Severe Thunderstorm Warning 51, NWS Detroit, MI

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
335 PM EDT SUN JUL 22 2001

PROBABLY THE HOTTEST FEELING DAY YET THIS SUMMER IN PROGRESS WITH
HEAT INDICES UP AROUND 100 DEGREES AT MANY LOCATIONS WITH TEMPS IN
THE LOWER 90S AND DEWS IN THE LOWER 70S. ATMOSPHERE VERY UNSTABLE
WITH SBCAPES RUNNING FROM 1500 TO 3000 J/KG ACROSS THE FA. WE ALSO
KNOW THAT THERE ARE PLENTY OF SURFACE BOUNDARIES AROUND, BESIDES THE
LAKE BREEZES, AS THEY HAVE BEEN EVIDENT IN THE VISIBLE IMAGERY ALL
AFTERNOON. ONE BOUNDARY MOVED SOUTH INTO THE SAGINAW VALLEY AND
THUMB EARLIER THIS MORNING FROM CONVECTION THAT MOVED ACROSS LAKE
HURON. DESPITE THE STRONG INSTABILITY AND PLETHORA OF BOUNDARIES,
VERY LITTLE IN THE WAY OF CONVECTIVE DEVELOPMENT HAS OCCURRED IN SE
LOWER. A COUPLE OF CELLS HAVE RECENTLY GONE UP ALONG THE LAKE BREEZE
IN HURON COUNTY. THE LACK OF CONVECTION MAY BE A RESULT OF WHAT IS
SURPRISINGLY SHALLOW SURFACE MOISTURE AS KDTX 12Z SOUNDING SHOWED A
LITTLE LESS THAN 100MB DEPTH TO THE JUICE. ALSO, OVERALL WEAK WIND
FIELD IS OBVIOUSLY LIMITING CONVERGENCE INVOF THE BOUNDARIES. THUS,
GUT FEELING WOULD BE TO GO DRY OVER ALL BUT THE LAKE BREEZE COUNTIES
THIS EVENING, BUT A FEW THINGS ARGUE FOR HANGING ON TO SOME POPS FOR
AT LEAST THE EVENING HOURS.

THE FIRST THING IS THE DYNAMIC CONVECTIVE COMPLEX OVER ERN WI ATTM.
THE CURRENT STRONG TO SEVERE STORMS FIRED ON AN OUTFLOW BOUNDARY
FROM AN EARLIER COMPLEX. THIS LINE OF STORMS IS APPROACHING THE LAKE
MICHIGAN LAKE BREEZE NEAR THE WI COAST ATTM. EXPECT ASSOCIATED MCV
TO CONTINUE TO INITIATE CONVECTION IN HIGHLY UNSTABLE AIRMASS ACROSS
THE LAKE AND INTO WESTERN LOWER THIS EVENING. CORFIDI VECTOR PROGS
FROM THE ETA SUGGEST MORE AND MORE OF A RIGHT TURN AS ANY ACTIVITY
APPROACHES SE LOWER, BUT CERTAINLY NOT OUT OF THE QUESTION THAT THIS
COULD AFFECT PARTS OF THE FA THIS EVENING, PARTICULARLY SW PARTS.
ELSEWHERE, THE NORTHERN LOWER LAKE BREEZES WERE GOING STRONG WITH
SOME SEVERE CONVECTION. THESE STORMS WERE ALSO DRIFTING SE AND COULD
GET INTO THE SAGINAW VALLEY THIS EVENING AS WELL. AND THEN THERE IS
THE POSSIBILITY THAT ANY OF THE BOUNDARIES IN PLACE ACROSS SE LOWER
COULD LIGHT UP WHILE THE SUN IS STILL HIGH IN THE SKY. BOTTOM LINE
IS CHANCE POPS ARE WARRANTED ACROSS ALL OF SE LOWER THIS EVENING.
THINGS SHOULD BE WINDING DOWN AND DEBRIS CLOUDS THINNING IN THE
OVERNIGHT HOURS WHICH WILL MAKE FOR ANOTHER PARTLY CLOUDY NIGHT WITH
AREAS OF FOG AROUND. COULD EVEN BE SOME NOCTURNAL CONVECTIVE
DEVELOPMENT WITH ANY LOCALIZED CONVERGENCE, BUT TRYING TO PICK ONE
AREA OVER ANOTHER IS IMPOSSIBLE.

ALMOST A REPEAT PERFORMANCE FOR MONDAY. AIRMASS WILL CERTAINLY BE
SIMILAR WITH AFTERNOON HIGHS AROUND 90 AND DEWS IN THE LOWER TO MID
70S RESULTING IN A HIGH CAPE SCENARIO ONCE AGAIN. HOWEVER, 950MB
WINDS ARE PROGGED TO BE STRONG ENOUGH TO PREVENT MUCH LAKE BREEZE
PENETRATION, SO THOSE PROBABLY WONT BE AS BIG A PLAYER IN THE
CONVECTIVE INITIATION GAME AS THEY HAVE BEEN THE LAST SEVERAL DAYS.
A BROAD AREA OF UPPER DIVERGENCE SPREADS ACROSS THE LAKES REGION BY
MONDAY AFTERNOON AND SOME SURFACE TROFFING LEADS TO BETTER LOW LEVEL
CONVERGENCE WITH THE COMBO PROBABLY RESULTING IN MORE SCATTERED
THUNDERSTORMS IN THE AFTERNOON. WHAT LOOKS TO BE A MORE ORGANIZED
THREAT FOR STORMS MOVES IN LATE MONDAY AFTERNOON AND EVENING AS ETA
SHOWS A SHORT WAVE TROF AND STRONG VORT MAX ROLLING INTO SOUTHERN
PORTIONS OF LOWER. DECENT LOW LEVEL CONVERGENCE/UPPER LEVEL
DIVERGENCE COUPLING PROGGED TO OCCUR AHEAD OF THIS WAVE OVER SE
LOWER DURING THE EVENING HOURS. INTUITION HERE WOULD SUGGEST AT
LEAST LIKELY POPS, BUT WITH MODEL QPF/POP TRACK RECORD OF LATE,
THINK IT PRUDENT TO CONTINUE TO PLAY POPS CONSERVATIVELY FOR AT
LEAST ONE MORE MODEL RUN. SPC DAY 2 HAS REGION IN SLIGHT RISK, BUT
WE ARE NOT CURRENTLY EXCITED ABOUT SEVERE CHANCES GIVEN HIGH WBZS
AND LITTLE 0-6 KM SHEAR MONDAY EVENING. WILL FINALLY START TO FLUSH
THE OPPRESSIVE AIRMASS ON TUESDAY AS A COLD FRONT SINKS SOUTH INTO
THE REGION. NOT MUCH UPPER SUPPORT FOR PRECIP, BUT AIRMASS WILL
REMAIN UNSTABLE AND WILL HAVE TO HANG ONTO A CHANCE FOR SHOWERS OR
STORMS UNTIL THE FRONT CLEARS THE FA.

WEAVER

LITTLE CHANGE FROM YESTERDAY'S FEELINGS IN THE EXTENDED PERIOD AS
GENERALLY MODELS ARE IN GOOD AGREEMENT ON PATTERN CHANGE EARLY-MID
WEEK. THE STAGNANT...WARM-HOT SUMMER AIRMASS SHOULD BE
TEMPORARILY...ANYWAY...HISTORY BY LATER TUE-WED. MODELS AGREE ON
PUSHING THE PRE-FRONTAL TROF THRU SOUTHEAST LOWER MICHIGAN EARLY-MID
TUE WITH MAIN COLD FRONT CATCHING UP WITH IT LATE TUE. THIS IS JUST
A TAD FASTER THAN YESTERDAY AND REALLY THE ONLY NOTABLE CHANGE.
OTHERWISE...STILL FEEL MOST OF THE SHOWERS/STORMS WILL FOCUS ALONG
PRE-FRONTAL TROF ON TUE...ESPECIALLY WHEN ONE LOOKS AT THE STABLE
AIR PREDICTED TO FOLLOW. STILL COULD BE A SHOWER AND/OR STORM TUE
EVE AS THE MAIN FRONT LEAVES...BUT AM LESS PESSIMISTIC THAN
YESTERDAY ABOUT WED AND WILL BACK OFF ON THE WORDING.

IMPRESSIVE COLD HUDSON BAY LOW AND HIGH PRESSURE THAT MOVES ACROSS
THE NORTHERN LAKES WILL PUSH IN SOME SEASONABLY COOL AND REFRESHING
CANADIAN AIR. PATTERN HAS MORE CHARACTERISTICS OF A BACK-DOOR COLD
FRONT AND SUBSEQUENT HIGH PRESSURE POSITIONING AND THUS...FRESH EAST
TO NORTHEAST WINDS WILL DOMINATE. BEAUTIFUL HIGH WILL BE WITH US FOR
AT LEAST A FEW DAYS (THU-SAT) AS IT MIGRATES EAST THRU ONTARIO INTO
QUEBEC/NEW ENGLAND. FRONT STILL SLATED TO PUSH WELL SOUTH OF THE
AREA AND WILL NOT DRIFT BACK NORTH UNTIL LATER SAT-SUN BUT KEPT SAT
DRY. THE RISK OF SHOWERS/STORMS WILL BE ON THE INCREASE LATER SAT
INTO SUN.

DEEDLER

.DTX...NONE.