Flood in Michigan, May 13 to 14, 2002

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
312 PM EDT SUN MAY 12 2002

THE LATEST SFC PRESSURE ANALYSIS HAS LOW PRESSURE CENTERED OVER
SOUTHWEST LOWER MICHIGAN WITH A WARM FRONT EXTENDING JUST NORTH OF
THE I-94 CORRIDOR INTO SE MICHIGAN. AREA RADARS SHOWING ANOTHER
AREA OF RAINFALL ALONG AND SOUTH OF THE CENTER OF LOW PRESSURE. THE
MODELS ARE HAVING DIFFICULTY TRACKING THE MOVEMENT OF THIS SURFACE
LOW AND CURRENT AREA OF RAINFALL ALONG THE MI/IN STATE LINE. THE
LATEST RUC SEEMS TO HAVE THE BEST HANDLE ON THE LOW...BRINGING IT TO
THE MI/OH STATE LINE BY 00Z. THUS...I WILL CARRY A MENTION OF
SCATTERED SHOWERS INTO THE EARLY EVENING ALONG AND SOUTH OF I-69.
OVER THE PAST 24 HOURS...SPOTTER REPORTS AND AUTOMATED OBSERVATIONS
HAVE INDICATED 2.5 TO 3.5 INCHES OF RAINFALL ACROSS LENAWEE AND
MONROE COUNTIES...CURRENTLY UNDER A FLOOD WATCH. RADAR TRENDS
SUGGEST THE HEAVIEST PRECIP WILL PASS TO THE SOUTH. WITH SPOTTER AND
LAW ENFORCEMENT NOT REPORTING ANY SIGNIFICANT FLOODING...I WILL LET
THE FLOOD WATCH EXPIRE.

THE IR SATELLITE LOOP IS SHOWING MID LEVEL CLOUDS PULLING OUT OF THE
REST OF THE FORECAST AREA...ONLY LEAVING LOW LEVEL MOISTURE. SOME
SFC REPORTS OF DRIZZLE WERE NOTED UPSTREAM. MESO-ETA SOUNDINGS FOR
TONIGHT SHOW THE LAYER BELOW 750MB (WARMER THAN -10C) NEARLY
SATURATED. WITH AMPLE SHEAR ATOP THE MOIST LAYER...AREAS OF DRIZZLE
TONIGHT STILL LOOKS WARRANTED.

THE 12Z MODEL SUITE ARE IN GOOD AGREEMENT IN DEVELOPING A CUT-OFF
UPPER LOW OVER THE EASTERN GREAT LAKES BY 06Z TUESDAY...THEN
DEEPENING THIS LOW AND MOVING IT INTO NEW ENGLAND. A COUPLE OF SHORT
WAVES WILL TRAVERSE THE BASE OF THE DEEPENING TROUGH AXIS TONIGHT
AND MONDAY. ONE CURRENTLY OVER WRN LK SUPERIOR WILL PUSH ACROSS THE
NORTHERN LAKES TONIGHT WHILE THE DEEPER SHORT WAVE OVER SW MANITOBA
WILL DROP DOWN INTO SOUTHERN LOWER MI MONDAY AFTERNOON. BOTH THE ETA
AND AVN QVECTOR FIELDS SHOW LITTLE CONVERGENCE DURING THE
AFTERNOON...LIKELY DUE TO THE LOW LEVEL COLD AIR ADVECTION. I WILL
THUS MAINTAIN THE DRY FCST...KEEPING MO CLOUDY SKIES GIVEN THE BROAD
CYCLONIC FLOW AND AMPLE LOW LEVEL MOISTURE. 850 TO 500MB LAPSE RATES
ARE PROGGED TO INCREASE TO 7C/KM MONDAY EVENING AS 500MB TEMPS FALL
TO -28C. GIVEN THE INCREASING LAPSE RATES...I WILL KEEP A CHANCE OF
SHOWERS MONDAY NIGHT. I WILL LEAN MORE TOWARDS THE COOLER MAV TEMPS
FOR MONDAY. PLENTY OF LOW CLOUDS MONDAY NIGHT WILL PREVENT TEMPS
FROM FALLING TOO FAR BELOW 40 DEG.

ON TUESDAY...COLD AIR ALOFT WILL MAINTAIN STEEP LAPSE RATES THROUGH
THE DAY. ETA MODEL SOUNDINGS ARE NEARLY DRY ADIABATIC FROM THE SFC
TO 700MB...WITH CLOSE TO 1000 J/KG OF CAPE. I THEREFORE EXPECT THE
DEVELOPMENT OF DIURNAL SHOWERS GIVEN CONTINUED CYCLONIC FLOW AT THE
SURFACE. BASED ON MODEL SOUNDINGS...THUNDER DOES NOT APPEAR OUT OF
THE QUESTION. IN COMPARISON WITH THE AVN...THE ETA IS A COUPLE
DEGREES COLDER AT 500MB AND THUS SHOWS A LITTLE HIGHER MID LEVEL
LAPSE RATES. AT THIS POINT...I WILL LEAVE THUNDER OUT (THINKING IT
MAY END UP BEING MORE AN ISOLATED EVENT) AND MONITOR ADDITIONAL
MODEL RUNS BEFORE ADDING IT TO THE ZONES.

THE AVN/CANADIAN AND UKMET CONTINUE TO BRING RIDGING ALOFT AND
SURFACE HIGH PRESSURE INTO THE REGION TUESDAY NIGHT INTO WEDNESDAY.
THIS SHOULD SCOUR OUT ANY REMAINING CLOUD COVER. ENOUGH OF A
PRESSURE GRADIENT LOOKS IN PLACE TUESDAY NIGHT WITH THE CENTER OF
HIGH PRESSURE TRACKING SOUTH THAT I WILL NOT DROP MINS BELOW
GUIDANCE...WHICH WOULD WOULD MEAN SOME PATCHY FROST NOT OUT OF THE
QUESTION. RETURN FLOW AROUND HIGH ON WEDNESDAY SHOULD BRING TEMPS
CLOSER TO NORMAL.

EXTENDED DISCUSSION...OVERALL THE MEDIUM RANGE MODELS ARE IN GOOD
AGREEMENT IN SHOWING AN UPPER TROUGH PUSHING INTO THE CENTRAL US BY
THE END OF THE WEEK...WITH A SLOW MOVING FRONTAL BOUNDARY MOVING
INTO THE GREAT LAKES FROM THE NORTHWEST. MODEL SOLUTIONS BRING THE
FRONT INTO WESTERN LOWER MICHIGAN AROUND 00Z FRI. ALTHOUGH THERE IS
GOOD AGREEMENT IN TIMING OF THE FRONT AMONG THE MODELS...SOME OF THE
ENSEMBLE MEMBERS (ESPECIALLY THOSE OF THE AVN/MRF) ARE SLOWER IN
TIMING OF FRONT INTO THE AREA. GIVEN PRECIP IS ALREADY IN THE
ZONES...I WILL MAINTAIN THE CHANCE POPS FOR THURSDAY. MODEL
SOLUTIONS ALSO ARE IN GOOD AGREEMENT IN SHOWING A WAVE DEVELOPING
ALONG THE FRONT IN THE MISSISSIPPI VALLEY AND MOVING NE ACROSS THE
OHIO VALLEY ON FRIDAY. TREMENDOUS INFLUX OF GULF MOISTURE WILL SPELL
A GOOD HEAVY RAINFALL POTENTIAL ACROSS THE MIDWEST (AVN/MRF...ETAXX
AND ECMWF POINT TO SOME HEAVIER RAINFALL POTENTIAL ACROSS THE
SOUTHERN 1/3RD OF THE FORECAST AREA ON FRIDAY). WITH THE CANADIAN
AND UKMET SOLUTIONS MUCH FARTHER SE WITH THE LOW AND GIVEN THE WIDE
VARIATION OF LOW PLACEMENT AND STRENGTH IN MRF ENSEMBLE MEMBERS...I
WILL LEAVE MENTION OF JUST CHANCE OF RAIN ATTM. AVN/MRF AND ETAXX
STABILITY PARAMETERS DO NOT SHOW THAT MUCH INSTABILITY ACROSS SE
MICHIGAN ON FRIDAY. GIVEN THE STRENGTH OF THE INFLOW TO THIS
SYSTEM...I HAVE TO BELIEVE THAT THERE WILL BE ENOUGH ELEVATED
INSTABILITY TO MENTION THUNDER ON FRIDAY. AVN/MRF BRING HIGH
PRESSURE IN FOR NEXT WEEKEND...SO I WILL CARRY A DRY FCST...WITH
TEMPS STILL A LITTLE BELOW CLIMO.

.DTX...NONE.

CONSIDINE