MESOSCALE PRECIPITATION DISCUSSION 0501
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
555 PM EDT SAT JUL 21 2018

AREAS AFFECTED...SOUTHERN UT...NORTHERN AZ...

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

VALID 212155Z - 220200Z

SUMMARY...MATURE CLUSTERS DRIFTING NORTH SLOWLY...1-2" TOTALS FOR
POSSIBLE FOR LOCALIZED FLASH FLOODING.

DISCUSSION...MCV AND ASSOCIATED CLOUD COVER DOMINATES MOHAVE
COUNTY INTO SOUTHERN NV AND HAS LED TO A STRONG INCREASE IN CINH
BUT ALONG THE EASTERN PERIPHERY MULTIPLE CLUSTERS WITH 10.3UM IR
TOPS TO -70C CONTINUE TO SLOWLY MOVE FROM SE (EXT SE COCONINO
COUNTY) TO THE APEX OF THE RIDGE ALONG THE UT/AZ BORDER BEFORE. 
HERE MASS CONVERGENCE AND SLOW CELL MOTIONS POSE THE GREATEST
FLASH FLOODING RISK OVER THE NEXT 3-4 HOURS.  ADDITIONAL NEW
CONVECTION ALONG THE SOUTHERN UT MOUNTAINS ARE TERRAIN LOCKED
CURRENTLY BUT DEEP MEAN FLOW ALOFT (SPEED DIVERGENCE IN ENTRANCE
OF JET) WILL SUPPORT SLOW NORTHEASTERLY MOTIONS TOO.  POSING FLASH
FLOODING RISK AS WELL THERE TOO.

RECENT VISIBLE/IR TRENDS SHOW A LINE OF DEVELOPMENT ACROSS THE
KAIBITO PLATEAU TOWARD THE BLACK MESA OF NORTHERN NAVAJO COUNTY. 
HERE RAP ANALYST SUGGEST MODERATE INSTABILITY TO SUPPORT THESE
VIGOROUS CELLS (OVER 1500 J/KG)...AND BEING DIRECTLY UNDER THE
RIDGE, CELL MOTIONS ARE LIKELY TO BE ZERO WITH PROPAGATION ONLY ON
OUTFLOW INTO UNCAPPED AREAS NORTH AND SOUTH.  LARGER SCALE
SUPPRESSION ACROSS N APACHE AND THE WESTERN MOGOLLON RIM SEEMS
EVIDENT CURRENTLY WITH THE FIELD OF CU CONTINUING TO PRODUCE
ORPHAN ANVILS SUGGESTING FURTHER EASTWARD EXPANSION OF THE AREA OF
CONCERN CURRENTLY.

GALLINA

ATTN...WFO...FGZ...GJT...SLC...VEF...

ATTN...RFC...CBRFC...

LAT...LON   39131282 38601246 38421125 37871102 37641081
            37121040 36731012 36490996 36021003 36241053
            36411107 36201132 35851129 35281088 34801063
            34511072 34441106 34751208 35671320 37561338
            37941393 38361400 38621390 38961359