MESOSCALE PRECIPITATION DISCUSSION 0254
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
145 AM EDT SUN SEP 15 2013
 
AREAS AFFECTED...SRN NE...NRN KS...FAR NE CO 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 150544Z - 151044Z
 
SUMMARY...SLOW MOVING STORMS WITH HEAVY RAIN WILL FOCUS NEAR A
DEVELOPING MESOSCALE CONVECTIVE VORTEX AND EXTEND EASTWARD IN A
ZONE OF FOCUSED WARM ADVECTION. DESPITE HIGHER FLASH FLOOD
GUIDANCE VALUES...EFFICIENT RAIN PROCESS MAY PRODUCE LOCALIZED 2-4
INCH STORM TOTALS BY MORNING...WITH ASSOCIATED RISK OF FLASH
FLOODING.

DISCUSSION...THE HIGH RESOLUTION MODELS...EVEN THOSE INITIALIZED
AT 00Z...ARE NOT WELL HANDLING THE CONVECTION OVER THE TRI-STATE
AREA OF CO/NE/KS. OBSERVATIONS...HOWEVER...ARE RATHER CLEAR CUT IN
SHOWING CONVECTION PERSISTING AND EVEN BLOSSOMING EASTWARD...IN
ASSOCIATION WITH A DEVELOPING MCV OVER NE CO WHERE THE GREATER
VOLUME OF CAPE HAS BEEN RELEASED...AND OUT INTO A ZONE OF
INCREASING UPGLIDE ON THE 305-310 K ISENTROPIC SURFACE. ALL THIS
IS LOCATED AT THE NORTHERN EDGE OF A RESERVOIR OF MUCAPE RUNNING
500-1000 J/KG OVER WESTERN KS.

GLOBAL MODELS SEEM A LITTLE MORE REASONABLE IN DEPICTING AN
EASTWARD EXTENSION OF QPF ALONG THE KS/NE BORDER EVEN INTO EASTERN
AREAS OF THOSE STATES BY 12Z TODAY. THE HI-RES GUIDANCE...AS IS
SOMETIMES THE CASE...MAY SIMPLY BE MIS-TIMED...AS THEY SHOW THIS
SAME AXIS OCCURRING 12-18Z. THE GUESS HERE IS THAT BASED ON THE
CLEAR TENDENCY FOR NEW DEVELOPMENT IN SRN NE AT 05Z...AND STRONGLY
FOCUSED UPGLIDE PREDICTED BY THE NAM ALONG THE STATE LINE AT
06-12Z...A CONVECTIVE EVENT WILL LIKELY CONTINUE TO UNFOLD AND
INCREASE IN COVERAGE THROUGH 12Z.

ENVIRONMENT IS CHARACTERIZED BY PW VALUES AROUND 1.2-1.4 INCHES.
RAIN RATES LOOK TO BE VERY EFFICIENT JUDGING BY DEPTH OF THE
STORMS...TOPS OBSERVED OVER 40 THOUSAND FEET...ABSENCE OF HAIL AND
PREVALENCE OF KDP VALUES 1.5-3.0 PER DUAL POL DATA. DUAL POL
PERFORMED WELL IN THE WARM RAIN PROCESSES OVER THE PAST FEW DAYS.
THE MID/UPPER ENVIRONMENT HAS DRIED...WHICH COULD YIELD SOME
OVER-ESTIMATION...BUT LEGACY AMOUNTS ARE ONLY 0.5-1.0 INCHES
LESS...AT AROUND 1.5-2.5 INCHES PER HOUR IN THE STRONGEST CORES.
CONCERN IS THAT WITH INDIVIDUAL CELL MOTION AND MCS MOTION
PREDICTED AT 5-15 KT IN THIS ZONE OF LIGHT UPPER WINDS BUT
SUSTAINED LOW LEVEL INFLOW...HEAVY RAIN TOTALS AND SOME FLASH
FLOODING COULD RESULT THROUGH MORNING.

BURKE

ATTN...WFO...TOP...GID...LBF...GLD...BOU...CYS...

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

LAT...LON   41550213 41190296 40160329 39550231 39419999 39489776
            39909737 40419752 40889838 41379999 41550213