Hazardous Weather Outlook for Mchenry Co., IL

FLUS43 KLOT 131624
HWOLOT

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1124 AM CDT MON JUL 13 2015


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-
1124 AM CDT MON JUL 13 2015

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 MAY BE SEVERE AND MAY PRODUCE:

EXTREME WIND GUSTS TO 80 MPH.
HAIL TO AT LEAST GOLF BALL SIZE.
TORNADOES...INCLUDING A STRONG TORNADO OR TWO.
TORRENTIAL DOWNPOURS AND FLASH FLOODING.

AREAS AFFECTED AND TIMING:

ISOLATED THUNDERSTORMS WILL BECOME INCREASINGLY POSSIBLE
FROM MIDDAY ON...WITH MORE RAPID DEVELOPMENT AND GREATER
COVERAGE EXPECTED BY MID-LATE AFTERNOON. THE PERIOD FROM
MID AFTERNOON THROUGH MID TO LATE EVENING APPEARS TO BE
THE TIME PERIOD MOST LIKELY FOR SEVERE WEATHER ACROSS THE
OUTLOOK AREA.

DISCUSSION:

ONE COMPLEX OF STRONG THUNDERSTORMS MOVED ACROSS THE AREA
EARLY THIS MORNING...BUT HAS MOVED INTO CENTRAL INDIANA AS
OF LATE MORNING. AN OUTFLOW BOUNDARY TRAILS WEST NORTHWEST
FROM THESE STORMS ACROSS CENTRAL ILLINOIS TO NEAR THE QUAD
CITIES. VISIBLE SATELLITE SHOWS A LACK OF EXTENSIVE CLOUD
COVER UPSTREAM...SUGGESTING THAT DESPITE THE COOLER AND
DRIER AIR NORTH OF THE OUTFLOW BOUNDARY FROM MORNING STORMS
THE AIR MASS MAY VERY WELL DESTABILIZE STRONGLY AS WE HEAD
INTO THE MID AFTERNOON HOURS. THE OUTFLOW BOUNDARY...WHICH
HAS COMBINED WITH A NEARLY STATIONARY WARM FRONT...WILL
LIKELY LIFT BACK TO THE NORTHEAST TOWARD THE WESTERN AND
SOUTHERN PARTS OF THE OUTLOOK AREA...AND WILL LIKELY BECOME
A FOCUS FOR SEVERE THUNDERSTORM DEVELOPMENT THIS AFTERNOON.
IN ADDITION...A SERIES OF MID-LEVEL DISTURBANCES UPSTREAM
MAY RESULT IN ADDITIONAL THUNDERSTORM DEVELOPMENT OVER
PARTS OF MINNESOTA AND WISCONSIN...WHICH WOULD THEN MOVE
SOUTHEAST INTO THE OUTLOOK AREA.

ANY DISCRETE SUPERCELL COULD PRODUCE A STRONG TORNADO OR
TWO...AND THE FAVORED AREA FOR THIS MAY END UP BEING IN A
CORRIDOR FROM NORTHWEST ILLINOIS TO THE FAR SOUTH AND
SOUTHWEST CHICAGO METRO AND POINTS SOUTH AND WEST. LARGE TO
VERY LARGE HAIL WILL ALSO BE POSSIBLE...ESPECIALLY IN THE
AFOREMENTIONED CORRIDOR. IF EVOLUTION TO ONE OR MORE FAST
MOVING THUNDERSTORM COMPLEXES OCCURS...THEN THE THREAT WILL
LIKELY EVOLVE TO WIDESPREAD HIGH END DAMAGING WINDS...WITH
AN ISOLATED TORNADO AND HAIL THREAT. A VERY MOIST AIRMASS
WILL REMAIN IN PLACE THROUGH TONIGHT...SO ANY INTENSE
THUNDERSTORM WILL PRODUCE EXCESSIVE RAINFALL RATES AND THE
POTENTIAL FOR RAPID FLASH FLOODING.

HEAT INDEX VALUES ARE EXPECTED TO BE AROUND 105 DEGREES THIS
AFTERNOON IN A CORRIDOR FROM KANKAKEE COUNTY TO LEE COUNTY AND
POINTS SOUTH.

PORTIONS OF THE ILLINOIS...IROQUOIS...VERMILLION AND KANKAKEE
RIVERS...AND SUGAR CREEK ARE IN FLOOD....WITH RENEWED RISES
POSSIBLE DUE TO ANY HEAVY RAIN TODAY AND TONIGHT.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

THERE IS A CHANCE FOR THUNDERSTORMS ON TUESDAY AND THEN A
PERIODIC CHANCE OF THUNDERSTORMS THURSDAY THROUGH SUNDAY.

PORTIONS OF THE ILLINOIS...IROQUOIS...VERMILLION AND KANKAKEE
RIVERS...AND SUGAR CREEK WILL REMAIN IN FLOOD.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL LIKELY BE NEEDED THROUGH TONIGHT.

&&

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