Severe Thunderstorm Warning 37, NWS Chicago, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
533 PM CDT FRI MAY 31 2013

.DISCUSSION...
336 PM CDT

THOUGHTS FROM THE EARLIER MESO DISCUSSION ARE STILL VALID AND HAVE
BEEN BOLSTERED BY THE SPREAD OF SHOWERS WITH ISOLATED TSRA INTO THE
FCST AREA THIS AFTERNOON WITH LITTLE ADDITIONAL DEVELOPMENT DIRECTLY
WEST OVER IOWA SO FAR.  0-6 KM BULK SHEAR CONTINUES TO BE MARGINAL
OVER MOST OF THE LOCAL REGION BUT IS BUILDING TOWARD 40 KTS IN THE
AREA OF APPROACHING CONVECTION TO OUR SOUTHWEST UNDER THE LEADING
EDGE OF AN UPPER LEVEL JET.  A FEW STORMS COULD BECOME ORGANIZED IN
SOUTHERN PORTIONS OF THE CWA...THOUGH THE SEVERE RISK OVERALL
APPEARS TO BE MARGINAL.  TRENDS FOR THIS EVENING AND OVERNIGHT
ALSO WOULD CONTINUE TO FAVOR SOUTHERN PORTIONS OF THE CWA FOR THE
HEAVIEST RAINFALL AMOUNTS AND THE CORRESPONDING FLOOD RISK...AND
THIS ALSO IS WHERE THE MOST RAIN HAS FALLEN OVER THE PAST WEEK.  FOR
THESE REASONS...AFTER COORDINATION WITH NEIGHBORS...WILL PLAN TO
DROP THE FLOOD WATCH FOR NORTHERN PORTIONS OF THE FORECAST AREA.

ALL OF THIS ACTIVITY IS BEING DRIVEN BY RICH BOUNDARY LAYER GULF
MOISTURE WRAPPING AROUND THE WESTERN SIDE OF A BERMUDA HIGH...AND
AHEAD OF AN APPROACHING FRONTAL ZONE TIED TO LOW PRESSURE OVER THE
DAKOTAS.  THIS FRONTAL ZONE PUSHES THROUGH THE AREA SATURDAY NIGHT
AND USHERS IN COOLER AND DRIER AIR FOR THE FIRST HALF OF NEXT WEEK.
UNSETTLED WEATHER WILL PERSIST UNTIL THAT TIME WITH THE FOCUS
GRADUALLY SHIFTING EASTWARD.  SHOWER AND THUNDERSTORM FORECAST
TRENDS FOR THIS EVENING AND OVERNIGHT ARE BASED ON CURRENT ACTIVITY
AND THE IDEA OF INCREASING DEVELOPMENT SUPPORTED BY LOW LEVEL
MOISTURE CONVERGENCE BEING DEPICTED IN THE RAP MODEL.  IF THESE RAP
FIELDS CONTINUE TO BE VALID TOWARD MORNING...THE NORTHWEST HALF OF
THE AREA WOULD APPEAR TO DRY OUT BY MIDNIGHT AND REMAIN SO INTO THE
MORNING HOURS.  THIS TREND ALSO IS SUPPORTED BY THE LATEST
NAM/ECMWF/GFS QPF FIELDS.  CHANCES THEN INCREASE AGAIN DURING THE
DAY TOMORROW AHEAD OF THE APPROACHING UPPER LEVEL VORT MAX AND THE
SURFACE FRONTAL ZONE.

AFTER A COOLER AND DRIER END TO THE WEEKEND AND START TO THE WORK
WEEK...THE NEXT UPPER TROUGH AND SFC LOW BEGIN TO APPROACH THE
AREA TOWARD THE MIDDLE OF NEXT WEEK ALONG THE SIMILAR DAKOTAS TRACK
THAT WE HAVE SEEN WITH THE CURRENT SYSTEM.  SFC WINDS TURNING
SOUTHEAST BY WEDNESDAY AND SOUTH BY THURSDAY WOULD ALLOW WARM MOIST
GULF AIR TO START WORKING BACK INTO THE AREA FOR LATE NEXT
WEEK...BUT AT THIS RANGE WILL ONLY PLAN TO CARRY CHANCE POPS.

LENNING

&&

.AVIATION...

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

* WINDS MAY BACK TO SE FOR TIME EARLY THIS EVENING

* CHANCE OF MVFR CIGS DEVELOPING THIS EVENING

* CHANCE OF SHRA/TSRA AGAIN SAT AFTERNOON

IZZI

//DISCUSSION...UPDATED 22Z...

HAVE REMOVED PRECIP FOR TONIGHT WITH AXIS OF MOST ORGANIZED
PRECIPITATION LIKELY TO REMAIN WELL SOUTH OF THE CHGO TERMINALS.
AM CLOSELY WATCHING AREA OF DEVELOPING LOWER END MVFR CIGS OVER
WC IL...IF THIS AREA CONTINUES TO EXPAND MAY NEED TO INTRODUCE
SOME MVFR CIGS LATER THIS EVENING INTO THE OVERNIGHT HOURS.

IZZI

UPDATED 18Z...

THE ACTIVE PERIOD CONTINUES BUT THERE IS VERY HIGH UNCERTAINTY
REGARDING WHERE AND WHEN CONVECTION WILL OCCUR TODAY.  TEMPS HAVE
CLIMBED INTO THE 70S WITH DEWPOINTS IN THE 60S WHICH SUGGESTS
FAVORABLE CONDITIONS.  A LOW PRESSURE SYSTEM IS OVER SOUTH DAKOTA
AND A LEFT OVER CONVECTIVE SYSTEM IS OVER NE MO/SE IA/W IL.  SHOWERS
ARE SLOWLY MOVING NORTHEAST WITH A FEW CONVECTIVE CELLS FORMING OVER
FORD COUNTY IL IN THE LAST FEW MINUTES.  EXPECTING THUNDERSTORMS TO
DEVELOP ACROSS NORTH CENTRAL IL AND PUSH EAST THROUGH THE EASTERN
TERMINALS.  SINCE THE AXIS OF BEST INSTABILITY IS EAST OF RFD...KEPT
TS OUT OF RFD.  THAT BEING SAID RFD MAY SEE A FEW STRAY SHOWERS OVER
THE NEXT FEW HOURS. GUSTY S WINDS ARE EXPECTED BUT MAY SEE A BRIEF
SHIFT TO SSE WINDS BEHIND THE THUNDERSTORMS.

EXPECTING A NARROW WINDOW OF TSRA OF ABOUT AN HOUR...FOLLOWED BY
SHOWERS.  THE AREA WILL REMAIN UNSTABLE OVERNIGHT WITH SCATTERED
SHOWERS EXPECTED OVERNIGHT. ANOTHER ROUND OF TSRA AND SHOWERS IS
EXPECTED LATE SATURDAY AFTERNOON/EARLY AS THE LOW PRESSURE SYSTEM
PASSES TO THE NORTH AND ITS COLD FRONT APPROACHES FROM THE WEST.
STRONG S WINDS ARE ONCE AGAIN EXPECTED TOMORROW...BUT GUSTS WILL NOT
BE AS STRONG.

JEE

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

* MEDIUM CONFIDENCE IN WINDS THIS EVENING

* LOW/MEDIUM CONFIDENCE IN CIGS TONIGHT

* LOW CONFIDENCE IN TSRA CHANCES SATURDAY

IZZI

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

SATURDAY NIGHT...CHC OF SHRA DURING THE EVE. MVFR POSSIBLE.
SUNDAY...SLT CHC OF MORNING SHRA.
MONDAY...VFR LIKELY.
TUESDAY...CHC OF MORNING MVFR.
WEDNESDAY & THURSDAY...CHC OF TSRA.

MTF

&&

.MARINE...
222 PM CDT

AN AREA OF LOW PRESSURE THAT HAS PERSISTED OVER THE NORTHERN PLAINS
WILL FINALLY BEGIN TO MOVE EAST TONIGHT...PASSING OVER NORTHERN LAKE
MICHIGAN LATE SATURDAY EVENING WITH A TRAILING COLD FRONT TURNING
MODERATE SOUTHERLY WINDS OF 15 TO 25 KT TO NORTHWESTERLY. MOIST FLOW
AHEAD OF THE FRONT HAS ALREADY LED TO DENSE FOG OVER MUCH OF THE
LAKE WHICH IS EXPECTED TO PERSIST UNTIL THE COLD FRONT PASSES
SATURDAY NIGHT. WINDS SHOULD THEN DIMINISH THROUGH THE DAY SUNDAY AS
HIGH PRESSURE BUILDS IN FROM THE WEST...BECOMING CENTERED OVER LAKE
MICHIGAN ON MONDAY. LOW PRESSURE WILL DEVELOP OVER THE CENTRAL
PLAINS MONDAY...THEN LIFT NORTHEAST TO LAKE MICHIGAN LATE THURSDAY
INTO EARLY FRIDAY.
BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FLASH FLOOD WATCH...ILZ021-ILZ022-ILZ023-ILZ032-ILZ033-ILZ039
     UNTIL 7 PM SATURDAY.

IN...FLASH FLOOD WATCH...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL 7
     PM SATURDAY.

LM...DENSE FOG ADVISORY...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
     LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ868-LMZ870-
     LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 9 PM SATURDAY.

     SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 10 PM FRIDAY.

&&

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
441 PM CDT FRI MAY 31 2013

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
012145-
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-
441 PM CDT FRI MAY 31 2013 /541 PM EDT FRI MAY 31 2013/

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

.DAY ONE...TONIGHT.

  WEATHER HAZARDS EXPECTED:

  THUNDERSTORMS...SOME MAY PRODUCE:

  DAMAGING WIND GUSTS IN EXCESS OF 60 MPH.
  HEAVY RAIN WHICH MAY CAUSE FLASH FLOODING.
  QUARTER SIZE HAIL.
  FREQUENT CLOUD TO GROUND LIGHTNING

  AREAS AFFECTED AND TIMING:

  THUNDERSTORMS ARE EXPECTED TO CONTINUE ACROSS CENTRAL
  ILLINOIS AND SHOULD OVERSPREAD EAST CENTRAL ILLINOIS AND
  NORTHWESTERN INDIANA DURING THE EVENING.

  DISCUSSION:

  SHOWERS AND THUNDERSTORMS ARE EXPECTED TO PERSIST TONIGHT ACROSS
  CENTRAL MISSOURI THROUGH ILLINOIS INTO NORTHWEST INDIANA. SOME
  OF THESE STORMS WILL HAVE THE POTENTIAL TO PRODUCE VERY HEAVY
  RAINFALL OF 1 TO 2 INCHES PER HOUR...WHICH WOULD RESULT IN FLASH
  FLOODING. THE ANTICIPATED CORRIDOR OF HEAVY RAIN HAS SHIFTED
  FARTHER SOUTH THAN PREVIOUSLY THOUGHT...AND NOW WILL BE MAINLY
  SOUTH OF INTERSTATE 80 ACROSS PORTIONS OF CENTRAL ILLINOIS AND
  NORTHWESTERN INDIANA. SOME OF THESE THUNDERSTORMS ALSO COULD
  BECOME SEVERE...WITH LARGE HAIL AND DAMAGING WIND GUSTS BEING
  THE MAIN THREAT.

PORTIONS OF THE ILLINOIS AND VERMILION RIVERS WILL REMAIN IN
FLOOD.

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

ANOTHER ROUND OF THUNDERSTORMS IS EXPECTED SATURDAY AFTERNOON
INTO SATURDAY EVENING...MAINLY ALONG AND EAST OF THE INTERSTATE
55 CORRIDOR. THESE STORMS MAY BECOME SEVERE WITH DAMAGING WINDS
THE MAIN THREAT. HEAVY RAIN AND FLASH FLOODING WILL ALSO BE
POSSIBLE.

THERE IS A CHANCE OF THUNDERSTORMS TUESDAY AFTERNOON THROUGH
THURSDAY.

PORTIONS OF THE ILLINOIS AND VERMILION RIVERS WILL REMAIN IN
FLOOD. RISES ON OTHER AREA RIVERS ARE POSSIBLE AS WELL.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED EARLY THIS EVENING...ESPECIALLY
SOUTH OF INTERSTATE 80.

&&

LMZ740>745-012145-
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-
441 PM CDT FRI MAY 31 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.

THERE IS A CHANCE OF THUNDERSTORMS TONIGHT.

STRONG WINDS WILL CREATE HAZARDOUS CONDITIONS FOR SMALL CRAFT IN
THE INDIANA NEARSHORE WATERS THROUGH THIS EVENING.

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

THERE IS A CHANCE OF THUNDERSTORMS SATURDAY AFTERNOON AND
EVENING. THESE STORMS MAY PRODUCE WIND GUSTS 35 KNOTS OR HIGHER
AS WELL AS LARGE HAIL.

THERE IS A CHANCE OF THUNDERSTORMS TUESDAY NIGHT THROUGH
THURSDAY.

&&

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-012145-
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-
441 PM CDT FRI MAY 31 2013

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

.DAY ONE...TONIGHT.

THERE IS A CHANCE OF THUNDERSTORMS TONIGHT.

AREAS OF DENSE FOG ARE EXPECTED ACROSS MOST OF THE LAKE TODAY
AND TONIGHT.

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

THERE IS A CHANCE OF THUNDERSTORMS SATURDAY AFTERNOON AND
EVENING. THESE STORMS MAY PRODUCE WIND GUSTS 35 KNOTS OR HIGHER
AS WELL AS LARGE HAIL.

AREAS OF DENSE FOG ARE EXPECTED TO PERSIST INTO SUNDAY.

THERE IS A CHANCE OF THUNDERSTORMS TUESDAY NIGHT THROUGH
THURSDAY.

&&

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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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
535 PM CDT FRI MAY 31 2013

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

0532 PM     TSTM WND GST     CHATSWORTH              40.75N 88.29W
05/31/2013  E40 MPH          LIVINGSTON         IL   TRAINED SPOTTER

            WINDS 35 TO 40 MPH.

&&

C

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
548 PM CDT FRI MAY 31 2013

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

0529 PM     TSTM WND DMG     CHATSWORTH              40.75N 88.29W
05/31/2013                   LIVINGSTON         IL   LAW ENFORCEMENT

            NUMEROUS TREES BEING REPORTED DOWN. A SEMI WAS REPORTED
            FLIPPED OVER.

&&

BEACHLER