Tornadoes and Flash Flood in Illinois, May 22, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
209 PM CDT SUN MAY 22 2011

.MESOSCALE DISCUSSION...
205 PM CDT

AS THE ATMOSPHERE CONTINUES TO QUICKLY DESTABILIZE EARLY THIS
AFTERNOON...THUNDERSTORMS CAN BE SEEN DEVELOPING ALONG A REMNANT
BOUNDARY/GRAVITY WAVE PROPAGATING EAST ACROSS PORTIONS OF CENTRAL
ILLINOIS. WITH CU RAPIDLY DEVELOPING AND LATEST GUIDANCE INDICATING
THAT THE ATMOSPHERE HAS BECOME MODERATELY TO STRONGLY UNSTABLE
ACROSS CENTRAL ILLINOIS...ITS QUITE POSSIBLE THAT THERE COULD BE
UPSCALE THUNDERSTORM GROWTH INTO THE SOUTHERN PORTIONS OF THE
CWA...WHICH WOULD INCLUDE AREAS SOUTH OF INTERSTATE 80. THIS IS
OUT AHEAD OF MAIN THUNDERSTORM DEVELOPMENT STILL ONGOING ACROSS
FAR WESTERN ILLINOIS AND EASTERN IOWA. STILL MONITORING THE
OVERALL SEVERE THREAT EARLY THIS AFTERNOON ACROSS THIS AREA...AS
THEIR IS ALMOST A RACE BETWEEN THIS GRAVITY WAVE PUSHING EAST AND
DESTABILIZATION OF THE ATMOSPHERE. EITHER WAY...THUNDERSTORMS TO
PUSH EAST EARLY THIS AFTERNOON ALONG AND SOUTH OF INTERSTATE 80
WITH DAMAGING WINDS AND HAIL THE MAIN THREATS...WITH THE TORNADO
THREAT ISOLATED AT THIS TIME AS FLOW REMAINS WEAKER AND MORE
UNIDIRECTIONAL...WITH HIGH DEWPOINT DEPRESSIONS IN PLACE.

STILL ANTICIPATE THUNDERSTORM DEVELOPMENT OFF TO THE WEST TO
CONTINUE TODAY WITH BETTER CHANCES FOR WIDESPREAD COVERAGE INTO
LATE AFTERNOON AND EVENING. TORNADO THREAT COULD STILL POSSIBLY
INCREASE THIS AFTERNOON INTO THE EVENING AS LOW LEVEL MOISTURE
INCREASES AND LLJ RAMPS UP.

RODRIGUEZ

PREVIOUS MESOSCALE DISCUSSION
1230 PM CDT

JUST LOOKING OUTSIDE RIGHT NOW...ONE WOULD NOT THINK OF ANY STORMS
CURRENTLY...BUT AS WE SPEAK THE ENVIRONMENT IS GEARING ITSELF UP
FOR THE POTENTIAL FOR WIDESPREAD THUNDERSTORMS ACROSS MUCH OF THE
REGION THIS AFTERNOON INTO THE EVENING.

MAIN THUNDERSTORMS TODAY WILL BE TIED TO AN UPPER LEVEL LOW
SPINNING ACROSS THE CENTRAL PLAINS WITH AN ATTENDANT SURFACE LOW
SITUATED OVER IOWA/MINNESOTA...AND COLD FRONT EXTENDING SOUTHWEST
FROM THIS LOW THROUGH PORTIONS OF IOWA SOUTHWEST BACK INTO KANSAS.
STRONG SOUTHWEST FLOW OUT AHEAD OF THIS SYSTEM IS USHERING A VERY
WARM AND MOIST AIRMASS BACK NORTH ACROSS THE REGION. A QUASI WARM
FRONT...PARTIALLY DUE IN PART TO THE PREVIOUS NIGHTS CONVECTION IS
CURRENTLY SITUATED ACROSS PORTIONS OF IOWA INTO ILLINOIS WHERE
DEWPOINTS ARE STAYING IN THE MID 50S TO THE NORTH...AND MID AND
UPPER 60S SOUTH OF THIS BOUNDARY. STRENGTHENING LOW LEVEL FLOW
TODAY WILL CONTINUE TO ADVECT THIS WARMER MORE MOIST AND UNSTABLE
ENVIRONMENT NORTH INTO THE AREA THROUGH THE EARLY AFTERNOON.

CURRENTLY AM MONITORING A MID LEVEL SPEED MAX OF 60-70KT/SHORT
WAVE TROUGH ROUNDING THE BASE OF THIS UPPER LEVEL LOW OFF TO THE
WEST. AS THIS INTERACTS WITH DECENT SURFACE CONVERGENCE ALONG
VARYING BOUNDARIES...THUNDERSTORM DEVELOPMENT WILL BE ON THE
INCREASE. GOING INTO THE AFTERNOON...CURRENT CAP IN PLACE ACROSS
NORTHERN ILLINOIS AND NORTHWEST INDIANA WILL ERODE VIA AN
ABUNDANCE OF SUNSHINE...AS LATEST VISIBLE IMAGERY IS SHOWING MAIN
CLOUD SHIELD REMAINING OFF TO THE WEST ACROSS EASTERN IOWA.
ALTHOUGH SATELLITE IS SHOWING SOME CU TRYING TO DEVELOP ACROSS
WESTERN ILLINOIS...DONT ANTICIPATE LARGE SCALE GROWTH TO OCCUR
UNTIL EARLY TO MID AFTERNOON ACROSS THE WESTERN CWA...AS LATEST
SHORT RANGE GUIDANCE IS INDICATING THAT THIS CAP WILL BREAK.

MAIN INSTABILITY AXIS CURRENTLY REMAINS OFF TO THE WEST FROM
CENTRAL IOWA SOUTH INTO MISSOURI. EXPECT THIS AXIS TO SHIFT EAST
THROUGH THE AFTERNOON WITH MLCAPE VALUES OF 2000-3000 J/KG
EXPECTED. AS THIS SPEED MAX/TROUGH TRANSLATES EAST/NORTHEAST...IT
WILL HELP TO PROVIDE 0-6KM BULK SHEAR VALUES OF 40-50KT...WHICH
WILL BE EFFICIENT FOR SUPERCELL DEVELOPMENT. EXPECT THIS DISCRETE
DEVELOPMENT TO OCCUR EARLY ON THIS AFTERNOON BEFORE THESE CELLS
CONGEAL INTO LINE SEGMENTS LATER THIS AFTERNOON/EVENING. WITH THIS
IN MIND...EXPECT THE GREATEST TORNADO THREAT TO BE EARLY ON ACROSS
WEST/NORTHWEST ILLINOIS WHERE THE BEST SHEAR WILL BE HAD AS WELL
AS BETTER BACKED SURFACE FLOW WILL RESIDE. ALTHOUGH...THERE STILL
REMAINS THE THREAT FOR ISOLATED TORNADOES ACROSS THE REMAINDER OF
NORTHEAST ILLINOIS WHERE INCREASED SHEAR/LOW LEVEL HELICITY COULD
BE REALIZED ALONG LIFTING FRONTAL BOUNDARY. ALTHOUGH EXPECT THIS
TO BE MORE ISOLATED WITH A LESSER CHANCE AS BETTER FORCING WILL
REMAIN FURTHER TO THE WEST.

THEN EXPECT LINE SEGMENTS TO DOMINATE BY LATE THIS
AFTERNOON/EVENING AS THIS SYSTEM AND BETTER FORCING SHIFT EAST.
LATEST GUIDANCE IS TAKING THE AFOREMENTIONED MID LEVEL SPEED MAX
MORE NORTHEAST WITH TIME...AND KEEPING OVERALL BETTER BULK SHEAR
VALUES TO THE WEST. ALTHOUGH...EXPECT THESE THUNDERSTORMS TO BREAK
AWAY AND SPREAD EAST AS A MODERATELY UNSTABLE AIR MASS WILL STILL
BE IN PLACE. ALSO...STRENGTHENING LOW LEVEL FLOW WILL INCREASE
0-3KM BULK SHEAR VALUES TO VALUES MORE THAN EFFICIENT TO HELP
SUSTAIN THUNDERSTORM DEVELOPMENT TO THE EAST. ITS DURING LATE
AFTERNOON/EARLY EVENING THAT THIS LINE WILL RAPIDLY PUSH EAST
REACHING NORTHEAST ILLINOIS AND NORTHWEST INDIANA. ALTHOUGH THERE
WILL STILL BE A CHANCE FOR TORNADOES...THE GREATER THREATS WILL BE
DAMAGING WINDS AND HAIL INTO THE LATTER PART OF THE EVENING.

RODRIGUEZ

&&

.DISCUSSION...
438 AM CDT

SHORT TERM CONCERNS ARE HOW QUICKLY THREAT OF THUNDERSTORMS
SPREADS FROM CENTRAL ACROSS THE LOCAL FORECAST AREA TODAY...AND
THE POTENTIAL FOR SEVERE THUNDERSTORMS LATER TODAY.

AN OUTFLOW BOUNDARY CONTINUES TO MOVE QUICKLY EASTWARD ACROSS
NORTH CENTRAL IL AND SOUTHEAST WI WHILE THE SOURCE THUNDERSTORM
CLUSTER WEAKENS AS IT LIFTS NORTH-NORTHEAST OVER EASTERN IA AND
SOUTHWEST WI. THIS OUTFLOW HAS INITIATED CONVECTION IN CENTRAL
AND PORTIONS OF NW IL EARLY THIS MORNING THOUGH INTENSITY OF
CELLS DIMINISH AS THE MOVE NORTHEASTWARD. THIS IS DUE TO MID
LEVEL TEMPERATURES OVER WEST CENTRAL IL SOME 3-4 DEGREES C COOLER
THAN OVER NORTHEAST IL...FURTHER REMOVED FROM THE CENTER OF THE
NORTHERN PLAINS UPPER LOW AND THE SHORT WAVE TROUGH ROTATING OVER
THE MID MO AND MID MS VALLEYS.

EXPECT A FEW SHOWERS AND THUNDERSTORMS TO CONTINUE TO BLOSSOM
OVER THE WESTERN AND SOUTHWESTERN SECTIONS OF THE FORECAST AREA
THIS MORNING WHERE STEEPER MID LEVEL LAPSE RATES IN PLACE AS THE
SHORT WAVE TROUGH CONTINUES TO LIFT NORTHEAST OVER THE LOCAL
AREA.

CANNOT EXCLUDE A LOW THREAT OF THUNDERSTORM DEVELOPMENT FURTHER
EAST LATER TODAY AS THE MID LEVELS COOL WITH THE UPPER LOW
TRACKING FURTHER EAST TO CENTRAL MN BY 00Z AND DAYTIME HEATING
AIDING DESTABILIZATION...PLUS REMNANTS OF THE OUTFLOW EXPECTED TO
BE AROUND TO PROVIDE A FOCUS FOR CONVECTIVE INITIATION.

LATER AFTERNOON AND THIS EVENING A VORT MAX CURRENTLY DROPPING
SOUTHEASTWARD FROM THE CENTRAL ROCKIES ON THE WEST SIDE OF THE
UPPER LOW WILL HAVE ROUNDED THE BASE AND BE  SWINGING
NORTHEASTWARD TO THE MID MS VALLEY ON THE EAST SIDE OF THE UPPER
LOW. WITH SIGNIFICANT CAPE IN PLACE ALONG WITH MINIMAL CIN THIS
IMPULSE EXPECTED TO INITIATE THUNDERSTORMS UPSTREAM IN THE
AFTERNOON...SUSTAINING THEM AS THE MOVE NORTHEAST TO THE LOCAL
AREA BY LATE AFTERNOON-EARLY EVENING. HIGH EQUILIBRIUM
LEVEL...SIGNIFICANT POSITIVE ENERGY AREA...A RELATIVELY LOW
FREEZING LEVEL AND SOMEWHAT DRY MID LEVELS COMBINED WITH
DIRECTIONAL BUT MORE SIGNIFICANTLY SPEED SHEAR IN THE LOWER
LEVELS POINT TO A RISK OF SEVERE THUNDERSTORMS LATER AFTERNOON
INTO THIS EVENING. THREAT OF STORMS AND ACCOMPANYING SEVERE DROPS
OFF MID EVENING ON BOTH DIURNALLY AND WITH SHORT WAVE TROUGH
MOVING OVER SOUTHEAST WI...NORTHEAST IL AND NORTHWEST IN.

WITH THE UPPER LOW AND ASSOCIATED SURFACE LOW CONTINUING ON TO
THE UPPER GREAT LAKES OVERNIGHT AND MONDAY MORNING THE TRAILING
COLD FRONT SLIPS SOUTH ACROSS THE LOCAL AREA AND THEN BECOMES
STATIONARY ACROSS CENTRAL IL INTO NORTHEASTERN IND LATER IN THE
DAY MON AS IT ALIGNS WITH THE UPPER FLOW. MODELS IN REASONABLE
AGREEMENT IN MOVING A SHORT WAVE EAST-NORTHEAST FROM THE CENTRAL
PLAINS TO SOUTHERN GREAT LAKES AND UPPER OH VALLEY DURING MON
NIGHT AND TUE...WITH AN ASSOCIATED SURFACE WAVE TRACKING ALONG
THE QUASITATIONARY BOUNDARY SOUTH OF THE LOCAL FORECAST AREA.
BACKING LOW LEVEL FLOW AHEAD OF THE SURFACE WAVE RESULTS IN
OVERRUNNING THE SURFACE BOUNDARY WHILE THE APPROACHING SHORT WAVE
PROVIDES INCREASING UPWARD VERTICAL MOTION PUTTING THE SOUTHERN
PORTIONS OF THE FORECAST AREA AT THE HIGHER THREAT OF SHOWERS AND
THUNDERSTORMS.

OUT AT 12Z WED MODELS STILL IN DECENT AGREEMENT IN TRACKING THE
NEXT UPPER LOW SLOWLY EAST OUT OVER THE CENTRAL PLAINS. STRONGER
DYNAMICS AND RETURN NORTHWARD OF THE SURFACE FRONT TO ACROSS THE
FORECAST AREA WARRANT LOWER END LIKELY POPS WED.

WARM AND SOMEWHAT HUMID CONDITIONS WILL PREVAIL UNTIL THE COLD
FRONT PUSHES THROUGH THE AREA LATE MON-MON NIGHT. MUCH COOLER AIR
ONCE AGAIN TAKES UP RESIDENCE OVER THE UPPER MIDWEST AND UPPER
GREAT LAKES SOUTH ACROSS THE LOCAL AREA TUE ON INTO NEXT WEEKEND.

TRS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* TIMING AND COVERAGE OF THUNDERSTORMS THIS AFTERNOON AND EVENING
* OUTFLOW AND WIND SHIFT TIMING AHEAD OF ANTICIPATED THUNDERSTORM
  SQUALL LINE THIS EVENING
* POTENTIAL FOR DAMAGING WIND GUSTS AND LARGE HAIL WITH SOME
  STORMS

ED F

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

PUSH OF WARM MOIST AREA CONTINUES TO SURGE NORTHWARD INTO CHICAGO
AIRSPACE THIS AFTERNOON COURTSEY OF 40 KT LOW LEVEL (5K FT) JET
STREAK AHEAD OF THE UPPER LEVEL LOW OVER MINNESOTA. AIRMASS WILL
CONTINUE TO DESTABILIZE AND WITH SUCH EXPECT TSTMS TO DEVELOP ALONG
OUTFLOW BOUNDARIES FROM EARLIER THUNDERSTORMS AND IN ADVANCE OF
DIFFUSE WARM FRONT ACROSS THE AREA. ONE SUCH BOUNDARY APPARENT ON
GOES VIS IMAGERY FROM NEAR PIA SW TO COU.

EXPECT TSTMS TO DEVELOP IN THE VICINITY OF THE TERMINALS AS EARLY AS
20-21Z WITH BEST PROBABILITY AND CONFIDENCE IN THUNDERSTORMS AT
THE TERMINALS COMING WITH A SQUALL LINE EXPECTED TO COALESCE AS A
RESULT OF MULTICELL CLUSTERS EARLY THIS EVENING.

TORNADO WATCH TO THE WEST OF CHICAGO MAY NEED TO BE EXTENDED
EASTWARD LATER... PLEASE MONITOR LATER FORECASTS.

ED F

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN THUNDERSTORMS DEVELOPING THIS AFTERNOON AND EVENING
* LOW CONFIDENCE IN TIMING AND COVERAGE OF THUNDERSTORMS THIS
  AFTERNOON
* MEDIUM CONFIDENCE IN EXPECTATION FOR A SQUALL LINE TO PLOW
  ACROSS THE AREA THIS EVENING
* LOW CONFIDENCE THAT DAMAGING WINDS OR LARGE HAIL MAY IMPACT
  TERMINALS - PLEASE MONITOR FOR LATER WARNINGS

ED F

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

MONDAY NIGHT...VFR. OCNL SHRA ISO TSRA W/MVFR CIGS.

TUESDAY THROUGH THURSDAY...VFR. OCNL MVFR WITH PERIODIC SHRA/TSRA.

FRIDAY...VFR.

SATURDAY...VFR TRENDING MVFR WITH SHRA.

BEACHLER

&&

.MARINE...
300 AM CDT

MARINE FORECAST CHALLENGES RESIDE IN TWO PARTS. THE FIRST IS IN
REGARDS TO INTENSITY OF FOG. THE SECOND CHALLENGE IS IN REGARDS TO
WAVE HEIGHTS DUE TO A SOUTHERLY FLOW ADVECTING WARM/MOIST AIRMASS
OVER A COOLER LAKE SURFACE. DISORGANIZED LOW PRESSURE REMAINS
CENTERED OVER THE DAKOTAS THIS MORNING...HOWEVER GUIDANCE SUGGESTS
THIS LOW WILL CONSOLIDATE INTO A MORE ROBUST LOW PRESSURE SYSTEM
AND STEADILY LIFT NORTHEAST TOWARDS THE GREAT LAKES REGION
TONIGHT. LOW PRESSURE WILL THEN PUSH NORTHEAST OF THE GREAT LAKES
MONDAY. A TRAILING FRONTAL BOUNDARY WILL SWEEP FROM WEST TO EAST
ACROSS THE REGION MONDAY...BECOMING WEST TO EAST ORIENTED JUST
SOUTH OF LAKE MICHIGAN TUESDAY. THEN HIGH PRESSURE BUILDS INTO
ONTARIO...PROVIDING FAVORABLE CONDITIONS FOR BUILDING WAVES FOR
THE SOUTH/SOUTHWEST PORTIONS OF THE LAKE MIDWEEK.

SATELLITE IMAGERY INDICATES PATCHY FOG OVER THE CENTRAL/NORTHERN
PORTIONS OF LAKE MICHIGAN. WITH WARMER LAKE TEMPERATURES IN THE
SHALLOW SOUTHERN SECTIONS FOG INTENSITY SHOULD REMAIN MINIMAL
EARLY THIS MORNING. SHIP OBSERVATIONS EARLY THIS MORNING SUGGESTED
VSBYS WERE AROUND ONE HALF NAUTICAL MILE. EXPECT SHORTLY AFTER
DAYBREAK STRONGER WIND GRADIENT SHOULD AID IN PUSHING THE FOG
FURTHER NORTH.

ONCE FOG DISSIPATES THE CONCERN FOR BREEZY CONDITIONS
INCREASES...HOWEVER WIND GUSTS WILL REMAIN BELOW SMALL CRAFT
CONDITIONS FOR THE NEARSHORE WATERS AS WARM AIR SLIDING OVER THE
COLD LAKE WILL LIMIT GUSTS AND WAVE BUILDING TODAY/TONIGHT.

BEACHLER

&&

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1056 AM CDT SUN MAY 22 2011

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
231600-
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-
1056 AM CDT SUN MAY 22 2011 /1156 AM EDT SUN MAY 22 2011/

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

* WEATHER HAZARDS EXPECTED:

  THUNDERSTORMS...SOME OF WHICH MAY PRODUCE:

  VERY LARGE HAIL.
  DAMAGING WINDS.
  A FEW TORNADOES...WITH A POTENTIAL FOR ISOLATED STRONG
  TORNADOES.

* AREAS AFFECTED AND TIMING:

  INITIATING ALONG AND WEST OF INTERSTATE 39 EARLY THIS AFTERNOON
  AND CONTINUING INTO THE EARLY EVENING HOURS.

  NORTHEAST ILLINOIS AND NORTHWEST INDIANA...INITIATING MID
  AFTERNOON...AND CONTINUING THROUGH THIS EVENING.

* DISCUSSION: LOW PRESSURE CENTERED OVER EXTREME EASTERN SOUTH
  DAKOTA WILL LIFT NORTHEAST ACROSS CENTRAL MINNESOTA TODAY. AS IT
  DOES SO...A POOL OF HIGH DEW POINT AIR MAKING ITS WAY NORTH
  ACROSS THE MID MISSISSIPPI VALLEY WILL QUICKLY OVERSPREAD THE
  OUTLOOK AREA AS A 40 KT LOW LEVEL JET SHIFTS EASTWARD FROM
  MISSOURI AND EASTERN IOWA...INTO ILLINOIS. MEANWHILE...A 70 KT
  MID LEVEL JET MAX WILL PUNCH ACROSS THE UPPER MISSISSIPPI
  VALLEY. THIS...COMBINED WITH AMPLE SUNSHINE WILL RESULT IN RAPID
  AIR MASS DESTABILIZATION THIS AFTERNOON. WIND PROFILES SUGGEST
  THAT SOME DISCRETE STORMS THAT FORM THROUGH MID AFTERNOON WILL
  LIKELY BECOME SUPERCELLULAR...WITH A POTENTIAL FOR A FEW STRONG
  TORNADOES AND VERY LARGE HAIL. THIS IS MOST LIKELY FROM EASTERN
  IOWA AND FAR NORTHEAST MISSOURI...NORTHEASTWARD ACROSS ADJACENT
  AREAS OF WISCONSIN...AND WESTERN THROUGH NORTH CENTRAL ILLINOIS.

  DURING THE EVENING HOURS...STORMS ARE EXPECTED TO EVOLVE INTO A
  SQUALL LINE AT THE NOSE OF THE MID LEVEL JET MAX. THIS WILL
  SUPPORT BOWING STRUCTURES WITHIN THIS LINE...WITH THE PRIMARY
  SEVERE THREAT SHIFTING MORE TO A DAMAGING STRAIGHT LINE WIND
  EVENT ACROSS NORTHEAST ILLINOIS AND NORTHWEST INDIANA THROUGH
  THE EVENING HOURS.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

THERE WILL BE PERIODIC CHANCES OF THUNDERSTORMS FROM MONDAY
THROUGH TUESDAY NIGHT OVER THE SOUTHERN PORTIONS OF THE OUTLOOK
AREA.

THUNDERSTORMS ARE LIKELY ACROSS THE AREA WEDNESDAY INTO WEDNESDAY
NIGHT. A CHANCE OF THUNDERSTORMS WILL REMAIN FROM EAST CENTRAL
ILLINOIS ACROSS NORTHWEST INDIANA ON THURSDAY.

PORTIONS OF THE KANKAKEE RIVER IN NORTHWEST INDIANA WILL REMAIN
IN FLOOD MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS WILL LIKELY BE NEEDED LATER THIS AFTERNOON.

&&

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

LMZ740>745-231600-
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-
1056 AM CDT SUN MAY 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...THIS AFTERNOON AND TONIGHT.

THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS NORTHEAST ILLINOIS
THIS AFTERNOON...AND MAY BEGIN TO REACH THE ILLINOIS AND INDIANA
SHORES BY LATE AFTERNOON. SOME THUNDERSTORMS MAY BECOME SEVERE
AND PRODUCE LARGE HAIL AND DAMAGING WINDS. WITH TIME...STORMS TO
THE WEST OF LAKE MICHIGAN ARE EXPECTED TO FORM INTO A SQUALL
LINE...WHICH WOULD BE APPROACHING THE ILLINOIS NEARSHORE WATERS
THIS EVENING.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

THERE IS A SLIGHT CHANCE OF THUNDERSTORMS MONDAY THROUGH
TUESDAY...MAINLY OVER THE FAR SOUTHERN END THE LAKE.

THUNDERSTORMS ARE LIKELY WEDNESDAY AND WEDNESDAY NIGHT...WITH A
SLIGHT CHANCE OF THUNDERSTORMS LINGERING INTO THURSDAY.

&&

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-
870-872-874-876-878-231600-
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-
1056 AM CDT SUN MAY 22 2011

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

THERE IS A CHANCE OF THUNDERSTORMS THIS AFTERNOON. THUNDERSTORMS
ARE LIKELY TONIGHT. STRONG STORMS ARE EXPECTED AND SOME MAY BE
SEVERE...PRODUCING LARGE HAIL AND DAMAGING WINDS.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

THUNDERSTORMS ARE LIKELY WEDNESDAY AND WEDNESDAY NIGHT ON
SOUTHERN
LAKE MICHIGAN WITH A CHANCE OF THUNDERSTORMS CENTRAL SECTIONS.

&&

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

MERZLOCK