MESOSCALE PRECIPITATION DISCUSSION 0318
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1232 AM EDT TUE JUN 13 2017

AREAS AFFECTED...SOUTHWEST & CENTRAL SD...EXT EASTERN
WY...NORTHWEST NEB

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 130430Z - 131000Z

SUMMARY...MULTIPLE LINES/CLUSTERS OF CONVECTION WITH POTENTIAL
TRAINING MAY LEAD TO 2-4" RAINFALL TOTALS OVER THE NEXT 6HRS OR SO
POSING FLASH FLOODING CONCERNS.

DISCUSSION...GOES SATELLITE MOSAIC DENOTES A VERY ROBUST UPPER LOW
OVER NE NV WITH WELL DEFINED CONVERGENT ARMS ALONG 2 WARM CONVEYOR
BELTS IN ADVANCE OF THE LOW ACROSS THE HIGH PLAINS.  THE HEIGHT
FALLS AND CONVERGENCE ALONG THE EASTERN MOST BAND ENHANCED BY LOW
LEVEL WESTERLIES AND MODEST REMAINING INSTABILITY AS HIGH AS 1000
J/KG MUCAPE IS SUPPORTING CONVECTIVE DEVELOPMENT FROM EXTREME
EASTERN WY ARCHING BACK NW TO SE MT UNDER INCREASING DIFFLUENT
FLOW.  NEAR 180 DEGREES OF LOW LEVEL CONVERGENCE WITH SFC TDS IN
THE LOWER 50S ALONG WITH MOISTENED MID-LEVEL ENVIRONMENT FROM
CONVECTION TO THE EAST SHOULD SUPPORT MODEST RAINFALL RATES OF
1.25-1.5"/HR GIVEN TPWS PER RAP UP TO 1.2" AND FLUX.  GIVEN FAIRLY
STRONG HEIGHT FALLS AND STRONGER MID-LEVEL MIXING...FORWARD
PROPAGATION MAY MITIGATE THE OVERALL TOTALS.  HOWEVER...PRECURSORY
HEAVY RAINFALL EARLIER THIS EVENING AS WELL AS YESTERDAY HAS
LOWERED SOIL CONDITIONS THAT MAY BE ECLIPSED AND LEAD TO RUN-OFF
PROBLEMS AND LOCALIZED FLASH FLOODING CONDITIONS.   THIS IS
PARTICULARLY THE CASE FOR THE SOUTHERN CELLS THAT NOT ONLY ARE
EXPOSED TO STRONGER MOISTURE FLUX FROM THE SOUTHEAST (NOT AFFECTED
BY CONVECTION TO THE EAST) BUT ALSO MORE FAVORABLE FLOW ALOFT TO
SUPPORT BACKBUILDING AS WELL AS ORIENTING TO THE MEAN FLOW
ALLOWING FOR TRAINING. THIS IS LIKELY TO AFFECT FAR NW NEB TOWARD
THE BADLANDS...AND MAY TRACK THROUGH AREAS AFFECTED FROM RAINS
EARLIER AS WELL...WITH 2-3" TOTALS POSSIBLE.

FURTHER EAST ACROSS CENTRAL SD...EARLY EVENING SUPERCELLS CONTINUE
TO MAINTAIN THEMSELVES AND POSE SEVERE THREAT (PLEASE SEE MCD 1006
FOR ADDITIONAL DETAILS) BUT ALSO ARE QUITE EFFICIENT HEAVY
RAINFALL PRODUCERS THAT MAY BECOME MORE EFFICIENT WITH TIME. 
EXPERIMENTAL GOES-16 SWIR 3.9UM IMAGERY SHOWS WARMING LOW LEVEL
ENVIRONMENT INDICATIVE OF REINFORCING UNTAPPED THETA-E BUBBLE
BEGINNING TO INTERSECT THE SE PERIPHERY OF EXPANSIVE CONVECTIVE
SHIELD OVER NW NEB...WHILE LOW LEVEL MOISTURE HAS BEEN MAINTAINED
AND IS GREATER THAN 65F TDS...MID-LEVEL FLUX ON 50KTS OF SE PER
LNX VWP IS ADVECTING MUCAPES UP TO 3500 J/KG INTO THE GROWING
COMPLEX.  THIS IS LIKELY TO REINVIGORATE CONVECTION AND EXPAND
CONVECTIVE CORES...GIVEN ORIENTATION OF THE LOW LEVEL FLOW
PERPENDICULAR TO THE MEAN RIGHT MOVING SUPERCELL MOTION VECTORS...
THIS SHOULD SUPPORT ADDITIONAL TRAINING.  EVEN WITH STRONG FORWARD
SPEED...RAIN RATES OVER 2"/HR ARE POSSIBLE ALLOWING FOR TOTALS OF
2-4" OVER THE NEXT 6HRS.  AS SUCH FLASH FLOODING IS POSSIBLE
THROUGH THIS SW TO NE TRACK THOUGH GREATEST THROUGH COMPROMISED
SOILS JUST NORTH OF I-90 FROM MCS TRACK A FEW DAYS AGO. 

GALLINA

ATTN...WFO...ABR...CYS...FSD...LBF...UNR...

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

LAT...LON   45799936 44929833 43150015 42400178 42500302
            42430397 42930436 44270421 44870355 45730190