MESOSCALE PRECIPITATION DISCUSSION 0333
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1253 PM EDT SAT JUN 17 2017

AREAS AFFECTED...CENTRAL LOWER MI

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 171653Z - 172253Z

SUMMARY...THUNDERSTORMS ARE EXPECTED TO INCREASE IN COVERAGE AND
INTENSITY AS THEY TRACK ACROSS THE REGION.  HOURLY RAIN RATES TO
1.75", WITH LOCAL AMOUNTS UP TO 3", ARE EXPECTED.

DISCUSSION...SHOWERS AND THUNDERSTORMS ARE DEVELOPING NEAR A
MESOSCALE WARM FRONT WEST OF GRAND RAPIDS.  ALOFT, A LOW-LEVEL
VORTICITY MAXIMUM IS MOVING IN FROM NORTHEAST IL (VIA VISIBLE
IMAGERY) WHILE A MID-LEVEL SHORTWAVE IS GLIDING INTO THE NORTHWEST
LOWER PENINSULA (PER WATER VAPOR IMAGERY) AND AN MCV MOVES NEAR
THE CENTRAL IL/IN BORDER (WHICH COULD BE ENHANCING THE WINDS
ALOFT).  INFLOW AT 850 HPA IS CONVERGENT AT 20-40 KTS WHICH IS
TAPPING MLCAPE VALUES OF 500-1000 J/KG.  PRECIPITABLE WATER VALUES
ARE ~1.75".  EFFECTIVE BULK SHEAR IS ~35 KTS.  THE DETROIT MI
SOUNDING SHOWS NEARLY UNIDIRECTIONAL FLOW WITH HEIGHT UP TO THE
350 HPA PRESSURE LEVEL.

SHOWERS AND THUNDERSTORMS SHOULD CONTINUE TO EXPAND IN COVERAGE
NEAR THE WARM FRONT TODAY, WITH A CORRESPONDING INCREASE IN
RAINFALL RATES AND AMOUNTS AS MLCAPE VALUES INCREASE ANOTHER
500-1000 J/KG IN AN AREA WITH PARTLY SUNNY SKIES.  THE MESOSCALE
GUIDANCE LOOKS WELL PLACED, AND AGREES ON THE IDEA OF LOCAL
AMOUNTS OF 3", WHICH APPEAR MORE LIKELY ON THE EASTERN SIDE OF THE
DISCUSSION AREA DUE TO STRONGER INFLOW AND GREATER TIME FOR
THUNDERSTORM DEVELOPMENT. CONSIDERING RAINS FROM LAST NIGHT, SOILS
ARE PARTIALLY SATURATED.  FLASH FLOODING IS A CONCERN,
PARTICULARLY WITHIN URBAN ENVIRONMENTS.

ROTH

ATTN...WFO...APX...DTX...GRR...

ATTN...RFC...NCRFC...

LAT...LON   44218424 43878248 42588250 42708441 42788628
            43368654 43858630