Flash Flood and Flooding in Illinois, June 26, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
145 PM CDT TUE JUN 26 2007

.DISCUSSION...UPDATED LATE MORNING
PESKY UPPER CIRCULATION OVER SRN IL PUSHING VERY SLOWLY NWD AND
SETTING OFF AN AREA OF TSTMS FROM AROUND CMI SOUTHWARD. THIS SYSTEM
SHOULD BE WHAT GOES FOR A FOCUS AREA THIS AFTERNOON AND EVENING AS
IT EDGES NNE TOWARD NW INDIANA. POPS HAVE BEEN INCREASED OVER SRN
CWA THIS AFTERNOON TO AROUND SUNSET. AIRMASS VERY MOIST BUT WIND
FIELD VERY LIGHT SO LOCAL HEAVY RAIN WOULD BE A POSSIBLE THREAT. FEW
CELLS WILL ALSO LKLY FORM ANYWHERE IN NRN IL OR NW IN DURING THE
AFTERNOON ESPECIALLY AS TEMPS RISE INTO THE UPPER 80S BUT POPS IN
ANY ONE SPOT WILL BE LOW.  MORE WIDEPSREAD ACTIVITY EXPECTED WED
BEFORE COOL DOWN LATTER HALF OF THE WEEK.  KL

PREV DISC
235 AM...HUMIDITY HAS RETURNED TO THE AREA WITH DEWPOINTS IN THE
UPPER 60S AND LOWER 70S THIS MORNING. LITTLE RELIEF FROM HUMID
CONDITIONS UNTIL COLD FRONT ARRIVES WEDNESDAY AFTERNOON/EVENING.
GUIDANCE RATHER CONSISTENT WITH HIGHS AROUND 90 TODAY AND WITH HIGH
HUMIDITY LEVELS WILL FEEL SOMEWHAT OPPRESSIVE AS HEAT/HUMIDITY
COMBINE TO PUSH HEAT INDICIES INTO THE MID 90S. WHETHER WE TAG 90 OR
LOWER 90S...LIKELY TO HINGE ON CLOUD COVER/PRECIP COVERAGE DURING
THE AFTERNOON. WEAK SHORTWAVE LIFTS NE ACROSS CENTRAL IL/IN THIS
AFTERNOON. WITH MOIST LOW LEVELS...SHOULD BE ENOUGH TO GENERATE A
BKN CU FIELD THEN POP SOME ISOLATED SHOWERS/TS DURING THE AFTERNOON
INTO THE EARLY EVENING HRS. BEST CHANCES FOR PRECIP WILL BE ACROSS
THE SOUTHERN CWA AND HAVE KEPT HIGHS IN THE UPPER 80S THERE. THIS
SHORTWAVE ONLY REACHES SOUTHWEST LOWER MI BY WEDNESDAY MORNING SO
IT IS POSSIBLE ACTIVITY MAY LINGER THRU THE NIGHT BUT WOULD EXPECT
COVERAGE TO DECREASE THRU THE EVENING HRS. TEMPS ONLY SLOWLY
DROPPING OFF INTO THE LOW/MID 70S TONIGHT INTO WEDNESDAY MORNING.
SOUTHWESTERLY FLOW INCREASES LATE MORNING INTO THIS AFTERNOON THUS
ANY LIGHT WINDS NEAR THE LAKESHORE WILL BECOME SW EARLY/MID
AFTERNOON BUT FOR A TIME...A SSE OR SE GRADIENT ALONG THE NORTH
SHORE MAY KEEP TEMPS A LITTLE COOLER THRU THE MORNING.

COLD FRONT APPROACHES THE AREA WEDNESDAY AFTERNOON AND THERE MAY BE
SOME ISOLATED ACTIVITY DURING THE MORNING BUT BULK OF THE PRECIP
SHOULD ACCOMPANY FROPA DURING THE AFTERNOON AND EVENING HRS. LITTLE
CHANGE IN DEWPOINTS UNTIL FROPA PASSES...SO DESPITE HIGHS BACK IN
THE MID 80S...PERHAPS A FEW UPPER 80S...WEDNESDAY ALSO SHAPING UP
TO BE QUITE HUMID. TRENDS CERTAINLY SUPPORT BEST PRECIP CHANCES AND
TIMING ACROSS THE NORTHERN CWA WED AFTERNOON AND WILL MAINTAIN
LIKELY POPS THERE. UPPER LEVEL SUPPORT WITH FRONT NOT THAT GREAT IN
TERMS OF SVR POTENTIAL INCLUDING A FREEZING LEVEL ABOVE 14KFT. MAIN
THREAT FROM ANY OF THE STORMS WEDNESDAY WILL BE HEAVY RAIN...
ESPECIALLY GIVEN RATHER WEAK STEERING WINDS ALOFT. COLD FRONT SLOWLY
PUSHES SOUTH ACROSS THE CWA WEDNESDAY NIGHT WITH ANOTHER SHORTWAVE
RIDING EAST ALONG THE FRONT THURSDAY MORNING. THIS WILL KEEP CHANCE
OF PRECIP GOING SOUTH OF I-80 WEDNESDAY NIGHT INTO THURS MORNING
WITH ACTIVITY FINALLY SAGGING SOUTH OF THE AREA BY THURSDAY EVENING.

HIGH PRESSURE PUSHES SOUTH ACROSS THE REGION THURSDAY AND THURSDAY
NIGHT AND MUCH COOLER AND DRIER NORTHEAST FLOW SETS UP FOR THE END
OF THE WEEK AND WEEKEND. DESPITE LAKE CONTINUING TO WARM...WITH
PLENTY OF LATE JUNE SUN...SHOULD SEE NE FLOW ENHANCED BY A LAKE
BREEZE EACH DAY INTO THE WEEKEND. ALSO...IN THIS PATTERN DEWPOINTS
TEND TO DROP SIGNIFICANTLY DURING THE AFTERNOON HRS AND HAVE DROPPED
THEM SEVERAL DEGREES AND THESE WILL LIKELY NEED TO BE ADJUSTED DOWN
FURTHER INTO THE WEEKEND. CMS

&&

.AVIATION DISCUSSION FOR 18Z TAFS...

WARM HUMID AIRMASS CONTINUES TO ENVELOP MUCH OF THE WESTERN GREAT
LAKES TODAY WITH DEWPOINTS WILL INTO THE LOWER TO MIDDLE 70S.  THIS
COMBINED WITH AN UPPER-LEVEL LOW PRESSURE SYSTEM CENTERED TO THE
SOUTH OF THE AREA WILL LEAD TO SCATTERED SHOWER AND THUNDERSTORM
DEVELOPMENT THIS AFTERNOON AND EARLY EVENING.  LATEST RADAR SHOWS
NUMEROUS CELLS DEVELOPING ACROSS THE REGION...WITH THE RADAR BEING
LITERALLY DOTTED WITH STORMS AT THE MOMENT.  MAIN PUSH STILL REMAINS
ACROSS THE SOUTH WITH HEAVIEST ACTIVITY NOW MOVING INTO SOUTHERN
PORTIONS OF LIVINGSTON...FORD...AND IROQUOIS COUNTIES.  EXPECT
COVERAGE OF SHOWERS AND STORMS TO INCREASE/PERSIST THROUGH THE
REMAINDER OF THE AFTERNOON AS VERY WARM TEMPERATURES HAVE PRODUCED A
RELATIVELY UNSTABLE ATMOSPHERE WITH CAPE VALUES APPROACHING 1500 -
2000 J/KG.  BECAUSE OF THIS...HAVE INTRODUCED VCTS GROUPS AT ALL TAF
LOCATIONS THROUGH THE REMAINDER OF THE AFTERNOON.  HAD TO GO WITH A
FEW TEMPO GROUPS FOR DPA/RFD AS ACTIVITY DEVELOPING OUT WEST HAS
EITHER MOVED OVER THE AREA (RFD) OR WILL MOVE INTO THE AREA SHORTLY
(DPA).

OTHER PROBLEM THIS AFTERNOON IS POSITION OF LAKE BREEZE BOUNDARY.
LATEST IMAGES FROM TDWR FROM MDW INDICATE BOUNDARY NOW CENTERED
ACROSS EASTERN COOK AND LAKE IL COUNTIES IS GRADUALLY MAKING A RUN
TO THE WEST.  MAIN CONCERN IS WHETHER OR NOT THIS FEATURE WILL MAKE
IT INTO ORD OR NOT.  FELT PRETTY CONFIDENT AT THE START OF THE SHIFT
THAT LAKE BREEZE WOULD NOT BE A CONCERN TODAY AS DECENT
SOUTH-SOUTHWESTERLY FLOW WAS ANTICIPATED.  HOWEVER LATEST OBS FROM
BOTH MDW/ORD HAVE INDICATED VRB WIND CONDITIONS...WHICH IS
NONE-THE-LESS ALLOWING FOR THE GRADUAL PUSH TO THE WEST.  FEEL RIGHT
NOW THAT BOUNDARY WILL NOT MAKE IT THAT FAR WEST AND WITH ANY
OUTFLOW FROM ANY STORMS CENTERED OFF TO THE WEST...FEEL THIS WILL
AID IN KEEPING BOUNDARY AT BAY FOR THE TIME BEING.

NEXT MAJOR CONCERN WILL BE APPROACH OF COLD FRONT THAT WAS CENTERED
ACROSS THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY REGION THIS
MORNING.  LATEST NAM12 SHOWS THIS BOUNDARY BEGINNING TO ENTER THE
REGION AFTER 00Z TOMORROW EVENING.  AHEAD OF THIS BOUNDARY...WINDS
MAY BECOME WESTERLY...ESPECIALLY AT RFD...HOWEVER AS TIME APPROACHES
WILL ADJUST WINDS AS NECESSARY.  FRONT IS EXPECTED TO PASS THROUGH
TOMORROW NIGHT...WITH GRADUAL RETURN TO NORTHERLY WINDS IN ITS
WAKE.  SHOWERS AND STORMS ASSOCIATED WITH THIS FEATURE WILL AGAIN BE
A CONCERN FOR TOMORROW AFTERNOON AND EVENING.  GITRO

&&

.MARINE...

FOR AFTERNOON UPDATE...SHOWERS AND THUNDERSTORMS EXPECTED TO
INCREASE THIS AFTERNOON ACROSS MUCH OF THE AREA...HOWEVER
STABILIZING EFFECT ACROSS LAKE WILL LIKELY LIMIT COVERAGE OVER THE
WATERS.  UPPER-LEVEL LOW CONTINUES TO MOVE NORTHEAST FROM SOUTHERN
IL THIS AFTERNOON...WHICH IS HELPING IN THE FORMATION OF THESE
SHOWERS AND STORMS.  MAIN CONCERN FOR THE NEXT COUPLE OF DAYS WILL
BE THE MOVEMENT OF A COLD FRONT DOWN THE LAKE ON WEDNESDAY.  AHEAD
OF THIS FRONT...SOUTHERLY TO SOUTHWESTERLY WINDS EXPECTED TO
CONTINUE ACROSS THE LAKE...WITH A SHIFT TO NORTHERLY AFTER FROPA.
GRADIENT ACROSS LAKE IS EXPECTED TO INCREASE AFTER FRONTAL PASSAGE
AS CANADIAN HIGH PRESSURE SETTLES INTO NORTHERN GREAT LAKES.
NORTHERLY FETCH WILL HELP CREATE WAVES IN THE 3 TO 5 FOOT RANGE
BEGINNING WEDNESDAY NIGHT AND LASTING THROUGH THURSDAY.  FAIR AND
DRY CONDITIONS ARE THEN ANTICIPATED TOWARDS THE END OF THE WEEK AND
BEGINNING OF THE UPCOMING WEEKEND.

&&

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

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
800 AM CDT TUE JUN 26 2007

ILZ003>006-008-010>014-019>022-023-032-033-039-INZ001-002-010-011-
019-270930-
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-
800 AM CDT TUE JUN 26 2007

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

.DAY ONE...TODAY AND TONIGHT.

  ISOLATED THUNDERSTORMS ARE EXPECTED TO DEVELOP BY MIDDAY AND
  CONTINUE INTO THE EARLY EVENING HOURS. WHILE NO ORGANIZED SEVERE
  WEATHER IS EXPECTED...SOME OF THE THUNDERSTORMS WILL LIKELY
  PRODUCE TORRENTIAL DOWNPOURS AND GUSTY WINDS.

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

  A COLD FRONT WILL MOVE ACROSS THE REGION WEDNESDAY AFTERNOON
  THROUGH THURSDAY MORNING. SCATTERED THUNDERSTORMS ARE POSSIBLE
  WITH THIS FRONT. NO ORGANIZED SEVERE WEATHER IS EXPECTED...BUT
  HEAVY RAINFALL WILL BE POSSIBLE.

.SPOTTER INFORMATION STATEMENT...

  SPOTTER ACTIVATION WILL NOT BE NECESSARY.

&&

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

LMZ740>745-766-270930-
WINTHROP HARBOR IL TO MICHIGAN CITY IN-
LAKE MICHIGAN-
800 AM CDT TUE JUN 26 2007

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

.DAY ONE...TODAY AND TONIGHT.

  ISOLATED THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON AND THIS
  EVENING...MAINLY OVER THE NEARSHORE WATERS.

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

  SCATTERED THUNDERSTORMS ARE POSSIBLE WEDNESDAY AFTERNOON AND
  WEDNESDAY NIGHT. NO ORGANIZED SEVERE WEATHER IS EXPECTED.

  A SMALL CRAFT ADVISORY MAY BE NEEDED THURSDAY AND THURSDAY NIGHT.

&&

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

IZZI

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
157 PM CDT TUE JUN 26 2007

ILZ021-022-261945-
GRUNDY IL-WILL IL-
157 PM CDT TUE JUN 26 2007

AT 157 PM...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORMS ALONG THE GRUNDY WILL COUNTY LINE...OR ABOUT
HALF WAY BETWEEN MORRIS AND WILMINGTON. THIS THUNDERSTORM IS CAPABLE
OF PRODUCING 40 TO 50 MPH WINDS AS WELL AS VERY HEAVY RAINFALL.

IN ADDITION...OUTFLOW FROM OTHER THUNDERSTORMS COULD PRODUCE WINDS
OF AROUND 30 MPH ACROSS WILL COUNTY THROUGH 3 PM.

IZZI