MESOSCALE PRECIPITATION DISCUSSION 0315
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
836 PM EDT SAT AUG 23 2014
 
AREAS AFFECTED...ERN SD...ERN ND...WRN MN 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 240035Z - 240635Z
 
SUMMARY...DIFLUENT UPPER FLOW AND ARRIVAL OF A MID LEVEL WAVE WILL
SUPPORT EXPANDING COVERAGE OF CONVECTIVE HEAVY RAINFALL INTO THE
EARLY NIGHTTIME. EXPECT RAIN RATES APPROACHING 2 INCHES PER HOUR
AND THE POTENTIAL FOR FLASH FLOODING.

DISCUSSION...A SHORTWAVE IS FORECAST TO ROTATE NE-WARD THROUGH
THIS REGION. A LOCAL MINIMUM OF INSTABILITY WAS ASSOCIATED WITH
REMNANT MORNING STRATUS ADVECTING THROUGH EASTERN SD...BUT PER
SEVERAL MODELS...MIXED LAYER CAPE WILL INCREASE WESTWARD AND
NORTHWARD OUT OF FAR ERN NE/SD THROUGH 06Z. AT 00Z...CONVECTIVE
CLUSTERS WERE BECOMING MORE NUMEROUS...AND DUAL-POL ALGORITHMS
DEPICTED GROWING COVERAGE OF HEAVY RAIN. DESPITE THE PRESENCE OF
SOME HAIL...THE AXIS OF 1.5-PLUS INCH PW ACROSS THIS AREA SUGGESTS
RECENT RADAR ESTIMATES OF 2-INCH PER HOUR RAINFALL ARE LIKELY
ACCURATE.

THE MODEL SIGNAL INSPIRES CONFIDENCE IN A LONGER TERM HEAVY RAIN
THREAT...WITH MOST OF THE SSEO COMPONENT MODELS AS WELL AS THE NAM
CONEST FORECASTING 2-3 INCH SWATHS WITH EMBEDDED ISOLATED 5 INCH
MAXIMA THROUGH 12Z. IN THE NEAR TERM...THE HRRR HAS BEEN SOMEWHAT
INCONSISTENT IN MAGNITUDE...BUT DOES SUPPORT THE NOTION OF
INCREASED CONVECTIVE COVERAGE...ESPECIALLY OVER EASTERN ND/SD. THE
ACTIVITY BLOSSOMING OVER NORTHEAST NE AT 00Z IS ALSO KEY...AS MOST
MODELS...INCLUDING THE 21Z AND 22Z HRRR... HAVE A SIGNAL FOR THIS
TO BECOME ANCHORED NEAR THE LEADING EDGE OF STRONG AND UNSTABLE
INFLOW. THIS COULD FOCUS A FLASH FLOOD THREAT WITHIN A RADIUS
SURROUNDING SE SD.

A SECOND...MORE PREDICTABLE FOCUS WILL BE NEAR/NORTH OF THE
QUASI-STATIONARY FRONT WHERE INCREASING LIFT AND INSTABILITY IS
EXPECTED FROM AROUND ABERDEEN TOWARD THE N AND NE. MODERATELY
SIZED FLASH FLOOD GUIDANCE NUMBERS SHOULD BE ACHIEVABLE GIVEN
EFFICIENT RAINFALL.

BURKE

ATTN...WFO...MPX...FGF...FSD...OAX...ABR...BIS...LBF...UNR...

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

LAT...LON   46959693 45629623 43879610 42969641 42309763 42169953
            42530064 43110106 43580090 44710049 46420003 47199877
            46959693