MESOSCALE PRECIPITATION DISCUSSION 0396
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
933 PM EDT TUE JUL 03 2018

AREAS AFFECTED...SOUTH DAKOTA...

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 040120Z - 040600Z

SUMMARY...STATIONARY SUPERCELL IN VICINITY OF FLOODED GROUNDS WITH
SLOW EXPANSION OF COMPLEX BEFORE MAIN HEIGHT-FALLS APPROACH FROM
THE WEST.  POSSIBLE TRAINING OVER LOWER FFG VALUES WITH THE
APPROACHING TROF EXPAND FLASH FLOOD THREAT TOWARD SW AS WELL.

DISCUSSION...01Z SFC ANALYSIS DEPICTS THE SLOW DEVELOPMENT OF WEAK
SURFACE LOW ACROSS SOUTH CENTRAL SD BUT ALSO SOME INCREASED
RIDGING OVER NE SD ALLOWING FOR INCREASED SURFACE CONVERGENCE FROM
PIR TO JUST SOUTH OF ABR.  00Z ABR SOUNDING DENOTES THE SLACKING
OF THE LOW LEVEL WINDS IN RESPONSE TO THIS DEVELOPMENT AND
APPROACH OF DEEPER HEIGHT-FALLS AND DPVA FROM SHARPENING TROF OVER
MT TO NE WY.   SATURATED GROUNDS BUT CLEAR SKIES TODAY ALLOWED FOR
A LOCAL MAXIMA OF LOW LEVEL MOISTURE TO CLIMB TO SFC TDS IN THE
MID TO UPPER 70S CURRENTLY IN THIS REGION.   THE COMBINATION OF
THE DEEP LOW LEVEL MOISTURE AND SHARPENING OF THE SFC BOUNDARY
SUPPORTED CONVECTIVE DEVELOPMENT IN FAULK COUNTY ALONG THE NW
PERIPHERY OF EXTREME TOTALS/FLOODED GROUNDS FROM LAST NIGHT'S MCS.
CURRENT KABR KDP SUGGESTS STRONG UPDRAFTS WITH THE 5000+ J/KG AND
3K FT DIFFERENCE IN WBZ AND FGZ LEVELS SHOW HAIL PRODUCTION AT
THIS TIME BUT ALSO SURROUNDED BY MODERATE TO HEAVY RAINFALL AS
WELL.

PROPAGATION VECTORS (INCLUDING BUNKERS RGT MOVING VECTORS) FROM
THE RAP MAY BE A BIT TOO HIGH IN THE 10-15 RANGE GIVEN THE ONGOING
SITUATION AND STRONGER SURFACE RIDGING (500-1000MB THICKNESS COL)
DEVELOPING IN THE VICINITY OF THE CELL.  AS SUCH THE SUPERCELL IS
EXPECTED TO REMAIN FAIRLY LOCKED FOR THE NEXT HOUR OR SO POSING
2-3" RAINFALL TOTALS EXACERBATING FLOODING WHICH COULD BE FLASHY
LOCAL TO THE DOWNDRAFT.  1-MINUTE VISIBLE IMAGERY FROM G16
SUGGESTS ADDITIONAL WEAKER CLD DEVELOPMENT ALONG AIDED BY
INCREASED MST CONVERGENCE ALONG OUTFLOW BOUNDARY EXPANDING IN
NEARLY ALL DIRECTIONS WITH EXCEPTION TO THE SOUTHEAST (WHICH
CONTINUES TO FEED WARM MOIST/UNSTABLE AIR INTO THE CELL TO
MAINTAIN IT).  AS SUCH FLASH FLOODING IS CONSIDERED LIKELY FOR
THIS SMALL ALREADY FLOODED AREA OF HYDE/HAND AND FAULK COUNTIES.

FURTHER UPSTREAM...THE STRONG DPVA/HEIGHT-FALLS HAS SPURRED NEW
CONVECTIVE CLUSTERS ACROSS SE MT INTO W SD. VWP AND GOES AMV
SUGGEST A WEAKNESS IN THE MID TO UPPER LEVEL FLOW BISECTING SD
FROM SW TO NE WHERE THE MID-LEVEL TROF AXIS MAY BEGIN TO ORIENT
MORE FAVORABLY FOR CELLS TO TRAIN FROM FALL RIVER TO STANLEY
COUNTY OVER THE NEXT 3-4 HOURS...THIS ALSO ALIGNS WITH A STRIPE OF
LOWERED FFG.  IF THIS TRAINING WERE TO OCCUR (PARTICULARLY LATER
TOWARD 4-6Z) THERE IS A LOWERED SUFFICIENT  POSSIBILITY FOR
EXCEEDING THE FFG LEADING TO POSSIBLE FLASH FLOODING AS WELL. 

GALLINA

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

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

LAT...LON   45619846 45469742 44619726 44499979 43820174
            44220214 44860120 45429987 45589938