MESOSCALE PRECIPITATION DISCUSSION 0587
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
710 PM EDT SUN OCT 18 2015
 
AREAS AFFECTED...S ARIZONA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 182311Z - 190311Z
 
SUMMARY...MARGINAL ISOLATED FLASH FLOODING POSSIBLE FOR LOCALIZED
REPEAT DEVELOPMENT.

DISCUSSION...VISIBLE IMAGERY SHOWS CONVECTIVE GROWTH OF LINEAR
CLUSTERS/WEAK WEDGE-LIKE COMPLEXES ACROSS SOUTHERN ARIZONA WITH
NUMEROUS SOUTH TO NORTH TCU/CU FEEDER LINES OUT OF
MEXICO...INDICATING CONTINUED POTENTIAL FOR REPEAT OR BACKBUILDING
DEVELOPMENT.  VWP SHOWS SUPPORTIVE 30KT INFLOW AT 7H WITH MODERATE
MOISTURE FLUX IN THE MID-LEVELS TO SUPPORT MODERATE RAINFALL
PRODUCTION IN THE 700-500MB LAYER WHERE PW VALUES OF .4-.6  ARE
INDICATED USING CIRA LAYERED TPW LOOP WITH TOTALS NEAR 1.0".

MITIGATING FACTOR IS THE 25-30F DEWPOINT DEPRESSIONS...WHICH WOULD
BE MORE SUPPORTIVE OF STRONGER DOWNDRAFTS.  HOWEVER...GIVEN
UPSTREAM S/W ENERGY AND CURRENT MAXIMIZED DIVERGENCE ALOFT TO
MAINTAIN BROAD AREA OF UVVS AND BACKBUILDING... ANY PROLONGED
RAINFALL MAY MOISTEN THE COLUMN ENOUGH TO ALLOW FOR HEAVIER RATES
IN EXCESS OF 1.25"/HR TO LEAD TO ISOLATED FLASH FLOOD PROBLEMS
PARTICULARLY IN HARD PAN AND URBAN SETTINGS. 

WV LOOP/TPW LOOPS DO INDICATE INCREASED MID-LEVEL DRY ADVECTION
WILL ALSO BE PROGRESSING INTO CENTRAL AND SOUTHERN AZ OVER THE
NEXT FEW HOURS...ALSO LIMITING THE WINDOW FOR ISOLATED FLASH FLOOD
THREATS TO THE NEXT 2-4 HOURS (WEST TO EAST ACROSS THE DISCUSSION
AREA).  

GALLINA

 

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

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

LAT...LON   34551095 34110947 33210907 32490921 32010955 
            31391044 31491134 31991214 32641285 33441281 
            34211231