MESOSCALE PRECIPITATION DISCUSSION 0228
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1050 PM EDT SUN MAY 22 2016
 
AREAS AFFECTED...N CENT NEBRASKA...S CENT SOUTH DAKOTA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 230249Z - 230619Z
 
SUMMARY...EXTREME RAIN RATES WITH LITTLE PROGRESSION TO PERSIST
FOR OVER THE NEXT 3-4 HOURS COMPOUNDING ONGOING FLASH FLOODING
SITUATION BEFORE EASTWARD PROPAGATION IS EXPECTED.

DISCUSSION...RADAR MOSAIC/SATL AND SURFACE ANALYSIS INDICATES A
STRONG CONFLUENCE OF BOUNDARIES AND WIND FLOW REGIMES CONVERGING
ACROSS THE NORTHERN SAND HILLS TO PROVIDE STRONG PERSISTENT ASCENT
AND MOISTURE FLUX FOR HIGHLY EFFICIENT RAINFALL PRODUCTION.   RAP
FORECAST INDICATORS POINT TO THIS CONVERGENCE 30-40 KTS POST
FRONTAL WNW FLOW...30-40 SOUTH AND SELY INFLOW JUST NORTH OF
SURFACE LOW/DRYLINE BULGE NEAR KSDY.  STRONG S/W OVER NE WY
CONTINUES TO LIFT NORTHWARD REDUCING SOME OF ITS INFLUENCE TO PUSH
THE FRONTAL ZONE EASTWARD CAN BE SEEN IN WV AS WELL.  THOUGH RADAR
MOSAIC INDICATES SOME OUTFLOW GENERATING...THE INCREASING LOW
LEVEL FLOW SHOULD HELP TO MITIGATE FORWARD MOTIONS INITIALLY
THOUGH ELEVATING THE BASES WITH GOOD ISENTROPIC ASCENT OVER THE
OUTFLOW TO KEEP UPDRAFTS MAINTAINED.  BY 06Z...THE MOST FAVORABLE
PARAMETERS START TO FALL OFF AND ALLOW THE LINE TO BECOME FORWARD
PROPAGATING ENDING THE FLASH FLOOD THREAT.  

FURTHER NORTH ALONG THE BORDER...STRONGER CONVECTION DEVELOPING
POST STATIONARY LINE WILL COMPOUND FLASH FLOODING SITUATION ACROSS
N CHERRY/SE TODD/S TRIPP INTO GREGORY COUNTIES IN THE NEAR TERM AS
WELL. AS SMALL MCV/BOWING ELEMENT ON THE NE SIDE OF THE LINE IS
LIKELY TO SUPPORT AN E-W INTERFACE FOR STRONG LLJ INTERSECTION
SUPPORTING ADDITIONAL ASCENT TO MAINTAIN CELLS WITH RATES OVER
2"/HR...WITH POTENTIAL TRAINING AS CELLS SHIFT MOTIONS FROM ENE TO
MORE ELY.
  
GALLINA

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

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

LAT...LON   43949904 43249758 42150013 41220127 41320208 
            42280164 43210110