Severe Thunderstorm Warning 63, NWS Grand Rapids, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
400 PM EDT FRI JUL 23 2010

LATEST UPDATE...SYNOPSIS SHORT TERM MARINE HYDROLOGY...

.SYNOPSIS...(400 PM EDT FRI JUL 23 2010)
A COLD FRONT WILL SWING THROUGH LOWER MICHIGAN SATURDAY.  AHEAD OF
THIS FEATURE WILL BE A WARM AND HUMID AIRMASS WITH SOME
THUNDERSTORMS.  SEVERE WEATHER AND HEAVY RAINFALL ARE POSSIBLE.  A
DRIER AIRMASS ARRIVES FOR SUNDAY.

&&

.SHORT TERM...(400 PM EDT FRI JUL 23 2010)
(THIS AFTERNOON THROUGH SATURDAY NIGHT)
THE MAIN CHALLENGE IS THE THUNDERSTORM COVERAGE AND INTENSITY THIS
EVENING INTO SATURDAY.

FOR THIS EVENING...WARM AND MOIST AIR ADVECTION IS UNDERWAY.  AZO
HEAT INDEX UP TO 106.  THIS HEAT AND HUMIDITY WILL PROVIDE THE FUEL
FOR LATER THUNDERSTORM DEVELOPMENT.  THE STORMS IN IOWA WILL LIKELY
MOVE INTO OR TRACK ACROSS SOUTHERN PARTS OF  LOWER MI THIS EVENING.
DEEP LAYER  SHEAR IS FAVORABLE FOR ORGANIZED CONVECTION. WITH
DAMAGING WINDS THE PRIMARY THREAT.

HEAT INDEX VALUES ARE UP TO 100 TO 105 ALONG INTERSTATE 94.  HOWEVER
ALONG AND NORTH OF INTERSTATE 96 VALUES WERE MUCH LOWER.  THE
POTENTIAL FOR 3 HOURS OF 100 DEG VALUES IS LIMITED SO I CANCELLED
THE NORTHERN PARTS OF THE ADVISORY.

THE NAM HAS SHOWN THE BEST INSTABILITY SOUTH OF JACKSON ON
SATURDAY.  THE GFS STILL HAS MUCH OF SOUTHERN LOWER MI
WITH STRONGER INSTABILITY DURING THE LATE MORNING INTO EARLY
AFTERNOON HOURS.  SO SOME UNCERTAINTY EXISTS WITH THE DEGREE OF
SEVERE POTENTIAL SATURDAY.  WILL MAINTAIN THE HIGHER POPS.

STILL LOOKING DRIER FOR SUNDAY.

&&

.LONG TERM...(316 PM EDT FRI JUL 23 2010)
MONDAY THROUGH FRIDAY)
UPPER TROUGH WILL PUSH A COLD FRONT THROUGH THE REGION WEDNESDAY.
TUE NITE/WED SHOULD BE THE FAVORED TIME FOR TSRA NEXT WEEK. MON/TUE
LOOK DRY WITH SFC HIGH OVERHEAD. EXACTLY HOW FAR SOUTH THE COLD
FRONT PUSHES WILL BE KEY FOR HOW MUCH TSRA ACTIVITY WE SEE. ATTM WE
HAVE VERY LOW CHC POPS FOR THE LATTER PART OF THE WEEK. EVENTUALLY
THE BOUNDARY WILL RETURN NORTH AS LOW PRESSURE DEVELOPS IN THE
PLAINS AND MOVES NORTHEAST. THE LATEST HIRES ECMWF IS SLOWER IN
MOVING THE FRONT BACK NORTH AND INSTEAD SHOWS NNE WINDS THU-FRI. THE
GFS IS A BIT QUICKER. CONFIDENCE ISN/T HIGH THAT WE/LL SEE TSRA
AFTER WEDNESDAY...SO POPS ARE GENERALLY BELOW 30 PERCENT.

&&

.AVIATION...(150 PM EDT FRI JUL 23 2010)
VISIBLE SATELLITE SHOWS CLEARING SKIES MOVING INTO LOWER MICHIGAN.
THIS WILL ALLOW THE ATM TO DESTABILIZE EVEN MORE THAN IT ALREADY IS.
MODERATE CU WAS NOTED IN NRN IL MOVING NE TOWARD THE CWA. WE/LL
WATCH TO SEE IF THESE CELLS DEVELOP INTO STORMS THIS AFTERNOON. A
HIGHER CHC OF STORMS WILL COME TONIGHT AS A SHORT WAVE MOVES TOWARD
THE CWA. CONSERVATIVELY WENT WITH 3-4SM TSRA OVERNIGHT. IT/S
POSSIBLE THAT VSBYS COULD BE LWR BECAUSE THE HEAVY RAIN THREAT IS
PRETTY HIGH.

&&

.MARINE...(400 PM EDT FRI JUL 23 2010)
DIMINISHING WINDS AND WAVES EXPECTED THIS AFTERNOON.  OMR HAD
SEVERAL BEACHES WITH 6 FOOT WAVES...SO MAINTAINED THE SMALL CRAFT
ADVISORY.  EARLIER I UPDATED THE SRF TO REFLECT HIGHER WAVES DOWN IN
THE SOUTHERN ZONES.  WILL ALLOW THE SMALL CRAFT ADVISORY TO EXPIRE
AT 5 PM.

&&

.HYDROLOGY...(400 PM EDT FRI JUL 23 2010)
THE STORMS IN IOWA ARE LIKELY TO CLIP OR MOVE INTO LOWER MI TONIGHT.
ANOTHER ROUND OF STORMS WITH HEAVY RAIN IS POSSIBLE SATURDAY AS THE
FRONT TRACKS THROUGH.  EFFICIENT PRECIPITATION AND TRAINING ARE
POSSIBLE GIVEN THE SLOW/STATIONARY BOUNDARY IN PLACE.  AS MUCH OF
AREA SAW HEAVY RAIN ON THURSDAY...RUNOFF WILL BE MORE EFFICIENT.
THUS MUCH OF THE AREA HAS BEEN PLACED UNDER A FLASH FLOOD WATCH.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI....HEAT ADVISORY SOUTHERN PARTS OF THE CWA TIL 8 PM.
      FLASH FLOOD WATCH INTO SATURDAY AFTERNOON FOR MUCH OF THE
      REGION.
LM....SMALL CRAFT ADVISORY THROUGH THIS AFTERNOON.

&&

SYNOPSIS:     MJS
SHORT TERM:   MJS
LONG TERM:    93
AVIATION:     93
MARINE:       MJS
HYDROLOGY:    MJS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1245 PM EDT FRI JUL 23 2010

MIZ037>040-043>046-050>052-056>059-064>067-071>074-240945-
MASON-LAKE-OSCEOLA-CLARE-OCEANA-NEWAYGO-MECOSTA-ISABELLA-MUSKEGON-
MONTCALM-GRATIOT-OTTAWA-KENT-IONIA-CLINTON-ALLEGAN-BARRY-EATON-
INGHAM-VAN BUREN-KALAMAZOO-CALHOUN-JACKSON-
1245 PM EDT FRI JUL 23 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST LOWER
MICHIGAN.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS ARE EXPECTED TODAY INTO TONIGHT. ISOLATED
SEVERE THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON AND THIS EVENING
NEAR AND SOUTH OF INTERSTATE 96. DAMAGING WIND GUSTS WOULD BE THE
PRIMARY CONCERN. AN ISOLATED TORNADO IS POSSIBLE.  AREAS OF HEAVY
RAINFALL MAY LEAD TO URBAN AND SMALL STREAM FLOODING.

HOT AND HUMID WEATHER WILL BE IN PLACE SOUTH OF ROUTE 10 THIS
AFTERNOON. TEMPERATURES SHOULD BE NEAR 90 DEGREES AND DEW POINTS
SHOULD BE IN THE MID 70S...THAT WILL RESULT IN HEAT INDEX VALUES
NEAR 100 DEGREE FOR SEVERAL HOURS. THIS WOULD INCREASE THE RISK OF
HEAT STROKE FOR ANYONE HAVING TO WORK OUTSIDE THIS AFTERNOON.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THE PASSAGE OF THE COLD FRONT SATURDAY WILL TOUCH OFF
STRONG TO SEVERE STORMS DURING THE DAY SATURDAY. DAMAGING
WINDS AND VERY HEAVY RAINFALL ARE EXPECTED WITH THESE STORMS. AREAS
OF FLOODING OF POOR DRAINAGE IS POSSIBLE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS POSSIBLE THROUGH SATURDAY.

LMZ844>849-240945-
ST JOSEPH TO SOUTH HAVEN MI-SOUTH HAVEN TO HOLLAND MI-
HOLLAND TO GRAND HAVEN MI-GRAND HAVEN TO WHITEHALL MI-
WHITEHALL TO PENTWATER MI-PENTWATER TO MANISTEE MI-
1245 PM EDT FRI JUL 23 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST LOWER
MICHIGAN.

.DAY ONE...TODAY AND TONIGHT

SOUTHWEST WINDS WILL UP TO 25 KNOTS THIS MORNING INTO EARLY THIS
AFTERNOON WILL SLOWLY BY EVENING. UNTIL THEN WINDS AND WAVES WILL BE
STRONG ENOUGH TO BE A HAZARD TO SMALL WATER CRAFT. AN INCREASED
RISK FOR RIP CURRENTS WILL EXIST TOO. SCATTERED THUNDERSTORMS ARE
EXPECTED TOO.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THE PASSAGE OF A STRONG COLD FRONT SATURDAY EVENING IS EXPECTED TO
TOUCH OFF STRONG TO SEVERE STORMS WITH GUSTY WINDS AND INCREASED
WAVE HEIGHTS.

STRONG SOUTH WINDS WILL LEAD TO HAZARDOUS CONDITIONS FOR SMALL
WATER CRAFT SATURDAY. WINDS WILL REMAIN STRONG BUT BECOME WESTERLY
SATURDAY NIGHT WITH THE PASSAGE OF A STRONG COLD FRONT DURING THE
EVENING. THE WIND AND WAVES WILL SLOWLY DIMINISH SUNDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS POSSIBLE THROUGH SATURDAY.

WDM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
526 PM EDT FRI JUL 23 2010

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0518 PM     FLOOD            BATTLE CREEK            42.32N 85.19W
07/23/2010                   CALHOUN            MI   EMERGENCY MNGR

            A FEW ROADS IN THE BATTLE CREEK AREA ARE BEGINNING TO
            FLOOD.

0519 PM     FLOOD            3 NW KALAMAZOO          42.31N 85.63W
07/23/2010                   KALAMAZOO          MI   AMATEUR RADIO

            RAVINE ROAD NEAR NICHOLS ROAD BEGINNING TO FLOOD

0519 PM     FLOOD            5 WNW KALAMAZOO         42.32N 85.68W
07/23/2010                   KALAMAZOO          MI   AMATEUR RADIO

            6500 BLOCK OF H AVE BEGINNING TO FLOOD

&&

CSCHOLTEN

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