Flash Flood Warning 1, NWS Detroit, MI

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1040 AM EDT FRI JUN 21 2002

...THUNDERSTORMS PRODUCING HEAVY RAINFALL THE MAIN CONCERN...

FRONTAL BOUNDARY WAS JUST TO THE NORTH OF FLINT EXTENDING TO THE
COUNTY BORDERS OF ST CLAIR AND SANILAC.  PLENTY OF CONVECTION FIRING
ALONG THE BOUNDARY WITH MOVEMENT QUITE SLOW TO THE EAST.  LATEST 88D
PRECIP RATES NEAR 1 PER HOUR IN SPOTS TO THE WEST WITH METARS
SHOWING ABOUT HALF AS MUCH (RAINFALL AMOUNTS LIKELY HIGHER OUTSIDE
OF METAR REPORTS).  88D CROSS SECTIONS SHOW THE HIGHEST
REFLECTIVITIES CLOSER TO THE SURFACE WHICH INDICATES PLENTY OF WATER
FALLING...NOT MUCH IF ANY HAIL.  WIND PROFILES ARE ALSO QUITE WEAK
HENCE THE SLOW MOVEMENT AND MINIMAL WIND DAMAGE POTENTIAL.

QUESTION FOR THE AFTERNOON IS THUNDERSTORMS.  AFOREMENTIONED
BOUNDARY ACROSS THE NORTH WITH ANOTHER WEAK AREA OF CONVERGENCE
ACROSS NORTHERN INDIANA AND NORTHWEST OHIO.  HIGH THETA-E AIR OVER
THE STATE WITH PWATS OVER 1.75 PER RAOBS AND LAPS SOUNDINGS.  LAPS
INFORMATION ALSO CONTINUES WITH LI/S NEAR -4C WITH CAPES AROUND 1K
J/KG.  BASED ON 850-300MB THICKNESS SCHEME AND THE THERMAL
WIND...THESE STORMS WILL BE SLOW MOVERS...EAST BETWEEN 10-15 MPH.
FAVORABLE THICKNESS DIFLUENCE OVER SOUTHEAST LOWER AND K INDEX
VALUES INTO THE LOWER 30S C.  FFG FROM THIS MORNING POINTS TO AROUND
2.5 OF RAIN WITHIN 3-6 HOUR TIME FRAME...SO THIS WILL HAVE TO BE
CLOSELY MONITORED.

WE WILL UPDATE THE CURRENT FORECAST TO SCATTERED AND WATCH SHORT
TERMS VERY CLOSELY.  NOW WITH SEVERAL OUTFLOW BOUNDARIES INTERACTING
WITH DAYTIME HEATING...THUNDERSTORMS WILL BE SCATTERED CWA-WIDE
THANKS TO DIFFERENTIAL HEATING.  WARM AND MUGGY CONDITIONS WILL
PREVAIL WITH DEWPOINTS NEAR 70F.

.DTX...NONE.

BGM

MIZ047>049-053>055-060>063-068>070-075-076-082-083-220200-

HAZARDOUS WEATHER OUTLOOK FOR SOUTHEAST MICHIGAN
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1105 AM EDT FRI JUN 21 2002

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

DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY.

HAZARD...
SCATTERED THUNDERSTORMS ARE EXPECTED ACROSS ALL OF SOUTHEAST LOWER
MICHIGAN THIS AFTERNOON.  THE MAIN HAZARD WITH THESE THUNDERSTORMS
WILL BE HEAVY RAINFALL...WITH SMALL HAIL ALSO POSSIBLE.

DISCUSSION...
A FRONTAL BOUNDARY JUST NORTH OF INTERSTATE 69 WILL BE THE MAIN
FOCUS FOR THUNDERSTORMS THIS AFTERNOON.  THE WINDS IN THE UPPER
LEVELS OF THE ATMOSPHERE ARE WEAK WHICH WILL RESULT IN SLOW
MOVEMENT OF THUNDERSTORMS.  WITH THE WATER CONTENT IN THE ATMOSPHERE
QUITE HIGH...THUNDERSTORMS WILL PRODUCE HEAVY RAINFALL RATES.  SOME
OF THESE RAINFALL RATES WILL BE NEAR 1 INCH PER HOUR...CAUSING
LOCALIZED FLOODING...ESPECIALLY IN LOW LYING AND POOR DRAINAGE
AREAS. ADDITIONAL BOUNDARIES SOUTH OF INTERSTATE 69 WILL AID IN THE
CONTINUED DEVELOPMENT OF THUNDERSTORMS THIS AFTERNOON.  AGAIN...THE
MAIN HAZARD HERE WILL CONTINUE TO BE HEAVY RAINFALL WITH PEA SIZE
HAIL POSSIBLE.

THUNDERSTORM MOVEMENT WILL BE TO THE EAST AT 10 AND 15 MPH.

SPOTTER ACTIVATION...
SPOTTER ACTIVATION IS NOT ANTICIPATED.

OUTLOOK FOR SATURDAY AND SUNDAY...
ADDITIONAL THUNDERSTORMS ARE EXPECTED ON SATURDAY WITH MAIN HAZARD
FROM HEAVY RAINFALL. DRY WEATHER IS FORECAST FOR SUNDAY.

STAY TUNED TO NOAA WEATHER RADIO...OR LOCAL MEDIA OUTLETS...FOR
THE LATEST FORECAST INFORMATION FROM YOUR NATIONAL WEATHER SERVICE.
YOU CAN ALSO OBTAIN THE LATEST FORECAST ON OUR NATIONAL WEATHER
SERVICE WEB SITE.

HTTP://WWW.CRH.NOAA.GOV/DTX/ (ALL LOWER CASE)

BGM