073
AWUS01 KWNH 070043
FFGMPD
NMZ000-AZZ000-070630-

Mesoscale Precipitation Discussion 1056
NWS Weather Prediction Center College Park MD
843 PM EDT Sat Sep 06 2025

Areas affected...Southern Arizona

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

Valid 070042Z - 070630Z

Summary...Slow moving showers and thunderstorms will continue
across southern Arizona for a few more hours. Heavy rainfall
capable of producing 0.5-0.75 inches in 15 minutes may create
instances of flash flooding.

Discussion...The regional radar mosaic this evening shows
continued development of showers and thunderstorms across much of
Arizona and New Mexico. This convection is forming within
favorable thermodynamics characterized by PWs measured on the TUS
00Z U/A sounding of 1.39 inches (near the 90th percentile for the
date) and 1500 J/kg of SBCAPE. A weak mid-level impulse embedded
in generally westerly flow is helping to drive broad ascent across
the region, while a weak surface convergence axis near the
Mexico/Arizona border, as well as remnant outflow boundaries and
collisions, are aiding to produce the activity this evening.
Although storms moving off the terrain are generally moving
progressively to the E/SE, clusters forming across southern AZ are
slower moving and exhibiting some back building behavior.

As the evening progresses, a local increase in coverage of
convection is progged by many of the available high-res CAMs
across southern Arizona, especially in the vicinity of Pima and
Santa Cruz counties. This will be in response to subtle moisture
convergence on weak 850mb flow along the gradient of some higher
PWs, but also in response to subtle SW drift of convection as
propagation vectors gradually veer into the higher moisture. With
mean 0-6km winds expected to remain light, and propagation vectors
additionally weak, these slow moving storms will linger across
some areas despite being of the pulse variety. The 15-min HRRR and
HRRR forced UA WRF both suggest intense rainfall could reach
0.75"/15 mins, which is additionally supported by 5-10%
neighborhood probabilities for 2"/hr from the HREF. Where these
storms linger, or where multiple rounds can occur, locally as much
as 2-3" of rainfall is possible.

0-10cm soil moisture across southern Arizona is generally below
normal according to NASA SPoRT, although there are some pockets of
wetter soils across the area. Regardless, if these intense rain
rates move atop the natural vulnerability of this region,
especially across any burn scars, urban areas, or sensitive
terrain, instances of flash flooding could result until convective
overturning occurs around 06Z.


Weiss

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

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

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

LAT...LON   32831100 32830976 32590916 32310900 31800895
            31390918 31080985 30971061 31141135 31381192
            31621251 31921300 32251350 32701352 32781264