Alert archive / Illinois / Severe Thunderstorm Warnings in 2007

Severe Thunderstorm Warning 76, NWS Chicago, IL

July 9, 2007DeKalb County, Kane County, Illinois

NWS Chicago, IL issued this severe thunderstorm warning at Jul 9, 2007, 5:49 PM CDT for DeKalb County, Kane County, Illinois. It was in force for 29 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: Jul 9, 2007, 5:49 PM CDT (22:49 UTC)
Expired: Jul 9, 2007, 6:18 PM CDT
In force: 29 min
Issued by: NWS Chicago, IL
Area: Counties, with a storm outline in the text

Counties DeKalb County, IL, Kane County, IL

The radar

The Chicago radar (KLOT), 55 km from the middle of the area, began a volume at 22:53 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.

Issued	Product	Office	Lasted
Jul 9, 2:23 PM CDT	Severe Thunderstorm Watch	SPC	6 hr

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 10.8 hours before the alert went out and 161 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: 1065 J/kg
Mixed-layer CIN: -50 J/kg
Mixed-layer LCL: 1222 m above ground
0-6 km bulk shear: 17 kt
0-1 km storm-relative helicity: 27 m²/s²
0-3 km storm-relative helicity: -19 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

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 Jul 9, 3:43 PM CDT, 2 hours 6 minutes earlier.

Area forecast discussion, Jul 9, 3:43 PM CDT, 2 hours 6 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
343 PM CDT MON JUL 9 2007

.DISCUSSION...

THE FRONT LIES FROM JUST NORTH OF MOLINE EAST OT JUST NORTH OF
CHICAGO AT 20 UTC. THIS WILL BE A CONVERGENCE LINE FOR THUNDERSTORMS
TONIGHT. AFTER THE SUN SETS THE STABILITY MAY INCREASE AND
THUNDERSTORMS MAY BECOME LESS NUMEROUS. HOWEVER THE FRONT WILL BE IN
NORTHERN ILLINOIS THROUGH EARLY WEDNESDAY MORNING. THE FRONT WILL
PASS SOUTH TO THE OHIO RIVER BY WEDNESDAY AFTERNOON. HIGH PRESSURE
IS FORECAST TO BUILD OVER EASTERN NEBRASKA AND EASTERN KANSAS BY
WEDNESDAY EVENING.

&&

.AVIATION...
100 PM CDT

FOR THE 1800 UTC TAFS...MAIN AVIATION FORECAST CONCERN WILL BE ON
CONVECTIVE POTENTIAL THIS AFTERNOON/EARLY THIS EVENING. SURFACE COLD
FRONT AT 17Z EXTENDS FROM SOUTH CENTRAL IOWA THROUGH SOUTHERN
WISCONSIN. FRONTAL BOUNDARY HAS ACCELERATED DOWN LAKE MICHIGAN
SHORELINE IN SOUTHWEST WISCONSIN THIS AFTERNOON...AND LATEST
THINKING IS THAT THIS BOUNDARY WILL REACH ORD IN THE 21Z-22Z TIME
FRAME. SCATTERED THUNDERSTORMS WILL CONTINUE TO DEVELOP ACROSS
SOUTHERN WISCONSIN AS THIS FRONT TRACK SOUTHWARD. FACTORS FAVORING
CONVECTION TODAY WILL BE LOW LEVEL CONVERGENCE WITH THE APPROACHING
FRONT AND RATHER IMPRESSIVE INSTABILITY WITH 100 HPA ML CAPES ON THE
ORDER OF 2000-2500 J/KG. FACTORS WHICH MAY LIMIT STORM ORGANIZATION
INCLUDE MARGINAL DEEP LAYER SHEAR AND RATHER ILL DEFINED MID/UPPER
LEVEL FORCING. AT THIS TIME WILL INCLUDE MENTION OF TSRA ACROSS
TERMINALS IN THE 21Z-24Z FRAME WITH THUNDERSTORMS GRADUALLY
DIMINISHING THIS EVENING WITH WEAKENING DIURNAL INSTABILITY...AND
FRONT GRADUALLY SHIFTING SOUTH OF THE TERMINALS. WINDS FOR
ORD/MDW/GYY WILL SHIFT TO THE NORTHEAST WITH FRONTAL PASSAGE THIS
AFTERNOON WHILE WINDS AT DPA/RFD ARE EXPECTED TO BE SOMEWHAT LIGHTER
FARTHER AWAY FROM THE LAKE...BUT LIKELY FAVORING NORTH.

FOR TONIGHT...FRONT LIFTS BACK NORTHWARD INTO SOUTHERN WISCONSIN
ALLOWING WINDS TO VEER AROUND TO THE SOUTH LATE TONIGHT. SOUTH WINDS
WILL THEN INCREASE INTO THE 10 TO 15 KNOT RANGE TOMORROW MORNING AS
SFC PRESSURES FALL ACROSS THE UPPER MIDWEST IN RESPONSE TO NEXT FAST
MOVING SYSTEM TO APPROACH THE AREA TOMORROW.

MARSILI

&&

.MARINE...
300 PM CDT
COLD FRONT CURRENTLY MOVING DOWN LAKE MICHIGAN IS EXPECTED TO
DISSIPATE LATER THIS EVENING.  MEANWHILE...LOW PRESSURE OF 29.4
INCHES IS EXPECTED TO DEVELOP ACROSS THE NORTHERN PLAINS AND
SOUTHERN CANADIAN PROVINCES THIS EVENING.  THIS LOW WILL MOVE
EASTWARD INTO ONTARIO PROVINCE TONIGHT AND ACCELERATE TOWARDS
EASTERN ONTATIO TOMORROW AFTERNOON.  MEANWHILE...A COLD FRONT
ATTACHED TO THIS SYSTEM IS EXPECTED TO BEGIN MOVING DOWN THE LAKE
TOMORROW...RESULTING IN SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THE DAY.  AFTER THE PASSAGE...HIGH PRESSURE OF 30.1 INCHES WILL
BUILD ACROSS THE WESTERN GREAT LAKES RESULTING IN FAIR AND DRY
CONDITIONS THROUGH THE REMAINDER OF THE WORK WEEK.

GITRO
&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.

&&

Hazardous weather outlook, Jul 9, 5:33 PM CDT, 16 minutes before

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In the hours before

Local storm report, Jul 9, 4:51 PM CDT, 58 minutes before

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Local storm report, Jul 9, 5:00 PM CDT, 49 minutes before

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Local storm report, Jul 9, 5:02 PM CDT, 47 minutes before

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Local storm report, Jul 9, 5:05 PM CDT, 44 minutes before

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Local storm report, Jul 9, 5:26 PM CDT, 23 minutes before

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Local storm report, Jul 9, 5:47 PM CDT, 2 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
Jul 9, 2:14 PM CDT	Severe Thunderstorm Warning	LOT	McHenry	61 min
Jul 9, 2:34 PM CDT	Severe Thunderstorm Warning	LOT	Lake	56 min
Jul 9, 2:37 PM CDT	Special Marine Warning	LOT		83 min
Jul 9, 2:54 PM CDT	Flash Flood Warning	LOT	McHenry	5 hr
Jul 9, 3:19 PM CDT	Severe Thunderstorm Warning	LOT	Kane, McHenry	56 min
Jul 9, 3:38 PM CDT	Severe Thunderstorm Warning	LOT	DeKalb, Kane	52 min
Jul 9, 3:44 PM CDT	Severe Thunderstorm Warning	LOT	Cook, DuPage, Kane	61 min
Jul 9, 4:07 PM CDT	Severe Thunderstorm Warning	LOT	Will	23 min
Jul 9, 4:25 PM CDT	Flash Flood Warning	LOT	DeKalb	4 hr
Jul 9, 4:27 PM CDT	Severe Thunderstorm Warning	LOT	DeKalb	41 min
Jul 9, 4:48 PM CDT	Severe Thunderstorm Warning	LOT	Will	36 min
Jul 9, 4:59 PM CDT	Severe Thunderstorm Warning	LOT	Lee	46 min
Jul 9, 5:38 PM CDT	Flash Flood Warning	LOT	Lee	4 hr
Jul 9, 5:56 PM CDT	River Flood Warning	LOT	DeKalb	3 hr

Nearby

Severe Thunderstorm Warnings in Illinois, 2007 Every severe thunderstorm warning in 2007

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.