Severe Thunderstorm Warning 70, NWS Detroit, MI

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

SHOWERS AND THUNDERSTORMS IN THE VICINITY OF THE CLOSED TROPOSPHERIC
VORTEX OVER SOUTHERN LOWER MICHIGAN WILL SLOWLY DECREASE IN COVERAGE
THROUGH THE EVENING AND OVERNIGHT HOURS WITH THE LOSS OF DIURNAL
FORCING. THE BEST COVERAGE WILL REMAIN OVER THE NORTHERN AND EASTERN
REACHES OF THE FORECAST AREA EMBEDDED WITHIN THE DEFORMATION ZONE/QS
CONVERGENCE AXIS. SEVERE THREAT WILL CONTINUE LATE THIS AFTERNOON
AND EARLY EVENING AND WILL BE HAIL AROUND AN INCH AND ISOLATED WIND
GUSTS FROM PRECIP LOADING. GIVEN THE PROXIMITY TO THE UPPER-LOW,
WOULDN/T BE SURPRISED TO SEE A FEW COLD AIR TYPE FUNNELS, EITHER.

NEAR-TERM NUMERICAL SUITE VARY SLIGHTLY WITH THE PROGRESSION OF THE
UPPER LOW AS IT EXITS THE LAKES REGION- WITH THE ETA OPENING THE
WAVE FASTER THAN THE AVN/ETA-XX/NGM LATE MONDAY. HOWEVER, BY THAT
TIME MOST OF THE DEEP MOISTURE WILL HAVE DECREASED ACROSS THE
FORECAST AREA. THE ETA/AVN INSIST THAT SOME SORT OF DIMINISHING
CONVECTIVE COMPLEX WILL APPROACH SOUTHERN LAKE MICHIGAN BY TUESDAY
NIGHT. GIVEN THE TRANSIENT NATURE OF THESE MODEL FEATURE, EXPECT
THIS SOLUTION TO CHANGE NEXT CYCLE.

DEFORMATION/QS CONVERGENCE IN THE 850-700MB LAYER SHOULD WEAKEN
THROUGH THE NIGHT AND EVEN MORE SO MONDAY MORNING AS THE UPPER LOW
FILLS. ANTICIPATE THAT SCATTERED SHOWERS WILL PERSIST THROUGH THE
OVERNIGHT HOURS ACROSS THE ENTIRE FORECAST AREA IN RESPONSE TO THE
QG FORCING. AS THE FORCING WEAKENS EARLY MONDAY, COVERAGE WILL
DECREASE QUICKLY ACROSS THE WESTERN COUNTIES WITH LINGERING CHANCES
INTO THE AFTERNOON ACROSS THE EAST (SIMILAR TO THE ETA/ETA-XX QPF
DEPICTION). SKIES SHOULD BREAK OUT ACROSS THE WEST DURING THE
AFTERNOON, MUCH LIKE THAT OBSERVED ACROSS EASTERN WISCONSIN.

SUBSIDENCE IN RESPONSE TO SHORTWAVE RIDGING ALOFT IN THE UPPER LOW/S
WAKE SHOULD SCOUR OUT THE CLOUDS MONDAY NIGHT. THE SURFACE LAYER
SHOULD DECOUPLE IN THE PRESENCE OF A SURFACE RIDGE, ALLOWING TEMPS
TO DROP INTO THE LOWER 50S ACROSS INTERIOR SECTIONS. AS WARM
ADVECTION RETURNS ACROSS THE REGION BEHIND THE SURFACE RIDGE TUESDAY
NIGHT, EXPECT MID/UPPER LEVEL CLOUDS TO INCREASE. ANTI-CYCLONIC FLOW
ALOFT SHOULD PREVENT ANY PRECIP FROM MAKING ITS WAY INTO THE AREA
TUESDAY NIGHT.

EXTENDED PROGS OFFERING SIMILAR SOLUTIONS THROUGH THURSDAY...THEN
DIVERGE SUBSTANTIALLY. RECENT TRENDS ON THE MRF/ETA-XX/CMC GLOBAL
HAVE BEEN TOWARD A SLOWER PROGRESSION OF THE NORTHERN STREAM TROUGH
AXIS FOR MIDWEEK. THE MRF IS STILL THE FASTEST, BUT TRENDING TOWARD
THE MORE CONSISTENT ETA-XX DEPICTION. ADDITIONALLY, THE MRF ATTEMPTS
TO DEVELOP AN MCS TUESDAY NIGHT OVER THE PLAINS THEN ADVANCE IT INTO
THE SOUTHERN LAKES REGION. CONFIDENCE ON THIS OCCURRENCE IS
EXTREMELY LOW. INSTEAD, EXPECT SOME SHOWERS AND STORMS ALONG A COLD
FRONT LATE WEDNESDAY INTO MID PORTIONS OF THURSDAY. TOWARD THE END
OF THE WEEK, THE MRF AGAIN DEVELOPS A CONVECTIVELY INDUCED LOW/VORT
CENTER, WHICH SWEEPS ACROSS THE SOUTHERN LAKES ON SATURDAY, WHILE
THE ETA-XX AND GLOBAL MAINTAIN SURFACE RIDGING WITH NO INDICATION OF
THE CONVECTIVE FEATURE. BASED ON TRENDS AND CONSISTENCY, ANTICIPATE
A PATTERN CLOSER TO THE ETA-XX TO EVOLVE. GIVEN THIS, A COLD FRONT
SHOULD APPROACH THE REGION ON SUNDAY, SLOWER THAN INDICATED BY THE
MRF, BRINGING THE CHANCE FOR PRECIP ONCE AGAIN.  TEMPS SHOULD BE AT
OR ABOVE MRF GUIDANCE, ESPECIALLY FOR NEXT WEEKEND.

.DTX...NONE.

MANN

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