Severe Thunderstorm Warning 27, NWS Detroit, MI

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
320 PM EDT MON MAY 28 2001

VISIBLE IMAGERY SHOWING WIDESPREAD DIURNAL CU DEVELOPMENT ACROSS
MUCH OF THE LOWER PENINSULA AWAY FROM LAKE MICHIGAN.  SCATTERED
SHOWERS AND A COUPLE OF THUNDERSTORMS HAVE EMERGED ACROSS THE
NORTHERN REACHES, AND SHOULD CONTINUE TO DO SO OVER THE NEXT SEVERAL
HOURS. COVERAGE SHOULD INCREASE ACROSS THE SOUTH AS A SHORTWAVE OVER
NORTHERN ILLINOIS DRIVES SOUTHEAST, NEUTRALIZING THE SUBSIDENCE OVER
THE REGION. SURFACE TEMPS HAVE REBOUNDED SOLIDLY (INTO THE LOW 70S
IN A FEW LOCATIONS) IN RESPONSE A FEW HOURS OF LATE MAY SUN,
LOWERING SURFACE BASED LI/S TO <-4C AND RAISING LAPS CALCULATED
CAPES >1.5KJ/KG. EXPECT THAT THE SHOWER AND ISOLATED STORM ACTIVITY
WILL WANE IN THE POST SUNSET HOURS WITH THE LOSS OF SURFACE HEATING.
THE CLOUD FIELD FROM THIS AFTERNOON/S DEVELOPMENT WILL SLOWLY LIFT
AND DISSIPATE, ONLY TO BE REPLACED BY CLOUDS ALONG A COLD FRONTAL
BAND CURRENTLY ALONG AND NORTH OF LAKE SUPERIOR AND CLOUDS IN
ADVANCE OF THE ILLINOIS SHORTWAVE. THERE COULD BE A FEW HOURS OF
PARTLY CLOUDY CONDITIONS DURING THE LATE EVENING BEFORE THESE
FEATURES REACH SOUTHERN LOWER, HOWEVER, WILL KEEP SIMPLIFIED WORDING
OF MOSTLY CLOUDY.

APPRECIABLE DIFFERENCES IN THE NEAR-TERM NCEP SOLUTIONS.  THE AVN
CONTINUES TO BE THE DEEPEST WITH THE NEXT NORTHWEST FLOW SHORTWAVE
TROUGH DIGGING INTO THE EASTERN LAKES REGION, PRODUCING LOWER
HEIGHTS ACROSS SOUTHEAST LOWER TUESDAY AND WEDNESDAY.  AS A RESULT,
THE AVN CONTINUES TO BE THE COLDEST SOLUTION OF THE BIG THREE- 850MB
TEMPS IN THE 0C TO -2C RANGE, AT LEAST 2-3C LOWER THAN THE ETA.  THE
12Z DTX ETA-XX (INITIALIZED FROM THE 12Z AVN) THERMAL FIELDS AND
HEIGHT STRUCTURES RESEMBLE THE OPERATIONAL ETA MORE THAN THE AVN,
ESPECIALLY WITH RESPECT TO THE WESTWARD EXTENSION OF THE THERMAL
TROUGH OVER THE WESTERN LAKES AROUND 24H- THUS FAVOR A MODERATED
SOLUTION FROM THAT OFFERED BY THE AVN (AND COOLER FAN/MAV).

AS THE WAVE POISED OVER WESTERN HUDSON BAY DIGS SOUTH THROUGH THE
DAY TUESDAY, THE AREA WILL BE IN A REGION OF MODEST 850-500MB DCVA.
THE GREATEST QG FORCING WILL BE TO THE EAST OF THE AREA. HOWEVER,
WEAK CONVERGENCE IN ASSOCIATION WITH A SURFACE TROUGH IN COMBINATION
WITH THE PRESENCE OF THE VORT MAX MAY BE ENOUGH TO PRODUCE A FEW
SHOWERS.  THE DTX ETA-XX AND ETA-6 ALONG WITH THE NSSL ETA-22
SOLUTIONS SUPPORT THIS, WHILE THE NCEP ETA-22 KEEPS THE AREA DRY.
MODEL SOUNDINGS CONTINUE TO INDICATE THAT THE LOWER LEVELS WILL
REMAIN QUITE MOIST, AS EVIDENCED BY CLOUD FIELD NORTH OF LAKE
SUPERIOR.  DNVA INDUCED SUBSIDENCE SHOULD BEGIN TO AFFECT THE
NORTHERN COUNTIES BY NOON TUESDAY AND REACH THE SOUTHERN COUNTIES BY
MID AFTERNOON.  THEREFORE, WILL TIME SHOWER CHANCES ACCORDINGLY
PRIOR TO THE PASSAGE OF THE SHORTWAVE TROUGH AXIS.  SKIES WILL BREAK
OUT DURING THE AFTERNOON, LEAVING PARTLY SUNNY CONDITIONS.

DEEP LAYER SUBSIDENCE BECOMES FIRMLY ESTABLISHED OVER THE STATE
TUESDAY NIGHT AND WEDNESDAY.  GOOD RADIATIONAL COOLING SHOULD OCCUR
TUESDAY NIGHT ALLOWING TEMPS TO DROP BELOW 40 IN SOME AREAS.  WILL
HOLD OFF ON FROST MENTION AT THIS TIME AS DEGREE OF HIGH CLOUDINESS
REMAINS IN QUESTION.  LEAN BOUNDARY LAYER MOISTURE (SFC DEWPOINTS
AROUND 40F) AND WARMING IN THE 850-700MB LAYER SHOULD PREVENT
DIURNAL CLOUD DEVELOP ON WEDNESDAY, ALSO INDICATED BY THE ETA CU
SCHEME.  AMPLE INSOLATION SHOULD SUPPORT MIXING TO AT LEAST 850MB,
AS INDICATED BY ETA SOUNDINGS, IF NOT DEEPER- PRODUCING MAX TEMPS IN
THE LOWER TO MID 60S (SIMILAR TO ETA 2M TEMPS AND BETWEEN THE COOL
MAV AND WARM FWC).  THE SAME DRY COLUMN WILL THEN ALLOW TEMPS TO
DROP QUICKLY ONCE AGAIN WEDNESDAY NIGHT, AS SOME AREAS COULD SLIP
FURTHER INTO THE 30S. THE WILD CARD AGAIN WILL BE THE DEGREE OF HIGH
LEVEL MOISTURE SPILLING OVER THE SHORTWAVE RIDGE THAT WILL BE
POSITIONED TO OUR IMMEDIATE WEST.

SIGNIFICANT PATTERN SHIFT SETTING UP FOR THE LATTER PORTIONS OF THE
THE EXTENDED PERIOD.  MEDIUM RANGES PROGS ALL INDICATE SOME
SEMBLANCE OF LONGWAVE RIDGING BECOMING ESTABLISHED OVER THE
EAST-CENTRAL CONUS BY THE END OF NEXT WEEKEND.  IN THE INTERIM, YET
ANOTHER NORTHERN STREAM SHORTWAVE TROUGH COMPLEX WILL AFFECT THE
REGION THURSDAY INTO SATURDAY.  THE MRF PRODUCES A MORE AMPLIFIED
SOLUTION THAN THE OTHER NCEP AND CMC ENSEMBLE MEMBERS, WITH A CLOSED
COMPACT VORTEX SWINGING ACROSS THE SOUTHERN LAKES REGION FRIDAY.
THEREFORE, IT ALSO PRODUCES A SLOWER PROGRESSION BECAUSE OF THIS
HEIGHT CONFIGURATION.  THE UKMET ADVERTISES YET ANOTHER LARGER
CLOSED SYSTEM OVER THE LAKES REGION.  THIS TYPE OF SOLUTION IS
SUPPORTED BY NEITHER THE OTHER DETERMINISTIC PROGS NOR THEIR
ENSEMBLE FAMILIES.  ON THE OTHER END OF THE SPECTRUM, THE ETA-XX IS
LEAST AMPLIFIED AND MOST PROGRESSIVE WITH THE NORTHERN STREAM
FEATURES, SUGGESTING THAT MID-LEVEL RIDGING WILL BECOME ESTABLISHED
OVER THE WESTERN LAKES BY LATE SATURDAY.  BASED ON THE MRF TREND TO
SLOW THE NORTHERN STREAM RIDGING (144H DPROG/DT), WHICH AGREES MORE
WITH THE NCEP ENSEMBLES HEIGHT MEAN, EXPECT THAT TIMING OF FEATURES
WILL BE CLOSER TO THE SLOWER MRF THAN THE FASTER ETA-XX.  THE CHOICE
OF TIMING IS MORE AN ADJUSTMENT FOR THE INITIAL PHASE SPEED OF THE
SHORTWAVE, AS OPPOSED TO FAVORING THE GREATER AMPLIFICATION OFFERED
BY THE MRF.  FURTHERMORE, THIS TREND IS SUPPORTED BY THE 12Z ETA AND
AVN DEPICTIONS.  IN FACT THE AVN IS ROUGHLY 12H SLOWER WITH THE
SHORTWAVE COMPLEX THIS CYCLE AND LESS AMPLIFIED ACROSS THE SOUTHERN
LAKES REGION.

.DTX...NONE.

MANN

MIZ047>049-053>055-060>063-068>070-075-076-082-083-290400-

SEVERE WEATHER OUTLOOK FOR SOUTHEAST MICHIGAN...CORRECTED DATE
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
215 PM EDT MON MAY 28 2001

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

DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY.

ISOLATED THUNDERSTORMS WILL DEVELOP IN SOUTHEAST MICHIGAN THIS
AFTERNOON AND THIS EVENING. THESE STORMS WILL NOT BE SEVERE...AND
SPOTTER ACTIVATION WILL NOT BE NEEDED.

THE LOW PRESSURE SYSTEM THAT AFFECTED THE AREA FOR THE LAST WEEK WAS
MOVING SLOWLY EAST THROUGH ONTARIO TODAY. THE WESTERN FRINGES OF
THIS SYSTEM...ALONG WITH ANOTHER WEAK LOW PRESSURE SYSTEM OVER
ILLINOIS...WILL KEEP SHOWERS IN THE FORECAST FOR THIS AFTERNOON AND
THIS EVENING. AT THE SAME TIME...INTERVALS OF SUNSHINE HAVE ALLOWED
TEMPERATURES TO RISE AROUND THE 70 DEGREE MARK IN A FEW LOCATIONS.
THIS RELATIVELY WARM AIR WILL HELP IN THE DEVELOPMENT OF ISOLATED
THUNDERSTORMS...THE STRONGEST OF WHICH WILL BE CAPABLE OF PEA SIZE
HAIL AND WIND GUSTS TO 40 MPH AS THEY MOVE SOUTHEAST AT 25 MPH. ANY
STORMS REMAINING AT SUNSET WILL THEN DISSIPATE BY 10 PM.

STAY TUNED TO NOAA WEATHER RADIO...OR YOUR FAVORITE MEDIA OUTLET...
FOR LATER WEATHER UPDATES FROM THE NATIONAL WEATHER SERVICE.

BT

MIZ047>049-053>055-060>063-068>070-075-076-082-083-290400-

SEVERE WEATHER OUTLOOK FOR SOUTHEAST MICHIGAN
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
215 PM EDT SUN MAY 27 2001

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

DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY.

ISOLATED THUNDERSTORMS WILL DEVELOP IN SOUTHEAST MICHIGAN THIS
AFTERNOON AND THIS EVENING. THESE STORMS WILL NOT BE SEVERE...AND
SPOTTER ACTIVATION WILL NOT BE NEEDED.

THE LOW PRESSURE SYSTEM THAT AFFECTED THE AREA FOR THE LAST WEEK WAS
MOVING SLOWLY EAST THROUGH ONTARIO TODAY. THE WESTERN FRINGES OF
THIS SYSTEM...ALONG WITH ANOTHER WEAK LOW PRESSURE SYSTEM OVER
ILLINOIS...WILL KEEP SHOWERS IN THE FORECAST FOR THIS AFTERNOON AND
THIS EVENING. AT THE SAME TIME...INTERVALS OF SUNSHINE HAVE ALLOWED
TEMPERATURES TO RISE AROUND THE 70 DEGREE MARK IN A FEW LOCATIONS.
THIS RELATIVELY WARM AIR WILL HELP IN THE DEVELOPMENT OF ISOLATED
THUNDERSTORMS...THE STRONGEST OF WHICH WILL BE CAPABLE OF PEA SIZE
HAIL AND WIND GUSTS TO 40 MPH AS THEY MOVE SOUTHEAST AT 25 MPH. ANY
STORMS REMAINING AT SUNSET WILL THEN DISSIPATE BY 10 PM.

STAY TUNED TO NOAA KWEATHER RADIO...OR YOUR FAVORITE MEDIA OUTLET...
FOR LATER WEATHER UPDATES FROM THE NATIONAL WEATHER SERVICE.

BT

MIZ047>049-053>055-060>063-068>070-075-076-082-083-290400-

SEVERE WEATHER OUTLOOK FOR SOUTHEAST MICHIGAN
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
520 PM EDT MON MAY 28 2001

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

DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY.

ISOLATED THUNDERSTORMS WILL CONTINUE TO AFFECT SOUTHEAST MICHIGAN
THIS AFTERNOON AND THIS EVENING. THESE STORMS WILL NOT BE SEVERE...
AND SPOTTER ACTIVATION WILL NOT BE NEEDED.

THE LOW PRESSURE SYSTEM THAT AFFECTED THE AREA FOR THE LAST WEEK WAS
MOVING SLOWLY EAST THROUGH ONTARIO TODAY. THE WESTERN FRINGES OF
THIS SYSTEM...ALONG WITH ANOTHER WEAK LOW PRESSURE SYSTEM OVER
ILLINOIS...WILL KEEP SHOWERS IN THE FORECAST FOR THIS AFTERNOON AND
THIS EVENING. AT THE SAME TIME...INTERVALS OF SUNSHINE HAVE ALLOWED
TEMPERATURES TO RISE AROUND THE 70 DEGREE MARK IN A FEW LOCATIONS.
THIS RELATIVELY WARM AIR WILL HELP IN THE DEVELOPMENT OF ISOLATED
THUNDERSTORMS...THE STRONGEST OF WHICH WILL BE CAPABLE OF HAIL TO
ONE HALF INCH...WIND GUSTS TO 40 MPH AS THEY MOVE SOUTHEAST AT
25 MPH. ANY STORMS REMAINING AT SUNSET WILL THEN DISSIPATE BY 10 PM.

STA5Y TUNED TO NOAA WEATHER RADIO...OR YOUR FAVORITE MEDIA OUTLET...
FOR LATER WEATHER UPDATES FROM THE NATIONAL WEATHER SERVICE.

BT