Alert archive / Illinois / Severe Thunderstorm Warnings in 2017

Severe Thunderstorm Warning 53, NWS Chicago, IL

May 18, 2017Cook County, Kankakee County, Will County, Illinois

NWS Chicago, IL issued this severe thunderstorm warning at May 18, 2017, 12:58 AM CDT for Cook County, Kankakee County, Will County, Illinois. It was in force for 47 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: May 18, 2017, 12:58 AM CDT (05:58 UTC)
Expired: May 18, 2017, 1:45 AM CDT
In force: 47 min
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Hail: 1.0 in
Wind: 60.0 mph

Counties Cook County, IL, Kankakee County, IL, Will County, IL

The radar

The Chicago radar (KLOT), 25 km from the middle of the area, began a volume at 06:02 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 nearest sounding before it

Lincoln, IL (KILX), launched 00:00Z, 6.0 hours before the alert went out and 163 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: 417 J/kg
Mixed-layer CIN: -29 J/kg
Mixed-layer LCL: 1639 m above ground
0-6 km bulk shear: 69 kt
0-1 km storm-relative helicity: 231 m²/s²
0-3 km storm-relative helicity: 309 m²/s²
Significant tornado parameter: 0.3
Supercell composite: 10.2

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 May 18, 12:37 AM CDT, 21 minutes earlier.

Area forecast discussion, May 18, 12:37 AM CDT, 21 minutes before

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Hazardous weather outlook, May 17, 3:29 PM CDT, 9 hours 29 minutes before

Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
329 PM CDT Wed May 17 2017

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
182030-
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-
329 PM CDT Wed May 17 2017 /429 PM EDT Wed May 17 2017/

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

.DAY ONE...Tonight.

WEATHER HAZARDS EXPECTED:
  Elevated Thunderstorm Risk...with an associated:
      Elevated Tornado Risk.
      Elevated Hail Risk...up to half dollar size.
      Elevated Thunderstorm Wind Damage Risk...up to 60 MPH.

  Limited Non Thunderstorm Wind Risk.

DISCUSSION:

A strong storm system deepening over the plains will keep a broad
area of southerly wind gusting up to 40 to 50 mph. Fast moving
thunderstorms are expected to move into the area from the west and
southwest from the late afternoon into the evening hours. Some
storms could be severe, with an associated risk for large hail,
damaging winds and isolated tornadoes. The severe threat,
including isolated tornado risk, is anticipated to be greatest
over portions of northwest, north-central and west-central
Illinois.

Flooding will continue along portions of the Illinois river.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Thursday...
  Limited Severe Thunderstorm Risk.
Friday...
  Limited Flooding Risk.
  Limited Thunderstorm Risk.
Saturday...
  Elevated Thunderstorm Risk.
Sunday through Tuesday...
  Limited Thunderstorm Risk.

Flooding will continue along portions of the Illinois River.

.SPOTTER INFORMATION STATEMENT...

Spotters will likely be needed this afternoon and evening.

GENERAL STORM MOTION OF THE DAY:

Moving northeast at 50 MPH...

&&

LMZ740>745-182030-
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-
329 PM CDT Wed May 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.

Gale Force Winds are likely.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Thursday through Saturday...

Hazardous Conditions for Small Craft are likely.

Saturday and Sunday...
There is a chance of thunderstorms.

Tuesday and Wednesday...
There is a chance of thunderstorms.

&&

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-182030-
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-
329 PM CDT Wed May 17 2017

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

.DAY ONE...Tonight.

There is a chance of thunderstorms through this evening...with a
limited risk for severe thunderstorms capable of producing strong
winds greater than 50 knots and large hail.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

There is a chance of thunderstorms on Saturday and Sunday and
again Tuesday and Wednesday.

&&

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In the hours before

Local storm report, May 17, 11:54 PM CDT, 1 hour 4 minutes before

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Local storm report, May 18, 12:03 AM CDT, 55 minutes before

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Local storm report, May 18, 12:08 AM CDT, 50 minutes before

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Local storm report, May 18, 12:24 AM CDT, 34 minutes before

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Local storm report, May 18, 12:28 AM CDT, 30 minutes before

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Special weather statement, May 18, 12:46 AM CDT, 12 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
May 17, 8:58 PM CDT	Severe Thunderstorm Warning	LOT	Lee, Ogle	62 min
May 17, 9:37 PM CDT	Severe Thunderstorm Warning	LOT	Ogle, Winnebago	23 min
May 17, 9:54 PM CDT	Tornado Warning	LOT	Lee, Ogle	21 min
May 17, 9:59 PM CDT	Severe Thunderstorm Warning	LOT	Boone, DeKalb, LaSalle, Lee, McHenry, Ogle and 1 more	61 min
May 17, 10:04 PM CDT	Tornado Warning	LOT	Boone, Winnebago	26 min
May 17, 10:22 PM CDT	Tornado Warning	LOT	Boone, McHenry	23 min
May 17, 10:43 PM CDT	Severe Thunderstorm Warning	LOT	DeKalb, Kane, Kendall, LaSalle, McHenry	47 min
May 17, 11:06 PM CDT	Special Marine Warning	LOT		114 min
May 17, 11:11 PM CDT	Severe Thunderstorm Warning	LOT	Cook, DuPage, Lake	49 min
May 17, 11:29 PM CDT	Severe Thunderstorm Warning	LOT	Kane, Kendall	31 min
May 17, 11:50 PM CDT	Severe Thunderstorm Warning	LOT	DuPage, Grundy, Kane, Kendall, Will	40 min
May 18, 12:19 AM CDT	Severe Thunderstorm Warning	LOT	Cook, DuPage, Will	41 min
May 18, 12:42 AM CDT	Special Marine Warning	LOT		93 min
May 18, 12:46 AM CDT	Special Weather Statement	LOT	Kankakee	14 min
May 18, 1:00 AM CDT	Severe Thunderstorm Warning	LOT	Cook	30 min
May 18, 3:53 AM CDT	Gale Warning	LOT		17 hr
May 18, 5:21 PM CDT	Special Weather Statement	LOT	Benton	24 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.