MESOSCALE PRECIPITATION DISCUSSION 0252
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1247 AM EDT WED AUG 06 2014
 
AREAS AFFECTED...SERN SOUTH DAKOTA / NERN NEBRASKA INTO WRN IOWA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 060445Z - 061045Z
 
SUMMARY...SUSTAINED OVERRUNNING AND TRAINING OF CONVECTION
THROUGHOUT MUCH OF THE NIGHT SHOULD LEAD TO A FLASH FLOOD THREAT
FROM THE ERN SOUTH DAKOTA / NEBRASKA BORDER INTO WRN IOWA.

DISCUSSION...AT 04Z...A STATIONARY FRONT WAS ANALYZED FROM NERN
COLORADO...EWD ACROSS SRN NEBRASKA AND SEWD INTO ERN KANSAS AND
WRN MISSOURI. 00Z RAOBS INDICATED THE GREATEST TROPOSPHERIC
MOISTURE WAS LOCATED JUST AHEAD OF A 700 MB TROUGH AXIS EXTENDING
SSEWD FROM WRN SOUTH DAKOTA INTO WRN NEBRASKA WITH RECENT WATER
VAPOR IMAGERY SHOWING A MID-LEVEL CIRCULATION NEAR LBF. BROAD
OVERRUNNING OF THE STATIONARY FRONT HAS LED TO SOMEWHAT
DISORGANIZED POCKETS OF CONVECTION ACROSS SRN SOUTH DAKOTA INTO
NEBRASKA AND WRN IOWA WITH VARIED MOTIONS BUT GENERALLY TOWARD THE
EAST. 

RAP AND HRRR MODEL FORECASTS SHOW INCREASING 850-700 MB FLOW
DEVELOPING OVERNIGHT ACROSS KANSAS AND ERN NEBRASKA...FEEDING
MOSTLY WEAK INSTABILITY TOWARD AN 850 MB FRONT WHICH BISECTS THE
THREAT AREA FROM NW TO SE. DESPITE THE WEAK
INSTABILITY...OBSERVATIONS NEAR RAPID CITY EARLIER TUE EVENING
SHOWED ONE HOUR RAINFALL RATES OF 1-2 INCHES PER HOUR. STORM
MOTIONS ARE EXPECTED TO CONTINUE EWD OR SEWD INTO IOWA
OVERNIGHT...WHILE CONVECTION CONTINUES TO REGENERATE AHEAD OF THE
SLOW MOVING SHORTWAVE INDICATED OVER W-CNTRL NEBRASKA. HI-RES
MODEL QPF HAS VARIED WITH THE RAINFALL AXIS...BUT RECENT RUNS OF
THE HRRR AND THE 12Z HRW NMM SEEM TO HAVE THE BEST HANDLE ON THE
COMPLEX SITUATION AND INDICATE RAINFALL RATES OF 1-2 IN/HR THROUGH
AT LEAST 10Z. GIVEN THE REPEATING NATURE OF THESE STORMS...FLASH
FLOODING WILL BE POSSIBLE.

OTTO

ATTN...WFO...DMX...FSD...OAX...ABR...LBF...UNR...

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

LAT...LON   40629374 41369682 42169844 42479979 42860024 43170029
            43569995 43699910 43559740 42789503 41559309 40629374