MESOSCALE PRECIPITATION DISCUSSION 0158
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
903 AM EDT SAT APR 29 2017

AREAS AFFECTED...SRN IL...SRN IN...SRN OH...NRN KY

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 291259Z - 291700Z

SUMMARY...CONTINUED FLASH FLOODING RAINFALL IS EXPECTED FOR AT
LEAST THE NEXT 3 HOURS ALONG THE OHIO RIVER WITH POSSIBLE
WEAKENING IN INTENSITY ALONG SRN IN/IL BETWEEN 15-16Z. ADDITIONAL
RAINFALL TOTALS OF 2-4 INCHES ARE EXPECTED FROM SRN IN INTO SRN OH
AND FAR NRN KY.

DISCUSSION...OBSERVATIONS IN SATELLITE AND RADAR TRENDS OVER THE
PAST HOUR OR TWO HAVE SHOWN THE ORGANIZATION OF AN AXIS OF
TRAINING RAINFALL EXTENDING JUST NORTH OF THE OHIO RIVER FROM SERN
IL INTO SERN IN. AT THE LEADIONG EDGE OF THIS AXIS OF TRAINING WAS
A FORWARD PROPAGATING SEGMENT OF CONVECTION ENTERING SWRN OH/FAR
NRN KY AT 1230Z. THE AXIS OF RAINFALL WAS OCCURRING ALONG OR JUST
NORTH OF A CONVECTIVELY REINFORCED STATIONARY BOUNDARY/OUTFLOW
BOUNDARY ALONG THE OHIO RIVER. A SHARP CUTOFF IN INSTABILITY WAS
NOTED AT 12Z WITH THE KILN SOUNDING SHOWING 62 J/KG WITH A MOST
UNSTABLE PARCEL LIFTED FROM NEAR 850 MB...LOWER THAN RAP/HRRR
ANALYSES. UNIDIRECTIONAL SWLY FLOW PARALLEL TO OR JUST ACROSS THE
STATIONARY FRONT FROM SOUTH TO NORTH IS HELPING TO SUPPORT THE
AXIS OF TRAINING CONVECTION WHILE CONTINUING TO TRANSPORT AMPLE
MOISTURE AND INSTABILITY INTO THE ONGOING CONVECTIVE AXIS.

DESPITE THE WEAKER INSTABILITY TO THE NORTH...S-CNTRL
IL/IN/OH...SOME INCREASE IN INSTABILITY IS EXPECTED OVER THE NEXT
FEW HOURS. VAD WIND PLOT OBSERVED 40-50 KT 850-700 MEAN FLOW IS
EXPECTED TO CONTINUE OVER THE NEXT FEW HOURS WITH MINOR
ADJUSTMENTS AND GRADUAL 700-500 MB HEIGHT RISES INTO THE LATE
MORNING. THIS AMY CAUSE ADDED MOISTURE TO BE ADVECTED NWD INTO THE
850-700 MB LAYER HELPING TO INCREASE INSTABILITY WHILE UPPER LEVEL
FLOW REMAINS RATHER DIVERGENT/DIFFLUENT. AN ADDITIONAL 2-4 INCHES
IS EXPECTED THROUGH 18Z WITH RAINFALL RATES OF 1-2 IN/HR.

OTTO

ATTN...WFO...CLE...ILN...ILX...IND...JKL...LMK...LSX...PAH...
RLX...

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

LAT...LON   40298246 39768227 38858284 38248442 37888584
            37448795 37448873 37668891 38528877 39138750
            39548584 40058402