MESOSCALE PRECIPITATION DISCUSSION 0551
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
945 AM EDT MON JUL 24 2017
AREAS AFFECTED...ARIZONA
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY
VALID 241345Z - 241900Z
SUMMARY...SATURATED ENVIRONMENT WITH SLOW CELL MOTIONS POSE FLASH
FLOODING THREAT. GREATEST THREAT ON NORTHERN/EASTERN OUTER BAND
OF SHORTWAVE (ACROSS CENTRAL AZ).
DISCUSSION...EXPERIMENTAL GOES-16 IMAGERY DEPICTS LARGE AREA
ACROSS AZ WHERE SCATTERED CONVECTION IS DEVELOPING. 12Z
74626(PHX) SOUNDING DENOTES NEARLY UNCAPPED HIGHLY SATURATED
ENVIRONMENT WITH 1700 J/KG AND TPWS NEAR 2.25" WHICH IS NEAR ALL
TIME RECORD TPW VALUES FOR THE REGION. ADDITIONALLY WINDS THROUGH
THE CLOUD BARING REGION ARE GENERAL VERY LIGHT. THE ONLY
EXCEPTION IS A SMALL SWLY WIND FLOW NEAR/JUST ABOVE 7H WHICH IS
ALSO SHOWN AT KIWA VWP. THIS CHANNEL OF FLOW SEEMS TO BE ALONG
THE CONFLUENCE ZONE ALONG THE EASTERN QUADRANT OF STRONG EASTERLY
WAVE (MCV) CURRENTLY ENTERING NORTHEAST LA PAZ COUNTY.
ADDITIONALLY...MASS CONVERGENCE FROM THE SWLY FLOW INTO THE SE
QUADRANT/BAND OF THE SHORTWAVE IS CONVECTING ALONG A WSW TO ENE
LINE EXTENDING ACROSS FROM YUMA TO EASTER PINAL. AN ADDITIONAL
CHANNEL OF INCREASED WIND FLOW IS AVAILABLE AT THE TOPS OF THE
CONVECTION NEAR -63C (WHICH IS BEING REACHED BY CONVECTION PER
10.3 IR CHANNEL)...WHERE 15-20 KTS IS AVAILABLE FOR OUTFLOW TO THE
LARGER SCALE ANTICYCLONE CENTERED ALONG THE CENTRAL AZ/NM BORDER)
PROVIDING SUFFICIENT ASCENT/EVACUATION FOR CONVECTIVE MAINTENANCE.
STILL OVERALL CELL MOTIONS AND HIGH RAINFALL EFFICIENCY DUE TO
SATURATED PROFILES WILL SUPPORT RAIN RATES OF 2.0"/HR AS DAYTIME
HEATING INCREASES INSTABILITY LEADING TO FLASH FLOODING POTENTIAL
THROUGHOUT THE SONORAN DESERT/PHOENIX METRO AND SURROUNDING
TERRAIN. GREATEST CONCERN AND POTENTIAL FOR FLASH FLOODING LIKELY
RESIDES IN THE CONFLUENCE BAND CURRENTLY OVER EASTERN
MARICOPA...WHERE WIND PROFILE AND CELL MOTIONS WILL SUPPORT
UPSTREAM DEVELOPMENT. TOWARD THE SOUTHEAST AND ALLOW FOR A
TRAINING ENVIRONMENT TO EXIST INCREASING TOTALS IN THE RANGE OF
2-3" POSSIBLE THROUGH EARLY MORNING. GIVEN PROXIMITY TO RUGGED
TERRAIN INCREASES THE THREAT OF FLASH FLOODING AND MUDSLIDES.
GALLINA
ATTN...WFO...FGZ...PSR...TWC...VEF...
ATTN...RFC...CBRFC...
LAT...LON 36171258 36051033 33761035 32590986 31691003
31681133 32131196 31941357 32541458 33071376
33481335 34211402 35301423
Last Updated: 945 AM EDT MON JUL 24 2017