Severe Thunderstorm Warning 9, NWS Detroit, MI

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
945 PM EDT MON APR 9 2001

BIG CELLS WENT UP LATE THIS AFTERNOON AND EVENING SOUTH OF SURFACE
BOUNDARY OVER NORTHERN INDIANA/OHIO. TEMPS S OF BOUNDARY REACHED
WELL INTO THE 80S TODAY RESULTING IN A VERY SHARP BAROCLINIC ZONE
FROM THERE NORTH INTO LOWER MICHIGAN WHERE LOW CLOUDS AND PRECIP
HELD TEMPS IN THE 40S AND 50S. THE STORMS CURRENTLY TO THE SOUTH
WILL REMAIN TO THE SOUTH, BUT REGIONAL RADARS SHOWING ADDITIONAL
SCATTERED DEVELOPMENT, ALTHOUGH MUCH LESS INTENSE, AROUND SOUTHERN
LAKE MICHIGAN ATTM. THIS WILL BE THE AREA TO WATCH FOR SE LOWER
OVERNIGHT.

RUC40 SUGGESTS THAT THESE STORMS ARE FORMING IN ASSOCIATION WITH A
BAND OF 850 MB THETAE ADVECTION. THE RUC ADVECTS THIS AREA EAST
ACROSS LOWER BETWEEN 03Z AND 09Z. KDTX 00Z SOUNDING NOT UNSTABLE
UNTIL AROUND 800MB, BUT LAPSE RATES ARE NEARLY DRY ADIABATIC FROM
725MB TO 550MB. 800MB LIS FROM 18Z ETA MARCH SUB-ZERO VALUES ACROSS
LOWER IN ASSOCIATION WITH THE THETAE ADVECTION. THIS ARGUES FOR
INTRODUCING THUNDER INTO THE FORECAST ACROSS NORTHERN SECTIONS FOR
THE OVERNIGHT HOURS. AMOUNT OF FORCING APPEARS TO BE LESS THAN LAST
NIGHT AND RADARS HAVE BEARED THIS OUT SO FAR. SCATTERED POPS SHOULD
BE A GOOD START. 800MB LIS GO POSITIVE AND LOW LEVEL THETAE
ADVECTION DECREASES MARKEDLY AROUND 09Z SO THINK MAJORITY OF
ACTIVITY SHOULD BE DONE WITH BY SUNRISE.

GIVEN NEARLY DRY ADIABATIC LAPSE RATES IN THE MID LEVELS ON LATEST
SOUNDING ALONG WITH RECENT TRACK RECORD, HAVE TO THINK THAT
POTENTIAL FOR MARGINAL SEVERE HAIL WILL EXIST WITH THESE STORMS AS
THEY MOVE THROUGH THE REGION OVERNIGHT, ESPECIALLY OVER SOUTHERN
SECTIONS. LATE EVENING UPDATE WILL BE ISSUED ASAP TO ADDRESS
OVERNIGHT TRENDS.

.DTX...NONE.

JW

MIZ047>049-053>055-060>063-068>070-075-076-082-083-101000-

SEVERE WEATHER OUTLOOK FOR SOUTHEAST LOWER MICHIGAN
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1014 PM EDT MON APR 9 2001

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

DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY.

SCATTERED THUNDERSTORMS WILL OCCUR ACROSS SOUTHEAST MICHIGAN UNTIL
AROUND 6 AM TUESDAY MORNING. THERE IS A SLIGHT CHANCE THAT A FEW OF
THESE STORMS COULD BECOME SEVERE. DUE TO THE EXPECTED ISOLATED
NATURE OF THIS EVENT...SPOTTER ACTIVATION IS NOT ANTICIPATED.

THE MAIN THREAT FOR ANY SEVERE STORMS WILL BE ALONG AND SOUTH OF AN
OWOSSO...FLINT...LAPEER...PORT HURON LINE. THIS AREA INCLUDES METRO
FLINT...METRO DETROIT AND POINTS ALONG THE OHIO BORDER. AN UPPER
LEVEL SYSTEM WILL CROSS SOUTHEAST MICHIGAN OVERNIGHT. SCATTERED
THUNDERSTORMS WILL ACCOMPANY THIS SYSTEM...WITH A FEW ISOLATED SEVERE
STORMS POSSIBLE. THE MOST LIKELY THREAT WITH THIS ACTIVITY WILL BE
HAIL TO ONE INCH IN DIAMETER. THESE STORMS WILL MOVE EAST AT 35 MPH.

STAY TUNED TO YOUR FAVORITE MEDIA OUTLET FOR THE LATEST WEATHER
INFORMATION FROM THE NATIONAL WEATHER SERVICE.

JW