MESOSCALE PRECIPITATION DISCUSSION 0309
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
842 PM EDT SUN JUL 05 2015
 
AREAS AFFECTED...SOUTH DAKOTA...NORTHERN NEBRASKA...SOUTHWEST
MINNESOTA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 060041Z - 060530Z
 
SUMMARY...FOCUSED HEAVY RAINFALL AND A THREAT FOR FLASH FLOODING
IS EXPECTED TO PEAK OVER EASTERN SOUTH DAKOTA AND ADJACENT STATES
AS LOW LEVEL JET STENGTHENS TOWARD 04-06Z.  

DISCUSSION...RADAR COMPOSITE AND SATELLITE IMAGERY SHOW SEVERE
CONVECTIVE TOWERS ACROSS SW SOUTH DAKOTA INTO THE WESTERN NEBRASKA
PANHANDLE OUT IN THE WARM SECTOR UNDER VERY BROAD AREA OF DEEP
MOISTURE CONVERGENCE.  LARGE LOW LEVEL DEWPOINT DEPRESSIONS AND
VERY HIGH SBCAPES IN EXCESS OF 4000-5000 J/KG SUGGEST FASTER
FORWARD PROPAGATION OF AN UPSCALE GROWING QLCS AS SUGGESTED BY
MOST RAPIDLY REFRESHING MODELS SUCH AS THE RAP AND LAST FEW RUNS
OF THE HRRR. DEEP STREAM OF STRENGTHENING SOUTHERLY LOW LEVEL JET
WILL INTERSECT ACROSS NORTHERN NEBRASKA ALONG THE INSTABILITY
AXIS...SHOULD BE SUFFICIENT MOISTURE FLUX/CONVERGENCES FOR HIGHLY
EFFICIENT CELLS WITH RATES IN EXCESS OF 1.75"/HR...QUICKLY LEADING
TO A TOTALS ABOUT 2-4".  FLASH FLOODING IS POSSIBLE PARTICULARLY
INTO FAR SOUTHEAST SOUTH DAKOTA/ NORTHEAST NEBRASKA BY 05Z...WHERE
FLASH FLOOD GUIDANCE VALUES ARE LOWER AND MOISTURE FLUX SHOULD BE
INCREASING WITH STRENGTHENING LOW LEVEL JET AFTER SUNDOWN. 

THIS IS DEPARTING FROM EARLIER HI-RES CONVECTION ALLOWING MODELS
WHICH SUGGESTED A SLOWER FURTHER NORTH DEVELOPMENT SCENARIO WHEN
THE UPPER LEVEL SUPPORT...AVAILABLE INSTABILITIES AND PEAK OF LOW
LEVEL JET CYCLE WERE MORE ALIGNED IN TIME AND SPACE ACROSS CENTRAL
AND EASTERN SOUTH DAKOTA.  OBSERVATIONAL AND MODEL STILL POINT TO
THE THREAT OF FLASH FLOODING BUT FURTHER SOUTH AND EAST CENTERED
NEAR KYKN AND LIKELY TO CONTINUE INTO ADJACENT MN/IA/NE THROUGH
THE OVERNIGHT HOURS.   

GALLINA

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

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

LAT...LON   45769595 45229523 43259607 42109715 42109941 
            42370075 42410140 42260299 42660370 43220363 
            43800215 44779979 45749704