Severe Thunderstorm Warning 82, NWS Chicago, IL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
545 PM CDT MON JUN 24 2013

.MESOSCALE DISCUSSION...
544 PM CDT

REPORTS CONTINUE TO COME IN OF WIND DAMAGE FROM STRONG APEX OF
STORMS WITH THE EMPHASIS ON RADAR NOW COMING RIGHT INTO THE
WESTERN/SOUTHWESTERN CHICAGO METRO AREA. JUST GUSTED TO 61 MPH
HERE AT THE WFO IN ROMEOVILLE. AREAS OF WIDESPREAD SEVERE WINDS
WILL OCCUR...INCLUDING CORRIDORS OF POTENTIALLY HIGHER END WINDS
/IN EXCESS OF 75-80 MPH/. CONTINUE TO SEE A SOMEWHAT TRANSIENT
MESO-VORTICY RADAR SIGNATURE...INCLUDING ON TDWR DATA...JUST
NORTH OF THE APEX MOVING INTO SOUTHWEST DUPAGE COUNTY. THE OVERALL
PRIMARY STORY FOR CHICAGOLAND IS DAMAGING WINDS.

SOUTH OF THE APEX THE OUTFLOW IS JUST AHEAD OF THE STORMS...WHICH
DOES POINT TOWARDS POSSIBLY NOT AS SEVERE OF WINDS.
HOWEVER...FORWARD SPEED ON THE OUTFLOW IN SOUTHERN WILL COUNTY ON
RADAR WAS AT 60 MPH SO SPEEDS OF AT LEAST THAT ARE LIKELY.

ISOLATED CELLS AHEAD OF THIS MAY DEVELOP SUCH AS IN LAKE COUNTY
IN. THESE COULD BE CAPABLE OF SMALL HAIL AND POSSIBLY DOWNBURST
POTENTIAL...ESPECIALLY IF ANY CAN DEVELOP A LARGER CORE.

ON THE LARGE SCALE RADAR AND SATELLITE THIS FORWARD-PROPAGATING MCS
LOOKS VERY WELL-ORGANIZED. THE ENVIRONMENT CONTINUES TO BE
FAVORABLE FOR SUSTAINABILITY...WITH DEEP CAPE IN ADVANCE...STEEP
LOW-LEVEL LAPSE RATES AND ASSOCIATED THETA-E DIFFERENCE...AND
STRONG 0-1 AND 0-3 KM SHEAR ADVECTING EAST WITHIN THE MCS FOR COLD
POOL SUSTAINABILITY. IN ADDITION...THE STORMS ARE PROPAGATING AS
QUICKLY AS THE OUTFLOW NEAR THE APEX...A SIGN THAT WARM MOIST AIR
IS CONTINUING TO FUEL INTO THE STORMS.

MTF

.DISCUSSION...
327 PM CDT

SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT...

A VERY ACTIVE PERIOD OF WEATHER IS EXPECTED...AT LEAST FOR PORTIONS
OF THE AREA...THROUGH WEDNESDAY. THIS INCLUDES A FEW PERIODS OF
SEVERE THUNDERSTORMS AND ALSO A GOOD THREAT FOR VERY HEAVY RAINFALL
AND POSSIBLE FLASH FLOODING. AS SUCH...THIS WILL BE THE FOCUS OF THE
FORECAST.

WE HAVE EXTENDED THE FLASH FLOOD WATCH FOR OUR WESTERN COUNTIES
THROUGH TONIGHT.

TEMPERATURES ACROSS NORTHERN ILLINOIS AND NW INDIANA HAVE JUMPED
INTO THE LOW TO MID 80S OVER THE PAST COUPLE HOURS AFTER THE MORNING
CLOUD COVER CLEARED. WITH DEW POINTS NEAR 70...THIS IS RESULTING IN
MLCAPES AROUND 2,000 J/KG ACROSS THE AREA...PER SPC MESOANALYSIS
PAGE. IN ADDITION...IT APPEARS THAT THE 0-6 KM SHEAR MAY END UP A
BIT STRONGER THAN PREVIOUSLY THOUGHT. VWP DATA INDICATES THAT A SPEED
MAX AROUND 50 KT ...ASSOCIATED WITH A MID LEVEL DISTURBANCE MOVING
INTO NORTHWESTERN IOWA...IS PUNCHING EASTWARD ACROSS IOWA. THUS IT
APPEARS THAT 40 KT OF DEEP LAYER SHEER MAY OVERSPREAD THIS AREA
LATER THIS AFTERNOON AND EVENING AS THIS SPEED MAX SHIFTS EASTWARD.
CURRENT THOUGHTS ARE THAT THE LINE OF CONVECTION TO THE WEST WILL
POSE A SEVERE THREAT FOR MOST OF THE AREA INTO THE EARLY EVENING
HOURS. STRONG DAMAGING WINDS...POSSIBLY IN EXCESS OF 80 MPH...WILL
BE THE PRIMARY THREAT ALONG WITH A SMALL POTENTIAL OF SOME
MARGINALLY SEVERE HAIL.

IT APPEARS THE MAIN FOCUS FOR CONVECTION MAY SHIFT NORTH INTO
WISCONSIN LATER TONIGHT AS THE LOW LEVEL JET FOCUSES FARTHER NORTH.
HOWEVER...THIS APPEARS TO BE SHORTED LIVED...AS CONVECTIVE CHANCES
WILL RETURN ON TUESDAY. IT APPEARS THAT ADDITIONAL PERTURBATIONS IN
THE MEAN QUASI-ZONAL MID LEVEL FLOW...WILL INTERACT WITH THE VERY
MOIST AND UNSTABLE ATMOSPHERE ACROSS THE AREA. IT APPEARS THE CAP
WILL REMAIN FAIRLY WEAK DURING THE DAY...SO IT APPEARS THAT AT LEAST
SOME WIDELY SCATTERED CONVECTION MAY OCCUR...MAINLY ACROSS FAR
NORTHERN ILLINOIS. THIS ACTIVITY COULD AGAIN POSS A SEVERE RISK
ACROSS NORTHERN ILLINOIS WITH STEEP MID LEVEL LAPSE RATES HELPING
PRODUCE MLCAPES IN EXCESS OF 3000 J/KG.

TUESDAY CONVECTION LOOKS LIKE IT WILL BECOME MORE NUMEROUS TUESDAY
EVENING/NIGHT. THE QUASI-ZONAL FLOW PATTERN ACROSS THE CONUS IS
EXPECTED TO BEGIN AMPLIFYING...IN RESPONSE TO AN UPPER LOW OVER THE
EASTERN PACIFIC. ULTIMATELY THIS WILL SET THE STAGE FROM A BUILDING
MID/UPPER LEVEL RIDGE ACROSS THE WESTERN CONUS AND FALLING HEIGHTS
ACROSS THE GREAT LAKES REGION. THIS PROCESS SHOULD ALLOW
ANOTHER...STRONGER...SHORT WAVE TO MOVE ACROSS THE AREA ON
WEDNESDAY. IT APPEARS THIS FEATURE WILL FOCUS THE NOSE OF A 40 KT
LOW LEVEL JET RIGHT ACROSS SOUTHERN WISCONSIN AND NORTHERN ILLINOIS
TUESDAY NIGHT INTO WEDNESDAY. THIS COULD SET THE STAGE FOR VERY HEAVY
RAINFALL ACROSS PORTIONS OF NORTHERN ILLINOIS INTO WEDNESDAY. THIS
LOOKS TO BE THE PERIOD TO REALLY WATCH FOR POSSIBLE FLOODING ACROSS
THE AREA. PWATS ARE PROGGED TO REACH NEARLY 2.00 INCHES...WHICH IS
AROUND THE 99 PERCENTILE. IN ADDITION...THE SOUTHWESTERLY ORIENTATION
OF THE LOW LEVEL JET COULD OFFSET THE MEAN CLOUD BEARING
FLOW...POSSIBLY RESULTING IN SLOW MOVING OR BACK BUILDING SEGMENTS
TUESDAY NIGHT.  HOWEVER...CONFIDENCE IN THE EXACT PLACEMENT OF THE
HEAVIEST RAIN REMAINS IN QUESTION AT THIS TIME...BUT GUIDANCE IS
HINTING THAT NORTHERN ILLINOIS COULD LIE IN THE FAVORED ZONE. THIS
WILL HAVE TO BE WATCHED...WITH THE POSSIBLY OF A FLASH FLOOD WATCH
NEEDED FOR PORTIONS OF NORTHERN ILLINOIS AND NORTHWESTERN INDIANA
DURING THIS PERIOD.

THE SEVERE CONVECTIVE THREAT SHOULD BEGIN TO WANE WEDNESDAY
EVENING AS THE MID LEVEL DISTURBANCE SHIFT EAST OF THE AREA.

TEMPERATURES LOOK TO CONTINUE TO BE PROBLEMATIC FOR THE NEXT COUPLE
OF DAYS...WITH ADDITIONAL BUST POTENTIAL WITH CONVECTIVE ACTIVITY.
HOWEVER...I ONLY MADE MINOR CHANCES TO THE GOING TEMP
FORECAST...MAINLY TO COOL THE NORTHERN AREAS BY A COUPLE DEGREES.

KJB

EXTENDED FORECAST...THURSDAY THROUGH MONDAY...

QUASI ZONAL FLOW IN THE SOUTHERN STREAM EARLY IN THE WEEK WILL
TRANSITION BY THE SECOND HALF OF THE WEEK TO AN INCREASINGLY
AMPLIFIED BROAD WESTERN CONUS RIDGE AND ITS CORRESPONDING LONGWAVE
TROUGH OVER THE EASTERN CONUS.  THIS WOULD PUT THE LOCAL AREA IN
NORTHWEST UPPER FLOW EARLY IN THE WEEKEND...AND THEN UNDER AN UPPER
LOW PUSHING SOUTHWEST ACROSS THE GREAT LAKES BY SUNDAY.  THE MOST
OBVIOUS RAMIFICATION WILL BE MUCH COOLER HIGHS...ESPECIALLY FOR THE
WEEKEND AND EARLY NEXT WEEK.  IN ADDITION...GFS/ECMWF ARE SUGGESTING
THE POSSIBILITY OF THUNDERSTORMS TRIGGERED BY SHORTWAVE ENERGY
DROPPING ACROSS THE AREA INTO THE BASE OF THE EASTERN TROUGH
THURSDAY AND FRIDAY...WHEN CONSIDERABLE LOW LEVEL MOISTURE REMAINS
IN PLACE OVER THE AREA.  DEWPOINTS FALL ALONG WITH THE TEMPERATURES
BY THE WEEKEND...BUT THE DEEPENING UPPER LOW ALSO SUPPORTS A
CONTINUED CHANCE OF SHOWERS INTO MONDAY.

EML

&&

.DISCUSSION...
327 PM CDT

SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT...

A VERY ACTIVE PERIOD OF WEATHER IS EXPECTED...AT LEAST FOR PORTIONS
OF THE AREA...THROUGH WEDNESDAY. THIS INCLUDES A FEW PERIODS OF
SEVERE THUNDERSTORMS AND ALSO A GOOD THREAT FOR VERY HEAVY RAINFALL
AND POSSIBLE FLASH FLOODING. AS SUCH...THIS WILL BE THE FOCUS OF THE
FORECAST.

WE HAVE EXTENDED THE FLASH FLOOD WATCH FOR OUR WESTERN COUNTIES
THROUGH TONIGHT.

TEMPERATURES ACROSS NORTHERN ILLINOIS AND NW INDIANA HAVE JUMPED
INTO THE LOW TO MID 80S OVER THE PAST COUPLE HOURS AFTER THE MORNING
CLOUD COVER CLEARED. WITH DEW POINTS NEAR 70...THIS IS RESULTING IN
MLCAPES AROUND 2,000 J/KG ACROSS THE AREA...PER SPC MESOANALYSIS
PAGE. IN ADDITION...IT APPEARS THAT THE 0-6 KM SHEAR MAY END UP A
BIT STRONGER THAN PREVIOUSLY THOUGHT. VWP DATA INDICATES THAT A SPEED
MAX AROUND 50 KT ...ASSOCIATED WITH A MID LEVEL DISTURBANCE MOVING
INTO NORTHWESTERN IOWA...IS PUNCHING EASTWARD ACROSS IOWA. THUS IT
APPEARS THAT 40 KT OF DEEP LAYER SHEER MAY OVERSPREAD THIS AREA
LATER THIS AFTERNOON AND EVENING AS THIS SPEED MAX SHIFTS EASTWARD.
CURRENT THOUGHTS ARE THAT THE LINE OF CONVECTION TO THE WEST WILL
POSE A SEVERE THREAT FOR MOST OF THE AREA INTO THE EARLY EVENING
HOURS. STRONG DAMAGING WINDS...POSSIBLY IN EXCESS OF 80 MPH...WILL
BE THE PRIMARY THREAT ALONG WITH A SMALL POTENTIAL OF SOME
MARGINALLY SEVERE HAIL.

IT APPEARS THE MAIN FOCUS FOR CONVECTION MAY SHIFT NORTH INTO
WISCONSIN LATER TONIGHT AS THE LOW LEVEL JET FOCUSES FARTHER NORTH.
HOWEVER...THIS APPEARS TO BE SHORTED LIVED...AS CONVECTIVE CHANCES
WILL RETURN ON TUESDAY. IT APPEARS THAT ADDITIONAL PERTURBATIONS IN
THE MEAN QUASI-ZONAL MID LEVEL FLOW...WILL INTERACT WITH THE VERY
MOIST AND UNSTABLE ATMOSPHERE ACROSS THE AREA. IT APPEARS THE CAP
WILL REMAIN FAIRLY WEAK DURING THE DAY...SO IT APPEARS THAT AT LEAST
SOME WIDELY SCATTERED CONVECTION MAY OCCUR...MAINLY ACROSS FAR
NORTHERN ILLINOIS. THIS ACTIVITY COULD AGAIN POSS A SEVERE RISK
ACROSS NORTHERN ILLINOIS WITH STEEP MID LEVEL LAPSE RATES HELPING
PRODUCE MLCAPES IN EXCESS OF 3000 J/KG.

TUESDAY CONVECTION LOOKS LIKE IT WILL BECOME MORE NUMEROUS TUESDAY
EVENING/NIGHT. THE QUASI-ZONAL FLOW PATTERN ACROSS THE CONUS IS
EXPECTED TO BEGIN AMPLIFYING...IN RESPONSE TO AN UPPER LOW OVER THE
EASTERN PACIFIC. ULTIMATELY THIS WILL SET THE STAGE FROM A BUILDING
MID/UPPER LEVEL RIDGE ACROSS THE WESTERN CONUS AND FALLING HEIGHTS
ACROSS THE GREAT LAKES REGION. THIS PROCESS SHOULD ALLOW
ANOTHER...STRONGER...SHORT WAVE TO MOVE ACROSS THE AREA ON
WEDNESDAY. IT APPEARS THIS FEATURE WILL FOCUS THE NOSE OF A 40 KT
LOW LEVEL JET RIGHT ACROSS SOUTHERN WISCONSIN AND NORTHERN ILLINOIS
TUESDAY NIGHT INTO WEDNESDAY. THIS COULD SET THE STAGE FOR VERY HEAVY
RAINFALL ACROSS PORTIONS OF NORTHERN ILLINOIS INTO WEDNESDAY. THIS
LOOKS TO BE THE PERIOD TO REALLY WATCH FOR POSSIBLE FLOODING ACROSS
THE AREA. PWATS ARE PROGGED TO REACH NEARLY 2.00 INCHES...WHICH IS
AROUND THE 99 PERCENTILE. IN ADDITION...THE SOUTHWESTERLY ORIENTATION
OF THE LOW LEVEL JET COULD OFFSET THE MEAN CLOUD BEARING
FLOW...POSSIBLY RESULTING IN SLOW MOVING OR BACK BUILDING SEGMENTS
TUESDAY NIGHT.  HOWEVER...CONFIDENCE IN THE EXACT PLACEMENT OF THE
HEAVIEST RAIN REMAINS IN QUESTION AT THIS TIME...BUT GUIDANCE IS
HINTING THAT NORTHERN ILLINOIS COULD LIE IN THE FAVORED ZONE. THIS
WILL HAVE TO BE WATCHED...WITH THE POSSIBLY OF A FLASH FLOOD WATCH
NEEDED FOR PORTIONS OF NORTHERN ILLINOIS AND NORTHWESTERN INDIANA
DURING THIS PERIOD.

THE SEVERE CONVECTIVE THREAT SHOULD BEGIN TO WANE WEDNESDAY
EVENING AS THE MID LEVEL DISTURBANCE SHIFT EAST OF THE AREA.

TEMPERATURES LOOK TO CONTINUE TO BE PROBLEMATIC FOR THE NEXT COUPLE
OF DAYS...WITH ADDITIONAL BUST POTENTIAL WITH CONVECTIVE ACTIVITY.
HOWEVER...I ONLY MADE MINOR CHANCES TO THE GOING TEMP
FORECAST...MAINLY TO COOL THE NORTHERN AREAS BY A COUPLE DEGREES.

KJB

EXTENDED FORECAST...THURSDAY THROUGH MONDAY...

QUASI ZONAL FLOW IN THE SOUTHERN STREAM EARLY IN THE WEEK WILL
TRANSITION BY THE SECOND HALF OF THE WEEK TO AN INCREASINGLY
AMPLIFIED BROAD WESTERN CONUS RIDGE AND ITS CORRESPONDING LONGWAVE
TROUGH OVER THE EASTERN CONUS.  THIS WOULD PUT THE LOCAL AREA IN
NORTHWEST UPPER FLOW EARLY IN THE WEEKEND...AND THEN UNDER AN UPPER
LOW PUSHING SOUTHWEST ACROSS THE GREAT LAKES BY SUNDAY.  THE MOST
OBVIOUS RAMIFICATION WILL BE MUCH COOLER HIGHS...ESPECIALLY FOR THE
WEEKEND AND EARLY NEXT WEEK.  IN ADDITION...GFS/ECMWF ARE SUGGESTING
THE POSSIBILITY OF THUNDERSTORMS TRIGGERED BY SHORTWAVE ENERGY
DROPPING ACROSS THE AREA INTO THE BASE OF THE EASTERN TROUGH
THURSDAY AND FRIDAY...WHEN CONSIDERABLE LOW LEVEL MOISTURE REMAINS
IN PLACE OVER THE AREA.  DEWPOINTS FALL ALONG WITH THE TEMPERATURES
BY THE WEEKEND...BUT THE DEEPENING UPPER LOW ALSO SUPPORTS A
CONTINUED CHANCE OF SHOWERS INTO MONDAY.

EML

&&

.HYDROLOGY...
433 PM CDT

A SHORT PERIOD OF HEAVY RAINFALL WILL ACCOMPANY THE LINE OF STORMS
CURRENTLY APPROACHING NORTH CENTRAL ILLINOIS. THIS COULD RESULT IN
SOME MINOR FLOODING...ESPECIALLY IN AREAS THAT WERE HIT WITH 1 TO 2
INCHES OF RAINFALL THIS MORNING. HOWEVER...ADDITIONAL PERIODS OF
HEAVY RAINFALL ARE EXPECTED LATE TUESDAY INTO WEDNESDAY. DURING THIS
PERIOD PRECIPITABLE WATER VALUES COULD BE AROUND 2 INCHES...WHICH
IS AROUND THE 99TH PERCENTILE. ANOTHER DECENT MID LEVEL DISTURBANCE
IS EXPECTED TO APPROACH THE AREA TUESDAY NIGHT AND INTO
WEDNESDAY...AND THIS SYSTEM LOOKS TO INDUCE A SOUTHWESTERLY LOW
LEVEL JET...THAT COULD OFFSET THE FORWARD STORM MOTION...RESULTING
IN SLOW MOVING OR BACK BUILDING THUNDERSTORMS TUESDAY NIGHT INTO
WEDNESDAY. AT THIS TIME...UNCERTAINTY REMAINS AS TO WHERE EXACTLY
THE HEAVIEST RAIN WILL FALL...BUT GUIDANCE CONTINUES TO HINT AT
NORTHERN ILLINOIS AND NORTHWESTERN INDIANA. THIS WILL HAVE TO BE
WATCHED FOR POSSIBILITY OF A FLASH FLOOD WATCH FOR MOST OF THE
AREA AS RAINFALL AMOUNTS IN EXCESS OF 2 INCHES IS CERTAINLY
POSSIBLE ACROSS PORTIONS OF THE AREA.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* SQUALL LINE/BOW ECHO TO IMPACT ORD/MDW AT 23Z
* POTENTIAL FOR DAMAGING WIND GUSTS OF 60-75 KTS
* VSBY REDUCED LESS THAN 1 MILE IN TORRENTIAL RAIN LASTING 15-25 MIN
* STRONGEST WINDS LASTING 5 TO 10 MIN
* PSBL FOG DEVELOPMENT OVERNIGHT INTO EARLY TUE.

ED F

//DISCUSSION...UPDATED 18Z...

WARM AND HUMID CONDITIONS IN PLACE ALONG WITH VARIOUS BOUNDARIES TO
KEEP NEXT ROUND OF SHRA/TSRA IN THE FORECAST INTO THIS EVENING.
ATMOSPHERE TO CONTINUE TO RECOVER FROM MORNING CONVECTIVE ACTIVITY.
THINKING IS A FEW TSRA ARE POSSIBLE BY MID AFTERNOON IN AREAS OF
LESSENING/THINNING OF CLOUD COVER AND MAY EXPAND IN COVERAGE BY LATE
AFTERNOON IF MORE WIDESPREAD SUNSHINE OCCURS.  CIRROSTRATUS SHIELD
ASSOCIATED WITH ORGANIZED AREAS OF TSRA/SHRA OVER IA MAY LIMIT
AMOUNT/DURATION OF SUN. TSRA CLUSTERS OVER IA EXPECTED TO ORGANIZE
FURTHER AND TRACK ACROSS NORTHERN ILLINOIS AND POSSIBLY NORTHWEST
INDIANA INTO THE EVENING.

SURFACE WARM FRONT EXPECTED TO REMAIN IN THE VICINITY OR JUST SOUTH
OF THE TERMINALS.  GIVEN HUMID ATMOSPHERE AND ADDITIONAL RAINFALL
AREAS OF MAINLY LIGHT FOG ARE LIKELY OVERNIGHT.

ZEBIC

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* HIGH CONFIDENCE IN SHRA/TSRA...MEDIUM CONFIDENCE IN PRECISE
  TIMING

* LOW CONFIDENNCE IN SPECIFC PEAK WIND GUST VALUE - BEST ESTIMATE
45-50 KTS BUT POTENTIAL FOR GUST TO 75 KTS EXISTS.

* LOW CONFIDENCE IN WIND FORECAST ONCE SQUALL LINE MOVES THROUGH...
MAY SEE PERIOD OF EAST WINDS.

* LOW CONFIDENCE IN OVERNIGHT FOG DEVELOPMENT REDUCING VSBYS.

ED F

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT THROUGH FRIDAY...PERIODIC CHANCES FOR
THUNDERSTORMS. OTHERWISE EXPECT VFR CIGS.

FRIDAY AND SATURDAY...CHANCE FOR SHOWERS. MAINLY VFR.

SUNDAY...VFR.

BEACHLER

&&

.MARINE...
411 PM CDT

HIGH PRESSURE REMAINS PARKED OFF THE CAROLINA COASTWHILE LOW
PRESSURE CONTINUES TO DRIFT NORTHWARD ACROSS CENTRAL MANITOBA AND
ONTARIO. ADDITIONAL LOW PRESSURE WILL DEVELOP FROM THE CANADIAN
PRAIRIES TO THE NORTHERN PLAINS TUESDAY AND MOVE EASTWARD INTO
WEDNESDAY WITH A CLOSED LOW DEVELOPING OVER THE WESTERN GREAT LAKES
BY WEDNESDAY NIGHT. A LARGER LOW WILL DEVELOP IVER THE GREAT LAKES
LATER FRIDAY AND LIKELY LINGER THROUGH THE WEEKEND BEFORE HIGH
PRESSURE BUILDS IN FROM THE WEST EARLY NEXT WEEK. SOUTHERN WINDS
WILL BE IN PLACE INTO WEDNESDAY WHEN THE FIRST SFC LOW PASSES WHICH
WILL TURN WINDS WEST AND NORTHWEST. SPEEDS WILL FLUCTUATE UP AND
DOWN UNTIL THE LOW PASSES SIMILAR TO PREVIOUS DAYS. A STABLE AIR
MASS OVER THE WATER WILL KEEP AREAS OF DENSE FOG GOING ACROSS MUCH
OF THE NORTHERN PART OF THE LAKE INTO TUESDAY AND PROBABLY INTO
WEDNESDAY FOR THAT MATTER SO THE DENSE FOG ADVISORY MAY NEED TO BE
EXTENDED. WIND SPEEDS LOOK TO REMAIN ON THE LIGHER SIDE FROM
WEDNESDAY THROUGH THE WEEKEND WITH A FAIRLY BAGGY PRESSURE GRADIENT
DEVELOPING AND THE DIRECTION WILL LIKELY VARY FROM WEST TO NORTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FLASH FLOOD WATCH...ILZ003-ILZ004-ILZ008-ILZ010-ILZ011-ILZ019
     UNTIL 7 AM TUESDAY.

IN...NONE.
LM...DENSE FOG ADVISORY...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565
     UNTIL 10 AM TUESDAY.

&&

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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WWW.YOUTUBE.COM/NWSCHICAGO

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
436 PM CDT MON JUN 24 2013

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
252145-
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-
436 PM CDT MON JUN 24 2013 /536 PM EDT MON JUN 24 2013/

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

.DAY ONE...TONIGHT.

  WEATHER HAZARDS EXPECTED:

   THUNDERSTORMS...THE STRONGEST MAY PRODUCE:
    DAMAGING WINDS...POTENTIALLY IN EXCESS OF 80 MPH.
    FREQUENT CLOUD TO GROUND LIGHTNING.
    HEAVY RAIN AND FLASH FLOODING.
    SMALL POSSIBLY OF AN ISOLATED TORNADO.
    HAIL TO THE SIZE OF DIMES.

  AREAS AFFECTED AND TIMING:

   A LINE OF SEVERE THUNDERSTORMS WILL MOVE ACROSS NORTHERN
   ILLINOIS THIS EVENING.

  DISCUSSION:

   AN UPPER LEVEL DISTURBANCE HAS INTERACTED WITH A MOIST AND
   UNSTABLE ENVIRONMENT TO RESULT IN A LINE OF SEVERE
   THUNDERSTORMS ACROSS WESTERN ILLINOIS. THIS LINE OF STORMS WILL
   CONTINUE EASTWARD AT 50 TO 60 MPH THIS EVENING. THE MAIN THREAT
   FROM THESE STORMS WILL BE STRONG DAMAGING WINDS IN EXCESS OF 80
   MPH. A BRIEF PERIOD OF HEAVY RAINFALL WILL ALSO ACCOMPANY THE
   LINE OF STORMS. HOWEVER...DUE TO THE FAST MOVEMENT...THE
   RAINFALL AMOUNTS SHOULD REMAIN UNDER AN INCH IN MOST AREAS. IN
   SPITE OF THIS...FLASH FLOODING DOES REMAIN A
   CONCERN...ESPECIALLY ACROSS AREAS THAT HAVE RECEIVED HEAVY
   RAINFALL IN THE PAST 24 TO 48 HOURS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

THERE WILL BE PERIODIC CHANCES FOR THUNDERSTORMS TUESDAY THROUGH
FRIDAY. SOME OF THESE STORMS COULD BE SEVERE TUESDAY THROUGH
WEDNESDAY.

THERE IS ALSO A CONTINUED THREAT OF VERY HEAVY RAINFALL ACROSS
NORTHERN ILLINOIS AND NORTHWESTERN INDIANA...PARTICULARLY TUESDAY
NIGHT AND INTO WEDNESDAY. THIS HEAVY RAINFALL COULD RESULT IN
FLASH FLOODING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS REQUESTED THROUGH EARLY THIS EVENING.

&&

LMZ740>745-252145-
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-
436 PM CDT MON JUN 24 2013

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

.DAY ONE...TONIGHT.

THUNDERSTORMS ARE EXPECTED. THESE STORMS MAY PRODUCE GUSTY WINDS
IN EXCESS OF 60 KT THIS EVENING.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

THERE WILL BE PERIODIC CHANCES FOR THUNDERSTORMS TUESDAY THROUGH
FRIDAY.

&&

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-252145-
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-
436 PM CDT MON JUN 24 2013

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

.DAY ONE...TONIGHT.

THUNDERSTORMS ARE EXPECTED...MAINLY ACROSS THE SOUTH HALF OF THE
LAKE. THESE STORMS COULD PRODUCE WINDS IN EXCESS OF 60 KT ACROSS
THE SOUTH HALF OF THE LAKE.

AREAS OF DENSE FOG ARE LIKELY MAINLY OVER THE NORTH HALF OF THE
LAKE THROUGH TONIGHT.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

DENSE FOG IS POSSIBLE...MAINLY OVER THE NORTH HALF OF THE LAKE
TUESDAY.

THERE WILL BE PERIODIC CHANCES FOR THUNDERSTORMS MONDAY THROUGH
FRIDAY.

&&

KJB

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO

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