537
AWUS01 KWNH 102359
FFGMPD
AZZ000-NVZ000-CAZ000-110530-
MESOSCALE PRECIPITATION DISCUSSION 1474
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
758 PM EDT SAT OCT 10 2026
AREAS AFFECTED...SOUTHERN CA...WESTERN AZ...FAR SOUTHERN NV
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 110000Z - 110530Z
SUMMARY...SCATTERED THUNDERSTORMS AHEAD OF TROPICAL STORM RACHEL
WILL PRODUCE UP TO 2"/HR MAXIMUM RAINFALL RATES AND MAY CAUSE
AREAS OF FLASH FLOODING THIS EVENING.
DISCUSSION...TROPICAL STORM RACHEL CONTINUES TO UNDERGO
EXTRATROPICAL TRANSITION AHEAD OF A CLOSED LOW TO THE WEST OF ITS
CIRCULATION. AS RACHEL'S MID-LEVEL CIRCULATION IS CAPTURED BY THE
CLOSED LOW THIS EVENING, RACHEL'S 500MB CENTER WILL BE DIRECTED
ALMOST DUE NORTH JUST WEST OF TIJUANA WHILE 200-500MB HEIGHTS
ALOFT BECOME NEGATIVELY TILTED, MAXIMIZING UPPER-LEVEL DIVERGENCE
OVER SOUTHERN CA. AT THE SAME TIME, RACHEL'S APPROACH WILL
ACCELERATE THE IVTS ALOFT TO EXCEPTIONALLY STRONG LEVELS FROM THE
PENINSULAR RANGE ON EAST THROUGHOUT THE LOWER COLORADO RIVER
VALLEY. BY 06Z TONIGHT, NAEFS SHOWS IVT VALUES >750 KG/M/S OVER
YUMA ON NORTH ALONG THE COLORADO RIVER, WHICH WOULD SURPASS THE
HIGHEST OBSERVED IVT VALUES FOR THIS TIME OF YEAR IN THE CFSR
CLIMATOLOGY (1979-2009). PLUS, THE ECMWF SHOW PWS THAT COULD
CHALLENGE MONTHLY RECORDS IN SOUTHERN CA AS RACHEL'S REMNANT
CIRCULATION MOVES ASHORE TONIGHT. PWS OVER 1.5" WILL BE COMMON,
WHICH ARE IN EXCESS OF THE 99.5 CLIMATOLOGICAL PERCENTILE
THROUGHOUT ALL OF SOUTHERN CA AND THE NORTHERN TWO-THIRDS OF AZ
THIS EVENING.
THESE PARAMETERS ALL HIGHLIGHT A REMARKABLE SOURCE OF MOISTURE
OVER THE DESERT SOUTHWEST FOR OCTOBER, THAT ALSO HAPPENED TO BE
PAIRED WITH RISING MUCAPE. RAP MESOANALYSIS SHOWS 200-400 J/KG OF
MUCAPE RISES OVER THE PAST 3-HOURS OVER THE LOWER CO RIVER VALLEY.
MUCAPE WITHIN THE HIGHLIGHTED AREAS ALONG AND EAST OF THE
PENINSULAR RANGE WILL RESIDE BETWEEN 500-1,000 J/KG, PROVIDING
SUFFICIENT INSTABILITY FOR STORMS WITHIN THIS MOIST OF AN
ENVIRONMENT TO PRODUCE 1.5-2.0"/HR RAINFALL RATES. STORMS
PERCOLATING OVER THE GULF OF CALIFORNIA WILL HAVE THE ABILITY TO
DRIFT NORTH INTO FAR SOUTHERN CA AND WESTERN AZ THANKS TO >30 KTS
OF EFFECTIVE BULK SHEAR AS WELL, HELPING TO SUSTAIN THESE STORMS
EVEN AS THEY EXIT THE HIGHER THETA-E ENVIRONMENT TO THE SOUTH.
WITH REPEATED ROUNDS OF STORMS TRACKING OVER AREAS THAT HAVE
ALREADY DEALT WITH ROUNDS OF STORMS THIS AFTERNOON, SOME SOILS
WILL BECOME MORE SATURATED AND AT-RISK FOR FLASH FLOODING THIS
EVENING. POOR DRAINAGE AREAS, RUGGED/STEEP TERRAIN, AND DRY WASHES
ARE ALSO VULNERABLE TO FLASH FLOODING THIS EVENING.
MULLINAX
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...PSR...SGX...VEF...
ATTN...RFC...RSA...STR...NWC...
LAT...LON 35781436 35761408 35471356 34721338 33611348
33231359 32621394 32301444 32311511 32311586
32281661 32451722 32741749 33111734 33631684
34201668 34691633 35151575 35561512
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