Severe Thunderstorm Warning 75, NWS Detroit, MI

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
340 AM EDT TUE SEP 10 2002

CONVECTIVE POTENTIAL WILL BE THE FIRST CONCERN FOR THIS FORECAST
FOLLOWED BY DETAILS ON A DRAMATIC COOLING TREND FOR TOMORROW AND
THURSDAY. NO ADDITIONAL PRECIPITATION IS EXPECTED UNTIL THIS WEEKEND
WHEN THE NEXT FRONTAL SYSTEM MOVES INTO SE MICHIGAN.

SATELLITE AND RADAR TRENDS SHOW CONVECTION TRYING TO BREAK LOOSE
FROM NE TO SW ALONG THE PREFRONTAL TROF AS MORE AND MORE OF THE LINE
BREAKS THROUGH A MODEST LOW LEVEL CAP. FORECAST SOUNDINGS MODIFIED
FOR 90/68 SHOW CAPE AROUND 2800 J/KG BUT WITH A WEAK HODOGRAPH.
WITHOUT A GOOD WIND FIELD IT WILL BE DIFFICULT TO GET ANY ORGANIZED
CONVECTION, BUT THE RELATIVELY HIGH CAPE ENVIRONMENT AND DEEP MID
LEVEL MOISTURE (PW=1.7,KINX=38 AT 00Z) WILL MAKE PRECIP LOADED WIND
GUSTS A CONCERN. CONTRIBUTING TO THAT WILL BE RELATIVELY WIDE T/TD
SPREADS BELOW CLOUD BASE. PLAN TO CONTINUE WITH SCATTERED COVERAGE
BUT TREND TOWARD NUMEROUS COVERAGE AS POST FRONTAL SHOWERS WORK INTO
THE AREA. SUPPORT FOR THIS INCLUDES A BEEFED UP MODEL QPF OVER THE
LAST COUPLE OF RUNS, WHICH SEEMS JUSTIFIED AS UPPER SUPPORT ARRIVES
IN THE FORM OF QVECTOR CONVERGENCE AND 850 TO 700 MB LAYER FGEN.

PRECIP WILL BE OUT OF SE MICHIGAN BY MIDNIGHT WITH CLOUDS AND COOLER
TEMPS THE ONLY CONCERN FOR OVERNIGHT AND WEDNESDAY. AFTER A PERIOD
OF PARTLY CLOUDY SKIES OVERNIGHT, COLD AIR INSTABILITY CU WILL BE
AUGMENTED BY LAKE CLOUDS OVER SE MICHIGAN WITH A MAINLY NORTH WIND
FLOW DURING WEDNESDAY. AFTERNOON TEMPS OVER MN AND WI SUPPORT
GUIDANCE TEMPS IN THE LOWER 70S, ESPECIALLY WITHOUT FULL SUN.

CLEAR SKIES WILL BE COUNTERED BY A STEADY NORTH WIND WEDNESDAY NIGHT
WHICH WILL KEEP TEMPS FROM REALLY DROPPING OFF A LOT. THE BEST
COOLING NIGHT LOOKS TO BE THURSDAY NIGHT AS HIGH PRESSURE SETTLES
OVER THE AREA AND ALLOWS LOW TEMPS TO RADIATE A LITTLE FARTHER INTO
THE UPPER 40S AT MOST LOCATIONS. WITH HIGH PRESSURE IN
CONTROL, EXPECT CLEAR CONDITIONS THURSDAY AND THURSDAY NIGHT.

HIGH CLOUDS WILL BE ON THE INCREASE ON FRIDAY AS RETURN FLOW AND MID
LEVEL WARM ADVECTION SETS UP IN THE PLAINS. THE SYSTEM FOR SATURDAY
IS A LITTLE SLOWER ON THE LATEST RUNS OF THE AVN/MRF BUT STILL LOOKS
ON TARGET FOR SATURDAY AND SATURDAY NIGHT. THE AVN NOW SHOWS THE
SYSTEM NEAR THE FOUR CORNERS REGION GETTING ABSORBED INTO THE
WESTERLIES AND BRINGING SOME GULF MOISTURE ALONG WITH IT. THIS WILL
OCCUR AS THE CENTRAL CANADIAN WAVE MOVES INTO THE PLAINS AND STARTS
TO CARVE OUT THE TROF OVER THE CENTRAL U.S. THIS TROF IS FORECAST BY
THE MODELS TO BE PROGRESSIVE ENOUGH THAT WE MAY BE ABLE TO TAKE THE
CHANCE OF RAIN OUT OF THE FORECAST FOR SUNDAY IF THE TREND HOLDS FOR
ONE MORE RUN. THE BEGINNING OF NEXT WEEK LOOKS DRY WITH TEMPS AROUND
NORMAL, EVEN IF THE FRONT VERIFIES A LITTLE SLOWER ON SUNDAY.

.DTX...NONE.

BT

MIZ047>049-053>055-060>063-068>070-075-076-082-083-110200-

HAZARDOUS WEATHER OUTLOOK FOR SOUTHEAST MICHIGAN
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1200 PM EDT TUE SEP 10 2002

DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY.

HAZARD...
SLIGHT CHANCE OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON/EARLY THIS
EVENING. SCATTERED SHOWERS AND THUNDERSTORMS CAN BE EXPECTED LATE
THIS AFTERNOON INTO THE EVENING HOURS. THERE IS A CHANCE THAT SOME OF
THE STORMS MAY BECOME SEVERE...WITH BOTH DAMAGING WINDS AND HAIL
BEING THE MAIN HAZARD. WIND GUSTS IN EXCESS OF 60 MPH...ALONG WITH
HAIL UP TO ONE INCH WILL BE POSSIBLE WITH THE STRONGEST STORMS. THE
BEST CHANCE FOR SEVERE WEATHER WILL BE BETWEEN 5 AND 8 PM.
THUNDERSTORM MOVEMENT WILL BE TO THE EAST AT 30 MPH.

DISCUSSION...
A STRONG COLD FRONT WILL MOVE THROUGH LOWER MICHIGAN EARLY THIS
EVENING. SUNSHINE WILL ALLOW TEMPERATURES TO RISE INTO THE
UPPER 80S TO LOWER 90S THIS AFTERNOON ACROSS SOUTHEAST MICHIGAN.
THIS WILL RESULT IN AN UNSTABLE AIRMASS...WHICH SHOULD ALLOW FOR
SCATTERED THUNDERSTORMS TO DEVELOP LATE THIS AFTERNOON AS THE COLD
FRONT APPROACHES. ALL SHOWER AND THUNDERSTORM ACTIVITY IS EXPECTED
TO END BY MIDNIGHT.

SPOTTER ACTIVATION...
SPOTTER ACTIVATION MAY BE NEEDED BETWEEN 4 AND 9 PM.

OUTLOOK FOR WEDNESDAY AND THURSDAY...
NO HAZARDOUS WEATHER EXPECTED.

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

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

SF