Flash Flood Warning 10, NWS Chicago, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 PM CDT THU JUL 27 2006

.DISCUSSION...

...HEAT WATCH FOR COOK COUNTY FROM NOON SATURDAY THROUGH 8 PM NEXT
TUESDAY WILL BE ISSUED WITH 330 PM ZONES TODAY...

FORECAST FOCUS REMAINS HEAT WAVE THIS WEEKEND INTO NEXT WEEK AND
POTENTIAL FOR SVR STORMS/HVY RAIN/DENSE FOG TONIGHT.

CONVECTION DEVELOPED ACROSS SOUTHERN WI AND ACROSS CENTRAL IL INTO
THE SOUTHERN PART OF THE CWA. SHORTWAVE MOVES ACROSS MO/IL THIS
EVENING AND OVERNIGHT. EXPECT PRECIP TO CONTINUE TO INCREASE IN
COVERAGE AND INTENSITY THIS EVENING AND OVERNIGHT ACROSS THE SOUTH.
EXPECT THREAT OF SVR TO BE RATHER ISOLATED AND JUST WIND WITH
FREEZING LEVELS ABOVE 15KFT...AND ONLY THRU SUNSET. MAIN PROBLEM
THIS EVENING LIKELY TO BE HEAVY RAIN AND POSSIBLY LOCALIZED FLOODING
WITH STORMS MOVING OVER THE SAME LOCATIONS AND PRECIPITABLE WATER
VALUES NEAR 2 INCHES. WHILE SOME AREAS DID SEE AN INCH OR TWO OF
RAIN ACROSS THE FAR SOUTHEAST LAST NIGHT...IF ANY FLOODING DOES
DEVELOP ACROSS THE SOUTHERN CWA...IT SHOULD BE RATHER ISOLATED AND
NO FLOOD WATCH AT THIS TIME. ACTIVITY SHOULD BE DECREASING FROM
NORTH TO SOUTH LATE EVENING AND OVERNIGHT AND WITH SOME CLEARING
SKIES AND CONTINUED LIGHT WINDS...EXPECT FOG TO BECOME A PROBLEM
AGAIN ACROSS THE NW CWA WITH SOME DENSE FOG POSSIBLE. A WEAK
SHORTWAVE MOVES ACROSS THE AREA FRIDAY AFTERNOON WHICH MAY BE
ENOUGH FOR AN ISOLATED STORM BUT WILL MAINTAIN DRY FORECAST.

FOCUS OF THE REST OF THE FORECAST REMAINS DEVELOPING HEAT WAVE AS
UPPER RIDGE BUILDS ACROSS THE MIDWEST. BIGGEST FORECAST PROBLEM
REGARDING SPECIFICS ON HEAT/HUMIDITY ARE THE DEWPOINTS. OTHER
CONTRIBUTING FACTORS ARE POTENTIAL LAKE BREEZES AND A WEAK FRONT
SAT EVENING. FIRST THE DEWPOINTS...WITH NO SIGNIFICANT CHANGES IN
THE AIRMASS EXPECTED OVER THE NEXT SEVERAL DAYS...LOWER/MID 70
DEWPOINTS LOOK ON TRACK. DEWPOINTS MAY REMAIN IN THE MID 70S OR TAG
UPPER 70S FROM TIME TO TIME BUT CONFIDENCE ON WHEN THIS MIGHT OCCUR
IS LOW. NORMALLY EXPECT MIXING OF LOW LEVELS TO ALLOW DRIER AIR TO
MIX TO THE SFC DURING THE AFTERNOON HRS. HOWEVER...LOOKING AT
FORECAST SOUNDINGS ACROSS THE AREA THIS WEEKEND AND NEXT WEEK SHOWS
LIMITED MIXING POTENTIAL AND DEWPOINTS STILL IN THE UPPER 60S
SEVERAL THOUSAND FEET ALOFT. THUS...MIXING WILL HAVE SMALL/IF ANY
AFFECT ON LOWERING DEWPOINTS. AS A RESULT HAVE MAINTAINED MAINLY
LOWER 70S DEWPOINTS THRU THE PERIOD.

LOW CLOUDS FRI MORNING LIMITING SUNSHINE TO START AND A LAKE BREEZE
FRI AFTERNOON SHOULD KEEP HIGHS AROUND 90 AND HEAT INDICES IN THE
UPPER 90S. TEMPS INCREASE A FEW DEGREES SATURDAY BUT THE WRF NOW
SHOWS A COLD FRONT SINKING SOUTH INTO FAR NE IL BY 00Z SUNDAY. THIS
WAS ORIGINALLY SEEN ON THE GFS 2 DAYS AGO SO THERE IS SOME HISTORY
WITH THIS FEATURE. FOR NOW HAVE GONE WITH THE GFS KEEPING SOUTHERLY
FLOW ACROSS THE AREA AND THIS BOUNDARY WELL NORTH. IF THE WRF DOES
PAN OUT...FRONT WILL LIKELY ARRIVE AFTER PEAK HEATING...THUS MID
90S AND HEAT INDICES 100+ SEEM REASONABLE. MODELS CONSISTENT WITH
SUNDAY AND MONDAY BEING THE TWO HOTTEST DAYS WITH HIGHS REACHING THE
MID 90S AND HEAT INDICES NEAR 105...WHICH IS BASED OFF LOWER 70S
DEWPOINTS. CERTAINLY POSSIBLE TO SEE HIGHER DEWPOINTS AND THUS
HIGHER HEAT INDICES DURING THIS TIME. SW FLOW SHOULD BE STRONG
ENOUGH TO PREVENT A LAKE BREEZE SUNDAY/MONDAY. LOW TEMPS BY THIS
TIME LIKELY ONLY IN THE MID 70S WITH CGX/DOWNTOWN REMAINING NEAR
80. TUESDAY REMAINS IN THE 90S WITH FROPA ARRIVING LATE TUESDAY
NIGHT...MORE LIKELY WEDNESDAY BRINGING THE NEXT CHANCE OF PRECIP
AND COOLER TEMPS.

&&

.AVIATION DISCUSSION CONCERNING 18Z TAFS...

SOUTHERN TAFS REMAIN UNDER ST/SC RESULTING FROM OVERNIGHT FG.
NORTHERN ONLY RECENTLY BEGINNING TO BREAK OPEN. CONERN WITH THIS IS
CHANCE FOR TSTM DEVELOPMENT THIS AFTERNOON. WITH WEAK UPPER SUPPORT
DELAY IN DIURNAL HEATING MAY WELL BE LIMITING FACTOR IN DEVELOPMENT
IN NORTHERN IL THIS AFTERNOON. ALTHOUGH THIS DOES NOT RULE OUT
ADVECTION PARTICULALY FROM STORMS NOW DEVELOPING OVER CENTRAL IL,
POINT CHANCE FOR PRECIP AT THIS TIME TOO DIFFICULT TO STATE WITH ANY
CERTAINTY. HAVE CHOSEN TO CONTINUE DRY FORECAST WITH UNDERSTANDING
THAT IF THERE IS DEVELOPMENT BEST CHANCES WOULD BE LATE THIS
AFTERNOON AND EARLY THIS EVENING.

ONCE SC BREAKUP IS COMPLETE ONLY EXPECT DEBRIS FROM SURROUNDING
STORMS IN TERMS OF CLOUD COVER UNTIL OVERNIGHT. WITH HIGH DEWPOINT
AIRMASS REMAINING OVER AREA WOULD EXPECT BR/FG DEVELOPMENT AGAIN
TONIGHT WITH ATTENDANT LOWERING OF CIGS. BEGIN THE PROCESS OF
LOWERING VSBYS ABY MIDNIGHT WITH CIGS BEGINNING TO DEVELOP BY 09Z.
LOWEST CIGS/VSBYS EXPECT AROUND SR. REMAINDER OF TAF PERIOD DEVELOPS
MUCH LIKE TODAY WITH DISSIPATION OF SC/BR THROUGH LATE MORNING.

WINDS TO REMAIND LIGTH -- AROUND 5KTS. THOUGH HAVE INDICATED VRB
WEAK GRADIENT SUGGESTS SOUTHWEST AS PREFERRED DIRECTION. GIVEN THAT,
SEE WIDE VARIATION IN OBSERVED DIRECTIONS. MAIN POINT IS THAT SPEEDS
REAMIN LIGHT.

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
.IL...HEAT WATCH COOK COUNTY NOON SATURDAY THRU 8 PM NEXT TUESDAY.
.IN...NONE.
.LM...NONE.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
400 PM CDT THU JUL 27 2006

ILZ003>006-008-010>014-019>022-023-032-033-039-INZ001-002-010-011-
019-280930-
WINNEBAGO-BOONE-MCHENRY-LAKE IL-OGLE-LEE-DE KALB-KANE-DU PAGE-COOK-
LA SALLE-KENDALL-GRUNDY-WILL-KANKAKEE-LIVINGSTON-IROQUOIS-FORD-
LAKE IN-PORTER-NEWTON-JASPER-BENTON-
400 PM CDT THU JUL 27 2006

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

.DAY ONE... TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE ENTIRE
AREA THIS EVENING. THE MAIN THREATS WILL BE DAMAGING WINDS AND
HEAVY RAIN...WHICH MAY CAUSE LOCALIZED FLOODING.

AREAS OF FOG WILL BE POSSIBLE AFTER MIDNIGHT. THE FOG MAY BE DENSE
ACROSS PARTS OF NORTHWEST ILLINOIS.

.DAYS TWO THROUGH SEVEN... FRIDAY THROUGH WEDNESDAY

HOT AND HUMID CONDITIONS WILL AFFECT THE ENTIRE AREA FROM SATURDAY
THROUGH TUESDAY. HIGH TEMPERATURES THROUGH THIS PERIOD WILL BE IN
THE MID 90S. THE COMBINATION OF THE HEAT AND HUMIDITY WILL PRODUCE
PEAK AFTERNOON HEAT INDICES BETWEEN 100 TO 105 SATURDAY THROUGH
TUESDAY.

THERE IS A CHANCE OF THUNDERSTORMS WEDNESDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS WILL BE NEEDED THIS EVENING.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE
NWS CHICAGO WEBPAGE: WEATHER.GOV/CHICAGO (LOWER CASE)

LMZ740>745-766-280930-
WINTHROP HARBOR IL TO MICHIGAN CITY IN-
LAKE MICHIGAN-
400 PM CDT THU JUL 27 2006

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

.DAY ONE... TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING. THE
MAIN THREAT WILL BE DAMAGING WINDS.

AREAS OF FOG WILL BE POSSIBLE AFTER MIDNIGHT.

.DAYS TWO THROUGH SEVEN... FRIDAY THROUGH WEDNESDAY

THERE IS A CHANCE OF THUNDERSTORMS WEDNESDAY.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE
NWS CHICAGO WEBPAGE: WEATHER.GOV/CHICAGO (LOWER CASE)

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
516 PM CDT THU JUL 27 2006

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

0502 PM     FUNNEL CLOUD     ORLAND PARK             41.61N 87.85W
07/27/2006                   COOK               IL   TRAINED SPOTTER

            179TH AND LAGRANGE RD.

&&

WEN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
517 PM CDT THU JUL 27 2006

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

0502 PM     HEAVY RAIN       JOLIET                  41.53N 88.12W
07/27/2006  E0.00 INCH       WILL               IL   OTHER FEDERAL

            1.88 INCHES OF RAIN IN 45 MINUTES.

&&

WEN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
524 PM CDT THU JUL 27 2006

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

0505 PM     FLOOD            LIBERTYVILLE            42.28N 87.97W
07/27/2006                   LAKE               IL   TRAINED SPOTTER

            STREET FLOODING - INTERSECTION OF IL-21 AND MAPLE AVE.

&&

WEN

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
549 PM CDT THU JUL 27 2006

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

0525 PM     FLOOD            JOLIET                  41.53N 88.12W
07/27/2006                   WILL               IL   TRAINED SPOTTER

            SPRINGFIELD AND GLENWOOD STREETS - 10 TO 12 INCHES OF
            WATER ON ROAD.

&&

WEN