046
AWUS01 KWNH 111700
FFGMPD
AZZ000-UTZ000-NVZ000-CAZ000-112300-
MESOSCALE PRECIPITATION DISCUSSION 1480
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1259 PM EDT SUN OCT 11 2026
AREAS AFFECTED...SOUTHERN UT...NORTHERN AZ...SOUTHEAST
CA...SOUTHERN NV
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY
VALID 111700Z - 112300Z
SUMMARY...POST-T.C. RACHEL AND AN AMPLIFYING LONGWAVE TROUGH OVER
THE WEST COAST WILL DIRECT EXCEPTIONAL AMOUNTS OF MOISTURE OVER
THE INTERIOR SOUTHWEST TODAY. ADDITIONAL FLASH FLOODING IS LIKELY
WITH THUNDERSTORMS CAPABLE OF PRODUCING BETWEEN 1-2"/HR RAINFALL
RATES. LOCALLY SIGNIFICANT AND LIFE-THREATENING FLASH FLOODING IS
POSSIBLE.
DISCUSSION...GOES SATELLITE IS TELLING QUITE AN ACTIVE STORY THIS
MORNING WITH RACHEL'S MOISTURE NOW FULLY MERGED WITH A ROBUST
UPPER-LEVEL TROUGH IN THE WEST. 12Z SOUNDINGS FROM A PAIR OF
SOUTHWEST SITES (LAS VEGAS, SAN DIEGO) ALL SHOWED HIGHLY SATURATED
ATMOSPHERIC PROFILES WITH PWS THAT WERE ABOVE THE 99.5
CLIMATOLOGICAL PERCENTILE. VISIBLE SATELLITE SHOWED SOLID SURFACE
BASED HEATING GETTING UNDERWAY IN SOUTHERN AZ AND EVEN IN PORTIONS
OF NORTH-CENTRAL AZ, WHERE INSTABILITY WILL GRADUALLY INCREASE
THIS MORNING. RAP MESOANALYSIS SHOWS >400 J/KG OF SBCAPE HAS
ALREADY STARTED TO DEVELOP OVER MUCH OF AZ. STRONG SOUTHERLY FLOW
OVER AZ AND INTO SOUTHERN UT IS ALSO AIDING IN UPSLOPE ENHANCED
RAINFALL RATES, WHICH PER MRMS 15-MINUTE RAINFALL RATES, SUGGEST
JUST UNDER 1"/HR RAINFALL RATES HAVE OCCURRED SOUTH AND EAST OF
FLAGSTAFF.
AS INSTABILITY INCREASES, SO TOO WILL THE RAINFALL RATES. THE
CONFIDENCE IN INCREASING RAINFALL RATES IS HELPED BY A HIGHLY
ANOMALOUS VAPOR MOISTURE TRANSPORT ALOFT. BOTH ECMWF AND NAEFS
SATS SHOW IVTS APPROACHING 750 KG/M/S, WHICH IS SURPASSING THE
MAXIMUM OBSERVED IVTS IN THE CFSR DATABASE (1979-2009). THIS IS
LARGELY DUE TO SWRLY 850-700MB WIND THAT ARE ABOVE THE 99TH
CLIMATOLOGICAL PERCENTILE, SIGNIFICANTLY INFLUENCING BOTH THE
MOISTURE TRANSPORT AND UPSLOPE ENHANCEMENT.
COMBINED WITH SOILS THAT ARE BECOMING OVERLY SATURATED WITH EACH
PASSING HEAVY SHOWER AND THUNDERSTORM, THE SETUP IS THERE FOR MORE
AREAS OF FLASH FLOODING TODAY. THE LATEST 12Z HREF PROBABILITIES
SHOW A CONCERNING SIGNAL FOR 35-45% ODDS FOR 6-HR QPF > 100YR ARIS
AROUND ZION NAT'L PARK BETWEEN 18-00Z THIS AFTERNOON. THE 15Z WOFS
SHOW THUNDERSTORMS CAPABLE OF PRODUCING 0.1-0.2"/5-MINUTE RAINFALL
RATES, INDICATING THE POTENTIAL FOR HOURLY RATES AS HIGH AS 2"/HR
SOUTH AND WEST OF THE MOGOLLON RIM AND ON TO THE LOWER CO VALLEY.
THESE PARAMETERS AND SIGNALS ALL CONCLUDE THAT ADDITIONAL AREAS OF
FLASH FLOODING ARE LIKELY TODAY, AND BOTH SIGNIFICANT AND
LIFE-THREATENING FLOODING IS POSSIBLE.
MULLINAX
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...FGZ...GJT...PSR...SLC...VEF...
ATTN...RFC...RSA...STR...NWC...
LAT...LON 38501167 38421023 38260955 37740918 36360961
35030935 34380997 34041067 34021111 33941167
33801236 33641322 33271382 33261433 33411464
33801498 34201542 34621568 35011609 35651605
36781584 37621537 38281429 38411304
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