MESOSCALE PRECIPITATION DISCUSSION 0481
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
330 AM EDT THU JUL 13 2017

AREAS AFFECTED...SOUTHERN AND SOUTHEASTERN NEBRASKA

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

VALID 130730Z - 131230Z

SUMMARY...PERSISTENT ISENTROPIC ASCENT WITHIN STATIONARY
DEFORMATION BAND ALONG COOL CONVEYOR WILL CONTINUE TO POSE FOCUS
FOR THUNDERSTORMS CAPABLE OF FLASH FLOODING.

DISCUSSION...STRONG MID-LEVEL CONCENTRIC WAVE CURRENTLY SEEN WELL
IN RADAR MOSAIC OVER FAR E CENTRAL CO. EAST OF THE BAND A BROAD
LLJ/WARM CONVEYOR BELT EXIST ACROSS CENTRAL KS OVERRUNNING A
SURFACE BOUNDARY THAT EXTENDS FROM GCK TO HYS/RSL TO JUST SOUTH OF
STJ.  NORTH OF THE BOUNDARY COOL CONVEYOR BELT HELPS TO LOCK
FRONTAL POSITION INCLUDING TO MID-LEVEL SHEAR/DEFORMATION AXIS
ACROSS S NEB AT OR ALONG I-80.  RAP ANALYSIS DENOTES GRADIENT OF
INSTABILITY TO BE TAPPED WITH VALUES AOA 1000 J/KG SUFFICIENT FOR
MAINTAINING UPDRAFTS.  GREATEST ASSET FOR FLOODING CONCERNS
REMAINS STRONG MST CONVERGENCE ALONG THE AXIS SUFFICIENT TO REACH
LFC FOR ELEVATED CONVECTION.  TO FURTHER COMPOUND FLOODING
CONCERNS...MEAN CLOUD BEARING FLOW IS GENERALLY WESTERLY WHICH
SHOULD SUPPORT TRAINING OF SHOWERS ALONG THE SHEAR AXIS.   A
FAIRLY SOLID COOL CONVEYOR BELT DENOTED BY SFC TO 925MB NE/ELY
WINDS ARE NEARLY 100% RH ALLOWING FOR NEARLY ZERO EVAPORATIVE LOSS
AND TPWS OVER 2"...SUPPORTING RAIN RATES OF 1.5-2"/HR OVER THE
NEXT HOUR OR SO.

ALREADY...OU CIMMS FLASH CREST SUGGESTS MAX UNIT STREAMFLOW ACROSS
YORK/SEWARD COUNTY TO BE OVER FF RATES (6CM/S) AND MAX FFG RATIOS
OVER 1 NEARING 1.5. 

LONGER TERM...THE DEEP MID-LEVEL WAVE IS EXPECTED TO SLOWLY DRIFT
NORTHEAST ALONG THE TROF AXIS NOT PERTURBING THE AXIS OF
CONVERGENCE ALLOWING FOR CONTINUED HIGHLY EFFICIENT RAINFALL
PRODUCTION ACROSS THE ENTIRE AXIS FOR THE NEXT 2-4 HOURS. 
DIMINISHING INSTABILITY/STABILIZING PROFILES WILL REDUCE
CONVECTIVE VIGOR AND DEPTH FOR RAINFALL PRODUCTION EFFECTIVELY
LIMITING RAIN RATES BUT EVEN AT OR BELOW 1"/HR...AFTER 2-4" TOTALS
OVER A 3-4 HOUR TIME PERIOD...THERE IS A GOOD POSSIBILITY OF
FLOODING EVEN IF THE RATES DO NOT INDUCE FLASH FLOODING.  

GALLINA

ATTN...WFO...GID...LBF...OAX...

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

LAT...LON   41209713 40979605 40469602 40549737 40249873
            40079986 40320016 40759982 41109840