to Sturgeon Bay WI-
Lake Michigan from Sturgeon Bay to Two Rivers WI 5 NM offshore to
Mid Lake-
Lake Michigan from Two Rivers to Sheboygan WI 5 NM offshore to
Mid Lake-
Lake Michigan from Sheboygan to Port Washington WI 5 NM offshore
to Mid Lake-
Lake Michigan from Port Washington to North Point Light WI 5 NM
offshore to Mid Lake-
Lake Michigan from North Point Light to Wind Point WI 5 NM
offshore to Mid Lake-
Lake Michigan from Wind Point WI to Winthrop Harbor IL 5 NM
offshore to Mid Lake-
Lake Michigan from Winthrop Harbor to Wilmette Harbor IL 5 NM
offshore to Mid Lake-
Lake Michigan from Wilmette Harbor IL to Michigan City IN 5 NM
offshore to Mid Lake-
Lake Michigan from Pentwater to Manistee MI 5 NM offshore to Mid
Lake-
Lake Michigan from Whitehall to Pentwater MI 5 NM offshore to Mid
Lake-
Lake Michigan from Grand Haven to Whitehall MI 5 NM offshore to
Mid Lake-
Lake Michigan from Holland to Grand Haven MI 5 NM offshore to Mid
Lake-
Lake Michigan from South Haven to Holland MI 5 NM offshore to Mid
Lake-
Lake Michigan from St. Joseph to South Haven MI 5 NM offshore to
Mid Lake-
420 PM CDT Sat Jun 17 2017

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE OPEN WATERS OF LAKE
MICHIGAN.

.DAY ONE...Tonight.

Thunderstorms are likely through this evening. Wind gusts in
excess of 33 knots are possible mainly across the south half.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

There are chances for thunderstorms through the period.

&&

Rodriguez

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In the hours before

Special weather statement, Jun 17, 4:26 PM CDT, 2 hours 5 minutes before

Special Weather Statement
National Weather Service Chicago/Romeoville Il
426 PM CDT SAT JUN 17 2017

ILZ003-008-172200-
Winnebago IL-Ogle IL-
426 PM CDT SAT JUN 17 2017

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN OGLE AND
SOUTHEASTERN WINNEBAGO COUNTIES UNTIL 500 PM CDT...

At 426 PM CDT, Doppler radar was tracking a strong thunderstorm near
Stillman Valley, or near Oregon, moving northeast at 30 mph.

Nickel size hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Rockford, Byron, Cherry Valley, Stillman Valley, Davis Junction and
New Millford.

Including the following interstate...
 I-39 between mile markers 103 and 121.

LAT...LON 4198 8928 4210 8933 4225 8898 4197 8898
TIME...MOT...LOC 2126Z 246DEG 26KT 4206 8923

RATZER

Special weather statement, Jun 17, 4:38 PM CDT, 1 hour 53 minutes before

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Local storm report, Jun 17, 4:45 PM CDT, 1 hour 46 minutes before

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Special weather statement, Jun 17, 4:45 PM CDT, 1 hour 46 minutes before

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Local storm report, Jun 17, 4:59 PM CDT, 1 hour 32 minutes before

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Local storm report, Jun 17, 5:33 PM CDT, 58 minutes before

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The office that day

Everything else NWS Chicago, IL issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 16, 7:03 PM CDT	Special Weather Statement	LOT	Iroquois	27 min
Jun 17, 4:17 PM CDT	Special Weather Statement	LOT	DuPage	28 min
Jun 17, 4:26 PM CDT	Special Weather Statement	LOT	Ogle	34 min
Jun 17, 4:38 PM CDT	Special Weather Statement	LOT	Cook	37 min
Jun 17, 4:40 PM CDT	Special Marine Warning	LOT		65 min
Jun 17, 4:45 PM CDT	Special Weather Statement	LOT	DuPage	30 min
Jun 16, 7:18 PM CDT	Special Weather Statement	LOT	Benton	27 min

Nearby

Severe Thunderstorm Warnings in Illinois, 2017 Every severe thunderstorm warning in 2017

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.