MESOSCALE PRECIPITATION DISCUSSION 0477
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
341 PM EDT WED JUL 18 2018

AREAS AFFECTED...NORTHERN ARIZONA...

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

VALID 181940Z - 190000Z

SUMMARY...ABOVE NORMAL MOISTURE AND SLOW CELL MOTIONS WITH TOTALS
OF 1.5-2" POSSIBLE POSE FLASH FLOODING RISK THROUGH THIS EVENING.

DISCUSSION...FSX AND GOES-16 MESO WINDOW IMAGERY CURRENTLY SHOW A
STRONG CONVECTIVE COMPLEX OVER THE SAN FRANCISCO PEAKS.  THESE
CELLS HAVE BEEN FED BY WEAK UPSLOPE INFLOW FROM THE SOUTH AND
SOUTHWEST IN THE LOW LEVELS BUT WITH MODERATE UPSTREAM SHORTWAVE
ENERGY ASSOCIATED WITH A 5H 15-20 SPEED MAX PROVIDES SOME
OROGRAPHIC ASCENT AND BACKBUILDING/UPSTREAM PROPAGATION VECTORS IN
THE SHORT-TERM.  THIS HAS RESULTED IN RECENT RAINFALL TOTALS OF
1.75-2" IN THE RANGE CLEARLY CAPABLE OF FLOODING CONCERNS.  

THE CONVECTIVE COMPLEX HAS RECENTLY ALSO SPAWNED AN OUTFLOW
BOUNDARY THAT WILL FURTHER SUPPORT NEW CONVECTIVE DEVELOPMENT
ALONG ITS LEADING EDGES.  CIRA LPW SHOWS A STRIPE OF MID TO UPPER
LEVEL MOISTURE ACROSS THE PLATEAU WITH A SMALL DRY SLOT CROSSING
SE AZ AT THIS TIME...SO CELLS THAT DO DEVELOP ALONG THIS OUTFLOW
OR WITHIN CONVERGENT LOW LEVEL FLOW ALONG THE MOGOLLON RIM WILL
HAVE ABOVE NORMAL MOISTURE THROUGH A DEEP LAYER TO REDUCE SOME
EVAPORATIVE LOSS AND STRONG RATES QUICKLY TO LEAD TO ADDITIONAL
FLASH FLOODING.  GIVEN RECENT DAYS OF RAINFALL...GROUNDS ARE
FAIRLY SATURATED FOR THE DESERT ENVIRONMENT TO FURTHER AID
FLOODING CONCERNS.

RAPID REFRESH GUIDANCE (RAP/HRRR) SUGGEST STRENGTHENING LOW LEVEL
INFLOW FROM THE VALLEY THROUGH THE AFTERNOON INTO EVENING
HOURS...SUPPORTING INCREASED PROPAGATION TOWARD DEEPER
MOISTURE/INSTABILITY OVER YAVAPAI AND TOWARD THE COLORADO RIVER
VALLEY IN MOJAVE AND WESTERN COCONINO COUNTY AS WELL.  WITH RATES
OF 1-1.5"/HR POSSIBLE GIVEN THE DEEPER MOISTURE FLASH FLOODING IS
POSSIBLE THROUGH 00Z IN THESE AREAS AS WELL...THOUGH STRONGER CAP
INTO THE LOWER COLORADO RIVER VALLEY WILL LIKELY LIMIT FURTHER
SOUTHWESTWARD EXPANSION.

GALLINA

ATTN...WFO...FGZ...PSR...VEF...

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

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            34581014 34311029 34131111 33821283 34081379
            34861426 35391421 36031404