Severe Thunderstorm Warning 165, NWS Grand Rapids, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
450 PM EDT MON OCT 2 2006

.SHORT TERM...
CONVECTION AND SEVERE POTENTIAL REMAINS THE MAIN FOCUS OF THE SHORT
TERM AS THE FORECAST AREA WILL BE SQUARELY IN THE WARM SECTOR OF A
STRONG FALL LOW PRESSURE SYSTEM. MCS ROLLED THROUGH THE AREA EARLY
THIS MORNING AND MUCH OF TODAY WITH CONVECTION NOW FIRING ON THE
EDGE OF WHERE THIS EARLIER CONVECTION MOVED. STORMS ARE LOCATED WEST
TO EAST ACROSS CENTRAL LOWER MICHIGAN...EXTENDING WESTWARD INTO
WISCONSIN. ADDITIONAL STORMS ARE LOCATED OVER SOUTHERN LAKE MICHIGAN
AND THE CHICAGO AREA. MAIN ITEM TO NOTE IN REGARD TO THE NEAR TERM
IS A SHORTWAVE SEEN SPINNING EASTWARD ACROSS MINNESOTA AND
WISCONSIN. THIS WAVE IS AIDING CONVECTIVE INITIATION ON THE
BOUNDARIES OF WHERE THE EARLIER STORMS MOVED. AIRMASS IS TRYING TO
RECOVER IN THE WAKE OF EARLIER CONVECTION ACROSS OUR AREA. FEEL
THERE WILL BE A FEW HOURS WHERE WE WILL BE IN A MIN FOR
CONVECTION...FOLLOWED BY AN INCREASE IN CONVECTION ONCE AGAIN FROM
THE WEST AND SOUTHWEST AS THE UPPER WAVE APPROACHES. HAIL AND HEAVY
RAIN WILL BE THE MAIN THREATS TONIGHT. STRONG THUNDERSTORM WINDS ARE
A POSSIBILITY AS WELL...BUT NOT AS GREAT AS THE OTHER TWO THREATS. A
MILD NIGHT BY OCTOBER STANDARDS.

TUESDAY...EXPECT SOME MORNING SHOWERS AND THUNDERSTORMS EXITING TO
THE EAST EARLY...GIVING WAY TO PROBABLY ANOTHER LULL FOR A GOOD
PORTION OF TUESDAY. SEVERE POTENTIAL RETURNS FOR TUESDAY EVENING
AS A STRONG LLJ IMPINGES ON THE AREA. SEVERE THREAT APPEARS TO BE
PRETTY SIGNIFICANT...AS WEAK SHORTWAVES MOVE THROUGH THE AREA. LOW
AND MID LEVEL WIND MAX/S ARE STRONG...WITH A 40-50 KT LLJ AND A
50-60 LT MID LEVEL JET. DEPENDING ON TIMING AND LOCATION OF
CONVECTION INITIATION TUESDAY AFTERNOON AND EVENING WE COULD BE
LOOKING AT ROTATING STORMS...FOLLOWED BY A TREND TO BECOME LINEAR.
GIVEN BULK SHEAR...SUPERCELLS WOULD BE LIKELY INITIALLY
TRANSITIONING INTO MORE BOWS AND LINE SEGMENTS.

ADDITIONAL SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE INTO WEDNESDAY
ALONG AND AHEAD OF A COLD FRONTAL PASSAGE. RAIN SHOULD COME TO AN
END IN THE SOUTH DURING THE AFTERNOON...WITH COOL HIGH PRESSURE
BUILDING IN FOR WEDNESDAY NIGHT.

PRECIPITABLE WATER VALUES ARE SIGNIFICANT FOR THIS TIME OF
YEAR...RANGING FROM AN INCH AND A QUARTER TO AN INCH AND THREE
QUARTERS FOR MUCH OF THE NEXT 36 HOURS OR SO. HEAVY RAIN IS A
DEFINITE CONCERN OVER THE COURSE OF THE NEXT COUPLE
DAYS...ESPECIALLY GIVEN THE RAINFALL OVER WESTERN PORTIONS OF THE
FORECAST AREA.

.LONG TERM (THURSDAY THROUGH MONDAY)...
MEDIUM RANGE GUIDANCE IS IN FAIRLY GOOD AGREEMENT IN SHOWING A
FAIRLY STRONG SFC HIGH PRESSURE RIDGE WILL MOVE FROM THE GREAT LAKES
REGION THURSDAY EAST TO NEAR LAKE ONTARIO FRIDAY. THIS FEATURE WILL
HELP TO PRODUCE CLEAR TO PARTLY CLOUDY SKIES ACROSS OUR AREA IN THAT
TIME FRAME AND NEAR TO SLIGHTLY BELOW NORMAL TEMPS. TEMPS WILL
MODERATE NEXT WEEKEND IN A SOUTHERLY FLOW WAA REGIME DUE TO THE SFC
HIGH IN THE EAST AND LOW PRESSURE SYSTEM APPROACHING FROM THE WEST.
THAT SYSTEM COULD TRIGGER THE DEVELOPMENT OF A FEW SHOWERS AND
STORMS IN OUR AREA BY LATE SATURDAY NIGHT THROUGH SUNDAY. FUTURE
SHIFTS MAY ALSO NEED TO CONTEMPLATE INCLUDING MENTION OF SHOWERS AND
STORMS INTO MONDAY BASED ON MEDIUM RANGE GUIDANCE TRENDS WITH
FRONTAL TIMING.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...SMALL CRAFT ADVISORY ST. JOSEPH
TO MANISTEE THROUGH LATE TONIGHT.

DUKE LAURENS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1259 PM EDT MON OCT 2 2006

MIZ037>040-043>046-050>052-056>059-064>067-071>074-031030-
MASON-LAKE-OSCEOLA-CLARE-OCEANA-NEWAYGO-MECOSTA-ISABELLA-MUSKEGON-
MONTCALM-GRATIOT-OTTAWA-KENT-IONIA-CLINTON-ALLEGAN-BARRY-EATON-
INGHAM-VAN BUREN-KALAMAZOO-CALHOUN-JACKSON-
1259 PM EDT MON OCT 2 2006

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

.DAY ONE...TODAY AND TONIGHT
STRONG TO SEVERE THUNDERSTORMS REMAIN A POSSIBILITY ACROSS THE
SOUTHWEST QUARTER OF LOWER MICHIGAN THIS AFTERNOON AND TONIGHT.
THE EXPECTATION IS THAT THERE WILL BE A LULL IN THUNDERSTORM
ACTIVITY THROUGH THE EARLY AND MID AFTERNOON HOURS...BUT THEN STORMS
WILL BECOME MORE LIKELY WITH TIME AS WE HEAD INTO THE EVENING AND
OVERNIGHT HOURS. THE MOST LIKELY TIME FRAME FOR STORMS WILL BE FROM
LATE EVENING INTO THE OVERNIGHT HOURS...SPREADING INTO THE AREA FROM
THE SOUTH AND WEST. STORMS HAVE THE POSSIBILITY OF BECOMING SEVERE
ANYWHERE IN SOUTHWEST LOWER MICHIGAN THIS AFTERNOON THROUGH
THE OVERNIGHT HOURS GIVEN THE INSTABILITY IN PLACE. THE MAIN THREATS
FROM STORMS WILL BE VERY HEAVY RAINFALL...LARGE HAIL AND DAMAGING
WINDS. CLOUD TO GROUND LIGHTNING STRIKES CAN BE EXPECTED AS WELL.
GIVEN THE RAINFALL MANY AREAS HAVE ALREADY RECEIVED...ADDITIONAL
HEAVY RAIN COULD LEAD TO FLOODING. THUNDERSTORM MOVEMENT WILL BE TO
THE EAST AT 30 MPH.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

ADDITIONAL SEVERE THUNDERSTORMS COULD DEVELOP TUESDAY INTO TUESDAY
NIGHT AS A STORM SYSTEM TRACKS THROUGH THE GREAT LAKES
REGION. LARGE HAIL AND DAMAGING WINDS REMAIN A THREAT AS WILL HEAVY
RAINFALL. THIS COULD LEAD TO HIGH WATER LEVELS ON AREA STREAMS
AND RIVERS.

FINALLY A COLD FRONT MOVING THROUGH THE AREA SUNDAY COULD BRING MORE
STRONG TO SEVERE THUNDERSTORMS AT THAT TIME.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION WILL BE POSSIBLE FROM THIS AFTERNOON THROUGH
TUESDAY NIGHT.

LMZ844>849-031030-
ST JOSEPH TO SOUTH HAVEN-SOUTH HAVEN TO HOLLAND-
HOLLAND TO GRAND HAVEN-GRAND HAVEN TO WHITEHALL-
WHITEHALL TO PENTWATER-PENTWATER TO MANISTEE-
1259 PM EDT MON OCT 2 2006

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

.DAY ONE...TODAY AND TONIGHT

SOUTHWEST WINDS TO 30 KNOTS WILL BRING WAVES TO 6 FEET TODAY INTO
THIS EVENING. THUNDERSTORMS WILL MOVE THROUGH THE AREA
AS WELL. GUSTY WINDS..FREQUENT CLOUD TO GROUND LIGHTNING AND HAIL IS
ALSO POSSIBLE WITH A FEW OF THE STORMS. ALL OF THESE CONDITIONS ARE
HAZARDOUS TO SMALLER CRAFT.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THE THREAT FOR WAVES TO 6 FEET AND THUNDERSTORMS CONTINUES INTO
EARLY WEDNESDAY MORNING AND IS AGAIN POSSIBLE ON SUNDAY.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION WILL BE POSSIBLE FROM THIS AFTERNOON THROUGH
TUESDAY NIGHT.

WDM DUKE

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