Alert archive / Illinois / Special Weather Statements in 2012

Special Weather Statement, NWS Chicago, IL

April 14, 2012LaSalle County, Illinois

NWS Chicago, IL issued this special weather statement at Apr 14, 2012, 10:40 PM CDT for LaSalle 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 outline as issued.

The facts

Issued
Apr 14, 2012, 10:40 PM CDT (03:40 UTC)
Expired
Apr 14, 2012, 11:15 PM CDT
In force
35 min
Issued by
NWS Chicago, IL

County LaSalle County, IL

The radar

The Chicago radar (KLOT), 60 km from the middle of the area, began a volume at 03:42 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, 3.7 hours before the alert went out and 145 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, Davenport, at 00:00Z on 2012-04-15Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 300 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, Davenport, at 00:00Z on 2012-04-15The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 124 square meters per square second.1939587897Sfc1 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
300 J/kg
Mixed-layer CIN
-50 J/kg
Mixed-layer LCL
726 m above ground
0-6 km bulk shear
69 kt
0-1 km storm-relative helicity
124 m²/s²
0-3 km storm-relative helicity
126 m²/s²
Significant tornado parameter
0.2
Supercell composite
1.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

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What forecasters said that day

The local office's own words before this special weather statement 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 special weather statement went out at Apr 14, 10:08 PM CDT, 32 minutes earlier.

Area forecast discussion, Apr 14, 10:08 PM CDT, 32 minutes before
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Hazardous weather outlook, Apr 14, 9:27 PM CDT, 1 hour 13 minutes before
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
927 PM CDT SAT APR 14 2012

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
160230-
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-
927 PM CDT SAT APR 14 2012 /1027 PM EDT SAT APR 14 2012/

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

.DAY ONE...OVERNIGHT.

WEATHER HAZARDS EXPECTED:

THUNDERSTORMS...SOME PRODUCING:

LOCALLY HEAVY RAINFALL...FREQUENT LIGHTNING...SMALL HAIL...AND
STRONG GUSTS TO 45 MPH.

AREAS AFFECTED AND TIMING:

THUNDERSTORMS ARE EXPECTED TO DEVELOP DURING THE LATE EVENING
OVER WEST-CENTRAL ILLINOIS AND SPREAD OVER MUCH OF NORTHERN
ILLINOIS AND INTO NORTHWESTERN INDIANA OVERNIGHT. THUNDERSTORM

DISCUSSION:

A WARM FRONT WILL CONTINUE TO LIFT NORTHWARD ACROSS CENTRAL AND
INTO NORTHERN ILLINOIS OVERNIGHT AS DEEPENING LOW PRESSURE IN THE
CENTRAL PLAINS LIFTS NORTHEAST INTO THE UPPER MISSOURI VALLEY.
THUNDERSTORMS ARE INITIALLY EXPECTED TO DEVELOP NORTH OF THE WARM
FRONT AS IT LIFTS THROUGH WEST-CENTRAL ILLINOIS. AS THE WARM
FRONT CONTINUES TO LIFT NORTHWARD OVERNIGHT...THE MAIN FOCUS FOR
THE THUNDERSTORMS SHOULD SHIFT INTO NORTHERN ILLINOIS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

MORE THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS NORTHWESTERN
ILLINOIS IN ADVANCE OF AN APPROACHING COLD FRONT ON SUNDAY.
THUNDERSTORM DEVELOPMENT SHOULD BEGIN BY LATE SUNDAY AFTERNOON
AND FOCUS ALONG AND WEST OF THE I-39 CORRIDOR...AND INITIALLY
SHOULD BE IN THE FORM OF DISCRETE SUPERCELLS WITH THE POTENTIAL
TO
PRODUCE STRONG...DAMAGING WINDS...LARGE HAIL AND ISOLATED
TORNADOES. BY EARLY EVENING...THUNDERSTORMS SHOULD EVOLVE INTO A
LINEAR SQUALL LINE...QUICKLY PROGRESSING EASTWARD THROUGH
NORTH CENTRAL AND NORTHEASTERN ILLINOIS AND INTO NORTHWESTERN
INDIANA OVERNIGHT. AFTER THE TRANSITION TO A LINEAR SQUALL
LINE...THE MAIN SEVERE WEATHER THREAT WILL BE STRONG...DAMAGING
WINDS. HOWEVER...HEAVY RAINFALL IN AREAS OF REPEATED ECHO
TRAINING
COULD LEAD TO LOCALIZED FLASH FLOODING.

SUNDAY WILL BE A WINDY DAY WITH SOUTHWEST GUSTS OF AROUND 40 MPH
DEVELOPING THROUGH THE DAY. THERE IS SOME CHANCE THAT WIND GUSTS
MAY
EXCEED 40 MPH LATE IN THE AFTERNOON EVEN WITHOUT THE PRESENCE OF
THUNDERSTORMS.

THERE IS A SLIGHT CHANCE OF THUNDERSTORMS WEDNESDAY...THURSDAY
NIGHT AND FRIDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NECESSARY LATE TONIGHT.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO
WEBPAGE: WEATHER.GOV/CHICAGO

LMZ740>745-160230-
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-
927 PM CDT SAT APR 14 2012

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

.DAY ONE...OVERNIGHT.

THUNDERSTORMS ARE LIKELY TONIGHT.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

SOUTH WINDS INCREASING TO 20 TO 25 KT BY DAWN WILL POSE HAZARDOUS
CONDITIONS FOR SMALL CRAFT DURING SUNDAY MORNING.

GALES ARE POSSIBLE FORM MIDDAY SUNDAY AND THROUGH THE EVENING.

THUNDERSTORMS ARE EXPECTED SUNDAY AND SUNDAY NIGHT. SOME
THUNDERSTORMS MAY BECOME SEVERE...PRODUCING WIND GUSTS IN EXCESS
OF 50 KT AND LARGE HAIL.

THUNDERSTORMS ARE POSSIBLE WEDNESDAY AND FRIDAY.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO
WEBPAGE: WEATHER.GOV/CHICAGO

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-160230-
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-
927 PM CDT SAT APR 14 2012

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

.DAY ONE...OVERNIGHT.

THUNDERSTORMS ARE POSSIBLE ACROSS MUCH OF LAKE MICHIGAN TONIGHT.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

THUNDERSTORMS ARE EXPECTED ACROSS MUCH OF LAKE MICHIGAN SUNDAY
AND SUNDAY EVENING. SOME OF THESE STORMS MAY BECOME SEVERE...
PRODUCING WIND GUSTS IN EXCESS OF 50 KT AND LARGE HAIL.

THUNDERSTORMS ARE POSSIBLE WEDNESDAY AND FRIDAY.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO
WEBPAGE: WEATHER.GOV/CHICAGO

In the hours before

Special weather statement, Apr 14, 10:40 PM CDT, 0 minutes before
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The office that day

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

IssuedProductOfficeCountiesLasted
Apr 14, 9:14 PM CDTSmall Craft AdvisoryLOT11 hr
Apr 14, 11:20 PM CDTSpecial Weather StatementLOTDuPage, Kendall40 min
Apr 14, 11:24 PM CDTSpecial Weather StatementLOTBoone, DeKalb, Kane, Ogle, Winnebago36 min
Apr 15, 12:00 AM CDTSpecial Weather StatementLOTCook, DuPage30 min
Apr 15, 12:04 AM CDTSpecial Weather StatementLOTKane, McHenry26 min
Apr 15, 12:32 AM CDTSpecial Weather StatementLOTCook28 min
Apr 15, 1:31 AM CDTSpecial Weather StatementLOTBoone, DeKalb, Kane, McHenry29 min
Apr 15, 1:37 AM CDTSpecial Weather StatementLOTLake23 min
Apr 15, 2:08 AM CDTAreal Flood AdvisoryLOTBoone, Cook, DeKalb, DuPage, Kane, Lake and 4 more3 hr
Apr 15, 2:38 AM CDTSpecial Weather StatementLOTDuPage22 min
Apr 15, 3:48 AM CDTGale WatchLOT24 hr
Apr 15, 3:48 AM CDTGale WarningLOT18 hr
Apr 15, 6:33 AM CDTSpecial Weather StatementLOTWill27 min
Apr 15, 9:51 AM CDTMarine Dense Fog AdvisoryLOT9 hr
Apr 15, 10:18 AM CDTWind AdvisoryLOTBoone, DeKalb, DuPage, Ford, Grundy, Iroquois and 10 more10 hr

Nearby

Special Weather Statements in Illinois, 2012Every special weather statement in 2012

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.