MESOSCALE PRECIPITATION DISCUSSION 0330
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
214 AM EDT SAT JUN 17 2017

AREAS AFFECTED...CNTRL TO SRN MS

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

VALID 170613Z - 171200Z

SUMMARY...A NARROW CORRIDOR OF TRAINING HEAVY RAIN IS EXPECTED TO
POSE A FLASH FLOOD THREAT OVER THE NEXT 3-6 HOURS FOR CNTRL TO SRN
MISSISSIPPI.

DISCUSSION...IN THE WAKE OF A FORWARD PROPAGATING MCS...OF WHICH
THE LEADING EDGE HAS MOVED INTO THE NRN GULF OF MEXICO AS OF
0530Z...NARROW AXES OF CONVECTION ORIENTED NNW TO SSE HAVE
DEVELOPED OVER PORTIONS OF CNTRL MISSISSIPPI. THESE NARROW AXES
ARE OCCURRING WITHIN A REGION OF WEAK ELEVATED
INSTABILITY...ESTIMATED TO BE 500-1000 J/KG PER THE LATEST SPC
MESOANALYSIS PAGE. MESOSCALE CONFLUENCE AND CONVERGENCE IN THE LOW
LEVELS...850-700 MB...APPEARS TO BE THE FOCUS FOR THE CONVECTIVE
ACTIVITY.

AN MCV ANALYZED OVER E-CNTRL MISSISSIPPI AT 0530Z IS FORECAST TO
SLOWLY DRIFT SEWD OVER THE NEXT 3-6 HOURS WITH CONTINUED LOW LEVEL
CONVERGENCE OCCURRING JUST TO ITS WEST. THE CONVERGENCE AXIS MAY
BEGIN TO PIVOT MORE WEST TO EAST IN DIRECTION AS THE MCV TRACKS TO
THE SOUTHEAST THROUGH 12Z. GIVEN A WIDESPREAD 1 TO 3 INCHES OF
RAIN HAS ALREADY FALLEN OVER THE PAST 6-12 HOURS WITH THE FORWARD
PROPAGATING MCS OVER CNTRL MISSISSIPPI...AND EXPECTED RAIN RATES
THROUGH THE MORNING OF 1 TO 1.5 IN/HR WHERE TRAINING AXES OF RAIN
PERSIST...FLASH FLOODING WILL BE POSSIBLE.

THE GREATEST LIMITING FACTORS FOR FLASH FLOODING MOVING FORWARD
ARE MARGINAL INSTABILITY AND UNKNOWN PERSISTENCE OF LOW LEVEL
CONVERGENCE HELPING TO SUPPORT CONTINUED REGENERATION OF CELLS.
VARIOUS RUNS OF THE EXPERIMENTAL HRRR SEEM TO BE DOING THE BEST
WITH THE HANDLING OF HEAVY RAINFALL BUT VARY SIGNIFICANTLY WITH 6
HR STORM TOTALS FROM 2 TO 6 INCHES ENDING 12Z.

OTTO

ATTN...WFO...JAN...MEG...MOB...

ATTN...RFC...LMRFC...

LAT...LON   34039056 34038981 33728937 32478900 31748876
            31298960 32029049 33429093