Severe Thunderstorm Warning 22, NWS Detroit, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
345 PM EDT THU MAY 11 2000

THE 2 MCSS THAT DEVELOPED OVERNIGHT DID NOT DISSIPATE PER THE USUAL
SCRIPT AND ARE NOW MOVING ACROSS THE FA...MAINLY ACROSS THE SOUTHERN
TWO TIERS OF COUNTIES. NORTHERN MCS AFFECTING SAGINAW VALLEY AND
NORTHERN THUMB ATTM. PERHAPS THESE SYSTEMS WERE ABLE TO MAINTAIN
THEMSELVES TODAY GIVEN THEIR MOVEMENT INTO SE LOW LEVEL FLOW AND
PERSISTENT WAA. THESE SYSTEMS SHOULD BE CLEAR OF AREA BY EARLY
EVENING. THE REFLECTIVITIES ON A COUPLE OF CELLS WITH THESE SYSTEMS
WERE EVEN STARTING TO LOOK RESPECTABLE SO WILL HAVE TO WATCH CLOSELY
NEXT COUPLE OF HOURS. LATEST SHORT RANGE MODELS SUGGEST MORE OF THIS
TYPE ACTIVITY TO COME DURING THE SHORT TERM PERIOD.

UNSEASONABLY STRONG SURFACE LOW WAS LOCATED OVER EASTERN NE LATE
THIS AFTERNOON. WARM FRONT EXTENDED FROM THE LOW ACROSS IA/NRN
IL/CNTRL IN. ATMOSPHERE HOT AND JUICED SOUTH OF THIS BOUNDARY WITH
SURFACE TEMPS IN THE MID 80S AND SURFACE DEWS AROUND 70. UPPER TROF
TO MOVE ACROSS NRN TIER OF STATES WITH AXIS JUST W OF LAKES BY
12Z/SAT. SERIES OF SURFACE LOWS WILL DEVELOP ALONG ASSOCIATED COLD
FRONT AS WHOLE SYSTEM MOVES SLOWLY E TOWARD THE REGION. AS INITIAL
LOW NOW OVER ERN NE MOVE NE TONIGHT, 50 KNOT 850 JET REDEVELOPS BY
00Z OVER ERN IL. ETA SUGGESTS THIS RESULTING IN MORE MCS
DEVELOPMENT OVER ERN WI AS HIGH THETAE AIRMASS IS LIFTED OVER
FRONTAL BOUNDARY. ASSUMING THIS MCS DEVELOPMENT OCCURS, IT WILL MOVE
ESE ACROSS MAINLY NORTHERN AND CENTRAL PORTIONS OF CWA THROUGH THE
LATE EVENING AND EARLY OVERNIGHT HOURS. ZERO TO 6 KM SHEAR VALUES GO
AS HIGH AS 60 M/S THIS EVENING WITH HELICITY VALUES JUST SHORT OF 4
DIGITS AT FNT. HOWEVER, SINCE CONVECTION WILL BE ELEVATED, WILL
PROBABLY NOT HAVE TO WORRY MUCH ABOUT THESE IMPRESSIVE PARAMETERS.
HOWEVER, ELEVATED CAPES WILL LIKELY SUPPORT MARGINALLY SEVERE HAIL
BY MIDNIGHT SO CANT WRITE OFF SVR THREAT.

MCS WILL BE MOVING E OF FA BY 12Z FRI WHICH SHOULD RESULT IN A
REPRIEVE PRECIP-WISE. IN FACT, WARM FRONTAL BOUNDARY PROGGED TO BE
NORTH OF FA BY THEN ALLOWING WARM AND HUMID AIRMASS TO FLOW IN.
THINNING DEBRIS CLOUDINESS WILL LIKELY ALLOW TEMPS TO WARM NEAR
THOSE SUGGESTED BY FWC AND SUPPORTED BY ETA. MEANWHILE, ANOTHER
SURFACE LOW WILL BE HEADING FOR LOWER AND ETA SHOWS WHAT APPEARS TO
BE ANOTHER WEAK BOUNDARY BISECTING THE FA BY 00Z/SAT. CAPE VALUES
PROGGED TO BE AROUND 3000 JOULES AT FNT/DTW DURING THE AFTERNOON AND
WEAK CAPPING INVERSION SHOULD HELP KEEP CONVECTION IN CHECK UNTIL
LATER IN THE AFTERNOON WHEN LOWER LEVEL CONVERGENCE PICKS UP SOME
WITH APPROACH OF SURFACE LOW AND LOW LEVEL BOUNDARY. A LITTLE
PERPLEXED AT ETA SHOWING A DROP OFF IN CAPE VALUES DURING THE LATE
AFTERNOON AND EVENING ON FRI. LOCAL LIFT PROGRAM SUGGESTS NEAR 4000
JOULES AT 00Z GIVEN A REPRESENTATIVE PARCEL INTO THE PROGGED KDTW
SOUNDING. MID LEVEL FLOW PICKS UP DURING THE EVENING AS WELL
RESULTING IN FAVORABLE CAPE/SHEAR PROFILES FOR SOME MAJOR LEAGUE
THUNDERSTORMS. AS ALWAYS, THERE ARE SEVERAL THINGS THAT CAN GO WRONG
WITH THIS SCENARIO, BUT POTENTIAL FOR ANOTHER ROUND OF SEVERE STORMS
CERTAINLY POSSIBLE LATE FRI AFT AND RIGHT THROUGH THE NIGHT AS MID
LEVEL TROF AND COLD FRONT APPROACH THE FA. SURFACE FRONT THRU EARLY
SAT FOLLOWED PERHAPS BY A BREAK IN THE CLOUDS. HOWEVER, AVN WRAPS A
LARGE AMOUNT OF LOW LEVEL MOISTURE BACK OVER THE LAKES BY AFTERNOON
AS SOME TRUE CANADIAN AIR RUSHES IN. SUPPOSE A FEW SHOWERS NOT OUT
OF THE QUESTION SAT AFT AS WELL BUT WILL HOLD OFF ON THAT FOR NOW.
COULD EVEN BE FALLING AFTERNOON TEMPS ON FRI GIVEN DEGREE OF CAA BUT
MAIN THEME FOR NOW WILL BE MOSTLY CLOUDY AND COOLER.

EXTENDED MODELS MORE INCONSISTENT THIS TIME AROUND WITH MRF SHOWING
A MUCH STRONGER NORTHERN STREAM SYSTEM THAN THE OTHER MODELS BY MID
WEEK. MRF AND ETAXX ARE STILL IN DECENT AGREEMENT ON LEE SURFACE LOW
DEVELOPMENT WITH SURFACE WARM FRONT TAKING SHAPE SOUTH OF REGION.
GEM HAS WEAKER BOUNDARY BUT NO SURFACE LOW DEVELOPMENT. WITH FAIR
CONSENSUS ON POSITION SURFACE WARM FRONTAL BOUNDARY AND ANTICYCLONIC
UPPER FLOW...FEEL MRF DEPICTION OF CAPPING INVERSION IN PLACE S OF
BOUNDARY TO BE ACCURATE. WITH STRONG ENOUGH 850 JET PROGGED, THINK
MCS DEVELOPMENT OVER UPPER MIDWEST/UPPER MISSISSIPPI VALLEY WILL BE
MAIN SOURCE FOR PRECIP MON NIGHT/TUE NIGHT WITH ADVECTION IN THE
GENERAL DIRECTION OF THE GREAT LAKES. THIS WOULD IMPLY BEST CHANCES
FOR SHOWERS/STORMS IN THE MORNING BUT CERTAINLY WONT TWEAK THE
TIMING THAT FAR OUT. IF MRF DEPICTION OF NORTHERN STREAM PLAYER
ACCURATE, WILL SEE MORE WIDESPREAD PRECIP WED/THU BUT RIGHT NOW THAT
SOLUTION IS ODD MAN OUT. SHOULD STILL SEE WARMER AND MOISTURE
AIRMASS BY WED/THU.

FMR TREND FOR SUN CONTINUES TO GET COOLER AND LATEST MRF/ETAXX SHOW
SUBZERO 850 TEMPS IN WAKE OF INCOMING FRONT ACROSS LOWER. ONCE
SURFACE HIGH SLIDES E OF THE REGION WILL BEGIN TO WARM AT MOST
LIKELY A QUICKER PACE THAN MRF SUGGESTS, PARTICULARLY WITH THE DEEP
SW FLOW PROGGED BY WED/THU.

.DTX...NONE.

JW

***THE NWS IN MICHIGAN IS CONDUCTING A SURVEY TO LEARN MORE ABOUT
HOW OUR CUSTOMERS USE THE AREA FORECAST DISCUSSION (AFD).  PLEASE
COMPLETE THIS SHORT SURVEY AT WWW.CRH.NOAA.GOV/DTX/AFDSURVEY.HTM
(ALL LOWER CASE).  THE FEEDBACK WE RECEIVE WILL HELP US PROVIDE
A BETTER PRODUCT FOR YOU.  IF YOU HAVE QUESTIONS OR IF YOU NEED A
PAPER VERSION OF THE SURVEY...CONTACT DICK WAGENMAKER AT 248 625
3309...EXTENSION 766.  THANK YOU FOR YOUR PARTICIPATION.***

MIZ047>049-053>055-060>063-068>070-075-076-082-083-120400-

SEVERE WEATHER OUTLOOK FOR SOUTHEAST LOWER MICHIGAN
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
154 PM EDT WED MAY 11 2000

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

DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY.

ISOLATED THUNDERSTORMS ARE EXPECTED THIS AFTERNOON. THESE STORMS
ARE NOT EXPECTED TO BE SEVERE.

THERE IS A CHANCE OF THUNDERSTORMS TONIGHT ACROSS ALL OF SOUTHEAST
MICHIGAN...AND A SMALL CHANCE THAT THESE COULD BECOME SEVERE.
SPOTTER ACTIVATION MAY BE NEEDED TONIGHT.

WARM AND HUMID AIR IS BEGINNING TO RETURN TO SOUTHEAST MICHIGAN. AS
THIS AIR MOVES NORTH...IT WILL IGNITE SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS THIS AFTERNOON. THESE THUNDERSTORMS COULD PRODUCE
BRIEF PERIODS OF HEAVY RAIN AND WIND GUSTS TO 40 MPH. ANY
THUNDERSTORMS THIS AFTERNOON WILL MOVE EAST AT 35 MPH.

AREAS OF SHOWERS AND THUNDERSTORMS ARE EXPECTED TO REDEVELOP TO OUR
WEST THIS AFTERNOON AND EVENING. THESE WILL MOVE EAST INTO SOUTHEAST
MICHIGAN TONIGHT. MOST OF THE THUNDERSTORMS WILL REMAIN BELOW SEVERE
LEVELS...BUT THE VERY STRONGEST STORMS COULD PRODUCE WIND GUSTS TO
65 MPH...AND HAIL AS LARGE AS QUARTERS. THUNDERSTORMS TONIGHT WILL
MOVE EAST AT AROUND 40 MPH.

STAY TUNED TO NOAA WEATHER RADIO...OR YOUR FAVORITE MEDIA OUTLET...
FOR THE VERY LATEST WEATHER INFORMATION.

ZOLTOWSKI