MESOSCALE PRECIPITATION DISCUSSION 0583
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
448 PM EDT SAT OCT 17 2015
 
AREAS AFFECTED...ARIZONA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 172047Z - 180117Z
 
SUMMARY...OVERALL CONVECTIVE COVERAGE AND INTENSITY INCREASING
WITH SOME SLOW CELL MOTIONS CAPABLE OF ISOLATED TOTALS CAPABLE OF
LOCALIZED FLASH FLOODING

DISCUSSION...VISIBLE AND IR IMAGERY SHOW INCREASING TCU AND CBS
NORTH AND EAST OF AN ELONGATED NW TO SE UPPER LEVEL CYCLONE WITH
THE APEX NEAR PHX EXTENDING INTO E SONORA. THIS HAS ALLOWED FOR A
SHORTWAVE RIDGE NEAR THIS APEX EXTENDING NEARLY EAST.  THIS ALLOWS
FOR A COL IN FLOW FOR SLOW MOVING CELLS AS WELL AS A NARROW
OUTFLOW CHANNEL TOWARD THE SOUTH FOR ACTIVE CONVECTION OVER SE
MOHAVE/NE LA PAZ COUNTY...TO MAINTAIN MODERATE UVVS FOR ADDITIONAL
CONVECTION TO DEVELOP UPSTREAM AS THE LOW LEVEL CORES MOVE
NORTHWARD...THOUGH THIS INCREASED VERTICAL TILT TO THE CONVECTION
SHOULD MODERATE CELL EFFICIENCY FOR HIGH TOTALS UNLESS UPSTREAM
DEVELOP REDEVELOPS OR TRAINS OVER THE SAME TRACKS...WHICH APPEARS
A BIT UNLIKELY BUT NOT OUT OF THE REALM OF POSSIBILITY FOR SOME
SPARSE TOTALS IN EXCESS OF 1.5".

FURTHER SOUTHEAST OVER SOUTHERN AND SE ARIZONA...STRENGTHENING LOW
LEVEL FLOW FROM THE EAST WITH 20-25KTS AT 85H FROM THE ESE AND
15-20KTS OF S 7H FLOW...LEADS TO MODERATE MOISTURE FLUX AND DEEP
MOISTURE CONVERGENCE...FROM SANTA CRUZ/E PIMA INTO PINAL COUNTIES.
 UPPER LEVEL DIVERGENCE IS MAXIMIZED IN THIS LOCATION PER RAP
ANALYSIS AS THE TILT OF THE TROF IS NEGATIVE.  AT THIS TIME
SBCAPES ARE INCREASING TO THE 1000-1500 J/KG RANGE PER GOES
SOUNDER WITH A BIT OF CONTINUED WEAK CINH.  AT THIS TIME COOLING
AND HIGH DIFFERENTIAL VERTICAL THETA-E AIR/STEEP LAPSE RATES ARE A
LIMITING FACTOR WITH A HIGH PROBABILITY OF COLD POOLS/DOWNDRAFT
DOMINANCE. BEST MOISTURE TO SUPPORT MORE SUSTAINED UPDRAFTS ARE
LIKELY TO BE FURTHER SOUTHEAST INTO MEXICO BUT SHORT BURST RATES
WITH TOTALS OF .75-1.25" IN A SHORT DURATION COULD POSE ISOLATED
FLASH FLOODING THREATS IN THIS VICINITY AS WELL. 

HI-RES MODELS CONTINUE TO SUPPORT THIS IDEA OF SCATTERED/ISOLATED
HIGH TOTALS IN THE 1-2" RANGE CAPABLE OF FLASH FLOODING. OVERALL
CONFIDENCE IN PIN POINTING EXACT LOCATIONS OR LARGER AREAL THREAT
IS FAIRLY LOW.  

PLEASE REFER TO SPENES ISSUED AT 1714Z FOR ADDITIONAL DETAILS

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

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

LAT...LON   35751325 34981124 33891018 31990940 31310969 
            31281086 31561200 32121254 33071258 33941313 
            34251366 34861400