MESOSCALE PRECIPITATION DISCUSSION 0178
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
325 AM EDT SAT JUL 05 2014
 
AREAS AFFECTED......PORTIONS OF NE/SD/IA... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 050724Z - 051224Z
 
SUMMARY...INTENSE DEEP CONVECTION IS LIKELY TO EXPAND THROUGH THE
EARLY MORNING HOURS...RESULTING IN LOW TO MODERATE PROBABILITIES
OF EXCEEDING FFG VALUES.

DISCUSSION...THE INTERACTIONS OF 3 DISTINCT SHORTWAVE TROUGHS
OUTLINED AS CROSSES ON THE MAP ARE CONTRIBUTING TO LOCAL
ACCELERATIONS OF THE LOW LEVEL JET OVERLAPPING WITH ENHANCED UPPER
LEVEL DIVERGENCE. AN AVERAGE OF GOES INSTABILITY PARAMETERS AND
RAP FORECAST SOUNDING SUGGEST MUCAPE VALUES NEAR 3000 J/KG WHICH
IS REALISTIC GIVEN ECHO TOPS ABOVE 50 THOUSAND FEET AND HIGH
REFLECTIVITY CORES.  RADAR RAINFALL ESTIMATES ARE PRESENTLY 0.5 TO
0.75 INCHES PER HOUR WITH CELL MOTIONS TOWARD THE EAST NORTHEAST
AT 15 TO 20 KNOTS. THE EXPANDING CONVECTION IS ENHANCING A
BOUNDARY ALREADY OVER THE REGION WITH A SOUTHWESTERLY LOW LEVEL
JET AROUND 50 KNOTS PROVIDING VIGOROUS ASCENT FOR RELEASE OF THE
HIGH INSTABILITY. 

GIVEN THE RAPID CONVECTIVE DEVELOPMENT ALONG WITH THE
SYNOPTIC/MESOSCALE SUPPORT FOR CONTINUATION THAT SHOULD LAST
ANOTHER 3 TO 6 HOURS...THE CURRENT ACTIVITY SHOULD CONTINUE TO
EXPAND WHILE MOVING EASTWARD.  GIVEN CURRENT AND ANTICIPATED CELL
MOTIONS AND PW VALUES NEAR 1.5 INCHES...AVERAGE HOURLY RATES MAY
REACH 1.25 TO 1.5 INCHES...BUT MAY CONTINUE FOR 2 OR MORE HOURS
WHICH WOULD BE SUFFICIENT TO EXCEED 3 HOURLY FFG VALUES. THE 00Z
HIRES ARW5/NMMB5 APPEAR TO HAVE A GOOD HANDLE ON THE CURRENT
DEVELOPMENT AND SUGGEST THAT SOME LOCATIONS MAY RECEIVE 2.5 TO 5
INCHES OF RAIN BEFORE ENDING AFTER 12Z.

JAMES

ATTN...WFO...ARX...DMX...FSD...OAX...LBF...

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

LAT...LON   43189906 43659848 43529721 42909628 42639517 42709401
            42999295 42139246 41129474 41389689 42459868 43189906