Severe Thunderstorm Warning 151, NWS Grand Rapids, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
440 PM EDT THU AUG 21 2003

THE COLD FRONT ACROSS EASTERN WISCONSIN WILL PUSH STEADILY
EASTWARD THROUGH SOUTHWEST LOWER MICHIGAN.  A CAP HAS KEPT
THE CONVECTION TO A MINIMUM ACROSS THE REGION...BUT IT
HAS ALSO ALLOWED THE HEAT TO BUILD UP...WITH HEAT INDICES
AROUND 100 DEGREES FOR MANY LOCATIONS.  WILL KEEP THE
HEAT ADVISORY UP FOR A COUPLE OF MORE HOURS.  FEEL THAT WITH
THE HEAT BUILDING AND THE FRONT PUSHING IN THAT A FEW
STORMS WILL DEVELOP HERE IN SOUTHWEST LOWER MICHIGAN.
WITH LIFTED INDICES OF -10 DEG C AND KGRR VAD WIND PROFILER
SHOWING 40 KNOT WESTERLY WINDS AT 7000 FEET...ANY STORMS THAT
DO FORM COULD TURN SEVERE.   WILL CONTINUE THE CHANCE
OF STORMS IN THE FORECAST UNTIL THE FRONT PUSHES THROUGH.

MUCH DRIER AIR ARRIVES LATER TONIGHT.  HIGH PRESSURE BUILDS
IN BEHIND THE FRONT...BRINGING IN A MUCH MORE STABLE AIRMASS.
CONSIDERING HOW WARM LAKE MICHIGAN IS AND THE COOLER AIR
COMING ACROSS THE LAKE...SOME LAKE CLOUDS COULD DEVELOP.  WAVES
SHOULD ALSO CONTINUE TO BE FAIRLY HIGH FOR AT LEAST PART OF THE
DAY AS WINDS WILL BE FROM THE NORTH...SHIFTING TO THE NORTHEAST
BY EVENING. THIS FAIR WEATHER SYSTEM WILL STAY WITH US INTO SUNDAY.

MJS

EXTENDED FORECAST

A BROAD UPR RIDGE OVER THE CENTRAL PART OF THE COUNTRY WILL FLATTEN
A BIT AS A SHORT WAVE MOVES EAST ACROSS SRN CANADA. ON MONDAY WELL
SEE A WARM FRONT PUSH NORTHEAST THRU THE CWA EARLY IN THE DAY AND A
COLD FRONT MOVING THRU THE UPR MS VALLEY AND INTO NW LWR BY LATE IN
THE DAY. WILL GO WITH CHC POPS MONDAY THRU TUE AM. LATEST GFS RUN IS
A BIT QUICKER WITH THE FRONTAL MOVEMENT THAN PREVIOUS RUNS. DOESNT
LOOK LIKE THE FRONT WILL SLIP TOO FAR SOUTH OF THE CWA AND WILL IN
FACT RETURN NORTH EARLY THURSDAY...DRAWN NORTH BY A WAVE ON THE
FRONT MOVING EAST. WILL MENTION THE CHC OF TSRA ON THURSDAY TO
ACCOUNT FOR THIS. EXPECT THE FRONT TO MOVE SOUTH OF THE FCST AREA
THU NIGHT. MUCH DRIER AIR WILL CLEAR SKIES LATE THURSDAY NIGHT.

93

.GRR...HEAT ADVISORY THROUGH THIS EVENING FOR MUCH OF SOUTHWEST
LOWER MICHIGAN.

MIZ037>040-043>046-050>052-056>059-064>067-071>074-221015-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1215 PM EDT THU AUG 21 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE SOUTHWEST QUARTER OF LOWER
MICHIGAN.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SEVERE THUNDERSTORMS ARE POSSIBLE ACROSS ALL OF THE SOUTHWEST
QUARTER OF LOWER MICHIGAN FROM MID AFTERNOON INTO THE EARLY EVENING
HOURS OF TODAY...AS A MODERATE COLD FRONT PUSHES INTO THE HOT AND
HUMID AIRMASS CURRENTLY OVER SOUTHWEST MICHIGAN.  THIS AFTERNOON AND
EVENING...THE GREATEST THREAT FOR SEVERE WEATHER IS DAMAGING WINDS
WITH GUSTS TO NEAR 70 MPH IN THE STRONGEST STORMS. ISOLATED REPORTS
OF LARGE HAIL ARE ALSO POSSIBLE...AS IS AN ISOLATED TORNADO.

A LINE OF THUNDERSTORMS IS LIKELY TO DEVELOP OVER EASTERN WISCONSIN
EARLY THIS AFTERNOON...AND SPREAD INTO SOUTHWEST MICHIGAN DURING THE
MID TO LATE AFTERNOON HOURS. IT IS THIS AREA OF THUNDERSTORMS THAT
HAS THE BEST CHANCE OF HAVING SEVERE THUNDERSTORMS ASSOCIATED WITH
IT. THESE STORMS WILL MOVE TO THE EAST AROUND 35 MPH.  THIS AREA OF
THUNDERSTORMS SHOULD BE SOUTH AND EAST OF LANSING...BY 700 PM AND
OUT OF SOUTHWEST MICHIGAN BY 1000 PM.

BESIDE THE THREAT FOR SEVERE WEATHER... TEMPERATURES RISING TO THE
LOWER 90S AND DEWPOINTS RISING INTO THE LOWER 70S WILL CAUSE THE
HEAT INDEX TO RISE TO NEAR 100 DEGREES FAHRENHEIT....IN LOCATIONS
SOUTH AND EAST OF GRAND RAPIDS FOR A FEW HOURS THIS AFTERNOON.

WAVES OF 3 TO 6 FEET THIS AFTERNOON AND TONIGHT WILL RESULT IN
HAZARDOUS BOATING CONDITIONS FOR SMALL CRAFT ON LAKE MICHIGAN.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. HOWEVER...SCATTERED
THUNDERSTORMS ARE POSSIBLE TUESDAY AS YET ANOTHER FRONTAL SYSTEM
MOVES INTO THE AREA.

RELATIVELY COLDER AIR MOVING ACROSS THE WARM WATERS OF LAKE
MICHIGAN WILL CREATE WAVES OF 3 TO 5 FEET ALONG THE LAKE
MICHIGAN SHORELINE FRIDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EVENING.

MJS WDM

MIZ037>040-043>046-212315-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
659 PM EDT THU AUG 21 2003

THE TORNADO WATCH THAT WAS IN EFFECT FOR PORTIONS OF THE SOUTHWEST
QUARTER OF LOWER MICHIGAN HAS EXPIRED. THE WATCH IS NO LONGER
IN EFFECT FOR THE FOLLOWING COUNTIES

IN WEST CENTRAL MICHIGAN
     MASON...LAKE...OCEANA AND NEWAYGO

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

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

MJS