655
AWUS01 KWNH 130018
FFGMPD
NMZ000-AZZ000-130515-

Mesoscale Precipitation Discussion 1191
NWS Weather Prediction Center College Park MD
815 PM EDT Sun Oct 12 2025

Areas affected...Southern AZ

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

Valid 130015Z - 130515Z

SUMMARY...Scattered areas of heavy showers and thunderstorms are
expected to continue through the evening hours. Additional areas
of flash flooding will be possible.

DISCUSSION...There continues to be the redevelopment of locally
heavy showers and thunderstorms across much of southern AZ, with
the late-day GOES-W IR satellite imagery showing scattered areas
of moderately cold-topped convection. The activity continues to be
fostered by an unstable and moist boundary layer characterized by
MLCAPE values of 1000 to 2000 J/kg along with presence of
favorable right-entrance region upper-level jet dynamics.

Moisture remains well-entrenched across the region with PWs of
1.25 to 1.5+ inches which for this time of the year are a solid 3
to 4 standard deviations above normal. Some of the moisture at
least in the low-levels across southern AZ is being aided by
southerly flow off the very warm and moist northern Gulf of CA
which has been facilitated by placement of a weak area of low
pressure and an associated surface trough.

This moisture coupled with the instability continues to support
convection capable of producing high rainfall rates of 1 to 2
inches/hour. Additionally, there is a fair amount of effective
bulk shear overhead with magnitudes of 30 to 40+ kts. This coupled
with the instability has been yielding some organized convective
structures with enhanced updrafts and thus sustainment of heavier
rainfall rates.

The loss of daytime heating suggests at least a gradual weakening
trend of convection by later this evening, but at least for the
near-term, there should continue to be sufficient levels of at
least modest deep layer jet-aided ascent and instability for
scattered showers and thunderstorms to persist. Local orographics
involving areas of terrain will also facilitate pockets of
convective sustenance.

Additional rainfall totals by late this evening may reach 2+
inches where any convective cells persist or locally repeat over
the same area. This may drive some additional pockets of flash
flooding which will mainly be a concern for the normally dry
washes, but could also involve some localized urban impacts around
the Tucson metropolitan area.

Orrison

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...EPZ...PSR...TWC...

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

LAT...LON   32860959 32520906 31880894 31470910 31220981
            31221119 31341186 31741295 32181308 32541273
            32661217 32671099