Alert archive / Illinois / Flash Flood Warnings in 2018

Flash Flood Warning 12, NWS Chicago, IL

August 7, 20184 counties in Illinois

NWS Chicago, IL issued this flash flood warning at Aug 7, 2018, 4:00 PM CDT for 4 counties in Illinois. It was in force for 3 hr. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Aug 7, 2018, 4:00 PM CDT (21:00 UTC)
Expired: Aug 7, 2018, 7:00 PM CDT
In force: 3 hr
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Flood severity: None

Counties Cook County, IL, DuPage County, IL, Kane County, IL, Lake County, IL

The radar

The Chicago radar (KLOT), 45 km from the middle of the area, began a volume at 21:02 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

Davenport, (KDVN), launched 12:00Z, 9.0 hours before the alert went out and 211 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: 600 J/kg
Mixed-layer CIN: -36 J/kg
Mixed-layer LCL: 632 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 25 m²/s²
0-3 km storm-relative helicity: 80 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.3

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this flash flood 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 flash flood warning went out at Aug 7, 3:04 PM CDT, 56 minutes earlier.

Area forecast discussion, Aug 7, 3:04 PM CDT, 56 minutes before

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Hazardous weather outlook, Aug 7, 11:53 AM CDT, 4 hours 7 minutes before

Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
1153 AM CDT Tue Aug 7 2018

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
081700-
Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-DeKalb-Kane-DuPage-Cook-
La Salle-Kendall-Grundy-Will-Kankakee-Livingston-Iroquois-Ford-
Lake IN-Porter-Newton-Jasper-Benton-
1153 AM CDT Tue Aug 7 2018 /1253 PM EDT Tue Aug 7 2018/

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

.DAY ONE...This Afternoon and Tonight.

Weather hazards expected...

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

DISCUSSION...

Shower and thunderstorm coverage will increase late morning into
the afternoon, with scattered thunderstorms possibly lingering
into this evening. Some thunderstorms may be capable of producing
isolated damaging winds, primarily over eastern portions of the
outlook area including the southern parts of the Chicago metro
area, kankakee, and parts of northwest Indiana. In addition,
locally heavy rainfall will be possible with some thunderstorms,
which could result in localized flooding.

Patchy dense fog is possible overnight.

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

Thursday through Sunday...
  Limited Thunderstorm Risk.

.SPOTTER INFORMATION STATEMENT...

While there may be a few stronger storms, spotter activation
is not anticipated this afternoon or tonight.

GENERAL STORM MOTION OF THE DAY:

Moving toward the east-northeast at 35 mph.

LMZ740>745-081700-
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-
1153 AM CDT Tue Aug 7 2018

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...This Afternoon and Tonight.

Weather hazards expected...

  Limited Thunderstorm Risk...with an associated:
     Limited thunderstorm wind gust risk...up to 45 knots.

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

Thursday through Sunday...
  Limited Thunderstorm Risk.

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-081700-
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 Holland to Whitehall MI 5 nm off shore to mid-
line of 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-
1153 AM CDT Tue Aug 7 2018

This Hazardous Weather Outlook is for portions of the open waters
of Lake Michigan.

.DAY ONE...This Afternoon and Tonight.

Weather hazards expected...

Limited Thunderstorm Risk across far southern Lake Michigan this
afternoon and tonight.

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

Wednesday through Sunday...
  Limited Thunderstorm Risk.

Ratzer

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In the hours before

Local storm report, Aug 7, 3:03 PM CDT, 57 minutes before

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Local storm report, Aug 7, 3:15 PM CDT, 45 minutes before

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Local storm report, Aug 7, 3:17 PM CDT, 43 minutes before

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Local storm report, Aug 7, 3:24 PM CDT, 36 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
Aug 6, 7:08 PM CDT	Special Weather Statement	LOT	Ford	22 min
Aug 6, 7:49 PM CDT	Special Weather Statement	LOT	Iroquois	26 min
Aug 6, 8:03 PM CDT	Special Weather Statement	LOT	Ford	27 min
Aug 6, 8:24 PM CDT	Severe Thunderstorm Warning	LOT	Ford, Iroquois	51 min
Aug 6, 9:02 PM CDT	Flash Flood Warning	LOT	Ford	3 hr
Aug 7, 3:04 PM CDT	Areal Flood Advisory	LOT	Cook, DeKalb, DuPage, Kane, Lake, McHenry	3 hr
Aug 6, 8:56 PM CDT	Flash Flood Warning	LOT	Benton, Jasper, Newton	111 min

Nearby

Flash Flood Warnings in Illinois, 2018 Every flash flood warning in 2018

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.