AWUS01 KWNH 241211
FFGMPD
AZZ000-241630-

Mesoscale Precipitation Discussion 1373
NWS Weather Prediction Center College Park MD
810 AM EDT Thu Sep 24 2026

Areas affected...Southwest to West-Central Arizona...

Concerning...Heavy rainfall...Flash flooding possible

Valid 241210Z - 241630Z

SUMMARY...Slow moving clusters of thunderstorms capable of
1-1.25"/hr and spots of 1.5-2" totals pose localized flash
flooding through early morning.

DISCUSSION...GOES WV suite shows a compact shortwave along the
southern AZ, NW Sonora border aiding an outflow channel/jet streak
across western AZ but with weakening convective activity near the
core has resulted in a northward shift providing increased
entrance region divergence across west-central AZ.  VWP shows
700mb convergent anti-cyclonic flow across the same general region
but with 25kts noted at KESX and KFSX slowing through the the area
of concern; this while surface to 850mb flow is weak but highly
confluent out of the Sun Valley westward toward the eastern
portions of the Lower Colorado River Valley.  CIRA LPW notes a
narrow stripe of overlap of enhanced 850-700 and 700-500mb layer
across La Paz to northern Maricopa county locally reaching 1-1.25"
of total PWats; so moisture flux convergence below cloud base
supports the 700mb cloud base inflow for increased rainfall
production, especially given that 700mb flow is about 10-15kts
stronger than expected/forecast in most hi-res CAMs. 

RAP also denotes this cluster of convective development across S
Yavapai/NE La Paz/NW Maricopa county shows some recent erosion of
the weak cap on a 500-750 J/kg MUCAPE to feed the solid vertical
ascent (enhanced by the aforementioned divergence aloft).  The
overlap of these elements has been sufficient but highly
conditional, hence why there is limited support in
evolution/development in the hi-res CAMs.   However, using
forecast fields from the RAP/HRRR combined with current trends,
suggests a few hours of additional maintenance is probable, in the
entrance region to the jet outflow.  Slow south to
south-southwestward propagation is likely given the placement of
the 700-500mb anticyclonic flow and may even encourage some
localized cell mergers.  So with rates up to 1-1.25" possible
given this environment/localized mergers.  Scattered spots of
1.5-2" are not out of the realm of possibility.  Given these rates
and totals are in the range of 1-3hr FFG values and spots of
rocky/limited soil for infiltation an incident or two of
focused/localized flash flooding is possible over the next few
hours.

Gallina


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

ATTN...RFC...STR...NWC...

LAT...LON   34591340 34421239 33701203 33111231 32911291 
            33021383 33531421 34011414 34381395 

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