Flash Flooding in Michigan, May 19 to 20, 2001

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
337 PM EDT SAT MAY 19 2001

SFC HIGH PRES IS CENTERED OVER WI AND MI LATE THIS AFTERNOON.
DIURNALLY ENHANCED SCT CU AND SOME MID/HIGH CLOUDS HAVE DEVELOPED
OVER NRN SECTIONS OF THESE STATE IN RESPONSE TO A WEAK AREA OF DPVA
PUSHING INTO THIS REGION. MAIN FORECAST CONCERN THRU SUNDAY IS
AMOUNT OF CLOUD COVER. FOCUS THEN TURNS TO OUR NEXT CHANCES OF
PRECIP ON MONDAY AND MONDAY NIGHT.

MORE AMPLIFIED AVN SOLUTION IS STRONGER IN ITS EVOLUTION OF THE NEXT
APPROACHING SYSTEM DEVELOPING IN THE PLAINS. NO SURPRISE THEN THAT
IT IS ALSO COOLER IN THE LOW LEVEL TEMP PROFILE AND SLIGHTLY MORE
MOIST AT MID LEVELS. TEND TO THINK THIS SOLUTION IS OVERAMPLIFIED
AND SLIGHTLY TOO COOL...WILL SIDE CLOSER WITH THE ETA.

TONIGHT...WEAK AREA OF VORTICITY WITH LIMITED MID/HIGH LEVEL MOISTURE
(700-500 LAYER MEAN RH OF AROUND 50 PCT) DRIFTS OVER THE CWA THIS
EVENING...AND THEN FURTHER WEAKENS AND DRIES OVERNIGHT AS IT RUNS
INTO SFC AND UPPER RIDGING. WILL LIKELY HAVE AREAS OF SCT-BKN
MID/HIGH CLOUDS MOVING OVER THE REGION THROUGHOUT MUCH OF THE
NIGHT...AS WELL AS SCT DIURNAL CU HOLDING ON ACROSS THE SE PORTIONS
OF THE CWA THRU SUNSET. WILL GO WITH PARTLY CLOUDY ALL ZONES.

SUNDAY...SFC HIGH SHIFTS E OF MI...WITH SOUTHERLY FLOW ACROSS THE
STATE GRADUALLY STRENGTHENING ON THE BACKSIDE OF THE HIGH. LOW LEVEL
MOISTURE WILL BEGIN TO INCREASE FROM S TO N AS WAA GRADUALLY
STRENGTHENS THROUGHOUT THE DAY. DO EXPECT SCT-BKN DIURNAL CU
DEVELOPMENT (SLIGHTLY GREATER THAN THIS AFTERNOON) FOR SUNDAY
AFTERNOON WITH INCREASING LOW LEVEL MOISTURE. CU SCHEME SUPPORTS A
PARTLY SUNNY FORECAST FOR NRN LOWER MI. LOW LEVELS REMAIN SLIGHTLY
DRIER ACROSS ERN UPR MI...BUT WILL STILL GO WITH PARTLY SUNNY WITH
THE ANTICIPATION OF ENHANCED LOW LEVEL CONVERGENCE AS LAKE BREEZES
DEVELOP IN THE AFTERNOON. TEMPS WILL ONLY BE A COUPLE OF DEGREES
WARMER THAN TODAY AS WAA WILL BE INITIALLY WEAK UNTIL THE APROACH OF
THE FRONT LATE SUNDAY NIGHT AND MONDAY.

SUNDAY NIGHT...AS MENTIONED ABOVE...WAA AND LOW LEVEL MOISTURE
FURTHER INCREASE WITH THE APPROACH OF A WARM FRONT ASSOCIATED WITH
THE DEVELOPING PLAINS SYSTEM. MID LEVEL DRY AIR WILL INITIALLY BE
DIFFICULT TO OVERCOME...BUT EXPECT DEEP MOISTURE WILL ARRIVE IN SW
PORTIONS OF THE CWA LATE...AS WILL MOIST ISENTROPIC ASCENT
(I305)...850-700 MB Q-VECTOR CONVERGENCE AND 850 MB FRONTOGENETIC
FORCING. THUS...WILL ADD MINIMAL CHANCE POPS TO THIS REGION LATE...
WITH INCREASING CLOUDS FROM SW TO NE ACROSS THE REST OF THE CWA.

MONDAY AND MONDAY NIGHT...SCT SHRA/TSRA WILL CONTINUE TO DEVELOP
ALONG AND N OF THE WARM FRONT MONDAY AS IT PUSHES NE THRU NRN LOWER
MI...WITH THE COLD FRONT FAST ON ITS HEALS...ARRIVING IN WRN
SECTIONS OF THE CWA BY MONDAY EVENING. MOIST ISENTROPIC ASCENT AND
MID LEVEL Q-VECTOR CONVERGENCE WILL CONTINUE THRU MONDAY AS AN
ELONGED VORT MAX ASSOCIATED WITH THE FRONT PROVIDES UPPER SUPPORT.
ENHANCED LOW LEVEL CONVERGENCE WITH THE ARRIVAL OF THE COLD FRONT
WILL LEND ADDITIONAL FOCUS FOR SHRA/TSRA DEVELOPMENT MONDAY NIGHT.
WILL INTRODUCE LIKELY POPS FOR BOTH MONDAY AND MONDAY NIGHT ACROSS
ALL ZONES.

EXTENDED FORECAST...LONG RANGE MODELS CONTINUE TO POINT TOWARD A
COOLER AND WETTER THAN NORMAL PATTERN SETTING UP FOR NEXT WEEK. MAIN
DIFFERENCE AMOUNG THE MODELS IS THE AMPLIFICATION OF THE LONG WAVE
PATTERN AS THE TRANSITION TO RIDGE WEST/TROUGH EAST TAKES PLACE. MRF
CONTINUES TO SUGGEST THE GREATEST AMPLIFICATION...DRIVING A VERY
DEEP CLOSED 500 MB LOW INTO THE WRN GREAT LAKES BY 12Z WED. ECMWF IS
THE LEAST AMPLIFIED...BRIEFLY CLOSING OFF A WEAKER 500 MB LOW OVER
THE SRN PLAINS THEN TRANSITIONING TO A MORE OPEN WAVE UPPER TROUGH
ACROSS THE ERN HALF OF THE US FOR THE LAST HALF OF NEXT WEEK.
CANADIAN SOLUTION FALLS IN BETWEEN...GRADUALLY BUILDING THE UPPER
TROUGH INTO THE GREAT LAKES...THEN CLOSING OFF THE 500 MB LOW BY 12Z
THU. MRF IS LIKELY TOO AMPLIFIED...AND SPLIT FLOW/STRONGER SRN
STREAM SOLUTION DEPICTED BY THE ECMWF IS LIKELY TOO WEAK WITH THE
NRN STREAM UPPER SYSTEM. THUS...WILL SIDE WITH THE MIDDLE-OF-THE-
ROAD CANADIAN WHICH PROVIDES A MORE GRADUAL UPPER WAVE TRANSITION.
DEEP CYCLONIC FLOW AND 1000-500 MB RH OF AOA 60 PCT REMAINS IN PLACE
ACROSS MI TUE THRU SAT...AS A SERIES OF SHORT WAVES RIDE THRU THE
THE UPPER TROUGH INTO THE STATE. WILL MAINTAIN A CHANCE OF SHOWERS
FOR EACH DAY OF THE EXTENDED FORECAST...WITH TEMPS ABOUT 5 TO 10
DEGREES BELOW NORMAL THRU THE PERIOD.

.APX...NONE.

EME