Severe Thunderstorm Warning 56, NWS Detroit, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
815 PM EDT FRI MAY 21 2004

.UPDATE...
CONVECTIVE POTENTIAL RECOVERING RAPIDLY AT THE END OF DAYTIME
HEATING. STORMS DEVELOPING OVER SW LOWER FOCUSED ON THE SURFACE TROF
FROM ABOUT PORT HURON TO LANSING. MID LEVEL LAPSE RATES ARE MODEST
IN THE SAGINAW VALLEY AND THUMB BUT CLOSE TO 7.5 C/KM NEAR THE OHIO
BORDER, ENOUGH TO HELP SUSTAIN THE MCS AS IT MOVES THROUGH LOWER
MICHIGAN THIS EVENING. EXPECT CONVECTION TO BE NEAR SEVERE LIMITS
ALONG AND SOUTH OF THE SURFACE TROF/INTERSTATE 69 THROUGH THE
EVENING AND EARLY OVERNIGHT HOURS. RAIN WILL BE WIDESPREAD OVER THE
SAGINAW VALLEY BUT STORMS LESS INTENSE. STILL HAVE A SHOT AT A LATE
NIGHT ROUND OF STORMS AS CONVECTION CONTINUES TO FORM OVER IOWA.

FORECAST UPDATE WILL REFLECT A TREND TOWARD INCREASING AREAL
COVERAGE DURING THE EVENING. FLOOD WATCH MESSAGE WILL BE UPDATED TO
REFLECT LATEST CONVECTIVE TRENDS.

&&

BT

.PREV DISCUSSION... ISSUED AT 300 PM TODAY
WE WILL EXTEND/HOIST FLOOD WATCH TO COVER ALL OF THE CWA THROUGH 6
PM SATURDAY (FOR NOW).  VERY ACTIVE WEATHER PERIOD SO THIS WILL BE
BRIEF.

SEVERE MCS/BOW ECHO PROGRESSING EAST WITH THE BOW APEX ACROSS
EXTREME SOUTHEAST LOWER MICHIGAN.  SEVERE WEATHER, FOR THE MOMENT,
WILL CLEAR THE REGION BY 20Z AS WE WILL BE ON THE SUBSIDENCE SIDE OF
THIS DEPARTING SYSTEM WITH RAIN GRADUALLY COMING TO AN END.  COLD
POOL ACROSS WISCONSIN HAS SENT THE OUTFLOW BOUNDARY ACROSS NORTHERN
ILLINOIS INTO CENTRAL IOWA.  NEW CONVECTION IS ALREADY DEVELOPING,
LIKELY INTO ANOTHER MCS, IN NORTHERN IOWA WHERE LOW LEVEL JET PER
PROFILERS IS FEEDING MOIST AIR NORTH ALONG THE BAROCLINIC BOUNDARY.
LATEST MODELS SUGGEST UPSTREAM MCS WILL TRACK INITIALLY NORTHEAST
THEN TURN EAST PER CORFIDI VECTORS AND THICKNESSES.  HOWEVER, THE
WARM FRONT WILL BE DISPLACED A BIT FURTHER SOUTH SO AT LEAST FOR NOW
THE THREAT FROM SEVERE WEATHER (HAIL/WIND) WILL BE LIMITED.  THE
MAIN CONCERN WILL BE FLOODING AS THE GROUND IS QUITE SATURATED AND
FLOOD GUIDANCE NUMBERS ARE LOWERING WITH TIME.

THE LOW LEVEL JET WILL STRENGTHEN OVERNIGHT (>50KTS) ACROSS THE
PLAINS AS TROF DIGS ACROSS THE ROCKIES.  THIS WILL BE SURE TO KEEP
ADDITIONAL THUNDERSTORMS DEVELOPING ALONG AND NORTH OF INTERSTATE 80
OVERNIGHT ACROSS THE PLAINS AND TRACK EAST ACROSS THE GREAT LAKES.
PWATS REMAIN WELL ABOVE 1.50 SO HEAVY RAINFALL A REAL CONCERN.

SEVERE WEATHER POTENTIAL PICKS UP ONCE AGAIN SATURDAY NIGHT INTO
SUNDAY AS IMPRESSIVE SURFACE WAVE DEEPENS A BIT AS IT TRACKS TOWARD
THE GREAT LAKES.  STRONG LOW LEVEL JET COMBINING WITH FRONTAL
BOUNDARY DRAPED ACROSS THE CWA COULD PROVE TO BE VERY INTERESTING.
EHI/S CLIMB OVER 2 WITH HELICITIES IN EXCESS OF 200
M2/S2...PRIMARILY ALONG AND NORTH OF INTERSTATE 69 WITH CAPES AROUND
2K J/KG.  OF COURSE, WITH ALL OF THIS CONVECTION IN THE MODELS, IT
WILL BE VERY DIFFICULT TO PIN DOWN FRONTAL PLACEMENT AND SEVERE
POTENTIAL.  WE ARE CERTAIN THAT WE WILL REMAIN IN THE MCS TRACK FOR
HEAVY RAINFALL AND FLOODING INTO THE WEEKEND.

LOOKS LIKE A BREAK ARRIVES FOR EARLY NEXT WEEK AS UPSTREAM TROF
RELOADS ACROSS THE PLAINS.  THIS WILL SEND ANOTHER COLD FRONT ACROSS
THE LAKES NEXT WEEK AS IT STILL LOOKS COOL AND WET FOR LATE WEEK
INTO THE HOLIDAY WEEKEND.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...FLOOD WATCH...THROUGH 6 PM
SATURDAY...ALL OF SOUTHEAST LOWER MICHIGAN.

&&

BGM

EXPERIMENTAL GRAPHICAL FORECASTS ARE AVAILABLE ONLINE AT
HTTP://WWW.CRH.NOAA.GOV/DTX  (ALL LOWER CASE)

HAZARDOUS WEATHER OUTLOOK FOR SOUTHEAST MICHIGAN
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
937 PM EDT FRI MAY 21 2004

MIZ047>049-053>055-221200-
BAY-HURON-MIDLAND-SAGINAW-SANILAC-TUSCOLA-
937 PM EDT FRI MAY 21 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE SAGINAW VALLEY AND THUMB

.DAY ONE...TONIGHT

A FLOOD WATCH IS IN EFFECT TONIGHT AS ADDITIONAL HEAVY RAINFALL IS
ANTICIPATED.  PLEASE REFER TO THE LATEST FLOOD WATCH STATEMENTS
ISSUED BY YOUR NATIONAL WEATHER SERVICE.

ANOTHER COMPLEX OF THUNDERSTORMS IS EXPECTED TO TRACK ACROSS THE
REGION TOWARD SUNRISE.  THE MAIN HAZARD WILL BE ADDITIONAL HEAVY
RAINFALL ON ALREADY SATURATED GROUND.  THESE THUNDERSTORMS ARE
DEVELOPING ALONG AND AHEAD OF WARM FRONT WHICH STRETCHES FROM THE
OHIO VALLEY INTO THE NORTHERN PLAINS. THUNDERSTORMS TONIGHT WILL
TRACK TO THE EAST AROUND 40 MPH.  WITHIN THE STRONGEST CELLS...HALF
INCH SIZED HAIL AND WIND GUSTS TO 50 MPH WILL BE POSSIBLE.

.DAY TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THUNDERSTORMS...POSSIBLY SEVERE...WILL LINGER THROUGH THE WEEKEND
ALONG WITH HEAVY RAINFALL POTENTIAL.  A FLOOD WATCH REMAINS IN
EFFECT THROUGH SATURDAY...BUT MAY NEED TO BE EXTENDED THROUGH SUNDAY
IF CONDITIONS WARRANT.

A PERSISTENT NEARLY STATIONARY FRONT WILL LINGER ACROSS THE STATE
THROUGH THE WEEKEND.  ADDITIONAL THUNDERSTORMS ARE EXPECTED ALONG
THE FRONTAL BOUNDARY AND SOME MAY BECOME SEVERE WITH LARGE
HAIL...DAMAGING WIND GUSTS...FLOODING RAINFALL ALONG WITH A
POSSIBLE TORNADO.  EXACT TIMING AND PLACEMENT OF THUNDERSTORMS WILL
BE DIFFICULT TO ASCERTAIN AND WILL LIKELY CHANGE THROUGH THE
WEEKEND.  YOUR NATIONAL WEATHER SERVICE WILL CONTINUE TO MONITOR THE
SITUATION CLOSELY.

.SPOTTER INFORMATION STATEMENT...

DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY.
SPOTTER ACTIVATION MAY ONCE AGAIN BE NEEDED TONIGHT AND INTO THE
WEEKEND.

MIZ060>063-068>070-075-076-082-083-221200-
GENESEE-LAPEER-LENAWEE-LIVINGSTON-MACOMB-MONROE-OAKLAND-SHIAWASSEE-
ST. CLAIR-WASHTENAW-WAYNE-
937 PM EDT FRI MAY 21 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST MICHIGAN

.DAY ONE...TONIGHT

ANOTHER LINE OF THUNDERSTORMS WILL MOVE THROUGH THE AREA TONIGHT AND
BRING A CHANCE OF SEVERE WEATHER ALONG AND SOUTH OF INTERSTATE 69.
THE BEST CHANCE OF SEVERE WEATHER WILL BE FROM 10 PM TO 2 AM. THE
STRONGEST STORMS WILL BE CAPABLE OF WIND GUSTS AROUND 60 MPH AND HAIL
AROUND 1 INCH...AS THEY MOVE EAST AT 50 MPH.

A FLOOD WATCH IS IN EFFECT TONIGHT AS ADDITIONAL HEAVY RAINFALL IS
ANTICIPATED.  PLEASE REFER TO THE LATEST FLOOD WATCH STATEMENTS
ISSUED BY YOUR NATIONAL WEATHER SERVICE.

ANOTHER COMPLEX OF THUNDERSTORMS IS EXPECTED TO TRACK ACROSS THE
REGION TOWARD SUNRISE.  THE MAIN HAZARD WILL BE ADDITIONAL HEAVY
RAINFALL ON ALREADY SATURATED GROUND.  THESE THUNDERSTORMS ARE
DEVELOPING ALONG AND AHEAD OF WARM FRONT WHICH STRETCHES FROM THE
OHIO VALLEY INTO THE NORTHERN PLAINS.

.DAY TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THUNDERSTORMS...POSSIBLY SEVERE...WILL LINGER THROUGH THE WEEKEND
ALONG WITH HEAVY RAINFALL POTENTIAL.  A FLOOD WATCH REMAINS IN
EFFECT THROUGH SATURDAY...BUT MAY NEED TO BE EXTENDED THROUGH SUNDAY
IF CONDITIONS WARRANT.

A PERSISTENT NEARLY STATIONARY FRONT WILL LINGER ACROSS THE STATE
THROUGH THE WEEKEND.  ADDITIONAL THUNDERSTORMS ARE EXPECTED ALONG
THE FRONTAL BOUNDARY AND SOME MAY BECOME SEVERE WITH LARGE
HAIL...DAMAGING WIND GUSTS...FLOODING RAINFALL ALONG WITH A
POSSIBLE TORNADO.  EXACT TIMING AND PLACEMENT OF THUNDERSTORMS WILL
BE DIFFICULT TO ASCERTAIN AND WILL LIKELY CHANGE THROUGH THE
WEEKEND.  YOUR NATIONAL WEATHER SERVICE WILL CONTINUE TO MONITOR THE
SITUATION CLOSELY.

.SPOTTER INFORMATION STATEMENT...

DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY.
SPOTTER ACTIVATION MAY ONCE AGAIN BE NEEDED TONIGHT AND INTO THE
WEEKEND.

BT

PRELIMINARY LOCAL STORM REPORT ... SUMMARY
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
430 PM EDT FRI MAY 21 2004

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

0135 PM     TSTM WND GST     VERNON                  42.94N 84.03W
05/21/2004  65 MPH           SHIAWASSEE         MI   TRAINED SPOTTER

            WIND GUST ESTIMATED.

0145 PM     HAIL             5 N ADDISON             42.06N 84.35W
05/21/2004  1.00 INCH        LENAWEE            MI   TRAINED SPOTTER

0145 PM     TSTM WND DMG     2 SE GREGORY            42.44N 84.06W
05/21/2004                   LIVINGSTON         MI   EMERGENCY MNGR

            TREES DOWNED.

0147 PM     HAIL             ADDISON                 41.99N 84.35W
05/21/2004  0.50 INCH        LENAWEE            MI   COUNTY OFFICIAL

            40 MPH WIND GUSTS

0150 PM     HAIL             2 E ADDISON             41.99N 84.31W
05/21/2004  1.75 INCH        LENAWEE            MI   LAW ENFORCEMENT

0150 PM     TSTM WND GST     2 E ADDISON             41.99N 84.31W
05/21/2004  70 MPH           LENAWEE            MI   LAW ENFORCEMENT

0153 PM     HAIL             CHELSEA                 42.31N 84.02W
05/21/2004  0.50 INCH        WASHTENAW          MI   PUBLIC

0155 PM     TSTM WND GST     CHELSEA                 42.31N 84.02W
05/21/2004  65 MPH           WASHTENAW          MI   PUBLIC

0159 PM     TSTM WND GST     1 NW TECUMSEH           42.02N 83.96W
05/21/2004  60 MPH           LENAWEE            MI   AIRPLANE PILOT

            MARBLE SIZE HAIL

0200 PM     HAIL             ADRIAN                  41.90N 84.04W
05/21/2004  0.75 INCH        LENAWEE            MI   TRAINED SPOTTER

0200 PM     HAIL             ADRIAN                  41.90N 84.04W
05/21/2004  0.75 INCH        LENAWEE            MI   TRAINED SPOTTER

0200 PM     TSTM WND DMG     HAMBURG                 42.45N 83.80W
05/21/2004                   LIVINGSTON         MI   EMERGENCY MNGR

            TREES AND WIRES DOWNED.

0201 PM     TSTM WND GST     SALINE                  42.18N 83.78W
05/21/2004  60 MPH           WASHTENAW          MI   EMERGENCY MNGR

            8 INCH TREE LIMBS BLOWN DOWN

0201 PM     HAIL             SALINE                  42.18N 83.78W
05/21/2004  1.00 INCH        WASHTENAW          MI   EMERGENCY MNGR

0203 PM     HAIL             ADRIAN                  41.90N 84.04W
05/21/2004  0.75 INCH        LENAWEE            MI   TRAINED SPOTTER

            HAIL COVERING THE GROUND

0205 PM     NON-TSTM WND GST ANN ARBOR               42.28N 83.73W
05/21/2004  61 MPH           WASHTENAW          MI   AWOS

            MEASURED BY ANN ARBOR ASOS

0205 PM     TSTM WND DMG     4 W ANN ARBOR           42.28N 83.81W
05/21/2004                   WASHTENAW          MI   LAW ENFORCEMENT

            SHERIFF DEPARTMENT REPORTED 9 OR 10 UTILITY POLES SHEARED
            OFF IN HALF ON WAGNER ROAD.

0205 PM     HAIL             YPSILANTI               42.24N 83.62W
05/21/2004  0.75 INCH        WASHTENAW          MI   TRAINED SPOTTER

            CROSS STREET AND SUMMIT - EASTERN MICHIGAN UNIVERSITY

0208 PM     HAIL             ADRIAN                  41.90N 84.04W
05/21/2004  1.00 INCH        LENAWEE            MI   TRAINED SPOTTER

0210 PM     TSTM WND GST     ANN ARBOR               42.28N 83.73W
05/21/2004  60 MPH           WASHTENAW          MI   TRAINED SPOTTER

            ALSO MARBLE SIZED HAIL

0215 PM     TSTM WND DMG     3 SE BRIGHTON           42.50N 83.74W
05/21/2004                   LIVINGSTON         MI   EMERGENCY MNGR

            TREES AND WIRES DOWNED.

0215 PM     TSTM WND GST     ANN ARBOR               42.28N 83.73W
05/21/2004  80 MPH           WASHTENAW          MI   TRAINED SPOTTER

            ESTIMATED WIND GUST DOWNTOWN ANN ARBOR ON UNIVERSITY OF
            MICHIGAN CAMPUS

0220 PM     TSTM WND GST     2 S MILAN               42.06N 83.68W
05/21/2004  95 MPH           MONROE             MI   PUBLIC

            ESTIMATED WIND GUST

0220 PM     HAIL             SALINE                  42.18N 83.78W
05/21/2004  1.00 INCH        WASHTENAW          MI   TRAINED SPOTTER

0220 PM     HAIL             2 W CARLETON            42.06N 83.43W
05/21/2004  0.75 INCH        MONROE             MI   TRAINED SPOTTER

0220 PM     TSTM WND GST     YPSILANTI               42.24N 83.62W
05/21/2004  70 MPH           WASHTENAW          MI   AWOS

            MEASURED BY YIP ASOS

0225 PM     HAIL             DEARBORN                42.31N 83.21W
05/21/2004  0.88 INCH        WAYNE              MI   TRAINED SPOTTER

            ALSO 60 TO 70 MPH WIND GUSTS ESTIMATED

0225 PM     TSTM WND GST     CLARKSTON               42.74N 83.42W
05/21/2004  60 MPH           OAKLAND            MI   PUBLIC

            5 INCH DIAMETER TREE LIMBS DOWN

0228 PM     HAIL             CANTON                  42.31N 83.48W
05/21/2004  1.00 INCH        WAYNE              MI   TRAINED SPOTTER

0228 PM     TSTM WND GST     ROMULUS                 42.22N 83.37W
05/21/2004  70 MPH           WAYNE              MI   PUBLIC

            NEAR DETROIT METRO AIRPORT

0228 PM     HAIL             CANTON                  42.31N 83.48W
05/21/2004  1.00 INCH        WAYNE              MI   TRAINED SPOTTER

0230 PM     HAIL             WESTLAND                42.32N 83.38W
05/21/2004  0.75 INCH        WAYNE              MI   TRAINED SPOTTER

0230 PM     HAIL             ROMULUS                 42.22N 83.37W
05/21/2004  1.75 INCH        WAYNE              MI   PUBLIC

0230 PM     TSTM WND GST     2 W BLOOMFIELD HILLS    42.58N 83.29W
05/21/2004  60 MPH           OAKLAND            MI   TRAINED SPOTTER

            WEST BLOOMFIELD

0233 PM     HAIL             3 E CARLETON            42.06N 83.33W
05/21/2004  0.75 INCH        MONROE             MI   PUBLIC

0235 PM     HAIL             REDFORD                 42.39N 83.29W
05/21/2004  0.75 INCH        WAYNE              MI   TRAINED SPOTTER

0235 PM     TSTM WND GST     TAYLOR                  42.23N 83.27W
05/21/2004  65 MPH           WAYNE              MI   TRAINED SPOTTER

0240 PM     TSTM WND GST     2 NW ROCHESTER          42.71N 83.15W
05/21/2004  63 MPH           OAKLAND            MI   TRAINED SPOTTER

            MEASURED WIND GUST

0250 PM     TSTM WND GST     TROY                    42.58N 83.14W
05/21/2004  65 MPH           OAKLAND            MI   TRAINED SPOTTER

            TREES DOWN ON LONG LAKE ROAD WEST OF ADAMS

0250 PM     HAIL             DOWNTOWN DETROIT        42.33N 83.05W
05/21/2004  0.75 INCH        WAYNE              MI   TRAINED SPOTTER

0256 PM     TSTM WND GST     1 E WARREN              42.49N 83.01W
05/21/2004  75 MPH           MACOMB             MI   TRAINED SPOTTER

            NUMEROUS TREES DOWN IN ROSEVILLE

0315 PM     TSTM WND GST     5 NE UTICA              42.68N 82.95W
05/21/2004  65 MPH           MACOMB             MI   TRAINED SPOTTER

            WINDS GUST ESTIMATED.

&&
CORRECTED ESTIMATED WIND SPEED FOR THE ANN ARBOR 215 PM REPORT.

RBP