Severe Thunderstorm Warning 131, NWS Grand Rapids, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1044 PM EDT THU AUG 18 2005

.UPDATE..
TORNADIC THUNDERSTORMS HAVE BEEN MOVING ACROSS SOUTHERN WISCONSIN
THIS EVENING.  0-1KM HELICITY VALUES ARE OVER 300M2/S2 OVER SE WI AS
OF 02Z.  HELICITY VALUES ABOVE 250M2/S2 HAVE PUSHING INTO THE SW
CORNER OF THE CWA AND MAY INCREASE AS A WARM FRONT LIFTS OVER THIS
REGION.  SEVERE WEATHER STILL POSSIBLE AS VWP SHOWS STRONG SHEAR IN
THE LOW LEVELS.  LCL LEVELS ARE QUITE LOW...AROUND 700 FT.  0-6KM
BULK LAYER SHEAR WAS MAXED OVER LAKE MICH AT 50KT.  THIS WOULD
SUGGEST THE STORMS WILL MAINTAIN THEMSELVES AS THEY CROSS THE LAKE.
SPC IS CONSIDERING A TORNADO WATCH FOR THE SW PORTION OF THE CWA.

OTHERWISE A STRONG SHORT WAVE WILL CROSS THE CWA OVERNIGHT LEADING
TO WIDESPREAD SHOWERS AND STORMS THROUGHOUT THE CWA.  WILL BUMP POPS
UP.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...NONE.

&&

JK

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
451 PM EDT THU AUG 18 2005

LMZ844>849-MIZ037>040-043>046-050>052-056>059-064>067-071>074-
190930-
ST JOSEPH TO SOUTH HAVEN-SOUTH HAVEN TO HOLLAND-
HOLLAND TO GRAND HAVEN-GRAND HAVEN TO WHITEHALL-
WHITEHALL TO PENTWATER-PENTWATER TO MANISTEE-MASON-LAKE-OSCEOLA-
CLARE-OCEANA-NEWAYGO-MECOSTA-ISABELLA-MUSKEGON-MONTCALM-GRATIOT-
OTTAWA-KENT-IONIA-CLINTON-ALLEGAN-BARRY-EATON-INGHAM-VAN BUREN-
KALAMAZOO-CALHOUN-JACKSON-
451 PM EDT THU AUG 18 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST LOWER
MICHIGAN.

.DAY ONE...THIS EVENING AND TONIGHT

ONE AREA OF SHOWERS AND THUNDERSTORMS WILL BE AFFECTING THE AREA
THROUGH THE EARLY EVENING HOURS. THESE THUNDERSTORMS ARE NOT
EXPECTED TO BE SEVERE. LOCALLY HEAVY DOWNPOURS AND CLOUD TO GROUND
LIGHTNING WILL BE THE MAIN HAZARDS FROM THESE STORMS.

A SECOND BATCH OF THUNDERSTORMS ARE EXPECTED TO DEVELOP AND MOVE
THROUGH THE AREA DURING THE OVERNIGHT HOURS. THESE STORMS WILL HAVE
THE POTENTIAL TO PRODUCE SOME ISOLATED SEVERE WEATHER OVER SOUTHWEST
LOWER MICHIGAN...WITH DAMAGING WINDS BEING THE MAIN THREAT. CLOUD TO
GROUND LIGHTNING AND LOCALLY HEAVY DOWNPOURS OF RAIN WILL ALSO BE
POSSIBLE.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

AN UNSEASONABLY STRONG COLD FRONT IS EXPECTED TO MOVE THROUGH
LOWER MICHIGAN SATURDAY AFTERNOON. PERIODS OF THUNDERSTORMS ARE
EXPECTED AHEAD OF THE COLD FRONT LATE FRIDAY NIGHT INTO SATURDAY
MORNING. IT WOULD NOT BE OUT OF THE QUESTION FOR A FEW OF THESE
STORMS TO REACH SEVERE LIMITS AND HAVE WIND GUSTS TO 60 MPH AND
HAIL TO 1 INCH IN DIAMETER.

COLD AIR COMING IN BEHIND THE COLD FRONT COMBINED WITH NORTHWEST
WINDS OF AT LEAST 15 TO 25 KNOTS WILL PRODUCE A HAZARD TO SMALL
CRAFT BEGINNING SATURDAY AFTERNOON AND CONTINUING THROUGH AT LEAST
SUNDAY MORNING. WAVES ARE EXPECTED TO BUILD TO AT LEAST 4 TO 6 FEET
SATURDAY AFTERNOON THROUGH AT LEAST SUNDAY MORNING.

AN INCREASED THREAT OF RIP CURRENTS WILL BE PRESENT DURING THIS TIME
PERIOD.

THERE WILL BE A POTENTIAL OF WATERSPOUTS ALSO LATE SATURDAY NIGHT
AND ON SUNDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED OVERNIGHT TONIGHT AND AGAIN LATE
FRIDAY NIGHT AND EARLY SATURDAY.

WDM NJJ