Severe Thunderstorm Warning 96, NWS Grand Rapids, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
345 PM EDT SUN SEP 9 2001

...THUNDERSTORMS THIS EVENING THEN CLEARING BY MIDDAY MONDAY...

THE COMBINATION OF A STRONG MID LEVEL SHORTWAVE... A MODERATE COLD
FRONT... AND DEEP MOISTURE WILL ASSURE A PERIOD OF SHOWERS AND
THUNDERSTORMS ACROSS THE CWA THIS EVENING AS THE FRONT MOVES
THROUGH.  THE BIGGEST QUESTION IS WILL THERE BE SEVERE WEATHER?
THERE IS EXTENSIVE CLOUD COVER UNLIKE THE LAST TWO DAYS AND AS A
RESULT THE CAPES ARE IN THE 1500 TO 2500 J/KG RANGE WITH SFC BASED
LIS IN THE -2C TO -4C RANGE. ON THE OTHER HAND... AS THE MID LEVEL
SHORTWAVE MOVES OUT OF THE CENTRAL PLAINS INTO THE GREAT LAKES
TONIGHT... THE LOW LEVEL JET STRENGTHENS TO 45 TO 50 KNOTS WHILE THE
RIGHT ENTRANCE REGION OF THE POLAR JET MOVES OVER THE LOW LEVEL
INFLOW JET.  GIVEN THE PRECIPITABLE WATER IS NEAR 1.8 INCHES (NEARLY
200 PERCENT OF NORMAL) THERE IS MORE THAN ENOUGH MOISTURE.  SO IN
ANY CASE... THE LARGE AREA OF SHOWERS BEHIND THE COLD FRONT WILL
MOVE ACROSS THE CWA THIS EVENING AS THE FRONT MOVES THROUGH. DUE TO
THE BACKING WINDS AHEAD OF THE SHORTWAVE AT THE SURFACE AND 40 TO 50
KNOTS OF WIND JUST ABOVE THE GROUND... ISOLATED TORNADOES WOULD BE
POSSIBLE IF THUNDERSTORMS DID INDEED DEVELOP.

ONCE THE FRONT COMES THROUGH THE MID LEVELS DRY RAPIDLY BY THE
CYCLONIC FLOW KEEPS THE LOW LEVEL MOISTURE IN PLACE UNTIL MID
MORNING MONDAY.  THEN THAT MOVES OUT AND VERY DRY AIR MOVES IN AS
THE MEAN 1000/850 RH FALLS TO 50 TO 55 PCT DURING THE AFTERNOON.
THERE IS AN INVERSION AROUND NEAR 10000 FT DURING THE AFTERNOON SO
SOME CU WILL LIKELY FORM AWAY FROM LAKE MICHIGAN.  SO SKIES WILL BE
MOSTLY SUNNY BY MID AFTERNOON ACROSS THE CWA.

A SECONDARY COLD FRONT MOVES THROUGH THE AREA MONDAY EVENING... BUT
THE AIR IS TO DRY FOR MUCH TO HAPPEN... SO WILL GO MOSTLY CLEAR
MONDAY NIGHT.  HIGH PRESSURE MOVES ACROSS MICHIGAN TUESDAY SO WITH
DRY AIR (MEAN 1000/850 RH MOSTLY NEAR 50 PCT) AND A VERY WEAK
INVERSION AROUND 6000 FT... ONLY SCT CU EXPECTED.  THUS MOSTLY SUNNY
ON TUESDAY.

ZONES BY 400 PM.

WDM

EXTENDED FORECAST...
A LOW OVR THE UPR MS VALLEY WILL DRAG A COLD FRONT THRU SW LWR LATE
WED. WILL KEEP THE INCREASING CLOUD WORDING AND ADD THE MENTION OF
THUNDER. HIGH PRESSURE OVER SC CANADA WILL USHER IN DRY AIR FOR MUCH
OF THE REMAINDER OF THE WEEK. WILL GO WITH INCREASING CLOUDS ON
SUNDAY AS ANOTHER LOW PUSHES A WARM FRONT NORTH INTO THE WRN LAKES.
WILL KEEP PCPN OUT OF THE FCST FOR NOW.

93

.GRR...NONE

WDM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND RAPIDS, MI
1204 PM EDT SUN SEP 9 2001

TIME(EDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0455 PM    3 NE MASON                MI   WIND DAMAGE
09/08/01   INGHAM                         NUMEROUS LARGE TREES
                                          DOWN...BARN DOOR BLOWN
                                          DOWN. REPORTED BY THE
                                          MEDIA.

GEO

MIZ037>040-043>046-050>052-056>059-064>067-071>074-101000-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
115 PM EDT SUN SEP 9 2001

...HAZARDOUS WEATHER POTENTIAL STATEMENT FOR THE SOUTHWEST QUARTER OF
LOWER MICHIGAN FOR TODAY AND TONIGHT...

DISPATCHERS...PLEASE PASS ALONG THIS INFORMATION TO YOUR EMERGENCY
MANAGERS.

HAZARDS...
ISOLATED SEVERE THUNDERSTORMS WITH WIND GUSTS UP TO 60 MILES AN HOUR
AND HAIL UP TO 3/4 INCH IN DIAMETER ARE POSSIBLE THIS AFTERNOON AND
TONIGHT.  AN ISOLATED...SHORT LIVED...SMALL TORNADO IS NOT OUT OF
THE QUESTION EITHER.  TORRENTIAL DOWNPOURS ARE LIKELY AS WELL IN THE
STRONGER STORMS. SOME URBAN AND SMALL STREAM FLOODING IS POSSIBLE
WITH THESE STORMS.  WHILE SEVERE WEATHER IS POSSIBLE OVER MOST OF
SOUTHERN LOWER MICHIGAN THIS AFTERNOON AND EVENING... THE GREATEST
THREAT IS EAST OF A LINE FROM MOUNT PLEASANT TO LANSING BETWEEN 300
PM AND 800 PM.  STORM MOTION WILL BE NORTHEAST AT 35 MPH.

DISCUSSION...
A COLD FRONT MOVING INTO A MOIST AND UNSTABLE AIR MASS WILL PRODUCE
SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING.  THE
COMBINATION OF MOIST UNSTABLE AIR AND A STRONG UPPER LEVEL
DISTURBANCE WILL COMBINE TO INCREASE THE RISK OF SEVERE WEATHER THIS
AFTERNOON OVER SOUTHERN MICHIGAN.  THE COVERAGE OF THUNDERSTORMS
WILL INCREASE SIGNIFICANTLY DURING THE MID AND LATE AFTERNOON AS THE
UPPER LEVEL DISTURBANCE GETS CLOSER TO THE COLD FRONT.  A FEW OF
THESE STORMS MAY BECOME SEVERE.  THE COLD FRONT WILL CLEAR SOUTHWEST
LOWER MICHIGAN AROUND MIDNIGHT.

SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EVENING.

...HAZARDOUS WEATHER POTENTIAL STATEMENT FOR MONDAY THROUGH
THURSDAY...

NO HAZARDOUS WEATHER IS EXPECTED IN THIS PERIOD.

WDM

MIZ038>040-044>046-050>052-056>059-064>067-071>074-100200-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
300 PM EDT SUN SEP 9 2001

THE STORM PREDICTION CENTER HAS ISSUED A TORNADO WATCH FOR PORTIONS
OF THE SOUTHWEST QUARTER OF LOWER MICHIGAN EFFECTIVE UNTIL 1000 PM
EDT SUNDAY EVENING. THIS WATCH INCLUDES THE FOLLOWING COUNTIES

IN SOUTH CENTRAL MICHIGAN
     INGHAM...CLINTON...JACKSON...IONIA...CALHOUN AND EATON

IN CENTRAL MICHIGAN
     OSCEOLA...GRATIOT...MONTCALM...MECOSTA...ISABELLA AND CLARE

IN WEST CENTRAL MICHIGAN
     MUSKEGON...NEWAYGO AND LAKE

IN SOUTHWEST MICHIGAN
     KALAMAZOO...KENT...VAN BUREN...OTTAWA...BARRY AND ALLEGAN

THIS WATCH INCLUDES THE ADJOINING COASTAL WATERS OF AFFECTED
LAKESHORE COUNTIES.

A TORNADO WATCH MEANS THAT CONDITIONS ARE FAVORABLE FOR THE
DEVELOPMENT OF THUNDERSTORMS CAPABLE OF PRODUCING TORNADOES. IF YOU
LIVE IN OR NEAR THE WATCH AREA YOU SHOULD REMAIN ALERT TO RAPIDLY
CHANGING WEATHER CONDITIONS. STAY TUNED TO NOAA WEATHER RADIO OR THE
LOCAL NEWS OUTLETS FOR THE LATEST UPDATES AND POSSIBLE WARNINGS.

WDM

NNNN