River Flood Warning 34, NWS Chicago, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
935 AM CDT TUE APR 26 2011

.DISCUSSION...
335 AM CDT

GOOD MORNING.  WEATHER THROUGH ABOUT THE NEXT 72 HRS WILL BE
CHARACTERIZED AS RATHER DISMAL WITH FREQUENT SHOWERS AS CLOSED LOW
OVER THE MID MO VALLEY THIS MORNING DEEPENS A BIT AS IT DRIFTS NEWD
...THEN WOBBLES AROUND THE UPPER MS VALLEY THROUGH MD WEEK BEFORE
EJECTING EAST ACROSS THE GREAT LAKES REGION.

SATELLITE IMAGERY SHOWS THE FIRST OF SERIES OF SHORT WAVES NOW
ROTATING NNEWD THROUGH THE MID MS VALLEY.  THIS FEATURE WILL
MAINTAIN A STEADIER RAIN/RAIN SHOWER AREA TO START THE FORECAST
PERIOD. JET MAX ASSD WITH THIS WAVE HAS PUNCHED NNEWD FROM THE
SRN PLAINS  TO SRN IL...AND HAS PUSHED THE PLUME OF HEAVIER
SHOWERS/T-STORMS GENERALLY E OF IL.  RADAR LOOPS ALSO SHOW THE MORE
CONVECTIVE AREA OF THIS PRECIPITATION SHIELD...FOR THE MOST
PART...ALREADY EAST OF THE FORECAST AREA...FROM WEST CENTRAL THROUGH
NORTH CENTRAL INDIANA.  THIS WOULD BE THE ZONE OF HEAVIER RAINFALL
THROUGH MID DAY...SO PRIMARY HYDROLOGIC CONCERNS LIE ACROSS THE
KANKAKEE BASIN THIS MORNING.  SURFACE LOW CENTER IS NOW OVER SERN
IA...JUST SOUTH OF OTM BASED ON RADAR/SATELLITE FIX.  THIS LOW WILL
BE TRACKING WEST OF THE REGION TODAY ALLOWING WINDS TO VEER TO S
AND SW LATER TODAY. AS REGION GETS DRY SLOTTED AND ENTERS THIS
MILDER POST OCCLUSION AIR...LOW LEVEL LAPSE RATES BECOME RATHER
STEEP.  THEREFORE...EXPECT MORE SHOWERS/THUNDER TO DEVELOP BY EARLY
AFTERNOON.  DID HAVE SOME CONCERN EARLIER THAT SOME OF THESE SHALLOW
TOPPED STORMS COULD BEGIN TO ROTATE GIVEN SOMEWHAT OF A TYPE D
PATTERN...BUT THIS THREAT IS EXPECTED TO BE JUST OFF TO THE E AND SE
OF THE REGION BY 18Z...WITH FLOW OVER NRN IL/MOST OF NWRN INDIANA
BECOMING MORE SUPPORTIVE OF SHORT...LINEAR CONVECTIVE ORGANIZATION.

A LULL IN PRECIPITATION IS EXPECTED TO DEVELOP DURING THE COURSE OF
THIS EVENING GIVEN LOSS OF DIURNAL HEATING.  HOWEVER...MODELS ARE
CONSISTENT IN BRINGING ANOTHER SHORT WAVE ACROSS THE SRN PLAINS TUE
NIGHT...THEN WRAPPING IT NNEWD ACROSS THE MIDWEST ON WEDNESDAY
RESULTING IN THE DEVELOPMENT OF A FRONTAL WAVE...FORECAST TO DEEPEN
AS IT REACHES WEST CENTRAL INDIANA BY WED EVENING. THIS WILL SPREAD
ANOTHER ROUND OF RAIN NWD ACROSS MOST OF THE FORECAST AREA LATE
TONIGHT AND WEDNESDAY.  LOW LEVEL CONVERGENCE ALONG AND AHEAD OF THE
PATH OF THIS WAVE SHOULD SUPPORT SOME EMBEDDED THUNDER...MAINLY FROM
E CENTRAL IL-NRN INDIANA.

COLDER AIR WILL WRAP IN BEHIND THE WEDNESDAY SYSTEM...AND WITH COLD
POOL ALOFT SETTLING ACROSS THE FORECAST AREA ON THURSDAY...EXPECT
SHOWER THREAT TO CONTINUE ON THURSDAY ACCOMPANIED BY SOMEWHAT
BLUSTERY AND RAW CONDITIONS.

UPPER LOW IS FINALLY PROGGED TO EJECT EAST ACROSS THE EASTERN GREAT
LAKES BY FRIDAY ALLOWING FOR A SURFACE RIDGE TO SHIFT EAST ACROSS
THE REGION.  RETURN OF SUNSHINE...LIGHT WINDS...AND TEMPERATURES
REBOUNDING TO WITHIN ABOUT 5 DEGREES OF NORMAL FOR LATE APRIL SHOULD
MAKE FRIDAY THE MOST PLEASANT DAY THIS WEEK.

MORE SHOWERS EXPECTED ON SATURDAY...BUT WITH THIS SYSTEM FORECAST TO
MOVE WELL TO THE NORTH OF THE REGION...AT LEAST THE TEMPERATURES
WILL BE WARMER AND PRECIPITATION SHOULD BE LIMITED TO A MUCH
NARROWER WINDOW.

MERZLOCK

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

*MVFR CEILINGS

*GUSTY SSW WINDS

*POTENTIAL FOR SHRA/TSRA

TRS

//DISCUSSION...UPDATED 14Z...

WARM FRONT HAS NORTH TO ALONG/JUST NORTH OF THE WI BORDER AT MID
MORNING TAKING RAIN WITH IT. WITH MOIST LOW LEVELS /SURFACE DEW
POINTS IN MID AND UPPER 50S/ ANY HOLES THAT OPENED IN THE ZONE
SUBSIDENCE BEHIND THE SHORT WAVE TROUGH THAT ROTATED NORTH INTO
SOUTHERN WI EARLIER THIS MORNING QUICKLY FILLED DUE TO SURFACE
HEATING.

WHILE THIS MOIST BOUNDARY LAYER AND SOME MID LEVEL COOLING
FOLLOWING THE SORT WAVE TROUGH PASSAGE RESULT IN INCREASED LOW
LEVEL CAPE VALUES AND SOMEWHAT STEEPER MID LEVEL LAPSE RATES
RESPECTIVELY...THE 700HPA ND 500HPA LOW CENTERS ARE PROGGED TO
LIFT NORTH-NORTHEAST AND TAKING THE POOL OF COOLEST MID LEVEL TO
AIR WITH IT TO OVER SOUTHEAST MN AND WEST CENTRAL WI WITH TIME
DURING THE AFTERNOON.

STRONG SURFACE HEATING LIMITED BY EXTENSIVE CLOUDINESS AND COLD
POOL ALOFT MOVING TO OVER THE UPPER MIDWEST ARE NEGATIVES FOR
WIDESPREAD SHRA AND/OR TSRA DEVELOPMENT WHILE LOW LEVEL CAPE
VALUES AND UVV PROGGED TO MOVE OVER NORTHERN IL DURING THE
AFTERNOON PRECEDING THE NEXT SHORT WAVE TROUGH TO ROTATE
NORTHEAST FROM IA AND MO ARE POSITIVES.

WITH BEST CONVECTIVE PARAMETERS CENTERED TO THE SE AND S OF KORD
AND KMDW THIS AFTERNOON WILL CONTINUE TRENT OF PREVIOUS FORECASTS
OF ONLY CARRYING TEMPO -TSRA FOR MID AFTERNOON.

CLOUDINESS ALSO INHIBITING STRONG MIXING IN THE BOUNDARY LAYER SO
WIND GUSTS CURRENTLY BEING LIMITED TO AROUND 25KT. A LITTLE
DEEPER MIXING WITH TIME AS TEMPERATURE CLIMBS INTO MID 60S WILL
BRING DOWN 25-30KT WINDS WITHIN ABOUT 0.5 KM OF SURFACE.

TRS

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

*HIGH CONFIDENCE CIGS REMAIN MVFR THROUGH AFTERNOON.

*HIGH CONFIDENCE SSW WINDS GUST 20-25KT THIS MORNING AND 25-30KT
 THIS AFTERNOON.

*MODERATE CONFIDENCE IN WIDELY SCATTERED SHOWER COVERAGE REST OF
 MORNING...SCATTERED COVERAGE OF SHRA/TSRA THIS AFTERNOON WITH
 MAIN AREA TO SE AND S OF CHI AREA.

TRS

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

WEDNESDAY...MVFR CIGS POSSIBLE. CHC -RA AT NIGHT.

THURSDAY...MVFR CIGS LIKELY.

FRIDAY...VFR.

SATURDAY...CHC TSRA.

SUNDAY...SLIGHT CHC -SHRA OTHERWISE VFR.

SHEA

&&

.MARINE...
315 AM CDT

...MAIN CONCERNS WILL BE THE GALE FORCE WINDS ACROSS
THE NORTHERN PORTIONS OF LAKE MICHIGAN THROUGH LATE THIS AFTERNOON
AND SMALL CRAFT ADVISORY CONDITIONS FOR THE NEARSHORE WATERS
THROUGH THIS EVENING...

LOW PRESSURE OVER NORTHERN MISSOURI WILL TRACK NORTHEASTWARD TO
CENTRAL WISCONSIN BY THIS AFTERNOON. MEANWHILE...HIGH PRESSURE
WILL BUILD ACROSS ONTARIO TO QUEBEC. THIS HAS GENERATED A
STRENGTHENING PRESSURE GRADIENT OVER LAKE MICHIGAN...WITH
NORTHEASTERLY TO EASTERLY WINDS INCREASING TO GALE FORCE OVER THE
NORTHERN PORTION OF THE LAKE BY EARLY THIS MORNING. FARTHER
SOUTH AND WEST...A SECOND AREA OF LOW PRESSURE IS FORECAST TO
MOVE ACROSS THE OZARKS TUESDAY NIGHT BEFORE MOVING NORTHEAST
ACROSS THE OHIO VALLEY AND THE EASTERN GREAT LAKES ON WEDNESDAY
INTO WEDNESDAY NIGHT.

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565 UNTIL 6
     PM TUESDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 PM TUESDAY.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
408 AM CDT TUE APR 26 2011

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
270915-
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-
408 AM CDT TUE APR 26 2011 /508 AM EDT TUE APR 26 2011/

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

.DAY ONE...TODAY AND TONIGHT.

  WEATHER HAZARDS EXPECTED:

  SCATTERED THUNDERSTORMS...SOME OF WHICH MAY PRODUCE:
  BRIEF GUSTY WINDS TO 45 MPH...AND SMALL HAIL.

  AREAS AFFECTED AND TIMING:

  SCATTERED THUNDERSTORMS WILL DEVELOP ACROSS THE REGION BY EARLY
  AFTERNOON. A FEW STORMS MAY LINGER INTO THIS EVENING BEFORE
  DISSIPATING WITH THE LOSS OF DIURNAL HEATING.

  IN ADDITION TO THE THUNDER THREAT...WINDS ARE EXPECTED TO VEER
  TO THE SOUTHWEST AND GUST TO 30 MPH OR MORE THIS AFTERNOON.

  DISCUSSION:

LOW PRESSURE OVER SOUTHEAST IOWA WILL TRACK WEST OF THE REGION
TODAY...ALLOWING WINDS TO VEER INTO THE SOUTH AND EVENTUALLY
SOUTHWEST...DRAWING MILDER AIR ACROSS THE AREA. THIS...IN
COMBINATION WITH COOLING ALOFT WILL RESULT IN ENOUGH INSTABILITY
TO SUPPORT SCATTERED THUNDERSTORMS THIS AFTERNOON AND EARLY
EVENING. AS SURFACE WINDS TURN SOUTHWEST EARLY THIS
AFTERNOON...WIND PROFILES WILL BECOME MORE SUPPORTIVE OF
SHORT...NARROW LINES OF THUNDERSTORMS SUGGESTING A POTENTIAL FOR
BRIEF STRONG WIND GUSTS.

PORTIONS OF THE KANKAKEE...DES PLAINES...IROQUOIS...AND ILLINOIS
RIVERS WILL REMAIN IN FLOOD. MANY OTHER AREA RIVERS WILL BE NEAR
BANKFULL.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

PORTIONS OF THE KANKAKEE...DES PLAINES...IROQUOIS...AND ILLINOIS
RIVERS WILL REMAIN IN FLOOD. MANY OTHER AREA RIVERS WILL BE NEAR
BANKFULL.

THERE IS ANOTHER CHANCE OF THUNDERSTORMS ABOUT SATURDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NECESSARY THROUGH TONIGHT.

&&

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

LMZ740>745-270915-
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-
408 AM CDT TUE APR 26 2011

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.

STRONG WINDS AND HIGH WAVES WILL LEAD TO HAZARDOUS CONDITIONS FOR
SMALL CRAFT THROUGH THIS EVENING.

THERE IS A CHANCE OF THUNDERSTORMS THIS AFTERNOON.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

STRONG WINDS AND HIGH WAVES MAY LEAD TO HAZARDOUS CONDITIONS THAT
MAY AGAIN AFFECT THE NEARSHORE WATERS THURSDAY INTO THURSDAY
NIGHT.

THERE IS ANOTHER CHANCE OF THUNDERSTORMS ON SATURDAY.

&&

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-
870-872-874-876-878-270915-
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-
408 AM CDT TUE APR 26 2011

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

.DAY ONE...TODAY AND TONIGHT.

GALE FORCE EAST WINDS ARE EXPECTED ACROSS NORTHERN LAKE MICHIGAN
TODAY.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

THERE IS A CHANCE OF THUNDERSTORMS ACROSS LAKE MICHIGAN
ON SATURDAY.

&&

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

MERZLOCK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
712 AM CDT TUE APR 26 2011

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

0700 AM     HEAVY RAIN       5 NNE VALPARAISO        41.54N 87.01W
04/26/2011  M1.21 INCH       PORTER             IN   CO-OP OBSERVER

0700 AM     HEAVY RAIN       WATSEKA                 40.78N 87.73W
04/26/2011  M1.06 INCH       IROQUOIS           IL   CO-OP OBSERVER

&&

ACS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
714 AM CDT TUE APR 26 2011

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

0700 AM     HEAVY RAIN       PEOTONE                 41.33N 87.80W
04/26/2011  M1.00 INCH       WILL               IL   CO-OP OBSERVER

&&

ACS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
728 AM CDT TUE APR 26 2011

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

0700 AM     HEAVY RAIN       RENSSELAER              40.94N 87.15W
04/26/2011  M1.36 INCH       JASPER             IN   CO-OP OBSERVER

&&

ACS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
753 AM CDT TUE APR 26 2011

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

0752 AM     HEAVY RAIN       MILFORD                 40.63N 87.70W
04/26/2011  M1.13 INCH       IROQUOIS           IL   CO-OP OBSERVER

0752 AM     HEAVY RAIN       FAIRBURY                40.75N 88.51W
04/26/2011  M1.00 INCH       LIVINGSTON         IL   CO-OP OBSERVER

&&

ACS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
817 AM CDT TUE APR 26 2011

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

0700 AM     HEAVY RAIN       PAXTON                  40.46N 88.10W
04/26/2011  M1.90 INCH       FORD               IL   CO-OP OBSERVER

&&

ACS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
909 AM CDT TUE APR 26 2011

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

0908 AM     HEAVY RAIN       CHESTERTON              41.60N 87.06W
04/26/2011  M1.25 INCH       PORTER             IN   TRAINED SPOTTER

&&

ACS