Severe Thunderstorm Warning 122, NWS Grand Rapids, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1100 AM EDT SUN AUG 03 2003

...WILL LOWER POP THIS AFTERNOON TO SCATTERED...

THE PRIMARY PROBLEM IS WHAT TO DO WITH THE POP THIS AFTERNOON.
CURRENTLY THERE IS AN SIX TENTHS AREA OF SHOWERS AND SCATTERED
THUNDERSTORMS THAT EXTEND FROM THE WESTERN UPPER PENINSULA OF
MICHIGAN ACROSS NORTHERN LOWER MICHIGAN...THEN SOUTH SOUTHEAST
TOWARD THE NORTHWEST OHIO.  THIS AREA IS LIFTING SLOWLY NORTH AND IS
ASSOCIATED WITH BOTH THE JET EXIT REGION LIFT (UPPER MI/NRN LWR) AND
A SHORTWAVE THAT SHOWS UP WELL ON THE WATER VAPOR LOOPS FROM WI INTO
LOWER MICHIGAN. THERE IS THE CLASSIC DRY SLOT POKING INTO SOUTHWEST
LOWER MICHIGAN.  ALSO... THERE IS A QUASI-COLD FRONT (DRY LINE MORE
SO) FROM THE SURFACE LOW NEAR MKE TO NEAR STL.  MEANWHILE THERE WAS
ALMOST NO ECHOS IN THE GRR CWA (OK...THERE ARE SOME OVER OUR N AND
ERN CWA).

SO...WHAT WILL HAPPEN?  MY GUESS IS THE PRIMARY WARM ADVECTION LIFT
(1000/925/850 WARM ADVECTION AND 700 MB ISENTROPIC LIFT) PLUS THE
DEEP MOISTURE CONVERGENCE (1000/850 THTE CONVERGENCE AND 850 DEW
POINT AXIS) ARE MOSTLY ALREADY EAST OF THE GRR CWA.  EVEN SO...THERE
IS A GOOD DEAL OF HIGH AND MID CLOUDS ASSOCIATED WITH WARM ADVECTION
PATTERN TO OUR EAST THAT IS STILL OVER MOST OF THE CWA.  THAT WILL
LIMIT THE INSTABILITY SOME.  THE SW CORNER OF THE CWA HAS THE BEST
CHANCE OF DECENT THUNDERSTORMS SINCE THAT COLD FRONT OF SORTS WILL
BE MOVING SLOWLY INTO THE CWA THERE AND THAT AREA WILL HAVE THE
GREATEST AMOUNT OF SUNSHINE.  RUC SOUNDINGS SUGGEST 2500 J/KG
POSSIBLE SOUTH AND WEST OF GRR BY 21Z.  EVEN SO... THE ETA AND RUC
SUGGEST SW LWR IS IN A AREA OF UPPER CONVERGENCE (NOT GOOD FOR
LIFT). THE REST OF THE AREA WILL LIKELY NOT DESTABILIZE ENOUGH AND
THE PRECIPITATION WITH THE WARM CONVEYOR BELT WILL BE EAST OF THE
CWA.  THUS I WILL LOWER THE CHANCE OF PRECIPITATION TO SCT FOR ALL
AREAS THIS AFTERNOON.  TONIGHT THE CONVECTION SHOULD END TOTALLY BY
MIDNIGHT OR SO (SURFACE HEATING GONE AND LITTLE DYNAMIC REASON TO
KEEP IT GOING).

THERE IS A SMALL RISK OF ISOLATED SEVERE THUNDERSTORMS OVER THE SW
PART OF THE CWA THIS AFTERNOON DUE TO THE CAPES NEAR 2500 J/K AND
FREEZING LEVEL NEAR 11,500 FT. SO HAIL WOULD BE THE MOST LIKELY TYPE
OF HAZARD. OF COURSE WIND IS POSSIBLE TOO BE THE WIND PROFILE SURE
DOES NOT SUPPORT ANY MAJOR SEVERE THREAT BY ITSELF DUE TO THE LACK
OF VERTICAL SHEAR AND ANY WIND OVER 25 KNOTS BELOW 20,000 FT.

ZONES BY 1115 AM.

.GRR...NONE.

WDM

MIZ037>040-043>046-050>052-056>059-064>067-071>074-041000-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
638 AM EDT SUN AUG 3 2003

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

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS WILL ONCE AGAIN BE POSSIBLE TODAY ACROSS ALL OF THE
SOUTHWEST QUARTER OF LOWER MICHIGAN.  A FEW OF THESE STORMS MAY
APPROACH SEVERE LEVELS. MOST STORMS WILL BE CAPABLE OF PRODUCING
HEAVY RAIN...CLOUD TO GROUND LIGHTNING STRIKES AND GUSTY WINDS TO 30
MPH. THE STRONGEST OF STORMS COULD PRODUCE HAIL TO AROUND THREE
QUARTERS OF AN INCH AND WINDS TO NEAR 60 MPH. THE UNSTABLE
CONDITIONS THAT HAVE BEEN IN PLACE THE LAST COUPLE DAYS WILL PERSIST
ONCE AGAIN. STORMS WILL BE POSSIBLE ANY TIME TODAY AND
TONIGHT...WITH THE HIGHEST LIKELIHOOD BEING THIS AFTERNOON AND
EVENING. THUNDERSTORM MOVEMENT WILL BE TO THE NORTH AT 20 MPH.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

THUNDERSTORMS REMAIN IN THE FORECAST FROM MONDAY THROUGH WEDNESDAY.
A FEW STRONG STORMS WILL BE POSSIBLE AGAIN ON MONDAY. LATER
STATEMENTS WILL DETAIL ANY THREATS FROM STORMS ON MONDAY...BUT
WIDESPREAD SEVERE WEATHER IN NOT ANTICIPATED.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED TODAY.

RJD