Alert archive / Illinois / Severe Thunderstorm Warnings in 1997

Severe Thunderstorm Warning 49, NWS Chicago, IL

May 18, 1997LaSalle County, Lee County, Illinois

NWS Chicago, IL issued this severe thunderstorm warning at May 18, 1997, 7:19 PM CDT for LaSalle County, Lee County, Illinois. It was in force for 56 min. 1 report came from inside the area while it was in force.

The area

The counties it named, with what was reported inside it.

The facts

Issued: May 18, 1997, 7:19 PM CDT (00:19 UTC)
Expired: May 18, 1997, 8:15 PM CDT
In force: 56 min
Issued by: NWS Chicago, IL
Area: Whole counties

Counties LaSalle County, IL, Lee County, IL

The radar

The Chicago radar (KLOT), 84 km from the middle of the area, began a volume at 00:22 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.

What was reported inside it

Time	Report	Where	Remark
May 18, 7:37 PM CDT	Thunderstorm Wind 52	Mendota, IL

NCEI Storm Data entries that began inside the alert's area while it was in force. Before 2003 the local storm report archive is thin, so this is the record of what happened rather than what was phoned in.

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 18, 5:30 PM CDT	Tornado Watch	SPC	6 hr

The nearest sounding before it

Davenport, (KDVN), launched 00:00Z, 0.3 hours before the alert went out and 117 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: 2339 J/kg
Mixed-layer CIN: -25 J/kg
Mixed-layer LCL: 1544 m above ground
0-6 km bulk shear: 49 kt
0-1 km storm-relative helicity: 145 m²/s²
0-3 km storm-relative helicity: 165 m²/s²
Significant tornado parameter: 1.0
Supercell composite: 9.0

Open this sounding in Storm Lab

The text

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

000 
TTAA00 KCHI 190017 RRA
SVRCHI
ILC103-099-190115-
 
BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE CHICAGO IL
719 PM CDT SUN MAY 18 1997
 
THE NATIONAL WEATHER SERVICE IN CHICAGO HAS ISSUED A
SEVERE THUNDERSTORM WARNING EFFECTIVE UNTIL  815 PM CDT
FOR PEOPLE IN THE FOLLOWING LOCATIONS...
 
IN NORTH CENTRAL ILLINOIS
 
   ...SOUTHERN LEE COUNTY
 
IN NORTHEAST ILLINOIS
 
   ...NORTHWESTERN LA SALLE COUNTY
 
AT 715 PM CDT RADAR INDICATED A LINE OF SEVERE THUNDERSTORMS FROM
CENTRAL LEE COUNTY NEAR AMBOY EXTENDING SOUTH INTO BUREAU COUNTY NEAR
NEW BEDFORD.
 
THE LINE OF SEVERE THUNDERSTORMS WAS MOVING TO THE EAST AT 35 MPH.
 
TOWNS IN THE PATH OF THIS STORM INCLUDE...
 
   IN LEE COUNTY   AMBOY...SUBLETTE...PAW PAW...
 
   IN LA SALLE COUNTY... MENDOTA AND EARLVILLE.
 
 
 
 
GO INSIDE A STURDY BUILDING AND STAY AWAY FROM WINDOWS!  A TORNADO
WATCH IS IN EFFECT.  SEVERE THUNDERSTORMS CAN PRODUCE TORNADOES.

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.

In the hours before

Special weather statement, May 18, 1:48 PM CDT, 5 hours 31 minutes before

ILZ003>006-008-010>014-019>023-032>033-039-INZ001>005-010>016-019>020-
191000-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHICAGO IL
1 45 PM CDT SUN MAY 18 1997

SEVERE THUNDERSTORM WATCH NUMBER 294 IS NO LONGER IN EFFECT
FOR LAKE...PORTER...JASPER...NEWTON AND BENTON COUNTIES
IN EXTREME NORTHWEST INDIANA.

ALTHOUGH SCATTERED THUNDERSTORMS ARE STILL OCCURRING IN THIS AREA
THEY ARE NO LONGER EXPECTED TO BE SEVERE.

HOWEVER THERE IS STILL A CHANCE OF SEVERE THUNDERSTORMS THIS EVENING
OR EARLY TONIGHT AS A COOL FRONT APPROACHES THE AREA FROM THE
NORTHWEST.

MORRISON

The office that day

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

Issued	Product	Office	Counties	Lasted
May 18, 7:00 PM CDT	Tornado Warning	LOT	Lake, McHenry	60 min
May 18, 7:09 PM CDT	Severe Thunderstorm Warning	LOT	Kane	66 min
May 18, 7:30 PM CDT	Tornado Warning	LOT	Kane	30 min
May 18, 7:42 PM CDT	Severe Thunderstorm Warning	LOT	Kendall, LaSalle	63 min
May 18, 7:47 PM CDT	Tornado Warning	LOT	DuPage, Will	58 min
May 18, 8:04 PM CDT	Tornado Warning	LOT	Grundy, Kankakee, Will	56 min
May 18, 8:04 PM CDT	Tornado Warning	LOT	Cook	56 min
May 18, 8:52 PM CDT	Severe Thunderstorm Warning	LOT	Ford, Iroquois, Kankakee	2 hr
May 18, 8:52 PM CDT	Severe Thunderstorm Warning	LOT	Livingston	2 hr
May 18, 9:18 PM CDT	Tornado Warning	LOT	LaSalle	57 min
May 18, 9:54 PM CDT	Severe Thunderstorm Warning	LOT	Grundy, Livingston	66 min
May 18, 10:50 PM CDT	Severe Thunderstorm Warning	LOT	Iroquois, Kankakee	55 min
May 18, 11:12 PM CDT	Severe Thunderstorm Warning	LOT	Ford, Iroquois, Livingston	63 min

Nearby

Severe Thunderstorm Warnings in Illinois, 1997 Every severe thunderstorm warning in 1997

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; verification from NCEI's Storm Data; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.