797
AWUS01 KWNH 110458
FFGMPD
AZZ000-NVZ000-CAZ000-111100-
MESOSCALE PRECIPITATION DISCUSSION 1476
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1257 AM EDT SUN OCT 11 2026
AREAS AFFECTED...SOUTHERN CALIFORNIA...SOUTHERN NEVADA...WESTERN
ARIZONA...
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY
VALID 110500Z - 111100Z
SUMMARY...POST T.C. RACHEL
DISCUSSION...INNER CORE OF POST T.C. RACHEL IS CONTINUING TO
WEAKEN FROM SMALL EMBEDDED CONVECTIVE ELEMENTS INTO A BROADER
SHIELD OF MODERATE PRECIPITATION ALONG THE DOWNSHEAR NORTHERN EDGE
COMING INTO FAR SW CALIFORNIA. HOWEVER, SOME VORTICITY STRETCHING
AND LOCALIZED CONVERGENT SURFACE TO BOUNDARY LAYER CONVERGENCE
RESPONSE IS STARTING IN EARNEST ALONG THE EASTERN SLOPES OF THE
PENINSULAR RANGE AS A SURFACE LOW SPREADS/STRETCHES THROUGH IN THE
LOWER COLORADO RIVER VALLEY. CONDITIONALLY UNSTABLE AIR SUPPORTED
BY THE WARM SHALLOW SEAS OF THE GULF OF CALIFORNIA ARE DRAWN
NORTHWARD AS MLCAPES INCREASE AS WEAK CAA ALOFT SPREADS ACROSS THE
LOWER COLORADO AS WELL; RAISING FROM 500 J/KG TOWARD 750-1000 J/KG
BY 08Z ACROSS SW AZ. MID-LEVEL VORTICITY CENTER IS ALSO ROUNDING
THE EASTERN SIDE OF THE DEEPER CYCLONE AND DPVA IS HELPING TO
SHARPEN AN DEFORMATION ZONE/ISENTROPIC BOUNDARY FROM THE CENTER OF
RACHEL THROUGH THE INLAND EMPIRE TOWARD SOUTHERN NEVADA. DEEP
LAYER CONVERGENCE FROM THE SOUTHEAST WILL FURTHER HELP TO EXPAND
THE CONVECTIVE CLUSTER CURRENTLY OVER NORTHERN BAJA CALIFORNIA
THROUGH THE INLAND EMPIRE. TOTAL MOISTURE HAS ALSO INCREASED
TOWARD 1.75" THOUGH CIRA LVT IN THE 850-700MB LAYER RANGES FROM
150-200 KG/M/S STARTING TO ENTER FAR SE CA/SW AZ. AS SUCH RATES
OF 1-1.5"/HR ARE BECOMING INCREASINGLY POSSIBLE ESPECIALLY GIVEN
ANY AID FROM UPSLOPE ALONG THE EASTERN PORTIONS OF THE PENINSULAR
RANGES. AS SUCH LOCALIZED TOTALS OF 1.5-2.5" IS BECOMING PROBABLE
THOUGH AN ISOLATED 3" TOTAL IS POSSIBLE AND LIKELY TO INDUCE
LOCALIZED FLASH FLOODING GIVEN 3-6HR FFG VALUES ARE GENERALLY
2-2.25".
FURTHER DOWNSTREAM, AS HEIGHT-FALLS CONTINUE FROM SW TO NE AND THE
DEFORMATION ZONE/FGEN SURFACE BEGINS TO SHARPEN THROUGH S NV;
SCATTERED NARROW THUNDERSTORMS WILL DEVELOP BUT FURTHER PROXIMITY
FROM THE LOW, CELL MOTIONS WILL BE MORE SOUTH TO NORTH OR SSE TO
NNW ACROSS E RIVERSIDE/SAN BERNADINO AND INTO W AZ. STRONGER
INSTABILITY AND INCREASING WIND SPEEDS UPSTREAM WILL HELP FOSTER
POTENTIAL FOR BACK-BUILDING AND THEREFORE SHORT PERIODS OF
REPEATING/TRAINING MAY ALLOW FOR SOME LOCALIZED .5-1" TOTALS
EVENTUALLY INTO S NV. THIS MAY EVEN INTERSECT URBAN LAS
VEGAS/HENDERSON AND WHICH WOULD BE PARTICULARLY CONCERNING BUT
OVERALL CONFIDENCE IN A SPECIFIC CELL OR TWO TO CROSS THE URBAN
CENTER IS STILL HARD TO LOCK DOWN GIVEN WIDELY SCATTERED TO
SCATTERED EXPECTED COVERAGE OVER THE NEXT 4-6HRS OR SO.
A MORE ISOLATED NATURE WITH EFFECTIVE WARM SECTOR WEAKLY ROTATING
CELLS MAY ALSO MANIFEST OVER THE LOW DESERTS, PERHAPS EVEN SUN
VALLEY OF WESTERNN AND SOUTH-CENTRAL AZ, EVENTUALLY TOWARD THE
WESTERN MOGOLLON RIM AREAS OF YAVAPAI AND MOHAVE COUNTIES. WHILE
MORE ISOLATED, THE STRONGER UPDRAFT ROTATIONS MAY ALSO RESULT IN
BROADER UPDRAFT/DOWNDRAFTS TO INCREASE RESIDENCY TIME (ALONG WITH
REDUCED FORWARD SPEED FROM CELL ROTATION). ISOLATED SPOTS MAY
RESULT IN LOCALIZED FLASH FLOODING CONDITIONS ACROSS THIS AREA AS
WELL.
GALLINA
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...FGZ...PSR...SGX...TWC...VEF...
ATTN...RFC...RSA...STR...NWC...
LAT...LON 37101508 36981411 36311257 34971184 33651160
32261168 31591214 32131379 32201419 32461505
32481611 32451707 32981745 33801750 35241704
36441630
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page