MESOSCALE PRECIPITATION DISCUSSION 0447
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
318 AM EDT SUN JUL 10 2016
 
AREAS AFFECTED...EASTERN SD...SOUTHERN MN...FAR NORTHWEST IA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 100720Z - 101220Z
 
SUMMARY...CELL MERGERS AND BACKBUILDING WITH AN MCS TRACKING
SOUTHEAST ACROSS EASTERN SD AND SOUTHERN MN COULD RESULT IN HOURLY
RAINFALL RATES NEAR 2.00 INCHES. THIS COULD IN TURN LEAD TO A
FLASH FLOOD THREAT THROUGH THE EARLY MORNING HOURS.

DISCUSSION...THE MCS IS NEARING THE MATURE PHASE ACROSS SOUTHEAST
ND AND WEST CENTRAL MN EARLY THIS MORNING...AS IR CLOUD TOPS HAVE
COOLED TO NEAR -72 C. A LOW LEVEL 25 TO 30 KNOT SOUTHWEST INFLOW
CONTINUES TO PUMP 1.75/2.00 INCH PRECIPITABLE WATER AIR (WHICH IS
ABOUT TWO STANDARD DEVIATIONS ABOVE THE MEAN) INTO THE SYSTEM. THE
MCS IS TRACKING ALONG AN INSTABILITY GRADIENT...WITH A MAXIMUM OF
NEARLY 4000 J/KG OF MLCAPE OVER EAST CENTRAL SD. 

THUS FAR...MOST OF THE ACTIVITY HAS BEEN OUTFLOW DRIVEN ACROSS
SOUTHEAST ND INTO PORTIONS OF CENTRAL MN...BASED ON THE RADAR
PRESENTATION FROM KMVX. HOWEVER... CELL MERGERS ACROSS PORTIONS OF
SOUTHEAST SD AND NEARBY WEST CENTRAL MN HAVE OCCURRED. BOTH THE
KMVX AND KABR RADARS HAVE INDICATED HOURLY RAINFALL RATES IN
EXCESS OF 2.00 INCHES WHERE THE MERGERS HAVE OCCURRED. THESE
AMOUNTS COULD BE HAIL CONTAMINATED...BASED ON THE HAIL REPORTS
NEAR THE MERGERS...AND STEEP LAPSE RATES BASED ON THE MOST RECENT
RAP SOUNDINGS IN SOUTHEAST ND. 

THE LATEST RAP INDICATED THAT THERE SHOULD BE SUFFICIENT
INSTABILITY (IN THE FORM OF 2000-2500 J/KG OF MLCAPE) AND MOISTURE
(WITH PRECIPITABLE WATER VALUES REMAINING NEAR 1.75 INCHES) TO
SUPPORT THE MAINTENANCE OF THE MCS AS IT TRACKS SOUTHEAST ACROSS
EASTERN SD AND SOUTHWEST MN THROUGH 11Z. AFTER THAT TIME...THE
DIURNAL WEAKENING OF THE LOW LEVEL INFLOW COULD ALLOW THE MCS TO
DROP OFF IN STRENGTH.

BEFORE THAT TIME...MERGERS AND TRAINING COULD SUPPORT LOCAL 2-5
INCH RAINFALL AMOUNTS. THESE RAINFALL AMOUNTS ARE SUPPORTED BY THE
MOST RECENT HRRR AND 00Z WRF ARW (INTERESTINGLY...BOTH THE 00Z NAM
CONUS NEST AND THE 00Z NSSL WRF HAVE HAD DIFFICULTY WITH THE
DEVELOPMENT OF THE MCS THUS FAR). IN ADDITION...RAP MODEL
SOUNDINGS SHOWED THE COLUMN BECOMING MOIST THROUGH AT LEAST 700
MB...WHICH COULD INCREASE THE RAINFALL EFFICIENCY OF THE CELLS.

ONE HOUR FLASH FLOOD GUIDANCE VALUES OVER EASTERN SD AND SOUTHERN
MN ARE GENERALLY BETWEEN 2.00 AND 2.5O INCHES...SO FLASH FLOODING
IS ONLY CONSIDERED POSSIBLE.

HAYES

ATTN...WFO...ABR...ARX...DMX...FGF...FSD...MPX...

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

LAT...LON   45969632 45969631 45949558 45659430 44909340 
            43999273 43329290 42969381 42999535 43229670 
            44119789 44819805 44819804 45459759 45849708