Severe Thunderstorm Warning 84, NWS Detroit, MI

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1100 AM EDT SUN SEP 9 2001

SHOWERS AND THUNDERSTORMS WERE MOVING NORTHEAST ACROSS SOUTHEAST
MICHIGAN IN A NARROW BAND EXTENDING FROM NEAR SAGINAW BAY TO
YPSILANTI AND ADRIAN.  CONDITIONALLY UNSTABLE AIR MASS ON THE 12Z
DTX RAOB...WITH THE PRECIPITATION HELPED IN LARGE PART DUE TO A WEAK
UPPER WAVE VISIBLE ON WATER VAPOR MOVING ACROSS LOWER MICHIGAN AT
THE MOMENT.  THIS WAVE COULD HAVE BEEN CONVECTIVELY INDUCED FROM
OVERNIGHT THUNDERSTORMS TO OUR SOUTHWEST.  THESE SHOWERS AND
THUNDERSTORMS SHOULD CONTINUE TO MOVE NORTHEAST AND EXIT THE THUMB
EARLY THIS AFTERNOON.  EARLY MORNING...RELATIVELY COOL SURFACE
TEMPERATURES SUPPORTING A SMALL SURFACE INVERSION HAVE...OVERALL...
APPEARED TO YIELD LITTLE IN THE WAY OF WIND GUSTS WITH THE NARROW
BAND OF STORMS DESPITE GOOD MID LEVEL DRY AIR ABOVE 700MB.  MORNING
RAOB...88D...AND MODEL PROGS OF THE WIND OVER SOUTHEAST MICHIGAN
THROUGH 18Z SHOWED A LULL IN SPEEDS FROM THE SURFACE THROUGH 850MB
WHICH HAS...IN PART...KEPT THE CONVECTIVE GUSTS DOWN.  OZW WIND
GUSTS MONITORED IN PERSISTENT CALLS YIELDED A TEENS WIND GUST DURING
THE HOUR.

CONSIDERABLE CLOUD COVER EVIDENT ON VISIBLE SATELLITE IMAGES OVER
INDIANA...SOME OF WHICH HAS SHOWN A TENDENCY TO FILL IN SINCE 10
AM.  STILL...THERE ARE SOME THIN PATCHES IN THE CLOUDS...AND THOUGH
CONSIDERABLE CLOUDINESS IS EXPECTED AS A RULE OVER SOUTHEAST
MICHIGAN THIS AFTERNOON...FEEL THERE WILL BE ENOUGH BREAKS TO ALLOW
MOST PLACES TO EDGE INTO THE LOWER 80S FOR HIGHS.  MODIFYING THE DTX
MORNING RAOB FOR LOWER 80S WITH DEW POINTS IN THE UPPER 60S PROVIDES
FOR CAPE OF 2400 J/KG.  INCREASING WIND FIELDS AGAIN LATE THIS
AFTERNOON AHEAD OF A STRONG UPPER WAVE ROTATING OVER IOWA AND
MISSOURI...AND SURFACE BOUNDARY CURRENTLY PLOTTED FROM NEAR THE
STRAITS...THROUGH THE MKE AND UIN AREAS...WILL ALLOW FOR
THUNDERSTORM DEVELOPMENT...LIKELY WITH VIGOR...MOVING INTO SOUTHEAST
MICHIGAN IN THE LATE AFTERNOON/EARLY EVENING TIME FRAME.  BEST
POTENTIAL FOR SEVERE WEATHER WOULD APPEAR TO BE AFTER 4 PM...LASTING
INTO THE LATE EVENING BEFORE MODEL PROGS SHOW THE DEEPEST MOISTURE
AND HIGHEST INSTABILITY ROTATING EAST OF THE AREA WITH A SURFACE
WAVE...CURRENTLY OVER WESTERN ILLINOIS...MOVING TO THE NORTHEAST.

.DTX...NONE.

DJF

MIZ047>049-053>055-060>063-068>070-075-076-082-083-100800-

SEVERE WEATHER OUTLOOK FOR SOUTHEAST LOWER MICHIGAN
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1157 AM EDT SUN SEP 9 2001

...SEVERE WEATHER POTENTIAL STATEMENT FOR SOUTHEAST MICHIGAN...

DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY.

NUMEROUS THUNDERSTORMS WILL OCCUR THROUGHOUT SOUTHEAST MICHIGAN
THROUGH TONIGHT.  SOME OF THESE THUNDERSTORMS WILL LIKELY BECOME
SEVERE.  SPOTTER ACTIVATION IS LIKELY AS WELL.

VERY MOIST AIR REMAINS OVER SOUTHEAST MICHIGAN AHEAD OF A COLD
FRONT.  THIS COLD FRONT...LOCATED OVER NORTHERN MICHIGAN AND
SOUTHERN WISCONSIN AROUND THE NOON HOUR...WILL SLOWLY MOVE EAST...
SWEEPING THROUGH SOUTHEAST MICHIGAN BY 4 AM.  AS THE COLD FRONT
MOVES EAST...A STRENGTHENING LOW PRESSURE CENTER WILL MOVE NORTH
ALONG THE FRONT THROUGH CENTRAL AND NORTHERN LOWER MICHIGAN...
REACHING NORTHERN LAKE HURON LATE THIS EVENING.  ALL OF THESE WILL
PROVIDE FOR NUMEROUS THUNDERSTORMS.

THE MOST LIKELY TIME FOR SEVERE THUNDERSTORMS IN SOUTHEAST MICHIGAN
WILL BE BETWEEN 4 PM AND MIDNIGHT.  THE MAIN THREAT FROM THESE
STORMS WILL BE DAMAGING WIND GUSTS TO 80 MPH...HAIL TO AN INCH IN
DIAMETER...AND HEAVY RAIN.  RAINFALL RATES COULD EXCEED AN INCH IN
A HOUR...RESULTING IN PONDING OF WATER.  AS THE SURFACE LOW PRESSURE
CENTER MOVES NORTH ACROSS MICHIGAN LATE IN THE DAY AND THIS
EVENING...AN ISOLATED THUNDERSTORM COULD BE CAPABLE OF PRODUCING A
TORNADO.  THIS THREAT WILL MAINLY BE NORTH OF M 46...WITH THAT THREAT
DIMINISHING BY 8 PM.

THUNDERSTORMS WILL TEND TO MOVE NORTHEAST AT 45 MPH.  STAY TUNED TO
NOAA WEATHER RADIO...OR YOUR LOCAL RADIO...TELEVISION...OR
CABLE TELEVISION STATION...FOR THE LATEST WEATHER INFORMATION.

DJF