Alert archive / Illinois / Severe Thunderstorm Warnings in 2017

Severe Thunderstorm Warning 43, NWS Chicago, IL

May 15, 2017Winnebago County, Illinois

NWS Chicago, IL issued this severe thunderstorm warning at May 15, 2017, 9:40 PM CDT for Winnebago County, Illinois. It was in force for 35 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 15, 2017, 9:40 PM CDT (02:40 UTC)
Expired: May 15, 2017, 10:15 PM CDT
In force: 35 min
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

County Winnebago County, IL

The radar

The Milwaukee radar (KMKX), 86 km from the middle of the area, began a volume at 02:39 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
May 15, 7:52 PM CDT	Severe Thunderstorm Watch	SPC	3 hr

The nearest sounding before it

Davenport, (KDVN), launched 00:00Z, 2.7 hours before the alert went out and 136 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: 865 J/kg
Mixed-layer CIN: -169 J/kg
Mixed-layer LCL: 1965 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 71 m²/s²
0-3 km storm-relative helicity: 148 m²/s²
Significant tornado parameter: 0.0
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 May 15, 9:03 PM CDT, 37 minutes earlier.

Area forecast discussion, May 15, 9:03 PM CDT, 37 minutes before

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Hazardous weather outlook, May 15, 3:17 PM CDT, 6 hours 23 minutes before

Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
317 PM CDT Mon May 15 2017

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
162030-
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-
317 PM CDT Mon May 15 2017 /417 PM EDT Mon May 15 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:
      Limited Tornado Risk.
      Elevated Hail Risk...up to quarter size.
      Elevated Thunderstorm Wind Damage Risk...up to 60 MPH.
  Limited Flooding Risk.

DISCUSSION:

Scattered thunderstorms remain possible through the evening hours
though confidence is low in the evolution of these thunderstorms and
how far south they will be. Latest guidance suggests that the
fairly strong cap over the area may keep storms confined to far
northern Illinois or even southern Wisconsin. If storms form farther
south, the amount of wind shear presents at least some severe risk.
The main severe threats, if severe thunderstorms occur, are
anticipated to be hail and damaging wind gusts.

In addition...minor flooding will continue along portions of the
Illinois and Kankakee Rivers.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

Wednesday...
  Limited Thunderstorm Risk.
  Limited Non Thunderstorm Wind Risk.
  Limited Fire Weather Risk.
Thursday through Saturday...
  Limited Thunderstorm Risk.

DISCUSSION:

An unseasonably strong storm system will affect the Midwest on
Wednesday. Thunderstorms are possible, with a conditional risk
for severe thunderstorms. In addition, very strong southerly wind
gusts up to or above 40 mph are possible.

In addition...minor flooding will continue along portions of the
Illinois and Kankakee rivers.

.SPOTTER INFORMATION STATEMENT...

Spotters may be needed this evening.

GENERAL STORM MOTION OF THE DAY:

Toward the east around 30 mph.

&&

LMZ740>745-162030-
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-
317 PM CDT Mon May 15 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.

There is a chance of thunderstorms this evening.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

Tuesday through Saturday...
  Hazardous Conditions for Small Craft are likely at times, first
  for southerly wind gusts later Tuesday into Thursday, and for
  high waves late in the week.

There is a periodic chance for thunderstorms Wednesday through Saturday
with the better chances late Wednesday and Saturday.

&&

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-162030-
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-
317 PM CDT Mon May 15 2017

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

.DAY ONE...Tonight.

There is a chance for thunderstorms this evening.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

There is a periodic chance for thunderstorms Wednesday through Saturday
with the better chances Wednesday across the lake and Saturday for
the south half.

&&

KMD

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In the hours before

Local storm report, May 15, 6:02 PM CDT, 3 hours 38 minutes before

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Local storm report, May 15, 6:05 PM CDT, 3 hours 35 minutes before

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Local storm report, May 15, 6:09 PM CDT, 3 hours 31 minutes before

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Local storm report, May 15, 6:14 PM CDT, 3 hours 26 minutes before

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Local storm report, May 15, 6:24 PM CDT, 3 hours 16 minutes before

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Special weather statement, May 15, 8:35 PM CDT, 1 hour 5 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 15, 8:35 PM CDT	Special Weather Statement	LOT	McHenry	25 min
May 15, 9:14 PM CDT	Small Craft Advisory	LOT		40 hr
May 15, 10:21 PM CDT	Special Marine Warning	LOT		114 min
May 16, 3:00 PM CDT	Gale Watch	LOT		12 hr
May 16, 3:00 PM CDT	Small Craft Advisory	LOT		4 days

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.