MESOSCALE PRECIPITATION DISCUSSION 0485
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
715 PM EDT FRI JUL 22 2016
 
AREAS AFFECTED...SOUTHWEST ND...NORTHWEST SD 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 222315Z - 230415Z
 
SUMMARY...MAINLY SEVERE THREAT MAY POSE LOCALIZED FLASH FLOODING
CONCERN WHERE CELLS ARE MERGING/SLOW MOVING...ESPECIALLY GIVEN
LOWER FLASH FLOOD GUIDANCE VALUES IN THE AREA OF CONCERN.

DISCUSSION...WV LOOP INDICATES TWO MAIN FEATURES AT PLAY ACROSS
THE NORTHERN PLAINS.  IN THE NEAR TERM...A WELL DEFINED WAVE
ACROSS E CENTRAL WY IS LIFTING SLOWLY INTO THE BLACK
HILLS...SUPPORTING SURFACE PRESSURE FALLS AND STRENGTHENING SELY
LL FLOW ACROSS SD.  THIS SUPPORTED CONVECTIVE INITIATION ALONG
SURFACE WARM FRONT IN NW SD AS WELL AS SOUTHWARD MOVING OUTFLOW
BOUNDARY ACROSS CENTRAL SD.  ORIENTATION TO THE OUTFLOW BOUNDARY
SUPPORTS SOME ELEVATED MST CONVERGENCE AOA 7H FROM STRONGER SWLY
FLOW...BUT WITH THIS LOW LEVEL SHEAR...SUPPORTS CELL ROTATION.
THOUGH MAIN THREAT IS SEVERE WINDS/HAIL ATTM...THE BUNKERS RIGHT
MOVING CELL VECTORS SUPPORT A SLOWER EASTWARD MOTION OF ABOUT
10-15 KTS PER THE RAP AND GIVEN BOUNDARY AND CELL ORIENTATION AND
INCREASING COVERAGE FOR CELL MERGERS AND POTENTIAL CELL TRAINING
ACROSS THE DISCUSSION AREA.  FLASH FLOOD GUIDANCE VALUES ARE
GENERALLY LOW WITH VALUES BELOW 1.5" IN 1 HR AND BELOW 2" IN 3HRS.
 ADDITIONALLY...CELLS FURTHER EAST TOWARD THE OUTFLOW ARE MORE
RESTRICTED IN FORWARD PROPAGATION DUE TO OUTFLOW AND UPSTREAM
HEIGHT FALLS. DUE TO MID-LEVEL SWLY FLOW ...THERE IS A CHANNEL OF
LOW LEVEL DRIER CONDITIONS ACROSS THE BLACK HILLS TOWARD N CENTRAL
SD...DENOTED WELL IN GOES-W WV LOOP...STILL CONVECTION RESIDES ON
THE TIGHT MOISTURE GRADIENT TO ALLOW FOR RAINFALL PRODUCTION IN
THE 1.5"/HR RANGE...CAPABLE OF ECLIPSING THE AFOREMENTIONED FFG.  

AS THE EVENING PROGRESSES...THE OUTER BAND OF HEIGHT FALLS
APPROACH FROM THE WEST ACROSS MT INTO NW ND.  THIS ALONG WITH
BEING ALONG THE NORTHERN EDGE OF THE SHORTWAVE IN WY/W SD WILL
CONTINUE TO ORIENT FAVORABLY BETWEEN THE TWO WAVES WSW-ENE FOR THE
POTENTIAL OF UPSTREAM REDEVELOPMENT THAT COULD REPEAT ACROSS THE
SAME TRACK/CONVECTIVE CORRIDOR TOWARD 03-06Z.  WILL CONTINUE TO
MONITOR THIS  EVOLUTION SCENARIO FOR LARGER FLASH FLOODING EVENT
LATER THIS EVENING. 

GALLINA

ATTN...WFO...ABR...BIS...UNR...

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

LAT...LON   47220009 46659952 45420022 45170093 45340232 
            45380308 45530364 45920399 46590386 46860341 
            47050232