MESOSCALE PRECIPITATION DISCUSSION 0578
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
727 PM EDT THU AUG 18 2016
 
AREAS AFFECTED...SERN SD...NERN ND...SRN MN...NRN IA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 182323Z - 190515Z
 
SUMMARY...SLOW MOVING AND TRAINING CONVECTION NEAR A COLD FRONT
MAY PRODUCE FLASH FLOODING WITH RAINFALL RATES OF 1-2 IN/HR ACROSS
SERN SD INTO SRN MN AND NRN IA THROUGH 03Z.

DISCUSSION...23Z OBSERVATIONS PLACED A 1006 MB SURFACE LOW JUST
EAST OF MHE WITH A COLD FRONT EXTENDING WSW FROM THE LOW INTO NWRN
NE...AND A WARM FRONT EXTENDING ESE INTO NRN IA. SPC MESOANALYSIS
AND THE RAP INDICATE A RELATIVELY NARROW AXIS OF STRONG UNCAPPED
INSTABILITY...MLCAPE OF 4000+ J/KG...NEAR THE SURFACE LOW AND
ACROSS THE WARM SECTOR IN IA. TRENDS IN 1-MIN SRSO VISIBLE IMAGERY
SHOWED THE EXPANSION OF CUMULUS TOWERS ALONG THE FRONT JUST WEST
OF THE LOW IN DOUGLAS AND HUTCHINSON COUNTIES WITH ONGOING STORMS
FARTHER WEST OVER THE SAND HILLS OF N-CNTRL NE. 

AS THE 700 MB REFLECTION OF A SECONDARY COLD FRONT CONTINUES TO
ADVANCE SOUTHEAST ACROSS SOUTH DAKOTA...RAPID DEVELOPMENT OF
CONVECTION IS EXPECTED NEAR THE SURFACE LOW IN THE NEXT HOUR OR
TWO. A NARROW OVERLAP OF ENHANCED LOW LEVEL FLOW JUST SOUTH OF THE
SURFACE LOW INTO THE WARM FRONT WITH UNIDIRECTIONAL WSWLY FLOW
WOULD PROMOTE A ZONE OF TRAINING RAINFALL RATES OF 1-2 IN/HR. A
GPS SITE NEAR FSD HAS INDICATED AN INCREASING TREND IN
PRECIPITABLE WATER WITH 1.57 INCHES REPORTED AS OF 22Z AS LOW
LEVEL MOISTURE CONTINUES TO BE TRANSPORTED INTO THE REGION.
ALTHOUGH WEAK...DIFFLUENT FLOW ALOFT IS ALSO PRESENT WHICH MAY
HELP TO ENHANCE LIFT ACROSS THE AREA. GIVEN FFG OF 1.5 TO 2.5
IN/HR AND THE POSSIBILITY OF TRAINING...FLASH FLOODING IS
CONSIDERED POSSIBLE.

OTTO

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

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

LAT...LON   44829561 44769430 44299365 43449403 43139646 
            42699867 42510017 42450087 43090112 43759967 
            44489817 44779694