Severe Thunderstorm Warning 101, NWS Detroit, MI

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1110 AM EDT SAT AUG 16 2003

SEVERE THUNDERSTORM POTENTIAL THIS AFTERNOON/EARLY EVENING FOR SOUTH
HALF OF CWA...

SURFACE FRONT KICKING OFF CONVECTION THIS MORNING ACROSS FAR NORTH
CWA. THIS FRONT WILL SAG SOUTH THROUGH THE AFTERNOON AND EVENING
PROVIDING A SOURCE OF LOW LEVEL CONVERGENCE AND LIFT. /CURRENTLY...
CONVECTION HAS TENDED TO WEAKEN AS IT MOVES INTO CWA. TWO FACTORS
HERE AT PLAY...CONVECTION OUTRUNNING LOW LEVEL FORCING AND POCKET OF
WARMER MID LEVEL OVER CWA. EXPECT BOTH OF THESE FACTORS TO BECOME
MORE SUPPORTIVE OF CONVECTION THROUGH THE AFTERNOON./ A POTENT UPPER
LEVEL JET WILL NOSE INTO SE LOWER MICHIGAN THIS AFTERNOON PLACING
SOUTH HALF OF CWA IN FAVORABLE LFQ OF EXIT REGION YIELDING
IMPRESSIVE UPPER LEVEL DIVERGENCE. /SHRA-TSRA ONGOING ON A MOP-MBL
LINE ARE ASSOCIATED WITH THE NOSE OF THIS JET./ DEW POINTS IN LOW 70S
INDICATIVE OF GOOD MOISTURE AVAILABILITY. MODIFIED DTX SOUNDING OF
87/70 YIELDS CAPES IN 3500 J/KG RANGE. MID LEVEL WIND FIELDS IN THE
35 TO 40 KNOT RANGE WILL AID IN CELL ORGANIZATION THIS AFTERNOON.
GIVEN TIMING OF SYSTEM INTO CWA...SEVERE THUNDERSTORM POTENTIAL WILL
BE M 59 SOUTH...INCREASING TOWARD THE OHIO BORDER. MAIN CONCERN HERE
LOOKS TO BE WIND...TO 70 MPH...WITH MID LEVEL JET WORKING IN...AND
DRY AIR NOTED IN MID LEVELS. HOWEVER...GIVEN HIGH INSTABILITY AND
RELATIVELY STRONG DYNAMICS...CANNOT RULE OUT HAIL TO ONE INCH IN
DIAMETER. SOMEWHAT STRONGER MID LEVEL FLOW WILL PROMOTE FASTER CELL
MOVEMENT TODAY THAN IN PREVIOUS DAYS...SO URBAN FLOOD POTENTIAL WILL
BE REDUCED...BUT NOT ENTIRELY ELIMINATED...AS MOIST ATMOSPHERE AND
VIGROUS DYNAMICS WILL PRODUCE HEAVY RAIN IN CELLS.

EARLY MORNING DISCUSSION FOLLOWS...

ONE MORE HUMID/HOT DAY.

MOIST AND UNSTABLE AIRMASS IN PLACE OVER SOUTHEAST MICHIGAN.
SURFACE DEW POINTS CONTINUE TO HOVER AROUND 70 DEGREES ACROSS MUCH
OF THE CWA. RELIEF IS ON THE WAY HOWEVER...AS A COLD FRONT IS
CURRENTLY DROPPING SOUTH THROUGH THE NORTHERN GREAT LAKES.
PRETTY GOOD CHANCE FOR SOME SEVERE THUNDERSTORMS THIS AFTERNOON
ACROSS THE SOUTHERN THIRD OF THE CWA (IF CONVECTION INITIATES).
WARM AIRMASS/MID LEVEL CAP MAY PREVENT STORMS FROM DEVELOPING.
THE CANADIAN MODEL IS SHOWING NO MEASURABLE QPF.
CAPES SHOULD BUILD TO AROUND 3000 J/KG. 500 MB COLD POOL (-12 C)
DROPS INTO NORTHERN LOWER MICHIGAN. FREEZING LEVELS WILL COME
CRASHING DOWN DURING THE DAY (FALLING TO 12000 FEET). MUCH BETTER
WIND FIELD TODAY AS WELL...AS 50 KNOT JET AT 500 MB NOSES INTO
SOUTHERN LOWER MICHIGAN. MESOETA SHOWS THE FRONT MOVING INTO
MONROE/LENAWEE COUNTIES AT 21Z...COINCIDENT WITH THE PEAK HEATING OF
THE DAY. ONE NEGATIVE IS THE WEAK FLOW IN THE LOW LEVELS. PLAN ON
CARRYING 50 POPS NEAR OHIO BORDER...WITH 20 POPS ACROSS THE FAR
NORTH. WILL CONTINUE THE MENTION OF MORNING FOG...AS SURFACE
VISIBILITIES ARE CURRENTLY BETWEEN 2 AND 3 MILES. MAX TEMPS IN THE
UPPER 80S LOOKS OK FOR TODAY.

AFTER THE FRONT SLIDES THROUGH LATE TODAY...QUIET WEATHER EXPECTED
THROUGH TUESDAY. LARGE UPPER LEVEL RIDGE OVER CENTRAL U.S. WILL
AMPLIFY AND EXTEND INTO CENTRAL CANADA...BEFORE FOLDING OVER INTO
THE GREAT LAKES REGION ON MONDAY. AT THE SURFACE...HIGH PRESSURE
(1020 MB) OVER MANITOBA/ONTARIO WILL SETTLE INTO THE CENTRAL GREAT
LAKES REGION BY MONDAY...PROVIDING A FEW DAYS OF DRY WEATHER
(BEGINNING SUNDAY). ETA CU RULE SUGGESTING PLENTY OF CU ON
SUNDAY...THUS WILL BE GOING WITH THE PARTLY SUNNY FORECAST. DRYER
AIR WILL CONTINUE TO FILTER INTO SOUTHEAST MICHIGAN SUNDAY
NIGHT/MONDAY AS SURFACE DEW POINTS FALL INTO THE 50S. NO CHANGES
MADE BEYOND MONDAY.

.DTX...NONE.

SF

EXPERIMENTAL GRAPHICAL FORECASTS ARE AVAILABLE ONLINE AT
HTTP://WWW.CRH.NOAA.GOV/DTX  (ALL LOWER CASE)

MIZ047>049-053>055-060>063-068>070-075-076-082-083-171000-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
209 PM EDT SAT AUG 16 2003

...SEVERE THUNDERSTORM WATCH 863 IN EFFECT UNTIL 8 PM FOR MUCH OF
SOUTHEAST LOWER MICHIGAN...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST LOWER MICHIGAN

.DAY ONE...THIS AFTERNOON AND TONIGHT

SCATTERED THUNDERSTORMS WILL OCCUR THIS AFTERNOON AND EARLY EVENING
IN AND SOUTH OF THE SAGINAW VALLEY. SOME OF THESE STORMS MAY BE
SEVERE. THE PRIMARY HAZARD WILL BE WIND GUSTS TO 70 MPH WITH HAIL TO
ONE INCH IN DIAMETER. AN ISOLATED TORNADO IS POSSIBLE AS WELL.
TIMING ON SEVERE THUNDERSTORMS WOULD PLACE THE STORMS IN THE SAGINAW
VALLEY...I 69 CORRIDOR...AND M 59 CORRIDOR BETWEEN 2 PM AND 6 PM...I
94 BETWEEN 3 PM AND 7 PM...AND ALONG THE OHIO BORDER BETWEEN 4 PM
AND 8 PM.

WARM AND HUMID AIR REMAINS IN PLACE OVER ALL OF SOUTHEAST MICHIGAN
THIS AFTERNOON. THIS WILL COMBINE WITH DAYTIME HEATING AND A COLD FRONT
TO PROVIDE THE OPPORTUNITY FOR THUNDERSTORMS. THE COLD FRONT WILL
MOVE FROM THE SAGINAW VALLEY AND THUMB...THEN INTO THE DETROIT AREA
BY MID AFTERNOON. STORMS THAT DEVELOP ALONG THE FRONT WILL MOVE
QUICKLY TOWARD THE SOUTHEAST AND BE OUT OF SOUTHEAST MICHIGAN BY 10
PM.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THERE IS ANOTHER CHANCE OF THUNDERSTORMS ACROSS SOUTHEAST MICHIGAN
ON WEDNESDAY.

.SPOTTER INFORMATION STATEMENT...

DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGER.
SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON.

&&

STAY TUNED TO NOAA WEATHER RADIO...OR LOCAL MEDIA OUTLETS...FOR THE
LATEST FORECAST INFORMATION FROM THE NATIONAL WEATHER SERVICE. YOU
CAN ALSO OBTAIN THE LATEST FORECAST ON THE NATIONAL WEATHER SERVICE
WEB SITE HTTP://WWW.CRH.NOAA.GOV/DTX/ (ALL LOWER CASE)

BT