Severe Thunderstorm Warning 121, NWS Grand Rapids, MI

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

LATEST WV IMAGERY CONTINUES TO SHOW THE UPPER LOW SPINNING ITS
WHEELS OVER THE NORTHWESTERN GREAT LAKES THIS MORNING. THE MAIN
FORECAST CONCERN IN THE SHORT TERM REVOLVE AROUND SHOWER AND
THUNDERSTORM CHANCES THROUGH MON NIGHT WITH THIS LOW ALONG WITH MAX
AND MIN TEMPERATURES THROUGH THE PERIOD. THE 00Z MODELS ARE IN
AGREEMENT FOR THE MOST PART IN GENERAL. THEY DO HAVE DIFFERENCES
CONCERNING TIMING AND STRENGTH OF INDIVIDUAL WAVES.

AS THE UPPER LOW WOBBLES SOUTH AND EAST TODAY CLOSER TO THE AREA...A
BIT OF ADDITIONAL MOISTURE IS ALSO GOING TO WORK INTO THE AREA. SOME
MID LEVEL MOISTURE IS EXPECTED TO MOVE IN WITH THE ASSOCIATED UPPER
LOW. SOME MOISTURE IS ALSO MOVING INTO THE STATE FROM THE SOUTHWEST.
TEMPS WITH THE ASSOCIATED COLD POOL REMAIN ABOUT THE SAME TODAY
AROUND -12C. AS LOW LEVEL THICKNESSES COOL A LITTLE...HIGHS ARE
EXPECTED TO BE NEAR OR A DEGREE OR TWO COOLER THAN YESTERDAY.
THIS WILL GIVE US HIGHS IN THE UPPER 70S FOR THE MOST PART. AS A
RESULT...INSTABILITY WILL BE A LITTLE LESS THAN YESTERDAY. HOWEVER
WITH ADDITIONAL MOISTURE AND A SFC LOW WITH AN ASSOCIATED FRONT/
TROUGH MOVING OVER THE STATE TODAY...SHOWERS AND THUNDERSTORMS
LOOK TO BE A GOOD BET...ESPECIALLY IN THE AFTERNOON AND EVENING. A
LAKE BREEZE SHOULD FORM AND HELP INITIATE CONVECTION ALONG WITH ANY
IMPULSES AROUND THE UPPER LOW IN THE AFTERNOON. THEN OUTFLOW
BOUNDARIES WILL HELP KICK OFF NEW CONVECTION AS WAS THE CASE IN WI
AND MN YESTERDAY. WILL GO WITH LIKELY POPS ACROSS THE AREA. THESE
SHOWERS AND STORMS WILL NOT MOVE VERY FAST WITH WINDS AOB 30 KTS
THROUGH 30K FEET. WITH FREEZING LEVELS AROUND 11K FEET...HAIL IS
POSSIBLE AGAIN.

CONVECTION WILL BE ONGOING THIS EVENING BEFORE WEAKENING
CONSIDERABLY AFTER SUNSET. HOWEVER AS IS THE CASE OVER IN WI...
OUTFLOW BOUNDARIES WILL CONTINUE TO KICK OFF A COUPLE SHOWERS/
STORMS INTO THE EARLY MORNING HOURS. WILL KEEP THE LIKELY GOING FOR
THE EVENING AND THEN GO WITH SCT WORDING OVERNIGHT. I HAVE ADDED FOG
TO THE GRIDS WITH RAIN EXPECTED OVER MOST OF THE AREA TODAY AND NO
DRY ADVECTION EXPECTED. LOWS SHOULD FALL TO NEAR 60 OR SO.

MON THE UPPER LOW IS OVERHEAD. THE ONLY DIFFERENCE MON IS THE SFC
LOW AND FRONT/TROUGH MOVING THROUGH TODAY SHOULD BE NORTH AND EAST
OF THE AREA FOR THE MOST PART WHILE WEAKENING. SHOWERS AND STORMS
SHOULD STILL DEVELOP IN THE AFTERNOON WITH THE CONTINUED UNSTABLE
CONDITIONS. WITH LESS LOW LEVEL FORCING...THE COVERAGE SHOULD BE
JUST A LITTLE LESS THAN TODAY. WILL GO WITH A SCT POP ACROSS THE
AREA. TEMPS WILL BE SIMILAR TO TODAY WITH SIMILAR THICKNESSES AND
PARTLY SUNNY SKIES.

MON NIGHT AGAIN WILL SEE SHOWERS AND STORMS CONTINUE INTO THE
EVENING BEFORE WEAKENING AFTER SUNSET. WILL GO WITH A DIMINISHING
TREND MON NIGHT ALSO. LOWS SHOULD BE IN THE UPPER 50S TO NEAR 60.

NJJ

EXTENDED FORECAST DISCUSSION...
EXTENDED LOOKS TO BE IN GOOD SHAPE...WITH GRADUALLY IMPROVING
CONDITIONS THE GENERAL THEME. UPPER LOW WILL BE WEAKENING WITH TIME
AND LIFTING NORTHEAST OF THE FORECAST AREA. THIS WILL PLACE THE AREA
IN NORTHWEST UPPER FLOW ON THE BACKSIDE OF THE TROUGH. COOL POOL OF
AIR ALOFT TRIES TO HANG ON INTO THE MIDDLE PORTIONS OF THE
WEEK...WHICH WILL MAKE DIURNAL SHOWERS AND THUNDERSTORMS A
POSSIBILITY. WILL KEEP SHOWERS AND THUNDERSTORMS BOTH TUES AND WED.
THURSDAY HAS A MENTION OF SHOWERS AND THIS STILL LOOKS LIKE A
POSSIBILITY WITH COOL AIR ALOFT AND NORTHWEST UPPER FLOW. RIDGING AT
THE SURFACE TRIES TO BUILD IN TOWARD THE END OF THE WORK WEEK AND
WILL THEREFORE KEEP FRIDAY AND SATURDAY DRY. WOULD NOT BE SURPRISED
THOUGH TO EVEN SEE SOME DIURNAL PRECIP KICK OFF ON FRIDAY TOO. TEMPS
AT 850MB/S THROUGH THE WEEK HARDLY CHANGE AND GUIDANCE REFLECTS
THIS. SEASONABLE VALUES SHOULD OCCUR WITH LOWS AROUND 60 AND HIGHS
AROUND 80

DUKE

.GRR...NONE.

MIZ037>040-043>046-050>052-056>059-064>067-071>074-031000-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
110 PM EDT SAT AUG 2 2003

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

.DAY ONE...TODAY AND TONIGHT

ISOLATED SEVERE THUNDERSTORMS ARE EXPECTED ACROSS SOUTHWEST LOWER
MICHIGAN THIS AFTERNOON AND EVENING. A LINE OF THUNDERSTORMS ALONG
THE LAKE BREEZE WILL MOVE SLOWLY INLAND OVER THE NEXT 2 HOURS...
REACHING U.S. 131 BY 300 PM.  MOST OF THESE STORMS WILL NOT BE
SEVERE.  HOWEVER...A FEW OF THE STORMS ON THAT LINE COULD REACH
SEVERE LIMITS AND PRODUCE HAIL UP TO 1 INCH IN DIAMETER. WIND GUSTS
TO 50 MPH ARE ALSO POSSIBLE FROM THE STRONGEST STORMS. THE SOUTH END
OF THE LINE IS CONTINING TO BUILD SOUTH INTO ALLEGAN COUNTY BY 200
PM.

ELSEWHERE... ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE OVER THE
AREAS INLAND OF U.S. 131 AFTER 300 PM. THE THREAT FOR SEVERE
THUNDERSTORMS WILL DIMINISH AFTER SUNSET.

ALL OF THESE STORMS WILL BE SLOW MOVING...MOSTLY TO THE NORTHEAST AT
AROUND 10 MPH. SO...LOCAL URBAN AND SMALL STREAM FLOODING IS
POSSIBLE FROM ANY OF THESE STORMS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THUNDERSTORMS WILL BE POSSIBLE EACH DAY FROM SUNDAY THROUGH
WEDNESDAY. STORMS MAY BE ON THE STRONG SIDE AGAIN ON SUNDAY. HAIL
WILL BE THE MAIN THREAT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER HAVE BEEN ACTIVATED FOR THIS AFTERNOON AND EVENING.

WDM