Severe Thunderstorm Warning 39, NWS Chicago, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
706 AM CDT FRI JUN 19 2009

.DISCUSSION...
324 AM CDT

ONGOING CONVECTION OCCURRING AS NOSE OF LOW LEVEL JET RIDES OVER
WARM FRONT WHICH WAS FROM DBQ TO MDW AS OF 08Z. EXTREMELY MOIST
AND UNSTABLE AIRMASS SOUTH OF THE WARM FRONT WITH DEW POINTS IN
THE MID 70S AND CAPES OVER 4000 EVEN AT THIS HOUR. AREA IS FAIRLY
WELL CAPPED SOUTH OF WARM FRONT. THUS MAIN FOCUS FOR THIS MORNING
WILL BE FAR NE IL INTO NW IN. EXPECT CONVECTION TO MOVE OFF AND
WEAKEN DIURNALLY THIS MORNING. THINNING CLOUDS SHOULD ALLOW GOOD
HEATING THIS AFTERNOON AS SHORT WAVE APPROACHES FROM THE PLAINS.
DEPENDING ON CLOUD COVER FROM THIS MORNINGS MCS...COULD SEE
TEMPERATURES IN THE LOWER 90S SOUTH OF WARM FRONT...WITH THE
EXCEPTION BEING NEAR THE WI STATE LINE WHERE RAIN HAS BEEN
FALLING AND MORE RECOVERY WILL BE NEEDED.

EXPECT STRONG TO SEVERE STORMS AGAIN THIS AFTERNOON INTO THIS
EVENING. SHORT WAVE TO MOVE OUT OF THE PLAINS INTO NORTHERN IL BY
EVENING. DEW POINTS WILL CONTINUE TO POOL IN MID 70S ALONG WARM
FRONT AND CAPE VALUES COULD EXCEED 4000-5000 J/KG AGAIN. 0-6KM BULK
SHEAR WILL ALSO BE SUFFICIENT FOR ORGANIZED SEVERE STORMS. WITH
PRECIPITABLE WATER VALUES OF AROUND 2 INCHES...FLASH FLOODING WILL
ALSO BE A CONCERN.

SHOULD SEE SUBSIDENCE IN WAKE OF SHORT WAVE AND CLEARING BY
SATURDAY MORNING. MODELS THEN BRING WARM FRONT BACK NORTH
SATURDAY NIGHT AND SUNDAY UNDER BUILDING UPPER RIDGE. GFS SEEMS
THE MOST AGGRESSIVE IN BRINGING CONVECTION INTO THE AREA. ECMWF KEEPS
LOW LEVEL JET MORE FOCUSED FROM KS TO IA INTO MN WITH 850 RIDGE
ACROSS IL. WILL INTRODUCE SLIGHT CHANCE POPS BUT NOT MUCH
CONFIDENCE IN CONVECTION SPREADING THIS FAR EAST.

SHARP RIDGE BUILDS MONDAY AND TUESDAY. THIS SHOULD SUFFICIENTLY
CAP THINGS AND THUS HAVE REMOVED SLIGHT CHANCE POPS. NAM AND ECMWF
BRING 850 TEMPERATURES UP TO 20-22C...ALTHOUGH GFS NOT QUITE AS
WARM. COULD SEE SUMMER LIKE TEMPERATURES AROUND 90 INTO MID WEEK. MEDIUM
RANGE MODELS BRING SHORT WAVE ACROSS SOUTHERN CANADA AND FAR
NORTHERN US WED OR THU NEXT WEEK. THIS MAY PUSH A SURFACE FRONT
DOWN TOWARDS NORTHERN IL AND BRING THE NEXT CHANCE OF
THUNDERSTORMS. BUT WILL NOT MAKE ANY CHANGES TO EXTENDED AT THIS
TIME.

ALLSOPP

&&

.AVIATION...

1200 UTC TAFS...MAIN CONCERN FOR THE TERMINALS IS THUNDERSTORM
DEVELOPMENT THROUGHOUT THE FORECAST PERIOD.

WAVE OF THUNDERSTORMS THAT MOVED ACROSS THE TERMINALS LATE LAST
NIGHT AND EARLY THIS MORNING HAVE SINCE DISSIPATED. THE MAIN
WAVE OF STORMS THAT MOVED INTO THE AREA PRODUCED AN OUTFLOW
BOUNDARY WHICH CURRENTLY STRETCHES ACROSS PORTIONS OF NORTH
CENTRAL ILLINOIS. THIS BOUNDARY MAY SERVE AS AN AREA OF FOCUS FOR
CONTINUED SHOWER DEVELOP THIS MORNING. WITH A FAIR AMOUNT OF
INSTABILITY PRESENT THIS MORNING...IT WOULD NOT BE OUT OF THE
QUESTION FOR SOME SCATTERED THUNDER TO ACCOMPANY SOME OF THE
SHOWERS...BUT NOTHING PREVAILING. CEILINGS HAVE BEEN SHOWING
UPWARD TRENDS OVER THE PAST HOUR...BUT THERE STILL REMAINS SOME
SCATTERED IFR CEILINGS WITH SOME OF THE HEAVIER SHOWERS. THESE
CEILINGS WILL CONTINUE TO IMPROVE TO VFR CEILINGS AS RAIN EXITS
AND WINDS SHIFT TO MORE OF A SOUTHERLY DIRECTION.

WITH MUCH OF THE AREA REMAINING IN A WARM AND MOIST AIR MASS...AND
THE ATMOSPHERE ONCE AGAIN BECOMING CONVECTIVELY
UNSTABLE...A REDEVELOPMENT OF THUNDERSTORMS WILL OCCUR BY EARLY
AFTERNOON. THESE SHOULD REMAIN MORE SCATTERED THROUGH THE
AFTERNOON. THUNDERSTORMS SHOULD BECOME MORE WIDESPREAD LATER THIS
EVENING AS AN AREA OF LOW PRESSURE...ASSOCIATED WITH A MID LEVEL
WAVE...MOVES THROUGH THE REGION AND DRAGS A COLD FRONT ACROSS THE
AREA. ONCE THIS MOVES THROUGH...SHOWERS AND THUNDERSTORMS SHOULD
QUICKLY COME TO AN END TONIGHT...WITH CLOUD COVER ALSO SCATTERING
OUT.

THE OUTFLOW BOUNDARY LEFT BEHIND FROM THE CLUSTER OF STORMS HAVE
HELPED KEEP WINDS MORE OUT OF THE EAST THIS MORNING. THINKING IS
THAT WINDS WILL CONTINUE TO VEER TO THE SOUTH AND EVENTUALLY
SOUTHWEST THROUGH THE DAY AS OVERALL SYNOPTIC FLOW TAKES OVER.
WINDS HAVE ALREADY BEGIN TO INCREASE THIS MORNING AND WILL CONTINUE
TO INCREASE WITH DECENT PRESSURE GRADIENT ACROSS THE REGION AND
DAYTIME MIXING.

RODRIGUEZ

&&

.MARINE...
212 AM CDT

MAIN THREAT OVER THE LAKE OVER THE NEXT FEW DAYS REMAINS THE
CHANCES FOR THUNDERSTORMS WITH STRONG WIND. LINE OF STORMS THIS
MORNING WILL CONTINUE TO ADVANCE SOUTH ALONG THE LAKE AND THEN
CLEAR OUT LATER IN THE MORNING. ANOTHER ROUND OF STRONG
THUNDERSTORMS ARE ANTICIPATED TO DEVELOP FRIDAY AFTERNOON AND ROLL
ACROSS THE LAKE. AN AREA OF LOW PRESSURE WILL MOVE ACROSS THE LAKE
FRIDAY INTO FRIDAY NIGHT AND DROP A COLD FRONT DOWN THE LAKE. HIGH
PRESSURE IS THEN EXPECTED TO SET UP ACROSS THE LAKE THROUGH THE
REST OF THE WEEKEND INTO EARLY NEXT WEEK KEEPING WINDS AND WAVES
DOWN.

HALBACH

&&

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
407 AM CDT FRI JUN 19 2009

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
200915-
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-
407 AM CDT FRI JUN 19 2009 /507 AM EDT FRI JUN 19 2009/

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

.DAY ONE...TODAY AND TONIGHT.

  WEATHER HAZARDS EXPECTED:

  THUNDERSTORMS...WHICH MAY PRODUCE:
  DAMAGING WINDS IN EXCESS OF 60 MPH.
  HEAVY RAIN WHICH COULD CAUSE FLASH FLOODING.
  LIGHTNING.
  HAIL TO 1 1/2 INCHES IN DIAMETER IS ALSO POSSIBLE.

  AREAS AFFECTED AND TIMING:

  NORTHERN ILLINOIS AND NORTHWEST INDIANA EARLY THIS MORNING AND
  AGAIN FROM MID AFTERNOON THROUGH THIS EVENING.

  DISCUSSION:

  STRONG STORMS WITH HEAVY RAINFALL EARLY THIS MORNING WILL BE
  DIMINISHING AND MOVING EAST OF THE AREA BY MID MORNING. BY MID
  AFTERNOON THE ATMOSPHERE WILL BECOME VERY WARM...MOIST AND
  UNSTABLE AHEAD OF AN APPROACHING COLD FRONT. MID AND UPPER LEVEL
  WINDS WILL BE SUFFICIENT TO PRODUCE ORGANIZED SEVERE STORMS. THE
  MAIN THREATS WILL BE HEAVY RAINFALL AND DAMAGING WINDS. WARM
  AIR ALOFT WILL LIMIT THE HAIL THREAT EXCEPT IN THE STRONGEST
  STORMS. WITH THE WARM FRONT LIFTING WELL NORTH OF ILLINOIS...THERE
  WILL NOT LIKELY BE SUFFICIENT LOW LEVEL WIND SHEAR TO SUPPORT
  SIGNIFICANT TORNADOES...HOWEVER AN ISOLATED TORNADO MAY BE
  POSSIBLE.

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

THERE IS A SLIGHT CHANCE OF A THUNDERSTORM LATE SATURDAY NIGHT OR
SUNDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS WILL LIKELY BE NEEDED...MAINLY LATE THIS AFTERNOON AND THIS
EVENING.

&&

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

LMZ740>745-200915-
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-
407 AM CDT FRI JUN 19 2009

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

.DAY ONE...TODAY AND TONIGHT.

THUNDERSTORMS ARE LIKELY...MAINLY FROM MID AFTERNOON THROUGH
EVENING. SOME STORMS MAY PRODUCE WIND GUSTS OVER 34 KNOTS...LARGE
HAIL...AND DANGEROUS LIGHTNING.

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

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

&&

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-
870-872-874-876-878-200915-
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 TOW 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-
407 AM CDT FRI JUN 19 2009

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

.DAY ONE...TODAY AND TONIGHT.

THUNDERSTORMS ARE LIKELY...MAINLY FROM MID AFTERNOON THROUGH
EVENING OVER THE SOUTH HALF OF THE LAKE. SOME STORMS MAY PRODUCE WIND
GUSTS OVER 34 KNOTS...LARGE HAIL...AND DANGEROUS LIGHTNING.

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

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

&&

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

ALLSOPP

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
807 AM CDT FRI JUN 19 2009

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

0802 AM     HAIL             ROCKFORD                42.27N 89.06W
06/19/2009  M1.00 INCH       WINNEBAGO          IL   TRAINED SPOTTER

            100 S. GARDINER AVE. IN CENTRAL ROCKFORD.

&&

CM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
808 AM CDT FRI JUN 19 2009

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

0807 AM     HAIL             ROCKFORD                42.27N 89.06W
06/19/2009  M1.50 INCH       WINNEBAGO          IL   TRAINED SPOTTER

            100 S. GARDINER AVE. IN CENTRAL ROCKFORD.

&&

NMARSILI

PRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
813 AM CDT FRI JUN 19 2009

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

0807 AM     HAIL             ROCKFORD                42.27N 89.06W
06/19/2009  M1.50 INCH       WINNEBAGO          IL   TRAINED SPOTTER

            EAST SIDE OF ROCKFORD ABOUT 7 MILES NORTH NORTHEAST OF
            ROCKFORD AIRPORT.

&&

NMARSILI

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
829 AM CDT FRI JUN 19 2009

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

0826 AM     HAIL             BELVIDERE               42.25N 88.85W
06/19/2009  M1.75 INCH       BOONE              IL   TRAINED SPOTTER

            FIFTH AVENUE AND SIXTH STREET.

&&

NMARSILI