Severe Thunderstorm Warning 33, NWS Detroit, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
340 AM EDT THU MAY 18 2000

MAIN CHALLENGE THIS FORECAST PERIOD FOCUSES ON CONVECTIVE POTENTIAL
TODAY...AND POTENTIAL FOR HEAVY RAINFALL THIS AFTERNOON AND TONIGHT
ACROSS SOUTHERN COUNTIES.

SOUTHWEST TO NORTHEAST ORIENTED BOUNDARY WILL DROP SOUTH TODAY AS
HIGH PRESSURE BUILDS SOUTH TO LAKE SUPERIOR. THE POSITION AND TIMING
OF THIS FRONT IS CRUCIAL FOR TODAY AND TONIGHT. WITH THE BOUNDARY
STILL ACROSS CENTRAL COUNTIES THIS MORNING AS WAVE RIDES ALONG
IT...POTENTIAL FOR SURFACE BASED INSTABILITY OVER SOUTHERN
COUNTIES...WITH CAPES AROUND 1000 J/KG OVER SOUTHERN TIER BY 18Z.
FORECAST SOUNDINGS INDICATING ELEVATED CONVECTION STILL A
POSSIBILITY OVER NORTHERN COUNTIES TODAY AS WELL. DYNAMICS COME
TOGETHER FOR POSSIBLE HEAVY RAINFALL ALONG AND NORTH OF THIS BOUNDARY
LATER THIS AFTERNOON INTO TONIGHT. BOUNDARY PROGGED IN NORTH CENTRAL
INDIANA AND OHIO THIS EVENING. UPPER JET STRUCTURE INDUCES
SIGNIFICANT DIVERGENCE...IN AREA ALONG THE SURFACE BOUNDARY. A
SOUTHWESTERLY TO WESTERLY ORIENTED 850 JET WILL FURTHER ACT TO
INDUCE LIFT ALONG THE SURFACE BOUNDARY. THE COMBINATION OF THE
BOUNDARY INDUCED SURFACE CONVERGENCE...THE JET INDUCED UPPER
DIVERGENCE AND THE LOWER LEVEL JET...WITH MOIST 850 THETA E
ADVECTION WILL LEAD TO HEAVY RAINFALL POTENTIAL ALONG AND NORTH OF
THIS BOUNDARY. WITH THE BOUNDARY NOT MOVING MUCH FURTHER TO THE
SOUTH INTO OVERNIGHT AND THE MAIN SURFACE WAVE RIDING EAST ALONG THE
BOUNDARY... LEADING TO TRAINING POTENTIAL. LOCATION FOR HEAVIEST
RAINFALL LATER TODAY AND TONIGHT IN CORRIDOR ALONG AND SOUTH OF
INTERSTATE 94. WITH THIS REGION NOT THAT WET FROM RECENT
RAINS...AREA COULD LIKELY HANDLE THE THREE QUARTERS TO AN INCH OF
QPF EXPECTED WITHOUT ANY SIGNIFICANT FLOODING PROBLEMS.

GIVEN UNCERTAINTY IN THE EXACT ORIENTATION OF THE BOUNDARY TONIGHT
AND THE MODEL TO MODEL DIFFERENCES IN QPF WILL HOLD OFF ON ANY FLOOD
WATCHES AT THIS TIME. RIGHT NOW AREAS TO RECEIVE HEAVIER RAINFALL
LATER TODAY AND TONIGHT ARE DRY...AND THE AREAS RECEIVING THE
HEAVIER RAINFALL NOW WILL BE DRYING. WILL WATCH MORNING RADAR TRENDS
TO DETERMINE IF ANOTHER ESF IS IN ORDER FOR SOUTHERN COUNTIES.

WILL KEEP RAIN CHANCE IN NORTHERN COUNTIES INTO TONIGHT AS WELL...AS
STRONG 850-700 FRONTOGENETIC FORCING CONTINUES. DRYING INDICATED
THROUGH LAYER FROM NORTH TO SOUTH OVERNIGHT...SO WILL TRAIL OFF
PRECIP CHANCES FROM NORTH TO SOUTH DURING THE OVERNIGHT. WITH HIGH
CONTINUING TO PUSH DRIER AIR FURTHER SOUTH INTO FORECAST AREA DURING
THE DAY FRIDAY...AND BEST DYNAMICS TO THE SOUTHEAST OF REGION...WILL
LIMIT PRECIPITATION POTENTIAL FOR SOUTHERN COUNTIES TO THE
MORNING.

FAN/FWC TEMPERATURES CLOSE...AND DO NOT PLAN TO STRAY FAR FROM THIS.

.DTX...NONE.

STRUBLE

MIZ047>049-053>055-060>063-068>070-075-076-082-083-191200-

SEVERE WEATHER OUTLOOK FOR SOUTHEAST LOWER MICHIGAN
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
910 AM EDT THU MAY 18 2000

...SEVERE WEATHER POTENTIAL STATEMENT FOR SOUTHEAST MICHIGAN...

DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY.

THUNDERSTORMS WILL BE WIDESPREAD ACROSS SOUTHEAST MICHIGAN TODAY...
ESPECIALLY NEAR AND SOUTH OF INTERSTATE 69. A FEW OF THESE STORMS
COULD BECOME SEVERE...AND SPOTTER ACTIVATION MAY BE NEEDED TODAY.

A COLD FRONT WILL SLOWLY MOVE SOUTH ACROSS SOUTHEAST MICHIGAN
TODAY...AND WILL EXIT THE STATE BY LATE AFTERNOON. THE FRONT WILL
IGNITE SHOWERS AND THUNDERSTORMS AS IT MOVES INTO A WARM AND HUMID
AIR MASS. THESE THUNDERSTORMS WILL THEN MOVE EAST AT 40 MPH.

THE STRONGEST STORMS...MAINLY NEAR AND SOUTH OF INTERSTATE 69...
COULD PRODUCE HAIL UP TO ONE INCH IN DIAMETER. WIND GUSTS TO 60 MPH
ARE POSSIBLE NEAR AND SOUTH OF ANN ARBOR AND DETROIT. IN
ADDITION...TORRENTIAL RAIN AND DANGEROUS LIGHTNING CAN BE EXPECTED
WITH ALL THUNDERSTORMS TODAY.

TONIGHT...WIDESPREAD THUNDERSTORMS ARE AGAIN EXPECTED NEAR AND SOUTH
OF INTERSTATE 69. THESE SHOULD NOT BE SEVERE...BUT WILL AGAIN POSE A
HEAVY RAIN THREAT. STORMS TONIGHT WILL MOVE EAST AT 20 MPH.

STAY TUNED TO NOAA WEATHER RADIO...OR YOUR FAVORITE MEDIA
OUTLET...FOR THE LATEST WEATHER INFORMATION.

ZOLTOWSKI