Severe Thunderstorm Warning 77, NWS Detroit, MI

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
215 PM EDT THU JUL 17 2003

SEVERAL SHORT TERM CONVECTIVE CONCERNS TO DEAL WITH THIS AFTERNOON.
AREA OF SHOWERS OVER NORTHERN CWA STRUGGLING AS MOISTURE REMAINS
LIMITED AND BETTER LOW LEVEL CONVERGENCE FARTHER NORTH ALONG FRONTAL
BOUNDARY. MAINLY ELEVATED CONVECTION ASSOCIATED WITH WEAK UPPER WAVE
AND SHOULD MOVE EAST OF CWA BY 21Z. NEXT CONCERN IS INCREASING
CONVECTION ALONG COLD FRONT OVER CENTRAL LOWER. FRONT NOW PLOWING
INTO MORE UNSTABLE AIRMASS WHERE CAPES ARE RUNNING BETWEEN 1500-2500
J/KG. FRONT INITIALLY PARALLEL TO 700 MB FLOW AND MAKING SLOW
SOUTHWARD PROGRESS...HOWEVER MODELS INDICATE FRONT BECOMING A LITTLE
MORE PERPENDICULAR TO 700 MB FLOW AND THUS ANTICIPATE A STEADY SLOW
SOUTHWARD SLIDE...EVEN THOUGH 500 MB TROF CONTINUES TO MIGRATE EAST
WITH LITTLE DIGGING. MODELS ALSO INDICATE A SLOW DECREASE IN 700 MB
TEMPERATURES ACROSS SOUTHERN LOWER IN ADVANCE OF THE FRONT AND THIS
SHOULD ERODE CAP THAT REMAINS OVER THAT REGION. THUS ANTICIPATE
CONVECTION TO INCREASE ACROSS ALL OF SOUTHEAST LOWER LATE THIS
AFTERNOON...BUT REMAINING BELOW SEVERE THRESHOLDS AS 0-6KM SHEAR
VECTOR 20M/S OR WEAKER. ALSO CONCERNED ABOUT MCS DEVELOPMENT OVER
CENTRAL WISCONSIN. CAP HAS ERODED NOW AND LAPS SHOWING CAPES AROUND
3800J/KG. CONCERNED FOR THE FAR SOUTHWEST PORTION OF THE CWA WITH
850-300 MB THICKNESS SCHEME INDICATING A SOUTHEAST TRACK AHEAD OF
THE FRONT AND JUST CLIPPING THE WESTERN PORTION OF THE CWA NEAR THE
OHIO BORDER. THIS WILL BE MOVE OF AN EVENING CONCERN AS THIS WILL
TAKE A FEW MORE HOURS TO DEVELOP AND THEN PROPAGATE INTO THE
CWA...PERHAPS BETWEEN 6-9 PM.

MODELS IN GENERAL AGREEMENT THROUGH 84 HOURS NOW...WITH THE
EXCEPTION OF TIMING OF INDIVIDUAL SHORT WAVES...GFS IS A LITTLE MORE
AGGRESSIVE ON SUNDAY. WILL CONTINUE WITH SCATTERED POPS THIS
AFTERNOON AND EVENING AS MOISTURE REMAINS LIMITED...UA PLOTS AND
WATER VAPOR LOOP STILL SHOWING SOME DRY MID LEVEL AIR OVER THE
SOUTHERN PORTION OF THE CWA AND OMEGA FIELD WEAKENS WITH TIME AS
FRONT CONTINUES TO DROP SOUTH OF UPPER SUPPORT. CONSIDERING
CONVECTIVE CONCERNS MENTIONED ABOVE...WILL PROBABLY GO WITH A 50 POP
FOR THE SOUTHERN 2/3 OF CWA ...WITH FRONT FINALLY MOVING SOUTH OF
THE BORDER AROUND 06Z. BOTH THE ETA AND GFS SHOWING ANOTHER UPPER
WAVE RIDING ALONG THE FRONT BETWEEN 06-12Z AND AFFECTING THE FAR
SOUTHERN PORTION OF THE CWA...HOWEVER WAVE IS NOT WELL DEFINED ON
SATELLITE AND WITH DIMINISHING DIURNAL AND SYNOPTIC SUPPORT WILL
IGNORE FOR NOW. THUS WILL END PCPN AROUND 06Z ALONG OHIO BORDER.

NEAR RECORDS LOW POSSIBLE SATURDAY MORNING AS MENTIONED IN PREVIOUS
DISCUSSION AS VERY DRY AIRMASS IN PLACE AND RIDGE AXIS OVER
SOUTHEAST LOWER. WILL HAVE TO REINTRODUCE PCPN INTO FORECAST ON
SUNDAY AS NORTHWEST FLOW STRENGTHENS AND NEXT SURFACE LOW RACES
SOUTHWARD. RETURN FLOW ALSO SETTING UP QUICKLY AS RIDGE AS SLIDES
SOUTH INTO OHIO VALLEY.

WILL LEAN TOWARD SLIGHTLY COOLER MAV GUIDANCE TEMPERATURES.

.DTX...NONE.

GSS

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

MIZ047>049-053>055-060>063-068>070-075-076-082-083-181200-

HAZARDOUS WEATHER OUTLOOK...UPDATE
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
245 PM EDT THU JUL 17 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST LOWER MICHIGAN

.DAY ONE...THIS AFTERNOON AND TONIGHT

A BROKEN LINE OF THUNDERSTORMS FROM OSCODA WESTWARD TO MANISTEE
ASSOCIATED WITH A COLD FRONT IS MOVING SOUTHEAST AT ABOUT 35 MPH.
THESE STORMS WILL BE MOVING THROUGH THE SAGINAW VALLEY AND THUMB
REGION BETWEEN 3 PM AND 5 PM...FROM THE INTERSTATE 69 TO INTERSTATE
96 CORRIDOR BETWEEN 5 PM AND 7 PM...AND DETROIT ON SOUTH BETWEEN 7
PM AND 9 PM.

SOME STORMS WILL LIKELY BE STRONG WITH WIND GUSTS TO 45 MPH AND
SMALL HAIL.  ISOLATED SEVERE STORMS ARE POSSIBLE WITH WIND GUSTS TO
70 MPH AND ONE INCH DIAMETER HAIL.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

THERE IS A CHANCE OF THUNDERSTORMS ON MONDAY AS ANOTHER COLD FRONT
MOVES THROUGH THE REGION.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED.

&&

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)

DRC