Hail and Damaging Winds in Michigan, July 28, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
415 AM EDT SUN JUL 28 2002

FORECAST CONCERNS ARE WITH SHRA/TSTM CHANCES TODAY THROUGH MONDAY.

CURRENT SURFACE ANALYSIS FINDING IT DIFFICULT TO PICK OUT LOCATION
OF WARM FRONT DUE TO ONGOING CONVECTION. SUSPECT THE FRONT MAY LIE
FROM NEAR LUDINGTON SE THROUGH LANSING WHERE SURFACE DEWPOINTS JUMP
INTO THE 70S. 00Z UPPER AIR CHARTS AND WATER VAPOR IMAGERY SHOWING
MAIN SHORTWAVE MOVING THROUGH NORTHERN WISCONSIN/WEST-CENTRAL UPPER
MICHIGAN...WITH A MID LEVEL DRY PUNCH SLIDING IN BEHIND THE WAVE.
LOW LEVEL JET/MOIST CONVERGENCE INTO THE BOUNDARY HAS INITIATED
ANOTHER ROUND OF SHRA/TSTMS CURRENTLY MOVING THROUGH CENTRAL AND
NORTHERN LOWER MICHIGAN. SOUNDINGS INDICATING 40 KNOTS OR GREATER
MID LEVEL FLOW THROUGH THE GREAT LAKES AIDING WITH TSTM
ORGANIZATION. VICINITY OF FRONT HAS LEAD TO DECENT STORM RELATIVE
HELICITY VALUES LAST EVENING AND OVERNIGHT...WITH A NUMBER OF
THUNDERSTORMS EXHIBITING ROTATION. HOWEVER...LACK OF SURFACE BASED
INSTABILITY HAS PRECLUDED MUCH IN THE WAY OF DAMAGING WIND GUSTS OR
TORNADIC SPIN UPS.

TODAY...AFTERNOON TEMPS AND INSTABILITY WILL LARGELY DEPEND ON HOW
QUICKLY CLOUD COVER CAN CLEAR OUT. ANTICIPATE AFTERNOON TEMPS MAY
RUN A COUPLE OF DEGREES COOLER THAT SATURDAY...PARTICULARLY FOR THE
NORTHERN AREAS WHERE THE CLOUD COVER HANGS ON THE LONGEST. EVEN
SO...WITH SURFACE DEWPOINTS STILL HOLDING IN THE MID TO UPPER 60S
AFTERNOON INSTABILITY WILL INCREASE AGAIN PRIMARILY IN NORTHERN
LOWER MICHIGAN. DIFFICULT TO KNOW EXACTLY WHERE WARM FRONT ENDS UP
THIS AFTERNOON...AS THIS WILL PLAY A BIG ROLE IN ANY ADDITIONAL
THUNDERSTORM DEVELOPMENT. MODELS SUGGEST BOUNDARY MAY BEGIN TO SAG
BACK FURTHER TO THE SOUTH THIS AFTERNOON AFTER PASSAGE OF MID LEVEL
WAVE TO THE NORTH. FOR NOW...WILL GO WITH IDEA THAT BOUNDARY SETS UP
JUST A LITTLE FURTHER NORTH THAN MODELS ADVERTISE. THUS SOUTHERN AND
EASTERN COUNTIES WILL HAVE BEST CHANCES FOR THUNDERSTORMS THIS
AFTERNOON...NEAR VICINITY OF FRONT AND ALONG ANY LAKE HURON MARINE
BOUNDARIES WHERE THE WESTERLY SYNOPTIC FLOW INTERSECTS THE MARINE
BOUNDARIES. AM INCLINED TO REMOVE AFTERNOON TSTMS FROM THE REST OF
THE CWA.

TONIGHT...500 MB RIDGING MOVES ACROSS NORTHERN MICHIGAN IN ADVANCE
OF NEXT UPSTREAM WAVE WITH SLIGHT MID LEVEL WARMING HELPING TO
STABILIZE THE ATMOSPHERE IN THE NORTHERN COUNTIES. HOWEVER...LOW
LEVEL MOISTURE (850 MB THETA-E AXIS) REMAINS THROUGH THE CENTRAL
PART OF CENTRAL AND SOUTHERN LOWER MICHIGAN WITH INSTABILITY
LINGERING THROUGH THE NIGHT. CANNOT RULE OUT CHANCE SHOWERS/TSTMS
THROUGH THE NIGHT AS A RESULT.

THEN...UPSTREAM WAVE ADVERTISED BY ETA/AVN MOVES INTO THE UPPER
MIDWEST BY MONDAY MORNING WITH PRECIP FROM THIS SYSTEM SPREADING
INTO WISCONSIN AND UPPER MICHIGAN LATE SUNDAY NIGHT. SOME SHRA/TSTMS
MAY TRY AND NOSE INTO THE FAR WESTERN PART OF THE CWA AND INTO
EASTERN UPPER MICHIGAN BEFORE 6 AM MONDAY MORNING...BUT GUT FEELING
IS THAT EVERYTHING FROM THIS SYSTEM WILL REMAIN TO THE WEST BEFORE
THAT TIME. SO...PLAN TO CARRY A DRY FORECAST FOR THE REST OF THE CWA.

MONDAY/MONDAY NIGHT/TUESDAY...NOT ANTICIPATING MANY CHANGES TO THE
ONGOING FORECAST FOR THESE PERIODS. UPPER LEVEL SYSTEM AND WEAK
SURFACE REFLECTION PROGGED TO CROSS THROUGH NORTHERN MICHIGAN MONDAY
AFTERNOON. ENTRANCE REGION OF 100 KNOT UPPER JET ALSO SLIDES
THROUGH THE NORTHERN GREAT LAKES RESULTING IN STRONG UPPER
DIVERGENCE/UVV MOVING THROUGH. WILL MAINTAIN LIKELY POPS DURING THE
DAYTIME MONDAY FOLLOWED BY A CLEARING TREND MONDAY EVENING AND DRY
FOR TUESDAY.

.APX...NONE.

ADAM