Severe Thunderstorm Warning 23, NWS Grand Rapids, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
215 PM EDT SAT MAY 10 2003

NEAR TERM FORECAST ISSUES ARE TWOFOLD...TYPE AND COVERAGE OF SEVERE
WEATHER TONIGHT AND HIGH WIND THREAT ON SUNDAY...AND POSSIBLY INTO
MONDAY AS WELL.

FOR TONIGHT...ALTHOUGH MCS MOVED ACROSS ILLINOIS AND INDIANA THIS
MORNING...CLEARING ON THE BACKSIDE OF THAT SYSTEM WILL ALLOW AIRMASS
RECOVERY THERE BY LATE AFTERNOON. STORMS ARE CURRENTLY FIRING ACROSS
THE DRY LINE SOUTH OF THE MAIN SFC LOW WHICH IS OVER EASTERN KANSAS
ATTM. EXPECT CONVECTION TO BE EXPANDING NORTHWARD THIS AFTERNOON AND
EVENING ACROSS NORTHERN MO AND WESTERN IL AS UPPER JET EJECTS OUT OF
THE BASE OF THE H5 TROUGH. EXPECT LINEAR CONVECTION TO BRING THE
THREAT OF WIDESPREAD DAMAGING WINDS TO AT LEAST THE SOUTHERN HALF OF
THE CWA BY LATE EVENING AND PERHAPS LASTING WELL PAST MIDNIGHT FOR
THE EASTERN CWA. ETA HAS BEEN CONSISTENT IN SHOWING SE FLOW THROUGH
THE OVERNIGHT AS SFC WARM FRONT PUSHES INTO SW LOWER MICHIGAN. THIS
PUMPS UP THE LOW LEVEL HELICITY VALUES. MEANWHILE..LCL HEIGHTS ARE
PROGGED TO BE BELOW 1 KFT. ANY STRONG UPDRAFTS MOVING IN THE
VICINITY OF THIS FEATURE...INCLUDING THOSE EMBEDDED IN LINES OF
CONVECTION...WILL NEED TO BE CLOSELY MONITORED FOR ROTATION.

BY 12Z...THE STEADIER RAIN SHOULD BE CLEARING THE EASTERN CWA AS
COLD FRONT PUSHES THROUGH AND DRY SLOT BRINGS AN END TO ALL BUT SCT
SHRA AND DRIZZLE. TEMPERATURES WILL BE FALLING AFTER 12Z WITH CLOUDS
AND STRONG CAA KEEPING TEMPS FROM GOING ANYWHERE INTO SUNDAY
AFTERNOON. HAVE CUT MAXES FOR SUNDAY. ETA PROGS 65 KNOT WINDS AT 3
KFT BY SUNDAY AFTERNOON IN THE CAA. SO HIGH WIND WATCH LOOKS GOOD.
VERY TIGHT PRESSURE GRADIENT PERSISTS THROUGH MONDAY AS DEEP SFC LOW
MOVES EAST ACROSS NORTHERN LOWER. STRONG SFC WINDS MAY CONTINUE INTO
MONDAY. NGM MOS HAS 25 PLUS KT SFC WINDS RIGHT THROUGH 00Z TUE AT
MKG.

HYDRO...EXPECT CONVECTION TO BE FAST MOVING OVERNIGHT...BUT RIVERS
SHOULD RESPOND WITH SHARP RISES AT A FEW SITES DUE TO LOCALLY HEAVY
RAIN...PRIMARILY ACROSS THE SOUTHERN CWA WHERE SOME HEAVY RAINS
OCCURRED RECENTLY. INTERESTINGLY...THE ETA IS SHOWING QPF WELL IN
EXCESS OF AN INCH ON SUNDAY AFTERNOON IN THE WRAPAROUND AS THE LOW
PASSES NORTH OF THE GRR CWA. THIS APPEARS TO BE OVERDONE...BUT NEEDS
TO BE WATCHED AS THIS COULD BE A PROBLEM FOR SMALLER RIVERS THAT
WILL STILL BE HIGH FROM THE THE RAINS EXPECTED TONIGHT.

OSTUNO

VERY LITTLE CHANGE REQUIRED TO THE EXTENDED FCST. A HIGH PRESSURE
RIDGE WILL NUDGE IN FROM THE WEST AT THE SFC AND ALOFT TUESDAY...
PRODUCING PARTLY CLOUDY SKIES. THE NEXT UPPER LEVEL SYSTEM WILL
APPROACH OUR AREA WEDNESDAY... BRINGING A CHANCE OF SHOWERS BY LATE
IN THE DAY. 12Z GFS GUIDANCE NOW INDICATES PCPN WILL LINGER INTO
THURSDAY AS LOW PRESSURE PASSES TO OUR SOUTH AND THE UPPER TROUGH
AXIS MOVES OVERHEAD.

HIGH PRESSURE WILL MOVE BACK IN LATE THIS WEEK... PRODUCING CLEAR TO
PARTLY CLOUDY SKIES WITH MILDER TEMPS FRIDAY AND SATURDAY.

LAURENS

.GRR...HIGH WIND WATCH FOR SUNDAY...OVER THE ENTIRE CWA.

MIZ037>040-043>046-050>052-056>059-064>067-071>074-111000-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
115 PM EDT SAT MAY 10 2003

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

A MODERATE RISK FOR SEVERE WEATHER EXISTS SOUTH OF A LINE FROM
HOLLAND TO JACKSON...MAINLY FOR TONIGHT.  FURTHER NORTH...THERE IS A
SLIGHT RISK OF SEVERE THUNDERSTORMS.  A SQUALL LINE IS EXPECTED TO
MOVE THROUGH SOUTHWEST LOWER MICHIGAN FROM 800 PM THROUGH 200 AM.
THE PRIMARY THREAT WILL BE WIDESPREAD STRONG DAMAGING WINDS IN
EXCESS OF 60 MPH AND LARGE HAIL. ISOLATED TORNADOES ARE POSSIBLE AS
WELL.

SCATTERED SEVERE THUNDERSTORMS COULD FORM AS EARLY AS MID AFTERNOON.
THE ATMOSPHERE WILL BECOME VERY UNSTABLE BY LATE AFTERNOON AND
ISOLATED STRONG DOWNBURST WINDS AND LARGE HAIL ARE POSSIBLE BY
EVENING.

THE SQUALL LINE IS EXPECTED TO FORM THIS EVENING IN RESPONSE TO A
DEEPENING LOW PRESSURE SYSTEM THAT WILL BE TRACKING FROM THE CENTRAL
PLAINS STATES TODAY...TO WISCONSIN BY SUNDAY.  ALTHOUGH THE PRIMARY
THREAT WILL BE DOWNBURST WINDS ALONG THE SQUALL LINE...A WARM FRONT
ACROSS LOWER MICHIGAN TONIGHT MAY PROVIDE LOW LEVEL TURNING OF THE
WINDS. THIS WILL ALLOW FAVORABLE CONDITIONS FOR TORNADOES TO BE
PRODUCED BY ANY STORMS MOVING IN THE VICINITY OF THE WARM FRONT.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

STRONG WINDS WILL FOLLOW THE PASSAGE OF THE LOW PRESSURE SYSTEM ON
SUNDAY. A HIGH WIND WATCH HAS BEEN ISSUED FOR SUNDAY AS SUSTAINED
WINDS OF 30 TO 40 MPH ARE PREDICTED...WITH GUSTS TO 60 MPH POSSIBLE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL LIKELY BE NEEDED LATE THIS AFTERNOON THROUGH
TONIGHT.

OSTUNO

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
0752 PM EDT SAT MAY 10 2003

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

1210 AM    1 W BROOKLYN              MI   1.00 IN HAIL
05/10/03   JACKSON                        HAIL ABOUT ONE INCH IN
                                          DIAMETER NEAR CLARK LAKE.

OSTUNO