Flash Flood Warning 28, NWS Chicago, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1014 PM CDT SAT AUG 30 2014

.DISCUSSION...
221 PM CDT

SYNOPSIS...SCATTERED THUNDERSTORMS ARE POSSIBLE NW OF I-55 WHILE A
LINE OF STORMS WILL IMPACT AREAS ALONG AND EAST OF I-55 THROUGH THIS
EVENING. TOMORROW WILL BE DRY BUT UNSETTLED WEATHER RETURNS MONDAY
WITH MULTIPLE CHANCES FOR THUNDERSTORMS.  SEVERE STORMS ARE POSSIBLE
MONDAY. TEMPERATURES WILL BE ABOVE NORMAL THROUGH THE PERIOD WITH A
COUPLE DAYS GETTING INTO THE MID 80S.

THROUGH TONIGHT...
AN UPPER LEVEL TROUGH IS OVER THE UPPER MISSISSIPPI RIVER VALLEY AND
IT WILL PASS OVER THE REGION THROUGH THIS EVENING. A SURFACE LOW IS
OVER THE NORTHERN END OF LAKE MI WITH ITS COLD FRONT EXTENDING
THROUGH WI AND EASTERN IA.  THE LOW WILL CONTINUE NE THROUGH THE
NIGHT.

HAVE MUCH HIGHER CONFIDENCE IN THE CONVECTIVE FORECAST TODAY
COMPARED TO YESTERDAY DUE TO CLEAR FORCING MECHANISMS.  EXPECTING TO
HAVE TWO AREAS TO MONITOR. THE FIRST IS NORTHWEST OF I-55 WHERE
ISOLATED TO SCATTERED STORMS WILL CONTINUE TO FESTER THROUGH THIS
AFTERNOON AHEAD OF UPPER LEVEL WAVE AND COLD FRONT.

THE BIGGER CONCERN WILL BE ALONG AND SE OF I-55 WHERE A LINE OF
SHOWERS AND STORMS HAS ALREADY DEVELOPED.  THE LATEST RAP ANALYSIS
SHOWS A NICE CORRIDOR OF MOISTURE CONVERGENCE WHERE THE CONVECTION
HAS FIRED.  THE LATEST AMDAR SOUNDINGS ARE CAPLESS WITH 1000-1500
J/KG OF CAPE.  HOWEVER...LAPSE RATES ARE POOR AND WIND SHEAR IS
MINIMAL AT BEST.  THE AMDAR SOUNDINGS DO HAVE LOW LEVEL INVERTED
V/S AND THE RAP ANALYSIS HAS AROUND 1000 J/KG OF DOWNDRAFT CAPE.
THEREFORE NOT EXPECTING WIDESPREAD SEVERE WEATHER...BUT A STORM OR
TWO MAY PULSE UP AND PRODUCE SEVERE WINDS.

HEAVY DOWNPOURS ARE ALSO EXPECTED WITH PWAT VALUES OF 1.6-1.8
INCHES.  BASED ON SHORT TERM GUIDANCE...THE AREA MOST CONCERNING IS
SOUTH OF A VALPARAISO IN TO GIBSON CITY IL LINE. STORMS WILL
CONTINUE TO DEVELOP AND MOVE OVER THIS REGION WITH AMPLE FORCING.
THEREFORE IF STORMS TRAIN OVER THE SAME AREA FOR AN EXTENDED PERIOD
OF TIME...FLASH FLOODING MAY OCCUR.

STORMS DIMINISH AND PUSH EAST OVERNIGHT WHILE HIGH PRESSURE SPREADS
OVER THE REGION. WINDS WILL DIMINISH AND FOG IS POSSIBLE.

SUNDAY...
SUNDAY LOOKS DRY WITH HIGH PRESSURE OVER THE REGION.  WE WILL BE IN
THE NEXT LOW/S WARM SECTOR WITH 850MB TEMPS AROUND 18C. THEREFORE
RAISED HIGH TEMPS INTO THE MID 80S AWAY FROM THE LAKE. THE WEAK
PRESSURE GRADIENT WILL ALLOW A LAKE BREEZE TO FORM AND KEEP THE IL
LAKEFRONT AROUND 80. GUIDANCE HAS SLOWED THE NEXT LOW SO PUSHED
BACK POPS SUNDAY NIGHT.

JEE

MONDAY...
UPPER WAVE DIGGING TOWARDS THE INTER-MOUNTAIN WEST THIS AFTERNOON
WILL LIFT ACROSS THE PLAINS INTO THE UPPER MIDWEST ON MONDAY WITH
ATTENDANT SURFACE LOW DEEPENING AS IT LIFTS ACROSS ONTARIO TO NEAR
JAMES BAY BY LATE MONDAY. A SURFACE FRONT WILL SLOWLY PUSH ACROSS
THE REGION MONDAY AND GUIDANCE HAS TRENDED TOWARDS A SLOWER SOLUTION
OVER THE LAST 24 HOURS. MODERATE TO STRONG INSTABILITY IS PROGGED TO
DEVELOP ALONG AND AHEAD OF THE FRONT WHERE THE GFS ADVERTISES A
CORRIDOR OF JUST OVER 2000 J/KG MLCAPE JUST TO THE WEST OF THE CWA
MONDAY AFTERNOON. THE BETTER CONVERGENCE ASSOCIATED WITH THE COLD
FRONT MAY ARRIVE JUST PAST THE MOST FAVORABLE DIURNAL TIMING IF
TIMING TRENDS HOLD TRUE...BUT THE RIGHT ENTRANCE REGION TO THE UPPER
JET IS PROGGED TO MOVE OVER THE AREA BY MID TO LATE IN THE EVENING
WITH DEEP LAYER SHEAR VALUES INCREASING TO AROUND 40 KT OR SO WHICH
WOULD BE SUFFICIENT FOR AN ORGANIZED SEVERE WEATHER THREAT...THOUGH
THIS THREAT SHOULD DIMINISH WEST TO EAST AS WE GET LATER INTO THE
OVERNIGHT HOURS AND THE BOUNDARY LAYER STABILIZES.

TUESDAY THROUGH THURSDAY...
A SECONDARY SHORTWAVE TROUGH IS PROGGED TO PUSH ACROSS THE REGION ON
TUESDAY BRINGING ADDITIONAL CHANCES FOR SHOWER AND THUNDERSTORMS
MAINLY ACROSS SOUTH/SOUTHEASTERN PORTIONS OF THE CWA WHERE THE
FRONTAL BOUNDARY MAY STILL SLOWLY BE MAKING A PUSH. MODERATE TO
STRONG HEIGHTS RISES QUICKLY BUILD IN BEHIND THIS FEATURE THOUGH AND
SHOULD RESULT IN A DRY WEATHER FOR MOST OF THE FORECAST AREA
TUESDAY. THE GFS IS PARTICULAR IS HOLDING ONTO SOME POPS NORTH OF
THE BOUNDARY WEDNESDAY INTO THURSDAY WHERE PERSISTENT WARM ADVECTION
WILL RESULT IN MID LEVEL ASCENT...THOUGH THE ECMWF REMAINS DRY THIS
PERIOD. WILL MAINTAIN SLIGHT CHANCE POPS IN THE MEANTIME.

FRIDAY THROUGH SATURDAY...
THERMAL RIDGE IS EXPECTED TO MOVE BACK OVERHEAD LATE IN THE WEEK
WITH H85 TEMPS PUSHING INTO THE LOW 20C RANGE WHICH WILL LEAD TO
ANOTHER WARM UP WITH TEMPS INTO THE UPPER 80S. ANOTHER SLOW MOVING
COLD FRONT WILL THEN SAG SOUTH ACROSS THE REGION BRINGING RENEWED
CHANCES FOR SHOWERS AND THUNDERSTORMS.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* SLIGHT CHANCE OF FOG/STRATUS EARLY SUNDAY MORNING
* CHANCE LAKE BREEZE/WIND SHIFT EASTERLY LATE SUNDAY AFTERNOON

IZZI

//DISCUSSION...UPDATED 00Z...

SCT'D TSRA WILL CONTINUE THIS EVENING TO THE SOUTHEAST OF THE
TERMINALS...WITH VFR CONDITIONS EXPECTED CLOSER TO THE TERMINALS.
THE TSRA ARE OCCURRING NEAR AND JUST AHEAD OF A WEAK FRONT JUST
SOUTH OF THE TERMINALS WITH SLIGHTLY DRIER/LESS HUMID AIR TO THE
NORTH OF THE FRONT. GIVEN THE LACK OF RAIN TODAY AND MIXING OUT OF
LOW LEVEL MOISTURE...PLUS THE URBAN HEAT ISLAND EFFECTS...NOT
ANTICIPATING FOG/STRATUS TO BE MUCH OF AN ISSUE FOR THE CHICAGO
TERMINALS. MODEL GUIDANCE IS STILL HITTING THE THREAT OF IFR
CIGS/VSBY PRETTY HARD...BUT CONDITIONAL CLIMO SUGGESTS THE CHANCES
OF IFR TOMORROW MORNING GIVEN CURRENT CONDITIONS IS FAR LESS THAN
10% SO HAVE GONE WITH VFR FOR MDW/ORD. MAINTAINED MVFR/IFR FOG AT
THE MORE FOG PRONE OUTLYING TERMINALS...PARTICULARLY GYY AND DPA.
ANY VSBY RESTRICTIONS/FOG THAT DOES FORM OVERNIGHT WILL QUICKLY
DISSIPATE BY MID MORNING SUNDAY WITH VFR CONDITIONS EXPECTED THE
REMAINDER OF THE DAY. WINDS SHOULD REMAIN LIGHT ENOUGH TO ALLOW A
LAKE BREEZE TO DEVELOP...BUT IF IT WERE TO THREATEN ORD/MDW IT
LIKELY WOULDN'T DO SO UNTIL VERY LATE IN THE AFTERNOON OR TOWARD
EARLY EVENING.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM-HIGH CONFIDENCE IN NO IFR AT ORD/MDW OVERNIGHT
* LOW-MEDIUM CONFIDENCE IN POTENTIAL LAKE BREEZE SUNDAY AFTERNOON
* HIGH CONFIDENCE IN ALL OTHER ELEMENTS

IZZI

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

MONDAY...PERIOD OR TWO OF SHRA/TSRA...STRONG TSRA POSSIBLE.

TUESDAY AND WEDNESDAY...PREDOMINANTLY VFR.

THURSDAY...SLIGHT CHANCE TSRA...OTHERWISE VFR.

FRIDAY...CHANCE TSRA.

IZZI

&&

.MARINE...
221 PM CDT

MODERATE SOUTHWEST FLOW IS CURRENTLY IN PLACE ACROSS LAKE MICHIGAN
WHERE SOUTHWEST WINDS ARE GUSTING 20 TO 25 KTS WITH OCCASIONAL 30 KT
WINDS. A SMALL CRAFT ADVISORY HAS BEEN ISSUED FOR THE NEARSHORE
WATERS THROUGH LATE THIS EVENING. THIS IS AHEAD OF LOW PRESSURE
CURRENTLY CENTERED NEAR GREEN BAY. THE LOW WILL DRAG A COLD FRONT
SOUTH ACROSS LAKE MICHIGAN TONIGHT TURNING WINDS TO THE NORTHWEST.
WINDS WILL ABATE BRIEFLY AS TRANSIENT HIGH PRESSURE PUSHES ACROSS
THE NORTHERN LAKES REGION...BUT BY MIDDAY SUNDAY WINDS ARE EXPECTED
TO BEGIN TO TURN SOUTHEAST AND START TO RAMP UP AGAIN AHEAD OF
ANOTHER AREA OF LOW PRESSURE. THIS NEXT WILL LOW LIFT FROM THE
NORTHERN PLAINS...DEEPENING AS IT HEADS TO HUDSON BAY MONDAY NIGHT
INTO TUESDAY. SOUTH WINDS ARE EXPECTED TO PEAK MONDAY OVER THE LAKE
WITH GUSTS SOLIDLY INTO THE 20 KT RANGE...APPROACHING 30 KT OVER THE
NORTH END OF THE LAKE. ANOTHER COLD FRONT WILL SAG SOUTH ACROSS LAKE
MICHIGAN MONDAY NIGHT.

DEUBELBEISS

&&

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

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
751 PM CDT SAT AUG 30 2014

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
010100-
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-
751 PM CDT SAT AUG 30 2014 /851 PM EDT SAT AUG 30 2014/

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

.DAY ONE...TONIGHT.

  WEATHER HAZARDS EXPECTED:

   THUNDERSTORMS...SOME OF WHICH MAY PRODUCE:
    ISOLATED WIND GUSTS TO 50 MPH.
    TORRENTIAL DOWNPOURS.
    CLOUD TO GROUND LIGHTNING.

  AREAS AFFECTED AND TIMING:

  SCATTERED THUNDERSTORMS ARE EXPECTED THIS EVENING ALONG AND EAST
  OF INTERSTATE 55 AND GENERALLY SOUTH OF INTERSTATE 80.

  DISCUSSION:

AN UPPER LEVEL WAVE IS OVER WISCONSIN AND FAR NW ILLINOIS WHILE A
COLD FRONT STRETCHES FROM NORTHEAST WISCONSIN THROUGH NORTH
CENTRAL ILLINOIS INTO CENTRAL MISSOURI. INSTABILITY IS MAXIMIZED
AHEAD OF THIS BOUNDARY ALONG WITH MOISTURE CONTENT. A STORM OR TWO MAY
PULSE UP TO SEVERE LIMITS AND PRODUCE SEVERE WIND GUSTS...BUT IN
GENERAL EXPECTING STORMS TO PRODUCE WIND GUSTS UP TO 50 MPH. THE
OTHER CONCERN IS HIGH MOISTURE CONTENT LEADING TO TORRENTIAL
DOWNPOURS. LOCALIZED FLOODING IS POSSIBLE PRIMARILY SOUTHEAST OF
INTERSTATE 55 ALONG THE INTERSTATE 57 CORRIDOR IN FORD AND
IROQUOIS COUNTIES.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

THERE IS A GOOD CHANCE FOR THUNDERSTORMS MONDAY INTO EARLY
TUESDAY. SOME OF THESE STORMS COULD BE SEVERE...ESPECIALLY ON
MONDAY. THESE STORMS WILL ALSO BE CAPABLE OF PRODUCING VERY HEAVY
RAINFALL...WHICH COULD LEAD TO LOCALIZED FLASH FLOODING.

THERE WILL BE ADDITIONAL SLIGHT CHANCES FOR THUNDERSTORMS
WEDNESDAY NIGHT AND THURSDAY...WITH A BETTER CHANCE OF
THUNDERSTORMS ON FRIDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS MAY BE NEEDED THIS EVENING ALONG AND EAST OF INTERSTATE 57.

&&

LMZ740>745-010100-
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-
751 PM CDT SAT AUG 30 2014

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

.DAY ONE...TONIGHT.

STRONG WINDS WILL LEAD TO SMALL CRAFT ADVISORY CONDITIONS THROUGH
EARLY EVENING.

THERE IS A CHANCE FOR THUNDERSTORMS THROUGH THIS EVENING.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED FOR HIGH WINDS
MONDAY.

THERE IS A GOOD CHANCE FOR THUNDERSTORMS MONDAY INTO TUESDAY
MORNING. SOME OF THESE STORMS COULD BE SEVERE WITH WIND GUSTS IN
EXCESS OF 50 KT...ESPECIALLY MONDAY AFTERNOON.

THERE WILL BE ADDITIONAL SLIGHT CHANCES FOR THUNDERSTORMS
WEDNESDAY AND THURSDAY...WITH A BETTER CHANCE OF THUNDERSTORMS
THURSDAY NIGHT THROUGH FRIDAY.

&&

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-010100-
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-
751 PM CDT SAT AUG 30 2014

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

.DAY ONE...TONIGHT.

ISOLATED THUNDERSTORMS ARE POSSIBLE TONIGHT OVER THE FAR SOUTHERN
END OF THE LAKE.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

THERE IS A GOOD CHANCE FOR THUNDERSTORMS MONDAY INTO TUESDAY
MORNING. SOME OF THESE STORMS COULD BE SEVERE WITH WIND GUSTS IN
EXCESS OF 50 KT...ESPECIALLY ACROSS SOUTHERN LAKE MICHIGAN ON
MONDAY.

THERE WILL BE ADDITIONAL CHANCES FOR THUNDERSTORMS WEDNESDAY
THROUGH FRIDAY.

&&

KMD

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FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
814 PM CDT SAT AUG 30 2014

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

0800 PM     FLASH FLOOD      3 S ONARGA              40.67N 88.02W
08/30/2014                   IROQUOIS           IL   LAW ENFORCEMENT

            WATER OF AN UNKNOWN DEPTH FLOWING ACROSS HIGHWAY
            45...HIGHWAY DEPARTMENT HAS BEEN DISPATCHED TO PUT UP
            BARRICADES.

&&

IZZI