ACUS11 KWNS 262201
SWOMCD
SPC MCD 262200=20
AZZ000-270000-

Mesoscale Discussion 2133
NWS Storm Prediction Center Norman OK
0500 PM CDT Fri Sep 26 2025

Areas affected...South-central Arizona

Concerning...Severe Thunderstorm Watch 621...

Valid 262200Z - 270000Z

The severe weather threat for Severe Thunderstorm Watch 621
continues.

SUMMARY...Thunderstorms will continue to develop along an outflow
boundary and along a surface trough over the next few hours across south-central Arizona. Instances of large hail and severe gusts
remain possible.

DISCUSSION...Over the past couple of hours, a cold pool has become
increasingly defined in surface observations and radar imagery over
and south of the Phoenix, AZ area. Low-level convergence on the
southern flank of the cold pool continues to promote new
thunderstorm development, and while convection moving over the cold
pool may be elevated in nature, VWP observations from KIWA continues
to sample adequate deep-layer shear for organized convection. Recent
MRMS vertically integrated ice/MESH data has show periodic upticks
in convective intensity capable of supporting severe hail, most
likely between 1-1.5 inches. Continued convective development will
help reinforce the cold pool and promote further southward
propagation into an air mass that has not yet fully overturned
(temperatures remain in the low 90s). Attempts at initiation along a
diffuse surface trough draped to the south of the cold pool are also
noted, but it remains unclear how intense or widespread convection
will become along this boundary. Regardless, additional
strong/severe thunderstorms remain possible for the next few hours
with an attendant threat of hail and perhaps sporadic severe
downburst gusts. Latest CAM guidance suggests that the severe threat
should begin to wane around/after 00-01z as the remaining effective
warm sector is eroded/overturned.

..Moore.. 09/26/2025

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!-dPcq56G3M_7oNpYmUP7B7kJNr-qJ0s6mIIJue4vhBRMdwo0xY7oOd5C13mERF8nISTJISQMT= vTSyXDBpLlxcbwp7ko$ for graphic product...

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

LAT...LON 31801173 32261186 32631214 32811241 33031255 33321247
33591213 33661178 33661145 33611117 33281077 32741030
32461018 32171022 31901037 31561109 31581139 31641162
31801173=20

MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 95 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN


=3D =3D =3D
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