Severe Thunderstorm Warning 61, NWS Detroit, MI

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
330 PM EDT WED AUG 8 2001

RECORDS HAVE FALLEN AT DTW AND FNT WITH 3PM READINGS OF 98 AND 97
RESPECTIVELY. WILL CONTINUE HEAT ADVISORY INTO THE EVENING HOURS AS
SOME LOCALES HAVE REACHED ADVISORY CRITERIA...WHILE OTHERS ARE
APPROACHING CRITERIA.../AND 100 DEGREE READINGS/.

TSRA ACTIVITY HAS BEEN MIGRATING SOUTH FROM MCS TRACKING INTO
NORTHERN LAKE HURON AND SOME OF THIS MAY CLIP NORTHERN COUNTIES.
KAPX 88D ALSO SHOWING OUTFLOW BOUNDARIES MOVING SOUTH AS WELL. WILL
NEED TO ACCOUNT FOR SOME ISOLATED ACTIVITY ACROSS NORTHERN COUNTIES.
SO FAR...NO EVIDENCE OF LAKE BREEZE FRONT IN VIS CU FIELD. IF
NOTHING IS EVIDENT PRIOR TO FORECAST ISSUANCE TIME WILL NOT HAVE
LAKE BREEZE SHRA MENTIONED FOR EVENING.

VIS LOOP SHOWS CU FIELD ASSOCIATED WITH BARRY MOISTURE SLOWLY TAKING
A CIRCUITOUS ROUTE TOWARD CWA. MESOETA SHOWS NARROW RIBBON OF 850
MB THETA-E ADVECTION TONIGHT MAINLY CENTERED TOWARD FNT. AVN ALSO
TARGETS A BROADER SWATH OF THETA-E ADVECTION TOWARD CWA OVERNIGHT
AND INTO TOMORROW. ETA REMAINS DRY...WHILE AVN PRODUCES MEASURABLE
PRECIPITATION ACROSS SOUTHERN HALF OF CWA INTO THE AFTERNOON. WITH
LITTLE IN THE WAY OF FOCUSING MECHANISM EVIDENT ON EITHER ETA OR
AVN...WILL CONTINUE WITH DRY FORECAST TONIGHT AND TOMORROW.
EXCEPTION WILL BE IN SAGINAW VALLEY WHERE WILL INSERT A LATE
AFTERNOON CHANCE FOR ACTIVITY APPROACHING WITH COLD FRONT. SLIGHTLY
COOLER 850MB ADVECTING IN FROM THE SOUTH WILL TEMPER HIGH
TEMPERATURES SLIGHTLY...BUT STILL PROVIDE FOR ANOTHER SWELTERING DAY
WITH TEMPERATURES INTO THE LOW TO MID 90S AND HEAT INDICES IN THE
100 TO 105 RANGE...WILL HIGHLIGHT THESE IN ZONES. GIVEN SUFFICIENT
SUNSHINE TOMORROW...MORE RECORDS COULD FALL. RECORDS AT MBS/FNT/DTW
ARE 95/94/96 RESPECTIVELY.

HEAT WAVE ENDS TOMORROW NIGHT AS COLD FRONT SWEEPS ACROSS CWA. BEST
DYNAMICS ASSOCIATED WITH THE FRONT ARE SURFACE CONVERGENCE AND UPPER
LEVEL DIVERGENCE. DPVA IS QUITE WEAK. DYNAMICS ARE MAXIMIZED ACROSS
NORTHERN HALF OF THE CWA AND WEAKEN IN THE SOUTH. CAPES ACROSS
NORTHERN HALF OF CWA AROUND 2000 J/KG COINCIDENT WITH THE
FRONT...DECREASE AS FRONT DROPS TO THE SOUTH. MID LEVEL WINDS AROUND
25 TO 30 KNOTS...COMBINED WITH CAPES AROUND 2000 J/KG WOULD SUPPORT
A WIND THREAT. TEMPERATURES WILL COOL OFF ACROSS NORTHERN THIRD OF
CWA OVERNIGHT...WHILE STICKY CONDITIONS WILL LINGER IN THE SOUTH.

DRIER AIR WILL FILTER IN FRIDAY...BRINGING CONSIDERABLY LOWER
TEMPERATURES AND DEW POINTS...WITH THE TREND CONTINUING INTO THE
WEEKEND.

EXTENDED...
WESTERN RIDGE-EASTERN TROUGH PATTERN CONTINUES THROUGH THE EXTENDED
WITH THE MRF REMAINING THE MOST AGGRESSIVE IN ITS DEVELOPMENT OF
UPPER LEVEL CUTOFF LOWS OVER CANADA. UPPER LEVEL LOWS ARE DEEPER ON
THE CURRENT MRF VS PREVIOUS...BUT DISPLACED NORTH...PRODUCING HIGHER
HEIGHTS ACROSS THE GREAT LAKES THAN PREVIOUS RUNS. STILL...EXTENDED
PERIOD WILL BE MARKED BY TEMPERATURES AT OR SLIGHTLY BELOW NORMAL.
RAINFALL CHANCES LOOK TO BE CONFINED TO LATE SUNDAY...MONDAY PERIOD
AS COLD FRONT TRIES TO WORK ACROSS CWA. CURRENT RUN OF MRF IS
SOMEWHAT FASTER THAN PREVIOUS RUNS IN PUSHING THE COLD FRONT ACROSS
REGION...SUGGESTING THE ADDITION OF SHOWERS TO SUNDAY PERIOD. WILL
HOLD OFF ON THAT MOVE FOR NOW. BETTER DYNAMICS WITH FRONT WILL SLIDE
NORTH AND EAST OF CWA...SO DO NOT EXPECT SIGNIFICANT RAIN PRODUCER
FROM THIS. OUTLIER IN THIS SCENARIO IS THE ETA-XX WHICH BUCKLES
SOUTHERN STREAM FLOW INDUCING WAVE DEVELOPMENT OVER THE SOUTHERN
PLAINS...AND TRACKING THE SYSTEM CLOSE ENOUGH TO SOUTHEAST LOWER ON
MONDAY TO PRODUCE RESPECTABLE QPF ACROSS SOUTHERN COUNTIES...WITH
DRY CONDITIONS PREVAILING IN THE NORTH. GIVEN MRF PERFORMANCE THIS
SEASON...WILL GIVE THE NOD TO THE MRF AND CONTINUE MONDAY POP
CHANCES BASED ON FROPA.

.DTX...HEAT ADVISORY EARLY THIS EVENING ALL OF SOUTHEAST MICHIGAN.

OKEEFE