Damaging Winds in Michigan, August 21, 2003

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
626 PM EST THU AUG 21 2003

AVIATION DISCUSSION FOR 00Z TAFS...

AS OF YET...THERE ARE NO STORMS ON THE RADAR. STILL VERY UNSTABLE
ATMOSPHERE AND AS THE FRONT MOVES THROUGH, THIS COULD KICK OFF SOME
STORMS. FRONT IS CURRENTLY ENTERING SOUTHERN LAKE MICHIGAN. CAPES
WILL STILL BE AROUND 1500-1800 WITH LI VALUES UP TO -5. THE WIND
WILL SHIFT TO THE NORTH AFTER THE FRONT PASSES EACH AIRPORT IN THE
EARLY MORNING HOURS.   BML

FORECAST DISCUSSION FOR TONIGHT AND FRIDAY...

FIRST...ISSUED A HEAT ADVISORY FOR REMAINDER OF THIS AFTERNOON AND
INTO THE EARLY EVENING HOURS. NORTHWEST TWO THIRDS OF COUNTY WARNING
AREA WILL EXCEED HEAT INDEX OF 100 FOR 3 HOURS THIS AFTERNOON.
EASTERN AREAS WILL LIKELY NOT REACH THIS CRITERIA BUT GIVEN THE
RELATIVELY COOL SUMMER AND LACK OF HEAT...PEOPLE WILL NEED TO BE
EXTRA CAUTIOUS WITH HEAT INDEX VALUES IN MID TO UPPER 90S. THEREFORE
ISSUED FOR ENTIRE AREA. EXPECTING DEWPOINTS TO STAY HIGH TIL FROPA
SO INDEX VALUES MAY ONLY DROP SLOWLY AFTER SUNSET AS RH RISES.

VERY UNSTABLE THIS AFTERNOON WITH SURFACE TEMPERATURES WELL INTO THE
90S MOST AREAS AND DEWPOINTS INTO THE 70S. MID LEVELS COOLING
SLIGHTLY BUT CAP HAS PREVENTED ANY DEVELOPEMENT. DTX SOUNDING FROM
18Z SHOWS THIS CAP NICELY. EXPECT AS FRONT NEARS AND INTERACTS WITH
INSTABILITY...CAP WILL BE BROKEN AND CONVECTION WILL FIRE. BEST
DYNAMICS REMAIN NORTH WITH BETTER WIND FIELD AND SHORTWAVE.
HOWEVER...DRY SLOT EVIDENT ON DTX 18Z SOUNDING COUPLED WITH HIGH
PWATS AND LARGE CAPES INDICATES STRONG DOWNBURST POTENTIAL. WILL ADD
SEVERE WORDING TO ZONES FOR ANY STORMS THAT DO DEVELOP. KEPT POPS IN
HIGH CHANCE CATEGORY GIVEN UNCERTAINTY WITH CAP. FRONT TO SLOWLY
MOVE ACROSS AREA OVERNIGHT. DIFFERENCES REMAIN IN TIMING ITS EXIT IN
THE SOUTHEAST FRIDAY MORNING. HAVE KEPT A SMALL CHANCE OF THUNDER
DURING THE MORNING HOURS UNTIL AT LEAST THE SLOWER ETA 850MB FRONT
CLEARS AREA. TEMPERATURES MUCH MORE SEASONABLE FRIDAY WITH LESS
HUMIDITY. FEEL THAT IT WILL TAKE AWHILE FOR SURFACE DEWPOINTS TO
REALLY COME DOWN BUT SHOULD BE A SLOW DECLINE IN THE AFTERNOON.

FORECAST DISCUSSION FOR FRIDAY NIGHT THROUGH THURSDAY...

BY FRIDAY NIGHT, THE FRONT WILL BE WELL TO OUR EAST AND SOUTH. AN
AREA OF HIGH PRESSURE WILL THEN MOVE INTO THE AREA THROUGH EARLY
TUESDAY. THE MRF HAS A WEAK TROUGH MOVING THROUGH LATE TUESDAY INTO
EARLY WEDNESDAY WHICH THE GEM IS IN ROUGH AGREEMENT WITH THIS. THEN
A BRIEF HIGH PRESSURE BEFORE A DEEPENING TROUGH MOVES INTO THE AREA
LATE THURSDAY. MAY BE SOME PRECIP WITH THIS TROUGH NEXT WEEK
THURSDAY BUT SINCE IT MIGHT NOT BE UNTIL LATE...HAVE LEFT NEXT
THURSDAY DRY FOR THE TIME BEING. WILL SEE WHAT THE MODELS DO WITH
THE TIMING OF THIS EVENT AS THAT DAY GETS CLOSER TO THE PRESENT.
HIGH TEMPERATURES ARE EXPECTED TO BE AROUND 80 TO THE LOWER 80S.
LOWS WILL START OUT IN THE 50S AND INCREASE SLIGHTLY TO AROUND 60
NEXT WEEK. OVERALL...NO SIGNIFICANT CHANGES TO PREVIOUS FORECAST.
BML

.IWX...
IN...HEAT ADVISORY FOR THIS AFTERNOON AND EVENING FOR ZONES
INZ003>009...INZ012>018...INZ020...INZ022>027...INZ032>034.

MI...HEAT ADVISORY FOR THIS AFTERNOON AND EVENING FOR ZONES
MIZ077>081.

OH...HEAT ADVISORY FOR THIS AFTERNOON AND EVENING FOR ZONES
OHZ001>002...OHZ004>005...OHZ015>016...OHZ024>025.

LASHLEY/LOTHAMER

INZ003>009-012>018-020-022>027-032>034-MIZ077>081-OHZ001-002-004-005-
015-016-024-025-221000-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORTHERN INDIANA
504 AM EST THU AUG 21 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHERN INDIANA...NORTHWEST
OHIO AND SOUTHWEST LOWER MICHIGAN.

.DAY ONE...TODAY AND TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGHOUT THE AREA
THIS AFTERNOON INTO THIS EVENING. STRONG GUSTY WINDS WILL BE THE
PRIMARY HAZARD...BUT SCATTERED LARGE HAIL CANNOT BE RULED OUT. AN
ISOLATED TORNADO WILL BE POSSIBLE NORTH OF A LINE FROM NAPOLEON...TO
HUNTINGTON...TO MONTICELLO. IN ADDITION...THE STORMS WILL BE CAPABLE
OF LOCALLY HEAVY RAIN. A COLD FRONT MOVING FROM NORTHWEST TO
SOUTHEAST ACROSS THE GREAT LAKES WILL BE RESPONSIBLE FOR THE
THUNDERSTORMS.

BEFORE THE STORMS DEVELOP...SUNSHINE AND HUMIDITY WILL COMBINE TO
MAKE A HOT AND STICKY DAY. AS TEMPERATURES CLIMB TO NEAR THE 90
DEGREE MARK BY THIS AFTERNOON...HEAT INDEX READINGS WILL APPROACH
100. TRY TO REMAIN IN AIR CONDITIONING AS MUCH AS POSSIBLE DURING
THE HEAT OF THE DAY. IF YOU MUST BE OUTSIDE...TAKE IT EASY...DRINK
PLENTY OF WATER...AND WEAR SUNSCREEN.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED THIS AFTERNOON AND EVENING.

STAY TUNED TO NOAA WEATHER RADIO FOR FURTHER DETAILS OR UPDATES, OR
CHECK OUR WEB SITE AT WWW.CRH.NOAA.GOV/IWX

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