Damaging Winds and Lightning Strike in Indiana, September 25, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
310 PM CDT TUE SEP 25 2007

.DISCUSSION...FOR AFTERNOON FORECAST
310 PM CDT

MAIN FORECAST CONCERN WILL BE NEAR TERM CONVECTIVE POTENTIAL...AND
THEN NEXT CHANCE OF PRECIPITATION FOR THE LATTER PART OF THE WEEKEND.

SYNOPTIC SCALE LIFT CONTINUES TO INCREASE LATE THIS AFTERNOON AS
UPPER LEVEL SHORT WAVE CONTINUES TO TRACK NORTHEAST ACROSS SOUTHERN
MINNESOTA. AREA OF THUNDERSTORMS DEVELOPED ACROSS FAR WESTERN
PORTIONS OF THE FORECAST AREA AND PRODUCED SOME ISOLATED SEVERE WIND
GUSTS. THESE THUNDERSTORMS APPEAR TO BE IN ASSOCIATION WITH A WEAK
MCV WHICH MOVED ACROSS THE AREA FROM EASTERN IOWA. ANOTHER AREA OF
MORE CONCENTRATED SHOWERS AND THUNDERSTORMS EXTENDS FROM FAR
NORTHEAST ILLINOIS EXTENDING SOUTHWESTWARD TO NEAR PONTIAC. THESE
SHOWERS/STORMS ARE JUST IN ADVANCE OF FRONTAL BOUNDARY TRACKING
EASTWARD ACROSS NORTHWEST ILLINOIS. WITH SFC TEMPS RUNNING IN THE
LOWER 80S AND DEW PTS IN THE UPPER 60S...SFC BASED CAPES ARE RUNNING
AROUND 2000 J/KG WITH MLCAPES OF 1000-1500 J/KG. DEEP LAYER SHEAR IS
NOT OVERLY IMPRESSIVE GENERALLY FROM 30-40 KNOTS. HOWEVER...DEEP
LAYER SHEAR SHOULD GRADUALLY BE ON THE INCREASE THROUGH THE
AFTERNOON BUT GREATEST SHEAR SHOULD CONTINUE TO JUST TRAIL PRIMARY
INSTABILITY AXIS. GIVEN MARGINAL SHEAR AND WEAK TO MODERATE
INSTABILITY WILL LIKELY HAVE TO CONTEND WITH MARGINAL SEVERE THREAT
FOR NEXT SEVERAL HOURS. SEVERE THREAT WILL GRADUALLY DIMINISH AFTER
SUNSET.

OTHERWISE...SATELLITE IMAGERY DEPICTING RATHER EXTENSIVE AREA OF
MVFR CIGS BEHIND THE FRONT WHICH IS EXPECTED TO AFFECT NORTHERN
ILLINOIS OVERNIGHT. SHOULD GRADUALLY SEE SKIES CLEAR ACROSS MOST OF
THE AREA LATE TONIGHT AND INTO WEDNESDAY MORNING. COOLER CONDITIONS
BEHIND THE FRONT ON WEDNESDAY...AND MIXING DOWN 900 HPA TEMPS FROM
WRF/GFS THERMAL PROGS YIELDS HIGH TEMPS FROM THE UPPER 60S FAR NORTH
TO THE LOWER 70S SOUTH. ONLY AREA OF CONCERN FOR ANY PRECIP TOMORROW
IS ACROSS FAR SOUTHEAST PORTIONS WHERE WEAK LOW LEVEL
CONVERGENCE/CONFLUENCE MAY LEAD TO AN ISOLD SHOWER DURING THE
AFTERNOON HOURS.

ANOTHER FAST MOVING UPPER LEVEL SHORT WAVE WILL MOVE ACROSS THE
WESTERN GREAT LAKES ON THURSDAY...BUT LOW LEVEL MOISTURE WILL BE
SOMEWHAT LACKING...AND EXPECTING ANY SHOWER ACTIVITY TO REMAIN NORTH
OF THE FORECAST AREA WITH SLIGHTLY STRONGER MID/UPPER LEVEL FORCING
IN WISCONSIN. DID NOT MAKE ANY SIGNIFICANT CHANGES TO THE FORECAST
POST-THURSDAY WITH NEXT CHANCE OF PRECIP LATE SATURDAY NIGHT. UPPER
RIDGING BUILDS BACK INTO THE REGION ON MONDAY WITH MEDIUM RANGE
MODELS IN GENERAL AGREEMENT ON A MORE AMPLIFIED WESTERN CONUS UPPER
TROUGH APPROACHING. HOWEVER...MEDIUM RANGE MODELS/ENSEMBLES DIFFER
QUITE A BIT REGARDING DETAILS/TIMING. WILL HOLD OFF ON INCLUSION OF
ANY POPS FOR NEXT TUESDAY.

MARSILI

&&

.AVIATION...

18Z TAFS

COMPLICATED FORECAST WITH THIS UPDATE AS CONVECTION HAS BEGUN FIRING
TO THE SOUTHWEST OF RFD TERMINAL.  ACTIVITY EXPECTED TO INCREASE IN
COVERAGE AS ATMOSPHERE REMAINS VERY MOIST AND WEAKLY UNSTABLE.
COVERAGE OF STORMS EXPECTED TO INCREASE THROUGH THE AFTERNOON WITH
GRADUAL DECREASE AFTER FROPA AROUND 01Z.  IN THE
MEANTIME...CONDITIONS WILL LIKELY FALL TO MVFR/IFR CATEGORIES WITH
THE HEAVIEST ACTIVITY THIS AFTERNOON.  IN ADDITION TO CURRENT
ACTIVITY NEAR RFD...CONVECTION ALSO NOTED TO THE SOUTHWEST ALONG THE
MISSOURI/ILLINOIS BORDER...WHICH WILL GRADUALLY LIFT
NORTHEASTWARD...AND LIKELY REMAIN A FACTOR AS THE AFTERNOON
CONTINUES ON.  AFTER FROPA...WINDS EXPECTED TO BECOME NORTHWESTERLY
WITH FRONTAL INVERSION CAPPING LOW-LEVEL MOISTURE...KEEPING THE
POSSIBILITY OF MVFR CEILINGS ACROSS THE AREA THROUGH MIDNIGHT.
AFTER WHICH...CLEARING GRADUAL EXPECTED WITH THE ARRIVAL OF HIGH
PRESSURE.

GITRO

&&

.MARINE...

202 PM CDT

LOW PRESSURE CENTERED ACROSS HUDSON BAY WILL CONTINUE MOVING
EASTWARD THIS AFTERNOON AND EVENING.  A COLD FRONT ATTACHED TO THIS
SYSTEM WILL GRADUALLY MOVE THROUGH THE WESTERN GREAT LAKES...WHICH
WILL BE FOLLOWED BY NORTHWESTERLY WINDS OVERNIGHT.  BY TOMORROW...
HIGH PRESSURE WILL BUILD ACROSS THE REGION AND WINDS DOWN THE LENGTH
OF THE LAKE ARE EXPECTED TO BECOME NORTHERLY.  MEANWHILE...ANOTHER
FRONTAL BOUNDARY IS EXPECTED TO IMPACT THE AREA ON
THURSDAY...LEADING TO ANOTHER ROUND OF SHOWERS AND STORMS AND A WIND
SHIFT TO THE WEST-NORTHWEST.  HIGH PRESSURE IS THEN EXPECTED TO
BUILD ACROSS THE REGION FOR THE BEGINNING OF THE UPCOMING
WEEKEND...LEADING TO FAIR AND DRY CONDITIONS.  BY SUNDAY HOWEVER
ANOTHER DISTURBANCE WILL MOVE INTO THE WESTERN GREAT LAKES...LEADING
TO ADDITIONAL CHANCES FOR SHOWER AND STORMS ALONG WITH ANOTHER COLD
FRONTAL PASSAGE.

GITRO

&&

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

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
530 AM CDT TUE SEP 25 2007

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
252045-
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-
530 AM CDT TUE SEP 24 2007

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

.DAY ONE...TODAY AND TONIGHT.

THUNDERSTORMS WILL BECOME LIKELY ACROSS THE AREA THIS AFTERNOON. A
FEW THUNDERSTORMS COULD PRODUCE DAMAGING WINDS OR LARGE HAIL THIS
AFTERNOON INTO EARLY THIS EVENING SOUTHEAST OF A LINE FROM RACINE TO
BELVIDERE TO STERLING. THUNDERSTORMS WILL BE ENDING FROM NORTHWEST
TO SOUTHEAST THIS EVENING AS A COLD FRONT MOVES THROUGH THE AREA.

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

THERE IS A CHANCE OF THUNDERSTORMS SATURDAY NIGHT AND SUNDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUESTED THIS AFTERNOON.

&&

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

LMZ740>745-766-252045-
WINTHROP HARBOR TO WILMETTE HARBOR IL-
WILMETTE HARBOR TO NORTHERLY ISLAND IL-
NORTHERLY ISLAND TO CALUMET HARBOR IL-
CALUMET HARBOR IL TO GARY IN-
GARY INDIANA TO BURNS HARBOR-
BURNS HARBOR TO MICHIGAN CITY-
LAKE MICHIGAN WINTHROP HARBOR IL EASTWARD TO THE MID POINT OF THE
LAKE AND SOUTHWARD TO MICHIGAN CITY MI BEYOND 5 NM FROM SHORE-
530 AM CDT TUE SEP 25 2007

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

.DAY ONE...TODAY AND TONIGHT.

THERE IS A CHANCE OF THUNDERSTORMS THIS MORNING...WITH THUNDERSTORMS
BECOMING LIKELY THIS AFTERNOON INTO THIS EVENING. SOME OF THE STORMS
COULD PRODUCE STRONG GUSTY WINDS AND ISOLATED LARGE HAIL.

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

THERE IS A CHANCE OF THUNDERSTORMS SATURDAY NIGHT AND SUNDAY.

&&

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

HALBACH

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
235 PM CDT TUE SEP 25 2007

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

0230 PM     TSTM WND DMG     ELGIN                   42.04N 88.29W
09/25/2007                   KANE               IL   AMATEUR RADIO

            WEST SIDE OF ELGIN. EXTENSIVE TREE DAMAGE WITH SOME ROADS
            CLOSED. 1 FT DIAMETER TREE LIMBS DOWN.

&&

HALBACH

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
257 PM CDT TUE SEP 25 2007

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

0215 PM     TSTM WND DMG     ELGIN                   42.04N 88.29W
09/25/2007                   KANE               IL   TRAINED SPOTTER

            N. WORTH AVE AND LARKIN. 4FT DIAMETER TREE DOWN. POWER
            LINES DOWN

&&

HALBACH

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
305 PM CDT TUE SEP 25 2007

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

0220 PM     TSTM WND DMG     MARENGO                 42.25N 88.60W
09/25/2007                   MCHENRY            IL   LAW ENFORCEMENT

            TREE DOWN IN MARENGO

&&

HALBACH

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
317 PM CDT TUE SEP 25 2007

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

0258 PM     TSTM WND GST     NORTHBROOK              42.13N 87.83W
09/25/2007  M51.00 MPH       COOK               IL   TRAINED SPOTTER

&&

ACS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
321 PM CDT TUE SEP 25 2007

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

0200 PM     TSTM WND DMG     ROCKFORD                42.27N 89.06W
09/25/2007                   WINNEBAGO          IL   BROADCAST MEDIA

            LARGE TREE DOWN AT BROOKE RD AND SANER RD ON SOUTH SIDE
            OF ROCKFORD.

&&

ACS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
353 PM CDT TUE SEP 25 2007

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

0200 PM     TSTM WND DMG     ROCKFORD                42.27N 89.06W
09/25/2007                   WINNEBAGO          IL   BROADCAST MEDIA

            3 OR 4 TWO FOOT DIAMETER TREE DOWNS AT 3610 CLARINE LANE.
            THREE TELEPHONE POLES SNAPPED. REPORTED BY WREX.

&&

ACS