734
AWUS01 KWNH 290854
FFGMPD
TXZ000-NMZ000-AZZ000-291445-

Mesoscale Precipitation Discussion 1395
NWS Weather Prediction Center College Park MD
453 AM EDT Tue Sep 29 2026

Areas affected...Southeast Arizona and Southern New Mexico

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

Valid 290852Z - 291445Z

Summary...Showers and thunderstorms will slowly expand across
southeast Arizona and southern New Mexico overnight. Hourly
rainfall of 1 inch is possible in stronger cells, which may lead
to flash flooding.

Discussion...GOES-E IR imagery tonight depicts pockets of cooling
cloud tops accompanying thunderstorm development from southern
Arizona into southern New Mexico. This activity is blossoming in
response to increasing deep layer ascent through diffluence along
the approaching upper jet streak pivoting to the northeast
overlapping convergence on the northern periphery of modest 10-15
kts 850mb winds. This region is positioned within an impressive
moisture plume noted via CIRA 700-500mb and 500-300mb LPWs that
are approaching the 99th percentile, coincident with deeply
saturated soundings on the 00Z RAOBs from ABQ and EPZ. Despite
modest MUCAPE which has been generally less than 500 J/kg to slow
convective development in this area tonight, a subtle surge has
begun to lift north, which within this extremely moist column is
sufficient to drive increasing LightningCast probabilities and be
the impetus for this new convective development.

While the CAMs are only modestly excited about overnight
convection in south-central New Mexico, both HREF and REFS
probabilities have an increased signal farther west. This is
likely due to more pronounced ascent (closer to the upper jet
core) occurring within a stronger draw of instability from the
south, and the CAMs indicate widespread thunderstorms by morning
in SE Arizona and SW New Mexico. This widespread activity is
formed through a combination of storms advecting in from the west,
as well as additional development occurring near the Sonora
/Chihuahua borders.

This more impressive signal from SW Arizona through SW New Mexico
is also reflected by the higher probability (10-30% from the REFS
and HREF) for hourly rainfall up to 1 inch, and these cells may
exhibit short-duration training thanks to modest organization on
30-40 kts of bulk shear and aligned mean winds/propagation
vectors. While these rates themselves could be sufficient to
overwhelm the soils (0-40cm soil moisture above the 98th
percentile and accompanying 1-hr FFG as low as 0.75"), any
training could produce locally as much as 3" of rain (10% chance)
which would enhance the flash flood risk. While the greatest risk
overnight appears to be across SE Arizona and SW New Mexico, the
vulnerability of the soils across this entire region indicates
that any intense rain could quickly become runoff leading to flash
flood impacts.

Weiss

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

ATTN...WFO...ABQ...EPZ...FGZ...MAF...PSR...TWC...

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

LAT...LON   34330669 34260547 33790439 33180389 32460396
            31860467 31460558 31160692 31190893 31191088
            31421175 31741225 32561130 33800964 34210816