Alert archive / Illinois / Flash Flood Warnings in 2011

Flash Flood Warning 19, NWS Chicago, IL

July 23, 20118 counties in Illinois

NWS Chicago, IL issued this flash flood warning at Jul 23, 2011, 12:36 AM CDT for 8 counties in Illinois. It was in force for 6 hr. 9 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued
Jul 23, 2011, 12:36 AM CDT (05:36 UTC)
Expired
Jul 23, 2011, 6:30 AM CDT
In force
6 hr
Issued by
NWS Chicago, IL
Area
Storm-based polygon
Flood severity
None

Counties Boone County, IL, Cook County, IL, DeKalb County, IL, Kane County, IL, Lake County, IL, McHenry County, IL, Ogle County, IL, Winnebago County, IL

The radar

The Milwaukee radar (KMKX), 84 km from the middle of the area, began a volume at 05:38 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

TimeReportWhereRemark
Jul 23, 12:43 AM CDTFLOODMachesney Park, ILSTREET FLOODING BEGINNING AT WINDSOR AND ROUTE 251.
Jul 23, 1:30 AM CDTHEAVY RAIN 2.51Mchenry, ILIN APPROXIMATELY 30 MINUTES. DELAYED REPORT.
Jul 23, 1:52 AM CDTHEAVY RAIN 3.09Wheeling, ILMEASURED RAINFALL OF 3.09 INCHES ENDING WITH THE 152 AM OBSERVATION.
Jul 23, 2:35 AM CDTHEAVY RAIN 4.641 E Palatine, ILSINCE RAIN BEGAN AROUND MIDNIGHT.
Jul 23, 2:45 AM CDTHEAVY RAIN 3.593 Sse Deerfield, ILRAINFALL FROM 1220 AM THROUGH 245 AM CDT.
Jul 23, 2:45 AM CDTHEAVY RAIN 3.61 E Palatine, IL2.99 IN THE HOUR FROM 145 AM TO 245 AM CDT.
Jul 23, 2:52 AM CDTHEAVY RAIN 4.84Wheeling, ILMEASURED RAINFALL OF 4.84 INCHES ENDING WITH THE 252 AM OBSERVATION.
Jul 23, 5:04 AM CDTHEAVY RAIN 5.52Arlington Heights, ILRAINFALL SINCE MIDNIGHT MEASURED AT HINTZ ROAD AND WINDSOR. STORM TOTAL SINCE FRIDAY 6.67 INCHES.
Jul 23, 6:00 AM CDTHEAVY RAIN 7.17Elk Grove Village, IL24 HOUR TOTAL. 5.95 INCHES FELL OVERNIGHT. MANY INTERSECTIONS IMPASSABLE DUE TO FLOOD WATERS.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

Did it verify

Not verified. The Iowa Environmental Mesonet's Cow found no qualifying storm report inside this flash flood warning while it was in force. That is not proof nothing happened: reports are thin where few people live.

Cow counts a report within 15 km of the polygon while the warning was in force: a tornado for a tornado warning; hail of 1 inch or more, a gust of 58 mph or more or wind damage for a severe thunderstorm warning; a flash flood report for a flash flood warning.

The nearest sounding before it

Davenport, (KDVN), launched 00:00Z, 5.6 hours before the alert went out and 159 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 2011-07-23Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 3095 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 2011-07-23The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 44 square meters per square second.193958Sfc1 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
3095 J/kg
Mixed-layer CIN
-39 J/kg
Mixed-layer LCL
1066 m above ground
0-6 km bulk shear
33 kt
0-1 km storm-relative helicity
44 m²/s²
0-3 km storm-relative helicity
59 m²/s²
Significant tornado parameter
0.6
Supercell composite
3.5

Open this sounding in Storm Lab

The text

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

366 
WGUS53 KLOT 230536
FFWLOT
ILC007-031-037-089-097-111-141-201-231130-
/O.NEW.KLOT.FF.W.0019.110723T0536Z-110723T1130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1236 AM CDT SAT JUL 23 2011

THE NATIONAL WEATHER SERVICE IN CHICAGO HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  BOONE COUNTY IN NORTH CENTRAL ILLINOIS...
  LAKE COUNTY IN NORTHEAST ILLINOIS...
  MCHENRY COUNTY IN NORTHEAST ILLINOIS...
  NORTHERN COOK COUNTY IN NORTHEAST ILLINOIS...
  NORTHERN DE KALB COUNTY IN NORTH CENTRAL ILLINOIS...
  NORTHERN KANE COUNTY IN NORTHEAST ILLINOIS...
  OGLE COUNTY IN NORTH CENTRAL ILLINOIS...
  WINNEBAGO COUNTY IN NORTH CENTRAL ILLINOIS...

* UNTIL 630 AM CDT

* AT 1235 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
  SLOW MOVING THUNDERSTORMS WITH VERY HEAVY RAINFALL ACROSS SOUTHERN 
  MCHENRY...SOUTHERN LAKE...AND NORTHERN COOK COUNTIES. THESE        
  THUNDERSTORMS WERE PRODUCING RAINFALL RATES OF UP TO 2 INCHES PER 
  HOUR...WHICH COULD QUICKLY CAUSE FLASH FLOODING. IN ADDITION...
  A LINE OF THUNDERSTORMS WAS MOVING EAST ACROSS WINNEBAGO AND OGLE  
  COUNTIES. THIS LINE WAS ALSO CAPABLE OF PRODUCING RAINFALL RATES   
  OF UP TO 2 INCHES PER HOUR. SOME AREAS IN THIS FLASH FLOOD WARNING
  MAY RECEIVE BETWEEN 2 AND 4 INCHES OF RAIN DURING THE EARLY        
  MORNING HOURS. THIS RAIN WILL BE IN ADDITION TO THE HEAVY RAIN     
  THAT FELL ACROSS PARTS OF NORTHERN ILLINOIS FRIDAY MORNING.

* RUNOFF FROM THIS EXCESSIVE RAINFALL WILL CAUSE FLASH FLOODING TO
  OCCUR ACROSS MANY AREAS NORTH OF INTERSTATE 88 AND INTERSTATE 290.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODING. IF FLASH FLOODING IS OBSERVED ACT QUICKLY. DO
NOT ENTER THE WATER. TURN AROUND AND MOVE UP TO HIGHER GROUND TO
ESCAPE FLOOD WATERS. DO NOT STAY IN AREAS SUBJECT TO FLOODING WHEN
WATER BEGINS RISING.

DO NOT DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE
ROADWAY. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO CROSS
SAFELY.

&&

LAT...LON 4250 8781 4227 8782 4201 8765 4192 8953
      4194 8969 4220 8970 4221 8940 4250 8940

$$

CMS
5 follow-up statements
461 
WGUS73 KLOT 230638
FFSLOT

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
138 AM CDT SAT JUL 23 2011

ILC007-031-037-089-097-111-141-201-231130-
/O.CON.KLOT.FF.W.0019.000000T0000Z-110723T1130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
KANE IL-MCHENRY IL-OGLE IL-WINNEBAGO IL-BOONE IL-DE KALB IL-LAKE IL-
COOK IL-
138 AM CDT SAT JUL 23 2011

...FLASH FLOOD WARNING REMAINS IN EFFECT FOR NORTHERN COOK...LAKE...
NORTHERN DE KALB...BOONE...WINNEBAGO...OGLE...MCHENRY AND NORTHERN
KANE COUNTIES UNTIL 630 AM CDT...

AT 138 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
THUNDERSTORMS WITH VERY HEAVY RAINFALL FROM NORTHERN WINNEBAGO 
COUNTY...SOUTHEAST INTO NORTHERN COOK COUNTY. THESE THUNDERSTORMS 
WERE PRODUCING RAINFALL RATES OF UP TO 2 INCHES PER HOUR. DOPPLER 
RADAR ESTIMATED BETWEEN 3 TO 4 INCHES OF RAIN HAS FALLEN ACROSS 
PARTS OF SOUTHERN MCHENRY AND SOUTHERN LAKE COUNTIES. ADDITIONAL 
RAINFALL AMOUNTS OF 1 TO 2 INCHES ARE POSSIBLE THROUGH 3 AM CDT.

RUNOFF FROM THIS EXCESSIVE RAINFALL WILL CAUSE FLASH FLOODING TO
OCCUR. VISIBILITIES WILL ALSO BE REDUCED TO NEAR ZERO UNDER THE    
HEAVIEST STORMS. ADDITIONAL THUNDERSTORMS WILL BE POSSIBLE DURING 
THE EARLY MORNING HOURS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODING. IF FLOODING IS OBSERVED...ACT QUICKLY. DO NOT
ENTER THE WATER. TURN AROUND AND MOVE UP TO HIGHER GROUND. DO NOT
STAY IN AREAS SUBJECT TO FLOODING WHEN WATER BEGINS RISING.

DO NOT DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE
ROADWAY. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO CROSS
SAFELY.

&&

LAT...LON 4250 8781 4227 8782 4201 8765 4192 8953
      4194 8969 4220 8970 4221 8940 4250 8940

$$

CMS
263 
WGUS73 KLOT 230751
FFSLOT

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
251 AM CDT SAT JUL 23 2011

ILC007-031-037-089-097-111-141-201-231130-
/O.CON.KLOT.FF.W.0019.000000T0000Z-110723T1130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
KANE IL-MCHENRY IL-OGLE IL-WINNEBAGO IL-BOONE IL-DE KALB IL-LAKE IL-
COOK IL-
251 AM CDT SAT JUL 23 2011

...FLASH FLOOD WARNING REMAINS IN EFFECT FOR NORTHERN COOK...LAKE...
NORTHERN DE KALB...BOONE...WINNEBAGO...OGLE...MCHENRY AND NORTHERN
KANE COUNTIES UNTIL 630 AM CDT...

AT 250 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
THAT THE HEAVIEST THUNDERSTORMS HAD MOVED SOUTHEAST OUT OF THE 
WARNED AREA...WITH A LARGE AREA OF LIGHT TO MODERATE RAIN...WHICH 
WILL CONTINUE TO DIMINISH THROUGH 4 AM CDT. DOPPLER RADAR ALSO 
ESTIMATED BETWEEN 3 AND 4 INCHES OF RAIN HAD FALLEN OVER A LARGE 
AREA FROM SOUTHERN MCHENRY AND SOUTHERN LAKE COUNTIES INTO NORTHERN 
COOK COUNTIES.

WHILE ADDITIONAL HEAVY RAIN IS NOT EXPECTED OVERNIGHT...RUNOFF FROM 
THE HEAVY RAIN THAT HAS ALREADY FALLEN WILL CONTINUE THROUGH THE 
EARLY MORNING HOURS WITH FLASH FLOODING STILL POSSIBLE...ESPECIALLY 
IN AREAS THAT RECEIVED HEAVY RAIN FRIDAY MORNING.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODING. IF FLOODING IS OBSERVED...ACT QUICKLY. DO NOT
ENTER THE WATER. TURN AROUND AND MOVE UP TO HIGHER GROUND. DO NOT
STAY IN AREAS SUBJECT TO FLOODING WHEN WATER BEGINS RISING.

DO NOT DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE
ROADWAY. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO CROSS
SAFELY.

&&

LAT...LON 4250 8781 4227 8782 4201 8765 4192 8953
      4194 8969 4220 8970 4221 8940 4250 8940

$$

CMS
503 
WGUS73 KLOT 230848
FFSLOT

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
348 AM CDT SAT JUL 23 2011

ILC007-031-037-089-097-111-141-201-231130-
/O.CON.KLOT.FF.W.0019.000000T0000Z-110723T1130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
KANE IL-MCHENRY IL-OGLE IL-WINNEBAGO IL-BOONE IL-DE KALB IL-LAKE IL-
COOK IL-
348 AM CDT SAT JUL 23 2011

...FLASH FLOOD WARNING REMAINS IN EFFECT FOR NORTHERN COOK...LAKE...
NORTHERN DE KALB...BOONE...WINNEBAGO...OGLE...MCHENRY AND NORTHERN
KANE COUNTIES UNTIL 630 AM CDT...

AT 348 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
A LINE OF THUNDERSTORMS EXTENDING FROM NORTHWEST ILLINOIS SOUTHWEST 
INTO EASTERN IOWA. THIS LINE IS EXPECTED TO MOVE ACROSS WINNEBAGO 
AND OGLE COUNTIES BETWEEN 4 AM AND 5 AM THIS MORNING AND CONTINUE 
EAST ACROSS NORTHERN ILLINOIS THROUGH SUNRISE. ANOTHER ROUND OF 
TORRENTIAL RAINFALL IS POSSIBLE WITH THESE THUNDERSTORMS WITH 
RAINFALL RATES UP TO 2 INCHES PER HOUR POSSIBLE WITH THE STRONGEST 
STORMS. THIS ADDITIONAL RAINFALL COMBINED WITH RAINFALL EARLIER THIS 
MORNING AND FRIDAY MORNING WILL QUICKLY LEAD TO ADDITIONAL FLASH 
FLOODING ACROSS THE WARNED AREA.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODING. IF FLOODING IS OBSERVED...ACT QUICKLY. DO NOT
ENTER THE WATER. TURN AROUND AND MOVE UP TO HIGHER GROUND. DO NOT
STAY IN AREAS SUBJECT TO FLOODING WHEN WATER BEGINS RISING.

DO NOT DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE
ROADWAY. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO CROSS
SAFELY.

&&

LAT...LON 4250 8781 4227 8782 4201 8765 4192 8953
      4194 8969 4220 8970 4221 8940 4250 8940

$$

CMS
399 
WGUS73 KLOT 231028
FFSLOT

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
528 AM CDT SAT JUL 23 2011

ILC007-031-037-089-097-111-141-201-231130-
/O.CON.KLOT.FF.W.0019.000000T0000Z-110723T1130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
KANE IL-MCHENRY IL-OGLE IL-WINNEBAGO IL-BOONE IL-DE KALB IL-LAKE IL-
COOK IL-
528 AM CDT SAT JUL 23 2011

...FLASH FLOOD WARNING REMAINS IN EFFECT FOR NORTHERN COOK...LAKE...
NORTHERN DE KALB...BOONE...WINNEBAGO...OGLE...MCHENRY AND NORTHERN
KANE COUNTIES UNTIL 630 AM CDT...

AT 521 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
THUNDERSTORMS WITH VERY HEAVY RAINFALL SPANNING MUCH OF OGLE AND 
WINNEBAGO COUNTIES...WITH CONTINUED DEVELOPMENT JUST TO THE WEST. 
EXPECT THESE THUNDERSTORMS TO CONTINUE MOVING EAST EARLY THIS 
MORNING AFFECTING MUCH OF THE WARNED AREA AND PROVIDING ADDITIONAL 
RAINFALL TO MANY LOCATIONS WHICH HAVE RECEIVED ONE TO THREE 
INCHES...TO AREAS NEAR LAKE AND COOK COUNTIES WHICH HAVE RECEIVED 
FOUR TO SEVEN INCHES OF RAINFALL.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

EXCESSIVE RUNOFF FROM THIS STORM WILL CAUSE FLOODING OF SMALL CREEKS
AND STREAMS...COUNTRY ROADS...NORMALLY DRY WASHES... AS WELL AS
FARMLAND ALONG THE BANKS OF CREEKS AND STREAMS.

DO NOT DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE
ROADWAY. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO CROSS
SAFELY.

REPORT FLOODING TO THE NEAREST LAW ENFORCEMENT AGENCY SO THAT THEY
MAY TAKE APPROPRIATE ACTION TO CLOSE FLOODED ROADWAYS. THEY WILL
RELAY YOUR REPORT TO THE NATIONAL WEATHER SERVICE IN CHICAGO.

&&

LAT...LON 4250 8781 4227 8782 4201 8765 4192 8953
      4194 8969 4220 8970 4221 8940 4250 8940

$$

RODRIGUEZ
979 
WGUS73 KLOT 231132
FFSLOT

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
632 AM CDT SAT JUL 23 2011

ILC007-031-037-089-097-111-141-201-231146-
/O.EXP.KLOT.FF.W.0019.000000T0000Z-110723T1130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
KANE IL-MCHENRY IL-OGLE IL-WINNEBAGO IL-BOONE IL-DE KALB IL-LAKE IL-
COOK IL-
632 AM CDT SAT JUL 23 2011

...THE FLASH FLOOD WARNING THAT WAS IN EFFECT FOR NORTHERN COOK...
LAKE...NORTHERN DE KALB...BOONE...WINNEBAGO...OGLE...MCHENRY AND
NORTHERN KANE COUNTIES HAS BEEN REPLACED WITH A NEW FLASH FLOOD 
WARNING THIS MORNING WITH FLOODING CONTINUING ACROSS MANY AREAS THIS 
MORNING.

LAT...LON 4250 8781 4227 8782 4201 8765 4192 8953
      4194 8969 4220 8970 4221 8940 4250 8940

$$

RODRIGUEZ

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 Jul 22, 9:59 PM CDT, 2 hours 37 minutes earlier.

Area forecast discussion, Jul 22, 9:59 PM CDT, 2 hours 37 minutes before
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
959 PM CDT FRI JUL 22 2011

.DISCUSSION...
354 PM CDT

HEAT AND THE PROSPECTS OF MORE HEAVY RAINFALL ARE THE MAIN FORECAST
CONCERNS OVER THE NEXT FEW DAYS.

AS FOR THE HEAT HEADLINES...I DECIDED TO CANCEL THE HEAT WATCH FOR
THE NORTHERN SECTIONS OF THE AREA...GENERALLY ALONG AND NORTH OF I-88
AS IT APPEARS UNLIKELY FOR THESE AREAS TO REACH THE DANGEROUS
CRITERIA.  IN SPITE OF THIS...THINGS SHOULD BEGIN WARMING BACK TO
NEAR 90 IN THESE AREAS...ESPECIALLY BY SUNDAY.  FARTHER
SOUTH...GENERALLY SOUTH OF I-80 I EXTENDED THE WARNING THROUGH 02
UTC ON MONDAY. IN THE MIDDLE I LEFT THE WATCH FROM 12 UTC SUNDAY TO
02 MONDAY. THIS IS FOR AREAS ALONG THE I-80 CORRIDOR.

A POTENT MID LEVEL SHORT WAVE WILL SHIFT EASTWARD ACROSS NORTH
DAKOTA TONIGHT INTO SATURDAY. IN RESPONSE TO THIS...A SURFACE LOW IS
EXPECTED SHIFT EASTWARD FROM THE NORTHERN HIGH PLAINS TO SOUTHERN MN
BY SATURDAY EVENING. THIS WILL CAUSE THE WARM FRONT...CURRENTLY
ACROSS THE AREA...TO MOVE NORTHWARD TO SOUTHERN WI TONIGHT. SEVERAL
MID LEVEL DISTURBANCES EJECTING OUT ACROSS CENTRAL PLAINS...WILL
CONTINUE TO DEVELOP CONVECTION ACROSS IOWA THIS EVENING. WITH TIME
TONIGHT GOOD MOIST ADVECTION WITHIN A WARM AIR ADVECTION REGIME
SHOULD ALLOW THIS ACTIVITY TO CONGEAL INTO ANOTHER MCS. IT APPEARS
THAT THIS MCS COULD HIT THE SAME AREAS AS THIS MORNINGS MCS.
ADDITIONALLY...GIVEN THAT THE ATMOSPHERIC PROFILE HAS CHANGED
LITTLE...IT CAN BE EXPECTED THAT THESE STORMS WILL ALSO BE EFFICIENT
RAINMAKERS. THIS ACTIVITY SHOULD CONTINUE ON SATURDAY MORNING ACROSS
THE AREA. IN ADDITION TO THE HEAVY RAIN...STRONG WINDS ARE AGAIN POSSIBLE
WITH THESE STORMS.

SIMILAR TO TODAY...IT APPEARS THERE WILL BE SOME DRY TIME IN THE
AFTERNOON. HOWEVER...ADDITIONAL CONVECTIVE DEVELOPMENT COULD OCCUR
AGAIN BY LATE AFTERNOON. HOWEVER...IF THE LOW LEVEL WIND FIELD IS
SIGNIFICANTLY DISRUPTED...AS IT WAS TODAY...IT MAY LIMIT THE
OVERALL THREAT ACROSS THE AREA...EXCEPT NEAR ANY BOUNDARIES THAT
BECOME ESTABLISHED.

A FINAL ROUND OF THUNDERSTORMS LOOKS TO BE IN THE WORKS BY SUNDAY
AFTERNOON AS THE COLD FRONT FINALLY PUSHES ACROSS THE AREA. THERE
COULD BE A SOME STRONG TO SEVERE STORMS DURING THIS PERIOD.
HOWEVER...THE MAIN STORY WITH THIS FRONT WILL BE THE PLEASANT AIR
MASS IT USHERS IN ACROSS THE REGION. SURFACE HIGH PRESSURE WILL
BUILD IN ACROSS THE WESTERN GREAT LAKES IN THE WAKE OF THIS FRONT ON
MONDAY AND TUESDAY. THIS WILL PRODUCE COOL AND DRY CONDITIONS FOR
MONDAY AND TUESDAY. UNFORTUNATELY...THIS WILL BE RELATIVELY SHORT
LIVED AS THE THE HEAT MAKES A RETURN BY WEDNESDAY AND THURSDAY AS
THE UPPER RIDGE BUILDS NORTHWARD AGAIN. THIS COULD PUT TEMPERATURES
BACK INTO THE MID 90S AREA WIDE BY THURSDAY

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* THUNDERSTORM POTENTIAL OVERNIGHT/SATURDAY.

RATZER

//DISCUSSION...UPDATED 0130Z...

THUNDERSTORM COMPLEX OVER CENTRAL IOWA HAS BECOME MORE ORGANIZED
OVER THE PAST 1-2 HOURS...WITH RADAR INDICATIONS OF REAR INFLOW
JET DEVELOPMENT AND SOME INCREASE IN FORWARD SPEED. COMPLEX IS
EXPECTED TO CONTINUE TO TRACK EAST-SOUTHEAST ALONG INSTABILITY
GRADIENT NORTH OF SURFACE FRONTAL BOUNDARY WHICH LIES OFF TO THE
SOUTH OF THE TERMINALS. HAVE SPED UP TIMING FROM 00Z ISSUANCE TO
AROUND 05Z AT KRFD...AND UPGRADED TO TEMPO TSRA THERE...AND MOVED
UP THE CHICAGO TERMINAL TIMING FOR VCTS TO 0630-0700Z. BULK OF
STRONGER TS MAY MOVE JUST SOUTH OF TERMINALS...BUT WILL MONITOR
NEXT 1-2 HOURS FOR POSSIBLE TEMPO TSRA FOR CHICAGO TERMINALS. IN
ADDITION...THUNDERSTORMS HAVE FORMED AS PREVIOUSLY DISCUSSED TO
THE EAST OF IKK...ABOUT 20 NM SOUTH OF KGYY TO NEAR KVPZ. THESE
SHOULD CONTINUE TO MOVE EAST AND NOT DIRECTLY AFFECT GYY OR OTHER
TERMINALS OTHER THAN ARRIVAL/DEPARTURE ROUTES INTO CHI. WOULD
EXPECT WEAKENING/DISSIPATION TREND OF THESE CELLS NEXT FEW HOURS.

RATZER

PREVIOUS DISCUSSION FROM 00Z...

ORD/MDW TDWRS DEPICTING WEAK LAKE BREEZE BOUNDARY HAS BEEN MAKING
SOME PROGRESS WESTWARD ACROSS COOK COUNTY EARLY THIS EVENING...AND
WAS ROUGHLY ALONG A PWK-NILES-BRIDGEPORT LINE AT 2330Z.
EXTRAPOLATION OF THIS FEATURE SUGGESTS IT HAS SLOWED JUST A BIT IN
THE LAST HOUR...THOUGH IT MAY IMPINGE UPON BOTH ORD AND MDW
IN THE 010-0130Z TIME FRAME. MESONET WINDS BEHIND SHOW LIGHT EAST
WIND QUICKLY BECOMING VARIABLE...SO SUSPECT IT WONT HAVE A VERY
PRONOUNCED AFFECT THOUGH EXPECT IT WILL INDUCE MORE OF A LIGHT
VARIABLE WIND FIELD RATHER THAN CURRENT LIGHT SOUTHWEST WINDS.

OTHERWISE...THUNDERSTORM TRENDS ARE THE MAIN CONCERN OVER THE NEXT
12-24 HOURS. VISIBLE SATELLITE SHOWS MOST OF FORECAST AREA
RELATIVELY CUMULUS FREE AT THIS HOUR...SAVE FOR A LITTLE CONGESTUS
ALONG OLD OUTFLOW BOUNDARY IN THE VICINITY OF KANKAKEE. WEAK
RETURN NOTED ON KLOT 88D IN THIS VICINITY SUPPORTS RECENT HRRR
FORECASTS OF SOME CONVECTIVE DEVELOPMENT THERE...THOUGH THESE
SHOULD NOT HAVE A DIRECT EFFECT ON IMMEDIATE TERMINAL AIRSPACE.
LARGER CONCERN OVER CONVECTION BACK ACROSS IOWA EARLY THIS EVENING
WHICH IS TIED TO MID LEVEL FEATURE WHICH IS PROGGED TO MOVE EAST
ALONG THE IA/MN BORDER TONIGHT AND ACROSS SOUTHERN WI SATURDAY
MORNING. GUIDANCE IN GENERAL AGREEMENT THAT THIS IS THE AREA TO
WATCH FOR CONTINUED CONVECTIVE DEVELOPMENT...WITH MID LEVEL
SUPPORT AND IN REGION OF BETTER LOW LEVEL JET FORCING OVERNIGHT
AND EARLY SATURDAY. MODEL FORECAST SUPPORT DEVELOPMENT OF COMPLEX
ACROSS NORTHERN IA/FAR SOUTHEAST MN/SOUTHWEST WI WHICH WOULD THEN
SPREAD SOUTHEAST INTO NORTHERN IL TOWARD MORNING. THUS VICINITY
THUNDER MENTION BEYOND 07-08Z AND LINGERING INTO SATURDAY MORNING
SEEMS PRUDENT. MAY UPGRADE TO A TEMPO IF COMPLEX CONTINUES TO
EXHIBIT INCREASING ORGANIZATION THIS EVENING.

TRENDS FOR SATURDAY WILL DEPEND HIGHLY ON DETAILS OF CONVECTION
THROUGH 15Z. WOULD EXPECT SOME DECREASE IN CONVECTIVE POTENTIAL
AFTER ANY MORNING COMPLEX...THEN A DIURNAL INCREASE IN POTENTIAL
DURING THE AFTERNOON. CONFIDENCE REALLY TOO LOW ON DETAILS BEYOND
15Z AT THIS TIME TO CHANGE CB CLOUD GROUP FOR THE LATER AFTERNOON
HOURS. SOUTH WINDS EXPECTED TO SHIFT JUST A BIT SOUTH-SOUTHEAST
LATER IN THE DAY AS LOW PRESSURE MOVES INTO MINNESOTA AND BACKS
LARGE SCALE LOW LEVEL FLOW OVER THE MIDWEST.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* HIGH CONFIDENCE OF NO CONVECTION IN IMMEDIATE ORD/MDW VICINITY
  THROUGH MIDNIGHT...THEN INCREASING POTENTIAL BEYOND 06Z.

* MEDIUM-LOW CONFIDENCE IN CONVECTION FORECAST BEYOND 06Z.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...

SUNDAY...CHC TSRA.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...VFR.

THURSDAY...VFR. SLGT CHC TSRA.

RATZER

&&

.MARINE...
414 PM CDT

GENERALLY SOUTHERLY FLOW IN PLACE ACROSS THE LAKE LATE THIS
AFTERNOON...WITH RATHER LIGHT WINDS ALSO IN PLACE AS PRESSURE
GRADIENT REMAINS BAGGY. TROUGH OF LOW PRESSURE TO THE NORTH WILL
CONTINUE TO SHIFT EAST WITH TIME TONIGHT...WITH A RIDGE OF HIGH
PRESSURE BUILDING IN OVER THE LAKE FROM THE NORTH. WINDS WILL
CONTINUE TO REMAIN LIGHT WITH THE EXCEPTION FOR AREAS ACROSS THE
NORTHERN HALF WHERE THIS BUILDING HIGH PRESSURE WILL HELP TO
TIGHTEN THE PRESSURE GRADIENT AS WELL AS INCREASE THE WINDS. THEN
AS A TROUGH OF LOW PRESSURE WORKS ITS WAY NORTHEAST THROUGH THE
PLAINS AND UPPER MIDWEST INTO THE CENTRAL GREAT LAKES REGION
SATURDAY NIGHT INTO SUNDAY...WINDS WILL TURN TO THE SOUTH.
ALTHOUGH A RIDGE OF HIGH PRESSURE BUILDING IN FROM THE WEST WILL
HELP THE WINDS TURN MORE NORTHERLY WITH WINDS PICKING UP ONCE
AGAIN BEFORE THE RIDGE AXIS SHIFTS OVERHEAD.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...EXCESSIVE HEAT WARNING...ILZ023-ILZ032-ILZ033-ILZ039 UNTIL 9 PM
     SUNDAY.

     EXCESSIVE HEAT WATCH...ILZ019-ILZ020-ILZ021-ILZ022...7 AM
     SATURDAY TO 9 PM SUNDAY.

IN...EXCESSIVE HEAT WATCH...INZ001-INZ002...7 AM SATURDAY TO 9 PM
     SUNDAY.

     EXCESSIVE HEAT WARNING...INZ010-INZ011-INZ019 UNTIL 9 PM SUNDAY.

LM...NONE.
&&
Hazardous weather outlook, Jul 22, 4:27 PM CDT, 8 hours 9 minutes before
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
427 PM CDT FRI JUL 22 2011

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
232130-
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-
427 PM CDT FRI JUL 22 2011 /527 PM EDT FRI JUL 22 2011/

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

.DAY ONE...TONIGHT.

  WEATHER HAZARDS EXPECTED:

  OPPRESSIVE HEAT AND HUMIDITY.

  THUNDERSTORMS...SOME MAY PRODUCE:
    HEAVY RAINFALL WITH FLASH FLOODING.
    WINDS OVER 60 MPH.
    FREQUENT LIGHTNING.

  AREAS AFFECTED AND TIMING:

   THE DANGEROUS HEAT AND HUMIDITY WILL CONTINUE...ESPECIALLY
   SOUTH OF INTERSTATE 80.

   THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS IOWA THIS
   EVENING...BEFORE THEY TRACK EASTWARD ACROSS SOUTHERN WISCONSIN
   AND FAR NORTHERN ILLINOIS LATE TONIGHT INTO SATURDAY MORNING.
   AREAS NORTH OF INTERSTATE 80 WILL HAVE THE BEST CHANCE OF
   THUNDERSTORMS.

  DISCUSSION:

   HEAT INDEX VALUES WILL LIKELY ONLY DROP TO THE LOW 90S BY
   MIDNIGHT TONIGHT FOR AREAS SOUTH OF I-80. THIS WILL CONTINUE TO
   LEAD TO DANGEROUS HEAT CONDITIONS.

   VERY HEAVY RAINFALL MAY AGAIN ACCOMPANY THE THUNDERSTORMS LATE
   TONIGHT INTO SATURDAY MORNING. THIS RAIN COULD FALL ON THE SAME
   AREAS THAT EXPERIENCED HEAVY RAIN THIS MORNING. RUNOFF FROM
   THIS RAIN COULD CAUSE ADDITIONAL FLASH FLOODING IN SOME AREAS.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

HEAT INDEX VALUES AROUND 100 DEGREES ARE EXPECTED ACROSS MUCH OF
NORTHERN ILLINOIS AND NORTHWEST INDIANA FOR THE WEEKEND. SOUTH OF
I-80 THE HEAT WILL BE MORE EXTREME...HEAT INDEX VALUES AROUND 110
DEGREES ARE EXPECTED.

THERE WILL BE PERIODIC CHANCES FOR THUNDERSTORMS THROUGH SUNDAY
AND AGAIN BY THE MIDDLE OF NEXT WEEK.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED LATE TONIGHT INTO SATURDAY
MORNING.

&&

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

LMZ740>745-232130-
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-
427 PM CDT FRI JUL 22 2011

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

.DAY ONE...TONIGHT.

THERE IS A CHANCE OF STORMS LATE TONIGHT CAUSING WIND GUSTS IN
EXCESS OF 35 KNOTS AND FREQUENT LIGHTNING.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

THERE WILL BE PERIODIC CHANCES FOR THUNDERSTORMS THROUGH SUNDAY
AND AGAIN BY THE MIDDLE OF NEXT WEEK.

&&

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-
870-872-874-876-878-232130-
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-
427 PM CDT FRI JUL 22 2011

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

.DAY ONE...TONIGHT.

THERE IS A CHANCE OF STORMS LATE TONIGHT CAUSING WIND GUSTS
IN EXCESS OF 35 KNOTS AND FREQUENT LIGHTNING.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

THERE WILL BE PERIODIC CHANCES FOR THUNDERSTORMS ACROSS THE LAKE
THROUGH SUNDAY.

THERE ARE ADDITIONAL CHANCES FOR THUNDERSTORMS TUESDAY NIGHT
THROUGH THURSDAY...MAINLY FOR THE NORTHERN HALF OF THE LAKE.

&&

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

KJB

In the hours before

Local storm report, Jul 22, 8:08 PM CDT, 4 hours 28 minutes before
PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
808 PM CDT FRI JUL 22 2011

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

0530 AM     HEAVY RAIN       7 W ROCKTON             42.45N 89.21W
07/22/2011  M0.92 INCH       WINNEBAGO          IL   CO-OP OBSERVER

            MEASURED BY SHIRLAND CO-OP OBSERVER.

0630 AM     HEAVY RAIN       1 W BEACH PARK          42.42N 87.88W
07/22/2011  M2.19 INCH       LAKE               IL   COCORAHS

            STORM TOTAL SO FAR. 0.70 INCHES MEASURED IN THE PAST 60
            MINUTES. STANDING WATER AND DITCHES FILLING UP.

0700 AM     HEAVY RAIN       2 W GURNEE              42.38N 87.98W
07/22/2011  M2.24 INCH       LAKE               IL   COCORAHS

0700 AM     HEAVY RAIN       HARVARD                 42.42N 88.62W
07/22/2011  M1.17 INCH       MCHENRY            IL   CO-OP OBSERVER

0700 AM     HEAVY RAIN       2 N SPRING GROVE        42.47N 88.24W
07/22/2011  M1.71 INCH       MCHENRY            IL   CO-OP OBSERVER

0700 AM     HEAVY RAIN       5 NW WOODSTOCK          42.36N 88.51W
07/22/2011  M1.48 INCH       MCHENRY            IL   CO-OP OBSERVER

0700 AM     HEAVY RAIN       2 N WAUKEGAN            42.40N 87.87W
07/22/2011  M2.10 INCH       LAKE               IL   COCORAHS

0700 AM     HEAVY RAIN       2 SE LAKEMOOR           42.32N 88.18W
07/22/2011  M1.69 INCH       LAKE               IL   COCORAHS

0700 AM     HEAVY RAIN       1 W BEACH PARK          42.42N 87.88W
07/22/2011  M1.49 INCH       LAKE               IL   COCORAHS

0700 AM     HEAVY RAIN       BEACH PARK              42.42N 87.86W
07/22/2011  M2.06 INCH       LAKE               IL   ASOS

            SINCE 100 AM AT WAUKEGAN REGIONAL AIRPORT.

0700 AM     HEAVY RAIN       2 NE GURNEE             42.40N 87.91W
07/22/2011  M2.38 INCH       LAKE               IL   COCORAHS

0725 AM     HEAVY RAIN       WADSWORTH               42.44N 87.92W
07/22/2011  M2.80 INCH       LAKE               IL   BROADCAST MEDIA

            0.50 INCHES BETWEEN 655 AM AND 715 AM.

0745 AM     FLOOD            BEACH PARK              42.42N 87.86W
07/22/2011                   LAKE               IL   EMERGENCY MNGR

            NORTH SHERIDAN ROAD SOUTH OF WEST WADSWORTH ROAD CLOSED
            FROM 745 AM TO 100 PM DUE TO 7-8 INCHES OF STANDING WATER
            ON ROAD SURFACE.

0750 AM     HEAVY RAIN       3 ENE MACHESNEY PARK    42.38N 88.98W
07/22/2011  M1.09 INCH       WINNEBAGO          IL   COCORAHS

0755 AM     HEAVY RAIN       GURNEE                  42.38N 87.94W
07/22/2011  M3.25 INCH       LAKE               IL   PUBLIC

            STORM TOTAL SO FAR.

0800 AM     HEAVY RAIN       WINTHROP HARBOR         42.48N 87.83W
07/22/2011  M1.28 INCH       LAKE               IL   COCORAHS

0842 AM     HEAVY RAIN       4 NW ROCKFORD           42.31N 89.12W
07/22/2011  M1.37 INCH       WINNEBAGO          IL   CO-OP OBSERVER

            STORM TOTAL SO FAR. 0.95 INCHES BETWEEN 715 AM AND TIME
            OF REPORT.

0900 AM     HEAVY RAIN       ARLINGTON HEIGHTS       42.09N 87.98W
07/22/2011  E0.00 INCH       COOK               IL   TRAINED SPOTTER

            ESTIMATED 1 TO 2 INCHES.

0920 AM     HEAVY RAIN       3 NNE ELBURN            41.93N 88.45W
07/22/2011  M0.63 INCH       KANE               IL   COCORAHS

            IN 15 MINUTES.

0933 AM     TSTM WND GST     DUPAGE AIRPORT          41.92N 88.25W
07/22/2011  M45.00 MPH       DUPAGE             IL   ASOS

0945 AM     TSTM WND GST     ELMHURST                41.90N 87.94W
07/22/2011  M56.50 MPH       DUPAGE             IL   TRAINED SPOTTER

            MEASURED WITH A CAR ANEMOMETER. BRYAN MIDDLE SCHOOL AT
            YORK ROAD.

0947 AM     TSTM WND GST     OHARE AIRPORT           41.98N 87.90W
07/22/2011  M43.00 MPH       COOK               IL   ASOS

0953 AM     HEAVY RAIN       ARLINGTON HEIGHTS       42.09N 87.98W
07/22/2011  M1.00 INCH       COOK               IL   TRAINED SPOTTER

            IN 15 MINUTES UP TO TIME OF REPORT.

0955 AM     HEAVY RAIN       OHARE AIRPORT           41.98N 87.90W
07/22/2011  M0.75 INCH       COOK               IL   ASOS

            MEASURED IN 8 MINUTES BETWEEN 947AM AND 955 AM. 0.55
            INCHES FELL BETWEEN 947 AM AND 951 AM.

0957 AM     HEAVY RAIN       1 NNE BLOOMINGDALE      41.96N 88.08W
07/22/2011  M0.87 INCH       DUPAGE             IL   COCORAHS

            MEASURED IN 25 MINUTES UP TO TIME OF REPORT.

1000 AM     HEAVY RAIN       3 ESE PLAINFIELD        41.60N 88.15W
07/22/2011  M0.76 INCH       WILL               IL   COCORAHS

            IN THE PAST 30 MINUTES.

1000 AM     HEAVY RAIN       GLEN ELLYN              41.87N 88.06W
07/22/2011  M1.16 INCH       DUPAGE             IL   COCORAHS

            RAINFALL IN ONE HOUR IN NORTH GLEN ELLYN.

1000 AM     HEAVY RAIN       1 W ROSELLE             41.98N 88.10W
07/22/2011  M0.91 INCH       DUPAGE             IL   COCORAHS

            BETWEEN 940 AM AND 1000 AM.

1006 AM     TSTM WND GST     MIDWAY AIRPORT          41.78N 87.75W
07/22/2011  M54.00 MPH       COOK               IL   ASOS

1013 AM     HEAVY RAIN       ARLINGTON HEIGHTS       42.09N 87.98W
07/22/2011  M0.85 INCH       COOK               IL   TRAINED SPOTTER

            IN 30 MINUTES UP TO TIME OF REPORT. INTERSECTION OF HINTZ
            RD AND WINDSOR.

1015 AM     MARINE TSTM WIND 4 NE CHICAGO            41.92N 87.57W
07/22/2011  M50.00 MPH       LMZ741             IL   C-MAN STATION

            43 KNOT GUST MEASURED AT HARRISON-DEVER CRIB. 35
            KNOT...OR 40 MPH...SUSTAINED WINDS. ANEMOMETER 85 FEET
            ABOVE LAKE SURFACE.

1026 AM     HEAVY RAIN       MARENGO                 42.25N 88.60W
07/22/2011  E1.80 INCH       MCHENRY            IL   PUBLIC

            MEASURED...BUT FIRST 10-15 MINUTES EXTREMELY HEAVY RAIN
            WAS BLOWING SIDEWAYS...SO TOTAL MAY BE SLIGHTLY UNDER
            WHAT ACTUALLY OCCURRED.

1030 AM     HEAVY RAIN       2 WSW ELK GROVE VILLAGE 41.99N 88.03W
07/22/2011  M1.72 INCH       DUPAGE             IL   COCORAHS

            1.13 INCHES FROM 930 AM TO 1030 AM. 1.72 INCHES IN LAST
            14 HOURS.

1030 AM     HEAVY RAIN       1 W BEACH PARK          42.42N 87.88W
07/22/2011  M3.80 INCH       LAKE               IL   COCORAHS

1053 AM     TSTM WND GST     GARY                    41.60N 87.34W
07/22/2011  M54.00 MPH       LAKE               IN   AWOS

            MEASURED AT GARY AIRPORT.

1054 AM     HEAVY RAIN       PEOTONE                 41.33N 87.80W
07/22/2011  M0.61 INCH       WILL               IL   TRAINED SPOTTER

            HEAVY RAIN FALL IN 16 MINUTES.

1058 AM     HEAVY RAIN       ENE COUNTRYSIDE         41.78N 87.88W
07/22/2011  M1.30 INCH       COOK               IL   COCORAHS

            IN THE PAST 60 MINUTES. AT 1030 AM AND 1035 AM RAIN RATE
            WAS 5 INCHES PER HOUR.

1100 AM     MARINE TSTM WIND 3 NNW BURNS HARBOR      41.65N 87.15W
07/22/2011  M44.00 MPH       LMZ745             IN   C-MAN STATION

            38 KNOT GUST MEASURED AT BURNS HARBOR GLOS WEATHER
            STATION. ANEMOMETER HEIGHT 33 FEET.

1100 AM     HEAVY RAIN       ELBURN                  41.89N 88.47W
07/22/2011  M1.32 INCH       KANE               IL   TRAINED SPOTTER

            RAINFALL TOTAL 1.32 INCHES FROM 1 AM THROUGH 10 AM.

1140 AM     HEAVY RAIN       BERWYN                  41.84N 87.79W
07/22/2011  M1.02 INCH       COOK               IL   TRAINED SPOTTER

0100 PM     HEAVY RAIN       BEACH PARK              42.42N 87.86W
07/22/2011  M3.42 INCH       LAKE               IL   ASOS

            STORM TOTAL SINCE 100 AM AT WAUKEGAN REGIONAL AIRPORT.
            1.36 INCHES BETWEEN 700 AM AND 100 PM.

0100 PM     HEAVY RAIN       OHARE AIRPORT           41.98N 87.90W
07/22/2011  M1.49 INCH       COOK               IL   ASOS

            STORM TOTAL SINCE 100 AM. 1.29 INCHES BETWEEN 700 AM AND
            100 PM.

0102 PM     HEAVY RAIN       REMINGTON               40.76N 87.15W
07/22/2011  M0.63 INCH       JASPER             IN   TRAINED SPOTTER

            MEASURED IN 40 MINUTES.

&&
THIS REPORT MAY BE REVISED IF ANY FURTHER REPORTS ARE RECEIVED.

BN
Local storm report, Jul 22, 11:55 PM CDT, 41 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1155 PM CDT FRI JUL 22 2011

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

1145 PM     HAIL             5 E LOWELL              41.29N 87.32W
07/22/2011  E0.25 INCH       LAKE               IN   LAW ENFORCEMENT

            INTERSECTION OF INTERSTATE 65 AND ROUTE 2. FROM INDIANA
            STATE POLICE.

&&

RATZER
Special weather statement, Jul 23, 12:11 AM CDT, 25 minutes before
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1211 AM CDT SAT JUL 23 2011

ILZ003-008-010-230615-
LEE IL-OGLE IL-WINNEBAGO IL-
1211 AM CDT SAT JUL 23 2011

...SPECIAL WEATHER STATEMENT...

AT 1207 AM...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED STRONG
THUNDERSTORMS ALONG A LINE EXTENDING FROM 11 MILES WEST OF LAKE
SUMMERSET TO FORRESTON TO POLO...MOVING EAST AT 30 MPH.

WINDS UP TO 50 MPH...FREQUENT CLOUD TO GROUND LIGHTNING...BRIEF HEAVY
DOWNPOURS...ARE POSSIBLE WITH THESE STORMS.

ADDITIONAL ISOLATED THUNDERSTORMS WERE DEVELOPING FARTHER EAST INTO
SOUTHERN MCHENRY AND LAKE COUNTIES.

LOCATIONS IMPACTED INCLUDE...
  POLO...               FORRESTON...          DURAND...
  LAKE SUMMERSET...     PECATONICA...         MOUNT MORRIS...
  WINNEBAGO...          STILLMAN VALLEY...    OREGON...
  BYRON...              ROSCOE...             ROCKTON...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

GUSTY WINDS MAY CAUSE SMALL BRANCHES TO BE BLOWN DOWN...AND LOOSE
OBJECTS TO BLOW AROUND. STAY AWAY FROM HIGH OBJECTS OUTDOORS SUCH AS
TREES. HEAVY RAINFALL CAN LEAD TO FLOODING OF LOW LYING AREAS SUCH AS
DITCHES...VIADUCTS...UNDERPASSES...CREEKS AND DRAINAGE AREAS. SEEK
SHELTER IN A STURDY STRUCTURE UNTIL THESE STORMS HAVE PASSED.

LAT...LON 4250 8896 4182 8896 4187 8964 4192 8963
      4193 8969 4220 8970 4221 8940 4250 8940

RATZER
Local storm report, Jul 23, 12:22 AM CDT, 14 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1222 AM CDT SAT JUL 23 2011

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

1221 AM     HAIL             FORRESTON               42.13N 89.58W
07/23/2011  E0.25 INCH       OGLE               IL   LAW ENFORCEMENT

            PEA HAIL AND 30 TO 40 MPH WINDS. FROM OGLE COUNTY
            SHERIFF.

&&

RATZER

The office that day

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

IssuedProductOfficeCountiesLasted
Jul 23, 12:11 AM CDTSpecial Weather StatementLOTOgle, Winnebago64 min
Jul 23, 12:41 AM CDTSevere Thunderstorm WarningLOTBoone, DeKalb, Lee, McHenry, Ogle, Winnebago64 min
Jul 23, 12:53 AM CDTSevere Thunderstorm WarningLOTCook, DuPage54 min
Jul 23, 12:58 AM CDTSpecial Marine WarningLOT2 hr
Jul 23, 1:19 AM CDTFlash Flood WarningLOTCook, DuPage6 hr
Jul 23, 1:50 AM CDTSpecial Weather StatementLOTDuPage55 min
Jul 23, 2:37 AM CDTFlash Flood WarningLOTCook, DuPage, Kane, Kendall, Will5 hr
Jul 23, 3:00 AM CDTSpecial Marine WarningLOT48 min
Jul 23, 3:40 AM CDTHeat AdvisoryLOTDeKalb, Grundy, Kane, Kendall, LaSalle, Lee and 2 more32 hr
Jul 23, 5:21 AM CDTRiver Flood WarningLOTCook38 hr
Jul 23, 5:21 AM CDTRiver Flood WarningLOTCook3 days
Jul 23, 6:14 AM CDTRiver Flood AdvisoryLOTWill9 hr
Jul 23, 6:30 AM CDTFlash Flood WarningLOTBoone, Cook, DeKalb, Kane, Lake, Lee and 3 more5 hr
Jul 23, 7:30 AM CDTFlash Flood WarningLOTCook, DuPage, Kane, Will4 hr
Jul 23, 9:37 AM CDTRiver Flood WarningLOTKane, McHenry11 hr
Jul 23, 9:37 AM CDTRiver Flood WarningLOTKane, Kendall23 hr
Jul 23, 11:13 AM CDTAreal Flood WarningLOTCook, DuPage, Lake19 hr
Jul 23, 2:46 PM CDTRiver Flood WarningLOTWill43 hr
Jul 23, 4:15 PM CDTFlash Flood WatchLOTBoone, DeKalb, DuPage, Kane, Kendall, Lake and 4 more18 hr

Nearby

Flash Flood Warnings in Illinois, 2011Every flash flood warning in 2011

Sources

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