Severe Thunderstorm Warning 43, NWS Detroit, MI

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
320 PM EDT SUN JUL 21 2002

...SEVERE WEATHER THREAT TODAY...

CONVECTION CONTINUES TO SLOWLY DIMINISH ACROSS WI AND THE DEBRIS
CLOUD WAS STRUGGLING TO MAKE IT INTO THE CWA. SOME ISOLATED
THUNDERSTORMS DEVELOPED ACROSS SOUTHWEST LOWER MI...NORTHWEST
INDIANA...AND SOUTHERN LAKE MI EARLY...BUT JUST SOME AC LEFT FROM
THAT AT 07Z. LOCAL CONVECTIVE INITIATION MODEL PICKED UP ON THE
ISOLATED CONVECTION AND DID NOT HAVE ANYTHING NEW DEVELOPING AFTER
07Z. THEREFORE...EXPECT THE REST OF THE MORNING TO BE DRY.

MODELS IN DECENT AGREEMENT WITH THE OVERALL PATTERN...AND PASSAGE OF
THE COLD FRONT. THE ETA IS THE QUICKEST WITH THE COLD
FRONT...THROUGH THE CWA BY 03Z...AND THE NGM IS THE SLOWEST. WILL
GO WITH MORE OF THE COMPROMISE OF THE AVN WHICH WOULD BRING THE
FRONT THROUGH THE CWA AROUND MIDNIGHT.

MAIN CONCERN WILL BE THE THREAT OF SEVERE WEATHER THIS AFTERNOON AND
EVENING. ALL OF THE FEATURES APPEAR TO BE IN PLACE...GOOD UPPER
DIVERGENCE ASSOCIATED WITH THE RIGHT REAR ENTRANCE REGION OF THE 125
KT JET...50H WINDS INCREASE TO 30 TO 40 KNOTS WHILE 80H WINDS WILL
BE AROUND 30 KTS.  THERE WILL ALSO BE GOOD CONVERGENCE ALONG THE
FRONT AT THE SURFACE TO 80H. RIGHT ALONG THE FRONT THERE WILL BE A
RIBBON OF HIGH THETA-E AIR AT 80H.  MID LEVEL DRY PUNCHES IN BEHIND
THE FRONT AS WELL. THEN COMBINE THAT WITH CAPES EXPECTED TO REACH TO
NEAR 3000 J/KG THIS AFTERNOON WITH TEMPS IN THE LOW TO MID 90S AND
DEW POINTS AS HIGH AS THE MID 70S. THIS COULD SET UP TO BE THE MOST
NUMEROUS SEVERE WEATHER EVENT THIS YEAR...GIVEN THE LIGHT SEVERE
SEASON SO FAR. GIVEN ALL OF THESE FACTORS...WILL WORD POSSIBLE
SEVERE STORMS IN THE ZONES. MAIN THREAT WILL BE WIND DAMAGE...BUT
WITH THE HIGH CAPES COULD GET AN UPDRAFT OR TWO TO PRODUCE MARGINAL
SEVERE HAIL.

CONVECTIVE INITIATION MODEL SUGGEST THUNDERSTORMS DEVELOPING NEAR
THE FRONT AROUND 16Z FROM JUST EAST OF THE BRIDGE TO GAYLORD TO MKG.
THEN STORMS SHOULD MOVE NORTHEAST ALONG THE FRONT...WITH THE SLOW
PROPAGATION SOUTHEAST AS THE FRONT MOVES TOWARD THE CWA. STORMS
SHOULD APPROACH THE TRI CITES AROUND 18Z...BUT MAY NOT REACH DETROIT
UNTIL CLOSER 00Z.

WILL HOLD OFF ON ANY HEAT ADVISORY TODAY. TEMPS AROUND 94 WITH DEW
POINTS AROUND 74 DOES GIVE A HEAT INDEX OF 105...BUT THIS SHOULD BE
THE PEAK CONDITIONS FOR METRO DETROIT. GIVEN THE POTENTIAL OF
CLOUDS...BOTH DEBRIS AND CU FORMING THIS MORNING...MIGHT BE A
STRUGGLE TO REACH MID 90S FOR MORE THAN A HOUR.

BEHIND THE FRONT...THERE WILL BE SOME MOISTURE AT 80H AND BELOW.
EXPECT SKIES TO CLEAR ABOUT 6 HOURS AFTER THE FROPA. THIS WILL LEAD
TO CLEARING SKIES LATE TONIGHT FOR THE TRI CITIES AND THUMB...AROUND
DAYBREAK FOR FNT...AND DURING TUESDAY MORNING FOR METRO DETROIT.
AFTER THAT...DRY AIR TAKES HOLD AND WILL BE IN FOR A SUNNY TUESDAY
AFTERNOON...CLEAR SKIES TUESDAY NIGHT AND MOSTLY SUNNY ON WEDNESDAY.

WILL GO TOWARD THE HIGHER ETA MOS FOR HIGHS TODAY...GIVEN SOME
DECENT SUN AND 80H TEMPS OF +20 TO +21C. THEN ALL THE NUMBERS ARE
CLOSE FOR TONIGHT THROUGH TUESDAY NIGHT...AND DID NOT DIFFER FROM
THEM.

.DTX...NONE.

RBP