Damaging Wind in Illinois, August 9, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
709 PM CDT SUN AUG 9 2009

.DISCUSSION...
325 PM CDT

DAY HAS TURNED OVER FROM PASSIVE HEAT THREAT TO EXPECTED ACTIVE
SEVERE STORMS. THE LATTER GOING HEAVY IN NW IL BUT BARELY LICKING AT
WINNEBAGO COUNTY SO FAR. WHILE EXPECTING A CAPPED ENVIRONMENT OVER
ALL NRN IL...ELEVATED CONVECTION ABOVE THIS CAP NEAR PROXIMITY OF
STNRY FRONT LAYING OVER IOWA AND SW WI HAS MANAGED TO INFECT PORTIONS
OF NRN IL. AXIS OF 3K JOULE CAPES OUT AHEAD OF THIS FRONT LINING UP
WELL WITH CONVECTION OUT OF NRN IOWA INTO SW WI. THIS AXIS FORECAST
IN SHORT TERM TO DROP SE THIS EVENING. PROFILE OF CONVECTIVE
ENVIRONMENT SUPPORTS WIND THREAT MORE THAN HAIL. BULK SHEAR IS
RATHER WEAK IN CWA...SUGGESTING STRAIGHT LINE WIND THREAT VS TORNADO
RISK. FREEZING LVL MORE THAN 15K FEET WUD PROVIDE A LONG MELTING
LAYER FOR ANY POST HAIL PRODUCTION. EVEN IF NOT SEVERE...WILL
CONTINUE THE TSTM CHANCES INTO THE EVENING FOR THESE NRN SECTIONS AS
PER EARLY MRNG FCST ISSUANCE AS CONVEYOR OF GULF MSTR FED BY BRISK
LLJ REMAINS INTACT. IF CONVECTION CONTINUES ALONG BORDER
OVERNIGHT...FLASH FLOOD WARNINGS MAY BE FORTHCOMING.

MEANWHILE...MID LVL CLOUD COVER OVER STORMY PORTION OF NRN IL HAS
KILLED LIKELIHOOD OF REACHING 90 DEGREES. WILL CARRY THE ADVISORY AS
FAR NORTH AS POSSIBLE OUTSIDE OF CLOUD COVER UNTIL 7PM...AND LET IT
EXPIRE AT 7PM.

MODELS ACTUALLY EXHIBITING A FEW WAVES AS THE DRIVING OR LIFTING
FORCE WITH THE BANDS OF STORMS ZIPPING NE FROM NRN IOWA INTO SRN WI.
THE FIRST WAVE IS PROGGED TO MOVE EAST OF LK MICHIGAN BY MIDNIGHT
WITH THE SECOND IMPULSE WORKING THRU IL BEFORE DAWN. WITH EACH
WAVE...MID LVL FLOW BECOMES MORE WESTERLY VS ITS CURRENT SW TO NE
ORIENTATION ALONG THE FRONTAL BOUNDARY. THIS BENDING SHUD PERMIT
MORE SUBSTANTIAL MOVEMENT OF THE FRONT SEWD ON MONDAY. UNTIL
THEN...STORM THREATS ARE TO REMAIN. WILL CARRY CHC POPS FOR MONDAY
BUT THESE MAY RAISE TO LIKELY WITH THE MRNG ISSUANCE.

MODELS VARY ON FROPA WITH GFS PUSHING IT THRU MONDAY AFTN AND ENDING
THREAT EARLY WHILE NAM FAVORS AN OVERNIGHT PASSAGE...SUGGESTING RAIN
THREAT INTO THE EVENING ON MONDAY. AM SIDING WITH WORST CASE
SCENARIO AND PROVIDING A SLOW PUSH THRU THE EVENING WITH CHC POPS
ENDING BY MIDNIGHT IN THE FAR SOUTHEAST PORTION OF THE CWA. BUT
CARRYING THUNDER ALL NRN IL AND NW INDY THRU THE DAYTIME HOURS
MONDAY.

AM LEAVING EXTENDED PORTION AS IS OUTSIDE OF A FEW INSIGNIFICANT
GRID TWEAKS. RATHER PROGRESSIVE UPPER TROUGH MOVES EAST AND WEAK
SURFACE HIGH PRESSURE SPREADS ACROSS THE AREA MID TO LATE WEEK.
SEASONABLY WARM TEMPS WITH LOWER HUMIDITY EXPECTED. WITH UPPER
RIDGING STILL EXPECTED TO INTENSIFY UP THE ATLANTIC COAST LATE SAT
THRU SUNDAY...MAY BE WORKING TOWARD A TENDENCY TO WARM UP NEAR 90 BY
NEXT MONDAY.

RLB

&&

.AVIATION...

0000 UTC TAFS...

THUNDERSTORMS WILL MOVE INTO THE NORTH CENTRAL ILLINOIS...
NORTHEAST ILLINOIS...AND NORTHWEST INDIANA TOWARDS MONDAY MORNING.
THE THUNDERSTORMS IN IOWA WILL DRIFT INTO THE REGION AFTER 09 UTC.
WILL PUT THUNDERSTORMS AFTER 07 UTC IN THE FORECASTS FOR ALL THE
AIRPORTS.

THIS EVENING...THERE MAY BE A SCATTERED THUNDERSTORM OR TWO IN
THE AREA. THERE ARE A LOT OF OUTFLOW BOUNDARIES FROM THE
THUNDERSTORMS THAT WERE IN WISCONSIN. THIS WILL GIVE SOME NORTH
WIND THIS EVENING. BUT THE WIND WILL BECOME SOUTHWEST BEFORE
MIDNIGHT.

THE FRONT WILL NOT MOVE THROUGH UNTIL MONDAY AFTERNOON.
THERE MAY BE THUNDERSTORMS AROUND THROUGH THE MORNING. THE UPPER
AIR SUPPORT FOR THUNDERSTORMS WILL BE OVER NORTHERN ILLINOIS
AROUND 14 UTC. THERE WILL PROBABLY BE THUNDERSTORMS IN THE REGION
THROUGH 17 UTC MONDAY. THE WIND WILL BECOME NORTHWEST AFTER 18
UTC. WE EXPECT SOME DRIER AIR BEHIND THE FRONT SO WE WILL KEEP THE
THE VFR CONDITIONS IN THE FORECAST. THERE WILL BE A CHANCE OF
THUNDERSTORMS AFTER 17 UTC BUT THE PROBABILITY WILL BE LOW.

&&

.MARINE...
311 PM CDT

LOW PRESSURE EASTERN ONTARIO MOVES EAST ACROSS QUEBEC
OVERNIGHT WITH THE TRAILING COLD FRONT SLIPPING SOUTH INTO
NORTHERN LAKE MICHIGAN.. ANOTHER LOW MOVES FROM THE CENTRAL
PLAINS NORTHEASTWARD ACROSS WISCONSIN. AS THIS LOW MOVES EAST
THROUGH THE GREAT LAKES THE COLD FRONT WILL PUSH SOUTHEAST ACROSS
CENTRAL AND SOUTHERN LAKE MICHIGAN. HIGH PRESSURE THEN BUILDS FROM
THE PLAINS ACROSS THE WESTERN GREAT LAKES MONDAY NIGHT THROUGH
TUESDAY NIGHT. THE CENTER OF THE HIGH WILL MOVE OVER THE LOWER
LAKES AND THE NORTHEASTERN U.S. WEDNESDAY THROUGH THURSDAY.

TRS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM SUNDAY.

&&

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
641 PM CDT SUN AUG 9 2009

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
102345-
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-
641 PM CDT SUN AUG 9 2009 /741 PM EDT SUN AUG 9 2009/

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

.DAY ONE...TONIGHT.

  WEATHER HAZARDS EXPECTED:

   SEVERE THUNDERSTORMS THIS EVENING.

   THUNDERSTORMS MAY PRODUCE:

   WIND GUSTS TO 70 MPH.
   HAIL OF 1 INCH OR MORE.
   CLOUD TO GROUND LIGHTNING.
   LOCALLY HEAVY DOWNPOURS...POSSIBLY PRODUCING FLASH FLOODING.

   AREAS AFFECTED AND TIMING:

  THUNDERSTORMS MOVING EAST FROM IOWA INTO NORTHERN ILLINOIS THIS
  EVENING ARE LIKELY TO BE SEVERE AS THEY DRIFT ACROSS NORTHWEST
  ILLINOIS INTO NORTH CENTRAL SECTIONS. THE AREA OF CONCERN IS THE
  NORTHWEST CORRIDOR FROM ROCKFORD SOUTH TO AMBOY AND AREAS WEST
  OF THERE. THERE WILL REMAIN A CHANCE OF STORMS AFTER MIDNIGHT
  OVER ALL OF NORTHERN ILLINOIS AND NORTHWEST INDIANA BUT THE MOST
  LIKELY PERIOD OF SEVERE STORMS WILL BE IN THIS NORTHWEST PORTION
  OF THE OUTLOOK AREA UNTIL 100 AM CDT. DAMAGING WINDS WILL BE THE
  MAIN CONCERN WITH THESE SEVERE STORMS. FLASH FLOODING MAY ALSO
  RESULT FROM REPEATED HEAVY STORMS OVER THE SAME AREAS.

  DISCUSSION:

   A SERIES OF WAVES MOVING NORTHEAST FROM IOWA ACROSS NORTHERN
   ILLINOIS HAS GENERATED SOME ELEVATED CONVECTION. THE CONTINUED
   PASSAGE OF THESE STORMS HAVE MOISTENED THE DRIER LOWER LAYERS
   ACROSS NORTHEAST ILLINOIS AND SET UP AN ENVIRONMENT CAPABLE OF
   SUPPORTING MORE DEVELOPMENT. HIGH CAPES AND SUBSEQUENT STRONG
   LIFT COULD PRODUCE LARGE HAIL. LACK OF STRONG BULK SHEER AND A
   RATHER UNIDIRECTIONAL WEST FLOW ALOFT WILL LIKELY ALLOW BOWING
   LINES OF STORMS WITH STRONG DAMAGING WINDS.

   SCATTERED THUNDERSTORMS ARE STILL POSSIBLE ACROSS THE ENTIRE
   FORECAST AREA OVERNIGHT. SOME OF THESE MAY HAVE THE POTENTIAL
   FOR BEING SEVERE.

 .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

THERE IS A CHANCE OF THUNDERSTORMS MONDAY ACROSS THE ENTIRE
OUTLOOK AREA...AND ACROSS AREAS MAINLY SOUTH OF INTERSTATE 80
MONDAY NIGHT AND TUESDAY. SOME OF THE THUNDERSTORMS MONDAY
AFTERNOON AND EVENING COULD BE SEVERE...WITH DAMAGING WINDS AND
LARGE HAIL THE PRIMARY SEVERE WEATHER THREATS.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ARE REQUESTED ESPECIALLY FOR WINNEBAGO SOUTHWARD THROUGH
LEE COUNTY THROUGH 100 AM CDT.

&&

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

LMZ740>745-102345-
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-
641 PM CDT SUN AUG 9 2009

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

.DAY ONE...TONIGHT.

THUNDERSTORMS ARE ALSO LIKELY FOR THE ILLINOIS AND INDIANA WATERS
OVERNIGHT...WITH WIND GUSTS IN EXCESS OF 40 KNOTS.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

THERE IS A CHANCE OF THUNDERSTORMS MONDAY. A FEW SEVERE STORMS
ARE POSSIBLE WITH THE POTENTIAL TO PRODUCE WIND GUSTS TO 50 KNOTS.

&&

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-
870-872-874-876-878-102345-
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 TOW 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-
641 PM CDT SUN AUG 9 2009

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

.DAY ONE...TONIGHT.

SEVERE THUNDERSTORMS ARE LIKELY FOR EASTERN LAKE MICHIGAN THIS
EVENING...WITH LARGE HAIL AND WINDS TO 70 KNOTS POSSIBLE. THERE
STILL REMAINS A THREAT OF THUNDERSTORMS OVER ALL LAKE MICHIGAN
OVERNIGHT TONIGHT...WITH SOME OF THESE STORMS CAPABLE OF PRODUCING
WIND GUSTS IN EXCESS OF 40 KNOTS.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

THERE IS A CHANCE OF THUNDERSTORMS MONDAY. A FEW SEVERE STORMS
ARE POSSIBLE ON THE SOUTHERN PORTIONS OF THE LAKE.

&&

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

RLB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1117 PM CDT SUN AUG 09 2009

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

1116 PM     TSTM WND GST     2 N WINNEBAGO           42.30N 89.24W
08/09/2009  E40 MPH          WINNEBAGO          IL   BROADCAST MEDIA

            40 MPH WINDS AT WREX.

&&

ALLSOPP