Severe Thunderstorm Warning 138, NWS Grand Rapids, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
232 PM EDT MON AUG 04 2003

...MORE OF THE SAME THROUGH THURSDAY...

THE MAIN PROBLEM ONCE AGAIN IS WHAT TO DO WITH THE AFTERNOON
CONVECTION EACH DAY.  BOTH THE ETA AND GFS SHOW NEG LI AND AND
1000/700 RH VALUES ABOVE 50 PCT THROUGH FRIDAY.  THE 1000/850 RH IS
MOSTLY ABOVE 70 PCT THROUGH FRIDAY. SFC WINDS WILL BE MOSTLY FROM
THE NORTH EACH DAY.  THUS LAKE BREEZES WILL FORM EACH DAY AND WITH
AN UNSTABLE ATMOSPHERE WHY WOULD THERE NOT BE AFTERNOON CONVECTION
EACH DAY?  WHEN WILL THIS END PATTERN END... THAT IS THE REAL
QUESTION?

YESTERDAY I WROTE ABOUT HOW THE 300 MB JET WOULD CROSS OUR CWA
TUESDAY AND THAT WOULD TAKE SOUTHWEST MICHIGAN OUT OF THE DEEP COLD
AIR AND END THIS CYCLE OF DAY TIME THUNDERSTORMS. HOWEVER... EVEN AS
I WRITE THIS THERE IS A SHORTWAVE CLIMBING THE UPPER RIDGE OVER MN.
IT REDEVELOPS THE TROUGH.  THIS IS SHOWN WELL BY BOTH THE GFS AND
CANADIAN THROUGH FRIDAY.  ACTUALLY ONE COULD ARGUE A SECONDARY COLD
FRONT WILL COME THROUGH WEDNESDAY (BASED MORE ON THE ETA THAN THE
GFS). IN ANY EVENT...WE DO NOT GET ENOUGH OF THAT CANADIAN HIGH THAT
WILL FINALLY DRY THINGS OUT ENOUGH TO STOP THE CONVECTION UNTIL
FRIDAY OR SATURDAY.  THIS PATTERN WILL ALLOW THAT CANADIAN HIGH TO
BLOCK THE NEXT WAVE ON THE SOUTHERN STREAM TO OUR WEST AND THAT WILL
KEEP THE WEATHER DRY INTO THE MIDDLE OF NEXT WEEK.  ALL THAT WITHOUT
MUCH IN THE WAY OF A REAL WARM UP EITHER.

SINCE THERE WILL BE LIGHT WINDS EACH NIGHT AND CONVECTION EACH DAY
IT MAKES SENSE TO HAVE PATCHY FOG DURING THE OVERNIGHT HOURS OF THE
NEXT THREE NIGHTS.

TEMPERATURES WILL BE CLOSE TO MOS WHICH ARE CLOSE TO THE 1000/850
AND 1000/925 THICKNESS BASED FORECASTS TOOLS WE USE IN THIS OFFICE.

ZONES BY 400 PM.

WDM

.GRR...NONE.

MIZ037>040-043>046-050>052-056>059-064>067-071>074-051000-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1150 AM EDT MON AUG 4 2003

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

.DAY ONE...TODAY AND TONIGHT

AS HAPPENED ON SUNDAY...WARM AND MOIST UNSTABLE AIR OVER LOWER
MICHIGAN THIS AFTERNOON WILL SET THE STAGE FOR SCATTERED
THUNDERSTORMS ONCE AGAIN. A FEW OF THESE THUNDERSTORMS COULD REACH
SEVERE LIMITS...MOSTLY BETWEEN 1:00 PM AND 9:00 PM. GIVEN THE MOIST
ENVIRONMENT AND LIGHT STEERING WINDS FOR THE STORMS...LOCALLY HEAVY
RAIN WILL ONCE AGAIN BE POSSIBLE. CLOUD TO GROUND LIGHTNING
STRIKES...WIND GUSTS TO 30 MPH AND PEA SIZE HAIL CAN ALSO BE
EXPECTED.  THE STRONGEST OF STORMS WILL HAVE THE CAPABILITY TO
PRODUCE HAIL TO AROUND ONE INCH IN DIAMETER AND WIND GUSTS TO 60
MPH. THUNDERSTORMS WILL HAVE VERY SLOW MOVEMENTS UNDER 10 MPH. SINCE
THE UPPER LEVEL STORM CENTER IS OVER LOWER MICHIGAN TODAY INSTEAD OF
WISCONSIN...LIKE IT WAS SUNDAY...MORE OF THE THUNDERSTORMS WILL BE
EAST OF GRAND RAPIDS TODAY THEN THEY WERE ON SUNDAY.  ONCE THE SUN
SETS THIS EVENING... THE THUNDERSTORMS WILL QUICKLY DIMINISH.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THUNDERSTORMS WILL BE POSSIBLE TUESDAY AFTERNOON AND EVENING WITH
LIGHTNING AND LOCALLY HEAVY RAINFALL BEING THE MAIN THREATS. A FEW
STORMS MAY CONTAIN HAIL UP TO ABOUT A HALF INCH IN DIAMETER.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED AGAIN THIS AFTERNOON AND EVENING.

RJD WDM