Severe Thunderstorm Warning 129, NWS Detroit, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
400 AM EDT WED AUG 9 2000

...THREAT OF SEVERE THUNDERSTORMS FOR THIS MORNING INTO EARLY
AFTERNOON...

THIS MORNING THE ETA MODEL INITIALIZED MUCH BETTER (AT LEAST
COMPARED TO YESTERDAYS) WITH AVN NOT THAT FAR BEHIND (IT FINALLY HAS
RESOLVED MID LEVEL FEATURES WITH RESPECT TO STRONG INTENSITY OF
WAVES OF LATE).

MAIN SURFACE BOUNDARY WAS JUST NORTH OF I-69 WITH WINDS VARIABLE TO
NORTH JUST NORTH OF THE FRONT.  SOUTH OF THIS FRONT DEWPOINTS WERE
AROUND 70 WITH A LIGHT SOUTHWEST WIND.  AIR MASS IS STABLE EARLY
THIS MORNING WITH CINH OVER 200 AND LI/S SLIGHTLY ON THE POSITIVE
SIDE.  EVEN TAKING 00Z SOUNDINGS AND LIFTING PARCELS FROM 800 MB DID
NOT YIELD MUCH IN THE WAY OF INSTABILITY.  IN ADDITION RFQ OF 300MB
JET OVER THE REGION SHOULD KEEP THINGS QUIET FOR NOW.  ALL THIS
WOULD EXPLAIN THE WEAKENING OF CELLS AS THEN MOVE INTO CENTRAL
MICHIGAN.

WHAT HAPPENS TOWARD 12Z AND LATER IS A DIFFERENT STORY.  THE
ETA...AND SOMEWHAT THE AVN...PICKED UP A MID LEVEL SHORT WAVE NOW
MOVING INTO IOWA.  THIS HAS ERUPTED THUNDERSTORMS EARLY THIS MORNING
AS PROFILERS 850 LLJ HAS INCREASED THE FUEL OVER THE CENTRAL PLAINS.
THIS WAVE IS FORECAST TO MOVE SOUTH OF THE CWA...ACROSS INDIANA AND
OHIO...THIS AFTERNOON.  WHETHER THIS MAY INHIBIT THUNDERSTORM
CHANCES THIS AFTERNOON IS STILL IN QUESTION AS THIS MIGHT ROB LOW
LEVEL MOISTURE AND RESULTING SINKING AIR TO TAKE AWAY OUR CHANCES
FOR STORM.  BUT ATMOSPHERE IS ALREADY QUITE MOIST SO DO NOT THINK
THIS WILL CAUSE A PROBLEM IN THE FORECAST FOR LATER TODAY.  SPC
SLIGHT RISK OVER THE WHOLE AREA TODAY WITH MODERATE RISK JUST TO OUR
SOUTHEAST.

500/700 MB SHORT WAVES OVER LAKE SUPERIOR THIS MORNING WILL MOVE
SOUTHEAST AS SURFACE WAVE DEVELOPS ACROSS THE STATE.  THINGS DO GET
QUITE UNSTABLE LATE THIS MORNING INTO THE EARLY AFTERNOON WITH LAPSES
RATES GREAT THAN 7/C ... CAPES OVER 4000 J/KG SOUTHEAST...3000 J/KG
NORTHERN CWA... LIS AROUND -6 BY 18Z WITH SWI -3.  WE ARE INITIALLY
CAPPED THIS AM WITH CINH -80 TO -120 THEN NOTHING TO SPEAK OF BY
MIDDAY.  SURF AND 850 THETA E RIDGE AXIS NOSES NORTHEAST ACROSS THE
CWA WITH SPEED SHEAR INCREASING DURING THE MORNING HOURS.  AS LOW
DEVELOPS THIS WILL INTENSIFY THE COLD FRONT AS IT SWING SOUTHEAST
ACROSS THE REGION BY MID AFTERNOON.  PERHAPS A SQUALL LINE
(INITIALLY A FEW SUPERCELLS MAY BE POSSIBLE) DEVELOPING BUT LOTS
WILL TELL ON THE TIMING OF FROPA.

TONIGHT DRY AIR ALONG WITH COLD AIR ADVECTION SHOULD MAKE FOR A
COMFORTABLE NIGHT.  NEXT FEATURE IS ON THURSDAY WITH THE AVN THE
STRONGEST BRINGING A STRONG 500 MB SHORT WAVE ACROSS THE EASTERN
COUNTIES.  WHILE THIS MAY OCCUR THINK THE ETA IS BETTER WITH A
STRING OF VORTICITY.  WITH CAPPING INVERSION AOA 700MB AND LOW LEVEL
CAPES NEAR 100 SHOULD SEE LOTS OF CU WITH EVEN A FEW
SPRINKLES/SHOWERS.

GUIDANCE TEMPS LOOK GOOD BUT THINK AVN MOS IS SLIGHTLY BETTER FOR
THURSDAYS HIGHS.  WILL MONITOR CONVECTION BREAKING OUT TO OUR
NORTHWEST BEFORE ISSUING ZONES AROUND 430 AM.

COORD WITH CLE...APX AND SPC...THANKS!

.DTX...NONE.

BGM

MIZ047>049-053>055-060>063-068>070-075-076-082-083-091600-

SEVERE WEATHER OUTLOOK FOR SOUTHEAST LOWER MICHIGAN
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
522 AM EDT WED AUG 9 2000

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

DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY.

SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP INTO A LINE OF
THUNDERSTORMS ACROSS MOST OF SOUTHEAST MICHIGAN THIS MORNING INTO
THE AFTERNOON HOURS.  SOME OF THESE STORMS WILL BECOME SEVERE WITH
LARGE HAIL...DAMAGING WINDS AND POSSIBLY EVEN A TORNADO.  SPOTTER
ACTIVATION WILL LIKELY BE NEEDED TODAY.

A WARM AND HUMID AIR MASS REMAINS IN PLACE ACROSS ALL OF SOUTHEAST
MICHIGAN.  A FRONTAL SYSTEM WAS JUST NORTH OF INTERSTATE 96 THIS
MORNING WITH THUNDERSTORMS ALREADY DEVELOPING ACROSS NORTHWEST LOWER
MICHIGAN.  SOME OF THESE STORMS COULD REACH THE SAGINAW VALLEY AS
EARLY AS 6 AM... AND COULD BE SEVERE WITH HAIL UP TO ONE INCH IN
DIAMETER. AS THE MORNING PROGRESSES A STRONG DISTURBANCE WILL
APPROACH THE REGION HELPING TO LIFT THE MOIST AIR AT THE SURFACE FOR
FURTHER THUNDERSTORM DEVELOPMENT. INITIALLY...THUNDERSTORMS WILL BE
SINGULAR IN NATURE BUT AS A COLD FRONT MOVES DOWN FROM THE
NORTHWEST LATE THIS MORNING...A LINE OF STRONG TO SEVERE
THUNDERSTORMS IS EXPECTED TO DEVELOP. THUNDERSTORMS THAT DEVELOP WILL
MOVE SOUTHEAST BETWEEN 25 AND 35 MPH.

THE BEST POTENTIAL FOR SEVERE THUNDERSTORMS WILL BE ALONG AND SOUTH
OF INTERSTATE 69.  HOWEVER AN ISOLATED SEVERE THUNDERSTORM WILL BE
POSSIBLE ANYWHERE THROUGH EARLY AFTERNOON.  THE COLD FRONT IS
EXPECTED TO CLEAR THE SAGINAW AND FLINT AREAS BY 3 PM DIMINISHING
THE SEVERE WEATHER THREAT.  SOUTH AND EAST OF THOSE LOCATIONS ACROSS
THE DETROIT METRO VICINITY SEVERE WEATHER WILL REMAIN A THREAT UNTIL
6 PM.

STAY TUNED TO YOUR FAVORITE MEDIA OUTLET FOR THE LATEST SEVERE
WEATHER INFORMATION.

BGM OKEEFE