Alert archive / Illinois / Severe Thunderstorm Warnings in 2015

Severe Thunderstorm Warning 18, NWS Chicago, IL

April 9, 20154 counties in Illinois

NWS Chicago, IL issued this severe thunderstorm warning at Apr 9, 2015, 8:40 PM CDT for 4 counties in 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
Apr 9, 2015, 8:40 PM CDT (01:40 UTC)
Expired
Apr 9, 2015, 9:15 PM CDT
In force
35 min
Issued by
NWS Chicago, IL
Area
Storm-based polygon
Hail
1.0 in
Wind
70.0 mph

Counties Grundy County, IL, Kendall County, IL, LaSalle County, IL, Will County, IL

The radar

The Chicago radar (KLOT), 35 km from the middle of the area, began a volume at 01:39 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.

IssuedProductOfficeLasted
Apr 9, 1:48 PM CDTTornado WatchSPC9 hr

The nearest sounding before it

Lincoln, IL (KILX), launched 00:00Z, 1.7 hours before the alert went out and 142 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-pSkew-T log-p diagram, Lincoln, IL at 00:00Z on 2015-04-10Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1160 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Lincoln, IL at 00:00Z on 2015-04-10The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 296 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
1160 J/kg
Mixed-layer CIN
-28 J/kg
Mixed-layer LCL
1435 m above ground
0-6 km bulk shear
55 kt
0-1 km storm-relative helicity
296 m²/s²
0-3 km storm-relative helicity
356 m²/s²
Significant tornado parameter
1.4
Supercell composite
15.8

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 Apr 9, 8:09 PM CDT, 31 minutes earlier.

Area forecast discussion, Apr 9, 8:09 PM CDT, 31 minutes before
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Hazardous weather outlook, Apr 9, 3:28 PM CDT, 5 hours 12 minutes before
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
328 PM CDT THU APR 9 2015

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
102030-
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-
328 PM CDT THU APR 9 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 BE SEVERE AND PRODUCE:

   LOCALLY HEAVY RAINFALL RESULTING IN LOCALIZED FLOODING.
   HAIL UP TO THE SIZE OF QUARTERS
   DAMAGING WINDS UP TO 70 MPH.
   FREQUENT CLOUD TO GROUND LIGHTNING.
   AND POSSIBLY AN ISOLATED TORNADO.

  AREAS AFFECTED AND TIMING:

   A COLD FRONT WILL SWEEP WEST TO EAST ACROSS NORTHERN ILLINOIS
 AND NORTHWEST INDIANA LATE THIS AFTERNOON THROUGH THE EVENING.

  DISCUSSION:

A COLD FRONT WILL SWEEP ACROSS THE REGION THIS EVENING BRINGING
PRIMARILY A THREAT FOR STRONG AND DAMAGING WINDS ALONG WITH A
CONCERN FOR A TORNADO. AHEAD OF THE MAIN LINE OF THUNDERSTORMS...
SCATTERED THUNDERSTORMS ARE POSSIBLE LATE THIS AFTERNOON INTO THE
EARLY EVENING. THE SEVERE WEATHER THREAT SHOULD DIMINISH QUICKLY
BEHIND THE FRONT. IN ADDITION TO THE SEVERE WEATHER THREAT...SOME
AREAS HAVE ALREADY SEEN HEAVY RAIN TODAY WITH SOILS SATURATED.
ADDITIONAL HEAVY RAIN WILL QUICKLY BE CONVERTED TO RUNOFF WITH A
CONCERN FOR AT LEAST LOCALIZED FLOODING.

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

THERE IS A CHANCE OF THUNDERSTORMS LATE SUNDAY AFTERNOON INTO
SUNDAY NIGHT...AND AGAIN TUESDAY NIGHT THROUGH THURSDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NECESSARY THROUGH TONIGHT.

&&

LMZ740>745-102030-
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-
328 PM CDT THU APR 9 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.

SCATTERED THUNDERSTORMS ARE LIKELY THROUGH LATE THIS EVENING.
SOME THUNDERSTORMS MAY BE SEVERE LATE THIS AFTERNOON AND EARLY
THIS EVENING.

GALE FORCE WINDS ARE EXPECTED LATE THIS EVENING AND OVERNIGHT.

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

GALE FORCE WINDS ARE LIKELY THROUGH MIDDAY FRIDAY...WITH
WINDS AND WAVES REMAINING HAZARDOUS FOR SMALL CRAFT INTO FRIDAY
EVENING.

THERE IS A CHANCE OF THUNDERSTORMS SUNDAY NIGHT...AND AGAIN
TUESDAY NIGHT THROUGH THURSDAY.

&&

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-102030-
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-
328 PM CDT THU APR 9 2015

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

THUNDERSTORMS ARE LIKELY ACROSS MAINLY THE SOUTH HALF OF THE LAKE
INTO THIS EVENING. SOME STORMS COULD BE SEVERE.

GALE FORCE WINDS ARE EXPECTED TONIGHT OVER THE SOUTHERN HALF OF
THE LAKE.

GALE FORCE WINDS ARE EXPECTED OVER THE NORTHERN HALF OF THE LAKE
AFTER MIDNIGHT TONIGHT.

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

GALE FORCE WINDS ARE LIKELY THROUGH MIDDAY THURSDAY ON THE
SOUTHERN HALF OF THE LAKE.

GALE FORCE WINDS ARE LIKELY THROUGH LATE THURSDAY AFTERNOON ON THE
NORTHERN HALF OF THE LAKE.

THERE IS A CHANCE OF THUNDERSTORMS ON SOUTHERN LAKE MICHIGAN
SUNDAY NIGHT...AND AGAIN TUESDAY NIGHT THROUGH THURSDAY.

&&

BMD/KREIN

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, Apr 9, 8:18 PM CDT, 22 minutes before
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Local storm report, Apr 9, 8:23 PM CDT, 17 minutes before
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Local storm report, Apr 9, 8:26 PM CDT, 14 minutes before
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Local storm report, Apr 9, 8:28 PM CDT, 12 minutes before
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Local storm report, Apr 9, 8:32 PM CDT, 8 minutes before
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Local storm report, Apr 9, 8:39 PM CDT, 1 minute before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
839 PM CDT THU APR 09 2015

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

0827 PM     HAIL             MCHENRY                 42.34N 88.29W
04/09/2015  E1.00 INCH       MCHENRY            IL   AMATEUR RADIO

            DARKMOR AND CRYSTAL LAKE RD.

&&

B

The office that day

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

IssuedProductOfficeCountiesLasted
Apr 9, 7:05 PM CDTTornado WarningLOTBoone, Ogle, Winnebago40 min
Apr 9, 7:16 PM CDTTornado Warning Tornado observedConsiderable damage threatLOTBoone, DeKalb, McHenry29 min
Apr 9, 7:19 PM CDTSevere Thunderstorm WarningLOTLee, Ogle26 min
Apr 9, 7:19 PM CDTTornado WarningLOTMcHenry26 min
Apr 9, 7:21 PM CDTAreal Flood AdvisoryLOTBoone, McHenry, Ogle, Winnebago3 hr
Apr 9, 7:36 PM CDTSevere Thunderstorm WarningLOTOgle, Winnebago24 min
Apr 9, 7:41 PM CDTTornado Warning Tornado observedConsiderable damage threatLOTMcHenry49 min
Apr 9, 7:51 PM CDTTornado WarningLOTLaSalle39 min
Apr 9, 7:53 PM CDTSevere Thunderstorm WarningLOTBoone, DeKalb, Kane, McHenry, Ogle, Winnebago37 min
Apr 9, 8:05 PM CDTSevere Thunderstorm WarningLOTMcHenry55 min
Apr 9, 8:21 PM CDTSevere Thunderstorm WarningLOTLaSalle24 min
Apr 9, 8:21 PM CDTSevere Thunderstorm WarningLOTLake24 min
Apr 9, 8:26 PM CDTSpecial Marine WarningLOT94 min
Apr 9, 8:58 PM CDTSevere Thunderstorm WarningLOTCook, DuPage, Kendall, Will32 min
Apr 9, 9:08 PM CDTSevere Thunderstorm WarningLOTCook, Will37 min
Apr 9, 9:25 PM CDTSevere Thunderstorm WarningLOTCook, DuPage, Will35 min
Apr 9, 9:34 PM CDTSpecial Marine WarningLOT116 min
Apr 9, 9:40 PM CDTSevere Thunderstorm WarningLOTFord, Iroquois35 min
Apr 9, 10:27 PM CDTWind AdvisoryLOTBoone, DeKalb, DuPage, Ford, Grundy, Iroquois and 10 more6 hr
Apr 10, 9:06 AM CDTRiver Flood AdvisoryLOTBoone36 hr
Apr 10, 10:52 AM CDTRiver Flood WarningLOTLake4 days
Apr 10, 11:19 AM CDTRiver Flood AdvisoryLOTCook3 days
Apr 10, 11:19 AM CDTRiver Flood AdvisoryLOTCook36 hr
Apr 10, 11:39 AM CDTRiver Flood AdvisoryLOTLake36 hr
Apr 10, 11:50 AM CDTRiver Flood AdvisoryLOTKane, Kendall5 days
Apr 10, 12:17 PM CDTRiver Flood WatchLOTKane, McHenry5 days
Apr 10, 2:17 PM CDTWind AdvisoryLOTBoone, DeKalb, DuPage, Ford, Grundy, Iroquois and 10 more5 hr

Nearby

Severe Thunderstorm Warnings in Illinois, 2015Every severe thunderstorm 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.