Severe Thunderstorm Warning 68, NWS Detroit, MI

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
337 PM SUN AUG 4 2002

MAIN CONCERN FOR THE CURRENT PACKAGE WILL BE HERE IN THE FIRST 12 TO
18 HOURS OR SO. STILL CONTINUE TO MONITOR SEVERE CHANCES ACROSS
SOUTHERN HALF OF THE CWA. AS HAS BEEN PREVIOUSLY DISCUSSED...
CURRENT SEVERE CHANCES HINGE ON ABILITY OF ATMOSPHERE TO BREAK THE
CAP CURRENTLY IN PLACE. CONVECTION THAT HAS INITIATED OVER SW LOWER
HAS CONSISTENTLY FELL APART AS IT APPROACHED THE CWA THIS AFTERNOON.
STILL BELIEVE THAT CAP WILL ERODE THIS EVENING AS WEAK SHORT WAVE
TROUGH LOWERS HEIGHTS AND BRINGS SLIGHTLY COOLER TEMPERATURES TO THE
MID LEVELS SUFFICIENT. VISIBLE SATELLITE LOOP SHOWING PLENTY OF
SUNSHINE ACROSS THE CWA AND THIS HAS BOOSTED TEMPERATURES TO NEAR 90
SOUTHERN CWA WITH DEW POINTS IN THE LOW TO MID 70S YIELDING CAPES
APPROACHING 4 KJ/KG. DIFFICULT TO DISCERN OUTFLOW BOUNDARIES IN THE
DATA ALTHOUGH IT DOES APPEAR AT LEAST ONE OUTFLOW HAS SLID INTO
NORTHERN OHIO. OTHER BOUNDARIES LIKELY ACROSS THE NORTHERN CWA WHERE
DIFFERENTIAL HEATING FROM MORNING RAIN/CLOUDS INTERACTING WITH
AFTERNOON SUNSHINE. FOR THIS EVENING...WILL CARRY SCATTERED SHOWERS
AND THUNDERSTORMS CWA-WIDE.

AVN AND ETA ARE IN AGREEMENT THAT FRONT HANGS UP NEAR THE OH/MI
BORDER OVERNIGHT AND MCS DEVELOPING OVER IL TRACKS ALONG THE
FRONT AND ACROSS SOUTHERN LOWER DURING THE PRE-DAWN TO POST-DAWN
HOURS MONDAY. THE SYSTEM WILL TRACK IN A POOL OF RICH MOISTURE AS
PWS WILL EXCEED 2 INCHES ACROSS SOUTHERN CWA DURING THE EARLY
MORNING HOURS...WITH K-INDICES NEAR 40. LOW LEVEL JET DYNAMICS ARE
NOT IMPRESSIVE WITH FLOW TO OUR WEST NEVER REALLY GETTING STRONGER
THAN 20 KNOTS...AND THEN BECOMING PARALLEL TO THE FRONT RATHER THAN
PERPENDICULAR. UPPER LEVEL JET DYNAMICS ARE LACKING AS WELL. STILL
GIVEN JUICY AIR...A PERIOD OF HEAVY RAIN IS POSSIBLE AND WILL ADD
MENTION OF THIS TO THE ZONES. TIMING ON THIS PRECIPITATION WOULD BE
AFTER MIDNIGHT...MOST LIKELY TOWARD SUNRISE.

BY TOMORROW AFTERNOON...STRONG CANADIAN HIGH TO DOMINATE THE WEATHER
THROUGH THE REMAINDER OF THE WEEK. HIGH WILL BUILD IN SHUNTING FRONT
TO THE SOUTH AND BRING A PROLONGED PERIOD OF DRY COOL WEATHER.
ONLY CONCERN WITH THIS SYSTEM WILL BE MONDAY NIGHT INTO TUESDAY
MORNING. 850MB TEMPERATURES ARE PROGGED TO DROP AS LOW AS 3C /PER
ETA/ ACROSS THE THUMB TUESDAY MORNING. WITH LAKE TEMPERATURES
RUNNING AROUND 23C...THE AIR/LAKE DELTA T WILL BE AROUND 20C.
INVERSION HEIGHTS WILL BE AROUND 5K FEET. AIR ABOVE THE INVERSION
WILL BE EXTREMELY DRY. FLOW AROUND THE HIGH WILL BE ANTICYCLONIC.
MESOETA OVERSPREADS NEARLY THE ENTIRE CWA MONDAY NIGHT INTO TUESDAY
MORNING WITH LAKE INDUCED CLOUD COVER. AIR/LAKE DELTA T/S CERTAINLY
SUPPORT SOME CLOUD DEVELOPMENT...BUT WITH EXTREME DRY AIR ABOVE THE
INVERSION AND ANTICYCLONIC LOW LEVEL FLOW WILL ONLY OPT FOR PARTLY
CLOUDY SKIES OVERNIGHT MONDAY INTO TUESDAY MORNING.

EXTENDED...
HIGH PRESSURE AT THE SURFACE AND ALOFT WILL DOMINATE THE EXTENDED
PERIOD INTO NEXT WEEKEND. DESPITE HEIGHTS BUILDING IN EXCESS OF 588DM
THROUGH THE PERIOD...STRONG CANADIAN HIGH PRESSURE WILL MAINTAIN
NEAR SEASONABLE THICKNESS LEVELS INTO THE WEEKEND. MRF AND CANADIAN
DEVELOP A SHARP UPPER NORTH-SOUTH SHORTWAVE ACROSS THE CENTRAL U.S.
THAT EVENTUALLY EXTENDS ACROSS THE WIDTH OF THE NATION BY MONDAY
MORNING. ENSEMBLE MEMBERS OF BOTH CANADIAN AND MRF SUGGEST THAT THE
OPERATIONAL SOLUTIONS ARE OVERPLAYING THIS FEATURE. THIS SOLUTION WOULD
TEND TO ENHANCE RIDGING ACROSS THE LAKES AND SLOW DOWN ANY FRONTS
APPROACHING. DESPITE THE OUTLIER NATURE OF THE TROUGH
SOLUTION...ENSEMBLE MEMBERS DO HOLD ONTO THE RIDGE REMAINING IN
PLACE ACROSS THE LAKES AND POINTS EAST. SO...A CONTINUED DRY
FORECAST INTO THE WEEKEND SEEMS PLAUSIBLE. WITH FLOW TURNING
SOUTHWEST DEW POINTS WILL BE ON THE INCREASE FOR THE WEEKEND AND A
WARMING TREND UNDERWAY.

.DTX...NONE.

OKEEFE

MIZ047>049-053>055-060>063-068>070-075-076-082-083-050000-

HAZARDOUS WEATHER OUTLOOK FOR SOUTHEAST MICHIGAN
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
416 PM EDT SUN AUG 4 2002

...SEVERE THUNDERSTORM WATCH 574 IN EFFECT FOR PART OF SOUTHEAST
LOWER MICHIGAN UNTIL 8 PM SUNDAY NIGHT...

DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY.

HAZARDS...
A SEVERE THUNDERSTORM WATCH HAS BEEN ISSUED FOR PART OF SOUTHEAST
MICHIGAN. COUNTIES IN THE WATCH INCLUDE SHIAWASSEE...GENESEE...
LAPEER...ST CLAIR...LIVINGSTON...OAKLAND...MACOMB...WASHTENAW...
WAYNE...LENAWEE AND MONROE. SOME COMMUNITIES IN THE WATCH ARE
OWOSSO...FLINT...LAPEER...PORT HURON...HOWELL...PONTIAC...MOUNT
CLEMENS...ANN ARBOR...DETROIT...ADRIAN...AND MONROE. SCATTERED
THUNDERSTORMS WILL OCCUR IN THE WATCH AREA THIS EVENING AND SOME OF
THESE STORMS MAY BE SEVERE. WINDS IN EXCESS OF 70 MPH ARE POSSIBLE
WITH THESE STORMS.

DISCUSSION...
A COLD FRONT WILL SLOWLY ADVANCE ACROSS SOUTHEAST MICHIGAN THIS
EVENING. THIS FRONT WILL TAP THE WARM HUMID AIR IN PLACE ACROSS THE
REGION...PRODUCING SCATTERED THUNDERSTORMS. SOME OF THESE STORMS
MAY BE SEVERE THIS EVENING PRODUCING WIND GUSTS TO 70 MPH. THE
THREAT OF SEVERE WEATHER WILL BE FOCUSED ALONG AND SOUTH OF I
69 THROUGH 8 PM THESE EVENING.

SPOTTER ACTIVATION...
SPOTTER ACTIVATION HAS OCCURRED.

OUTLOOK FOR MONDAY AND TUESDAY.
NO HAZARDS ARE EXPECTED.

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)

OKEEFE