Flash Flood Warning 4, NWS Detroit, MI

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1125 AM EDT SUN AUG 19 2001

THE CURRENT WATER VAPOR LOOP NICELY DEPICTS THE CLOSED 500MB LOW
SITUATED OVER SOUTH CENTRAL LOWER MICHIGAN. AT THE SURFACE...THE
LATEST OBS PLOT SHOWS LOW PRESSURE OVER SOUTHWEST LOWER...WITH A
SECONDARY LOW ROUGHLY OVER LANSING. THE RUC SEEMS TO HAVE THE BEST
HANDLE ON THE SURFACE PATTERN. IT SHOWS THE LOW OVER SOUTHWEST LOWER
WEAKENING AS THE SECOND LOW OVER THE LANSING AREA DEEPENS SLIGHTLY
AND MOVES ALMOST DUE EAST THIS AFTERNOON (WHICH LINES UP WELL WITH
MSAS 3 HOUR PRESSURE CHANCE PLOTS). AREA RADARS SHOW MAINLY
SCATTERED SHOWERS AND THUNDERSTORMS ACROSS SOUTHEAST MICHIGAN...WITH
THE MORE WIDESPREAD PRECIP ASSOCIATED WITH DEEPER WRAP AROUND
MOISTURE AND DEFORMATION AXIS ACROSS CENTRAL AND NORTHERN LOWER
MICHIGAN.

THIS AFTERNOON....THE LATEST RUC BRINGS THE UPPER LEVEL LOW
EAST-NORTHEAST INTO THE THUMB AND SOUTHERN LAKE HURON BY 00Z AND IT
BEGINS TO FILL IN THE UPPER LEVEL LOW. THE SURFACE LOW IS PROGGED TO
BE CENTERED OVER THE DETROIT METRO AREA BY 00Z. 850 TO 700MB QVECTOR
CONVERGENCE...1000-500MB RH GREATER THAN 70 PCT ALONG WITH
INCREASING DIURNAL INSTABILITY WITH THE 500MB COLD POOL ALOFT WILL
KEEP PRECIP ACROSS SOUTHEAST MICHIGAN THROUGH THE AFTERNOON. HIGHEST
1000-500MB LAYER MOISTURE IS PROGGED TO REMAIN ACROSS THE NORTHERN
COUNTIES THROUGH THE AFTERNOON...THUS THIS IS WHERE I EXPECT THE
MORE WIDESPREAD COVERAGE TO BE. MUCH OF SOUTHEAST MICHIGAN (SOUTH OF
THE TRI CITIES) HAS BEEN PLACED IN A SLIGHT RISK OF SEVERE WEATHER
FOR THIS AFTERNOON AND EARLY THIS EVENING. WITH THE COLD POOL ALOFT
OVER THE SOUTHERN GREAT LAKES THIS AFTERNOON (500MB TEMP OF -16C ON
12Z KDTX SOUNDING). THIS WILL ALLOW 700 TO 500MB LAPSE RATES TO
REMAIN AROUND 6C/KM. MODIFIED 12Z KDTX SOUNDING FOR 74/64 GIVES CAPE
AROUND 1500 J/KG. WITH FREEZING LEVELS PROGGED TO DROP TO AROUND
10K FT...WITH FAIRLY WEAK WIND FIELDS ALOFT...PRIMARY SEVERE WEATHER
THREAT THIS AFTERNOON WILL BE LARGE HAIL AND DAMAGING WIND GUSTS
ASSOCIATED WITH WET MICROBURSTS. ONE BIG LIMITING FACTOR TO SEVERE
CONVECTION WILL BE CLOUD COVER AND PRECIP KEEPING TEMPS DOWN (AND
THUS KEEPING SBCAPES MARGINAL).

.DTX...NONE.

CONSIDINE

MIZ047>049-053>055-060>063-068>070-075-076-082-083-200000-

SEVERE WEATHER OUTLOOK FOR SOUTHEAST LOWER MICHIGAN
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1140 AM EDT SUN AUG 19 2001

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

DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY.

SCATTERED THUNDERSTORMS WILL CONTINUE ACROSS SOUTHEAST MICHIGAN THIS
AFTERNOON AND INTO THE EARLY EVENING HOURS. SOME OF THESE STORMS MAY
BE SEVERE AND SPOTTER ACTIVATION MAY BE NEEDED.

A LOW PRESSURE SYSTEM OVER SOUTHERN LOWER MICHIGAN WILL GRADUALLY
DRIFT EAST TOWARDS THE DETROIT METRO AREA BY THIS EVENING.
UNSEASONABLY COLD AIR ALOFT WILL PROVIDE ENOUGH INSTABILITY TO
MAINTAIN WIDESPREAD SHOWERS AND SCATTERED THUNDERSTORMS THIS
AFTERNOON UNTIL 8 PM THIS EVENING. THE PRIMARY THREAT WITH THESE
THUNDERSTORMS WILL BE HAIL TO ONE INCH...WIND GUSTS TO 60 MPH AND
LOCALLY HEAVY RAINFALL. THE PRIMARY THREAT LOCATION WILL BE SOUTH OF
A SAGINAW TO BAD AXE LINE. THUNDERSTORMS ARE EXPECTED TO MOVE
NORTH-NORTHWEST AT 15 MPH.

STAY TUNED TO NOAA WEATHER RADIO...OR YOUR FAVORITE MEDIA
OUTLET...FOR THE LATEST WEATHER INFORMATION.  YOU CAN ALSO ACCESS
THE LATEST INFORMATION FROM THE INTERNET.
HTTP://WWW.CRH.NOAA.GOV/DTX/START.HTM (ALL LOWER CASE)

CONSIDINE