Alert archive / Illinois / Flash Flood Warnings in 2015

Flash Flood Warning 42, NWS Chicago, IL

September 18, 2015Lee County, Ogle County, Illinois

NWS Chicago, IL issued this flash flood warning at Sep 18, 2015, 1:15 AM CDT for Lee County, Ogle County, Illinois. It was in force for 8 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: Sep 18, 2015, 1:15 AM CDT (06:15 UTC)
Expired: Sep 18, 2015, 9:15 AM CDT
In force: 8 hr
Issued by: NWS Chicago, IL
Area: Storm-based polygon
Flood severity: None

Counties Lee County, IL, Ogle County, IL

The radar

The Chicago radar (KLOT), 107 km from the middle of the area, began a volume at 06:18 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 00:00Z, 6.3 hours before the alert went out and 103 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: 1343 J/kg
Mixed-layer CIN: -47 J/kg
Mixed-layer LCL: 1492 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 211 m²/s²
0-3 km storm-relative helicity: 495 m²/s²
Significant tornado parameter: 1.1
Supercell composite: 15.7

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 Sep 18, 12:38 AM CDT, 37 minutes earlier.

Area forecast discussion, Sep 18, 12:38 AM CDT, 37 minutes before

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Hazardous weather outlook, Sep 17, 3:38 PM CDT, 9 hours 37 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
338 PM CDT THU SEP 17 2015

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
182045-
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-
338 PM CDT THU SEP 17 2015

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

  WEATHER HAZARDS EXPECTED:

   THUNDERSTORMS...SOME MAY PRODUCE:
    HAIL TO THE SIZE OF QUARTERS.
    WINDS GUSTING TO 60 MPH.
    FREQUENT CLOUD TO GROUND LIGHTNING.

  AREAS AFFECTED AND TIMING:
   THUNDERSTORMS ARE LIKELY THROUGH EARLY EVENING WITH A MARGINAL
   THREAT FOR SEVERE WEATHER. MOST STORMS WILL BE CAPABLE OF WINDS
   TO 35 MPH AND WITH HEAVY DOWNPOURS. A FEW ISOLATED SEVERE STORMS
   WILL BE POSSIBLE THROUGH 6PM. ANOTHER ROUND OF STORMS IS EXPECTED
   LATE TONIGHT. STORMS ARE EXPECTED TO MOVE WEST TO EAST ACROSS THE
   OUTLOOK AREA TONIGHT. THE GREATEST THREAT FOR SEVERE WEATHER WILL
   PRIMARILY BE ACROSS NORTH CENTRAL ILLINOIS LATE TONIGHT.

  DISCUSSION:

  A STORM COMPLEX IS CURRENTLY MOVING EAST ACROSS NORTHERN ILLINOIS.
  A CHANCE FOR THUNDERSTORMS WILL CONTINUE INTO THIS EVENING. WHILE
  THIS SYSTEM IS EXPECTED TO DIMINISH IN INTENSITY WITH TIME ...A FEW
  THUNDERSTORMS COULD CREATE GUSTY WINDS AND LIGHTNING. A SECOND ROUND
  OF THUNDERSTORMS IS EXPECTED TO DEVELOP AHEAD OF A COLD FRONT LATE
  TONIGHT.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE AGAIN FRIDAY
AFTERNOON AND EVENING. LOCALLY HEAVY RAINFALL IS POSSIBLE INTO
FRIDAY NIGHT.

HIGH WAVES WILL CREATE HAZARDOUS SWIMMING CONDITIONS FOR ILLINOIS
AND INDIANA BEACHES ON SATURDAY AND SATURDAY EVENING. THESE HIGH
WAVES COULD ALSO RESULT IN MINOR COASTAL FLOODING AND EROSION
ALONG THE SOUTHERN SHORES OF LAKE MICHIGAN.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NECESSARY THROUGH TONIGHT.

&&

LMZ740>745-182045-
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-
338 PM CDT THU SEP 17 2015

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

THUNDERSTORMS ARE EXPECTED THROUGH EARLY THIS EVENING AND AGAIN
LATE TONIGHT.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE FRIDAY AFTERNOON
EVENING.

NORTHERLY GALE FORCE WINDS ARE POSSIBLE LATE FRIDAY NIGHT INTO
SATURDAY MORNING...WITH LARGE WAVES HAZARDOUS TO SMALL CRAFT
LIKELY LINGERING INTO SATURDAY EVENING.

&&

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-182045-
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-
338 PM CDT THU SEP 17 2015

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

THUNDERSTORMS ARE EXPECTED ACROSS LAKE MICHIGAN THIS EVENING
AND AGAIN TONIGHT. SOME THUNDERSTORMS COULD BE SEVERE PRODUCING
STRONG WINDS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

THUNDERSTORMS ARE LIKELY ACROSS THE ENTIRE LAKE FRIDAY THROUGH
FRIDAY NIGHT. STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE MAINLY
ACROSS THE SOUTHERN HALF OF LAKE MICHIGAN.

NORTHERLY GALE FORCE WINDS ARE POSSIBLE LATE FRIDAY NIGHT INTO
SATURDAY MORNING...ESPECIALLY ACROSS THE SOUTHERN HALF OF THE
LAKE.

&&

MM/KB

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO

In the hours before

Local storm report, Sep 17, 10:19 PM CDT, 2 hours 56 minutes before

PRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1019 PM CDT THU SEP 17 2015

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

0530 PM     TSTM WND DMG     1 SW FORRESTON          42.12N 89.59W
09/17/2015                   OGLE               IL   BROADCAST MEDIA

            FLATTENED CORN ALONG TOWNLINE ROAD. FROM WTVO ROCKFORD.

&&

RCASTRO

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 18, 12:31 AM CDT	Flash Flood Warning	LOT	Lake, McHenry	8 hr
Sep 18, 3:43 AM CDT	Flash Flood Watch	LOT	Boone, DeKalb, DuPage, Grundy, Kane, Kendall and 6 more	23 hr
Sep 18, 9:38 AM CDT	River Flood Warning	LOT	Lake	5 days
Sep 18, 9:38 AM CDT	River Flood Warning	LOT	Lake	6 days
Sep 18, 9:57 AM CDT	River Flood Watch	LOT	Kane, McHenry	7 days
Sep 18, 9:57 AM CDT	River Flood Watch	LOT	Kane, Kendall	4 days
Sep 18, 9:57 AM CDT	River Flood Watch	LOT		63 hr
Sep 18, 3:01 PM CDT	Gale Warning	LOT		20 hr
Sep 18, 3:16 PM CDT	Beach Hazards Statement	LOT	Lake	31 hr
Sep 18, 4:44 PM CDT	Tornado Warning	LOT	Cook, Will	31 min
Sep 18, 5:32 PM CDT	Flash Flood Warning	LOT	Cook, Kendall, Will	6 hr
Sep 18, 6:27 PM CDT	Flash Flood Warning	LOT	DeKalb, Grundy, Kane, Kendall, LaSalle	6 hr
Sep 18, 6:51 PM CDT	Flash Flood Warning	LOT	Cook, DeKalb, DuPage, Kane, Lake, McHenry	6 hr

Nearby

Flash Flood Warnings in Illinois, 2015 Every flash flood warning in 2015

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.