MESOSCALE PRECIPITATION DISCUSSION 0395
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
140 PM EDT WED JUN 29 2016
 
AREAS AFFECTED...SOUTHEAST AZ 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 291739Z - 292339Z
 
SUMMARY...AN EXPANDING CU FIELD ACROSS SOUTHWEST NM AND SOUTHEAST
AZ IS BEGINNING TO LEAD TO SHOWER DEVELOPMENT.  LATER TODAY,
HOURLY RAIN RATES UP TO 2", WITH LOCAL AMOUNTS IN THE 2-4" RANGE,
COULD LEAD TO FLASH FLOODING/DEBRIS FLOWS.

DISCUSSION...MID AND HIGH LEVEL CLOUDS ASSOCIATED WITH OVERNIGHT
THUNDERSTORM ACTIVITY ACROSS SOUTHEAST AZ HAS BEGUN TO THIN ACROSS
THE REGION. THE ENVIRONMENT IS CHARACTERIZED BY AN UPPER LEVEL
CIRCULATION OVER SOUTHERN NV AND AN INVERTED TROUGH/LINE OF
CYCLONIC WIND SHEAR AT 700 HPA WHICH IS SLOWLY RETROGRADING ALONG
THE EASTERN AZ/MEXICAN BORDER TO ITS SOUTHEAST.  CUMULUS
DEVELOPMENT IS SEEN FROM SOUTHWEST NM INTO SOUTHEAST AZ IN RECENT
SATELLITE IMAGERY.  RADAR INDICATES THAT THE FIRST COUPLE SHOWERS
APPEAR TO BE DEVELOPING NEAR THE AZ/NM BORDER.  PRECIPITABLE WATER
VALUES ARE 1-2" ACROSS THE REGION, 3-4 SIGMAS ABOVE THE MEAN FOR
LATE JUNE.  INFLOW AT 700 HPA IS EAST-SOUTHEAST AT 15 KTS, WHICH
IS ABOVE THE MAGNITUDE OF THE MEAN 850-400 HPA WIND.  MLCAPES ARE
500-1500 J/KG, AND CIN IS ERODING FROM EAST TO WEST PER SPC
MESOANALYSES.

THERE IS A MODEST BUT GROWING SIGNAL WITHIN THE CAM/MESOSCALE
GUIDANCE FOR LOCALLY HEAVY RAINFALL IN THIS REGION.  MLCAPES ARE
EXPECTED TO GROW PAST 2000 J/KG, WHICH SHOULD ALLOW CONVECTION TO
EXPAND IN INTENSITY AND COVERAGE.  RAP FORECASTS OF THE 700 HPA
ZONE OF CYCLONIC WIND SHEAR SUGGEST ACTIVITY COULD MOVE AS FAR
WEST AS THE CENTRAL AZ/MEXICO BORDER.  THE 12Z GFS-BASED
GALVEZ-DAVISON INDEX INDICATES VALUES RISING TO ABOVE 50 ALONG THE
EASTERN AZ/MEXICO BORDER, INDICATIVE OF SCATTERED TO NUMEROUS
THUNDERSTORMS.  HOURLY RAIN RATES UP TO 2" ARE POSSIBLE AS THE
CONVECTION SHIFTS WEST TO WEST-SOUTHWEST INTO THE INSTABILITY POOL
FROM THE AZ/NM BORDER AND POTENTIALLY FROM THE RUGGED TOPOGRAPHY
OF SOUTHEAST AZ.  CELL MERGERS AND CELL TRAINING ARE CONSIDERED
THE BIGGEST HEAVY RAIN THREAT.  LOCAL AMOUNTS OF 2-4" ARE
CONSIDERED POSSIBLE, MOST IN LINE WITH THE 12Z SPC WRF GUIDANCE. 
THE 06Z SSEO NEIGHBORHOOD PROBABILITIES SUGGEST CONVECTION SHOULD
REACH ITS PEAK IN THE 18-00Z TIME FRAME.

ROTH

ATTN...WFO...ABQ...EPZ...FGZ...PSR...TWC...

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

LAT...LON   34230936 33100884 31900902 31250907 31250981 
            31261110 31601223 31921272 32811248 33681116