Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0751 AM CDT Tue Sep 29 2026

Valid 291300Z - 301200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN
ARIZONA/NEW MEXICO TO WEST TEXAS...

...SUMMARY...
Isolated severe thunderstorm wind gusts and possibly a tornado or
two could occur this afternoon into tonight from southern and
eastern New Mexico into west Texas, and across southeast Arizona.

...Synopsis...
A mid/upper-level low and attendant trough will move across the
Desert Southwest through the period. In response to the approaching
deep trough, Hurricane Polo is forecast to move from the Gulf of
California into Sonora this morning. While the tropical cyclone is
forecast to weaken over the mountainous terrain of northern Mexico
later today, a phasing of the mid-level remnants of Polo with the
approaching deep mid/upper-level trough will result in a
consolidating surface low that is forecast to deepen and move across
eastern New Mexico and west Texas tonight.

...Southern/eastern New Mexico to west Texas...
Widespread convection is ongoing and expected to generally continue
into this afternoon and tonight from southern/eastern New Mexico to
west Texas, as increasing large-scale ascent overspreads a very
moist environment. The influence of the remnant tropical system will
result in poor mid-level lapse rates, but increasing deep-layer
flow/shear and enlarging low-level hodographs will favor some storm
organization, especially later this afternoon and evening. The
widespread storm coverage will result in a tendency toward complex
or linear storm modes with time, though a few/episodic supercells
will also be possible. The weak lapse rates and modest buoyancy are
expected to limit the overall magnitude of severe potential, but a
localized tornado and severe-gust threat could accompany any
organized storm structures, particularly this afternoon and evening,
influenced by a nocturnally strengthening low-level jet.

...Southern Arizona...
A moist environment resides in close proximity to the Southwest
Deserts mid/upper-level low, with a belt of very strong deep-layer
winds sampled in available 12z upper-air data and regional WSR-88D
VWPs. Scattered thunderstorms are common this morning, and while
this convection/related cloud cover will generally hinder overall
destabilization, modest diurnal heating will probably lead to some
convective intensification during the day. The strong nature of the
wind profiles could support a few at least weak/transient
supercells, and potentially more organized convective bands later
today, with at least some potential for strong thunderstorm winds
and mostly sub-severe hail.

..Guyer/Bentley.. 09/29/2026

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1120 AM CDT Tue Sep 29 2026

Valid 291630Z - 301200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTHERN
ARIZONA ACROSS SOUTHERN/EASTERN NEW MEXICO INTO WEST TEXAS...

...SUMMARY...
Isolated severe thunderstorm wind gusts and possibly a tornado or
two could occur this afternoon into tonight from southeast Arizona
across southern and eastern New Mexico into west Texas.

...Synopsis...
Fairly complex synoptic evolution is anticipated today through
tonight as a remnants of what is currently Hurricane Polo become
absorbed within the circulation of the deepening mid-latitude
cyclone currently centered over the Lower CO River Valley. In
general, the Lower CO River Valley cyclone is forecast to deepen as
it gradually shifts eastward. In response, Hurricane Polo is
forecast to move quickly northeastward across Sonora and into New
Mexico. Polo is forecast to weaken over the mountainous terrain of
northern Mexico, but will likely maintain some of its warm-core
characteristics through at least tomorrow morning. Additionally,
mass response across the southern High Plains will result in
increasing low-level moisture advection across the southern Plains
while also aiding in surface cyclogenesis across central and eastern
NM late tonight/early tomorrow.

...Southern Arizona... 
Recent surface analysis reveals a very moist airmass over southern
AZ, with a corridor of mid to upper 60s dewpoints extending from the
central southern border into the Phoenix vicinity. Surface analysis
also places a weak low over south-central AZ. VAD profiles from IWA
and EMX both show fairly long hodographs, supported by 30 to 40 kt
of low/mid-level southwesterly flow. Widespread showers and
thunderstorms will likely continue throughout the day, with limited
diurnal heating and weak tropical lapse rates keeping buoyancy
modest. Even so, the strong nature of the wind profiles could
support a few at least weak/transient supercells, and potentially
more organized convective bands later today, with at least some
potential for strong thunderstorm wind gusts.

...Southern High Plains...
Thunderstorm coverage is expected to increase notably this
afternoon/evening as the core of Polo progresses into the region.
Tropical character of the airmass will keep lapse rates poor while
cloud cover also limits heating, limiting the overall buoyancy.
Nonetheless, buoyant thermodynamic profiles are still expected to
result in updrafts deep enough for lightning production.
Additionally, low-level wind profiles are expected to lengthen
significantly after 00Z as the remnants of Polo interact with a
dynamically strengthening low-level jet. The widespread storm
coverage will result in a tendency toward complex or linear storm
modes with time, though a few/episodic supercells will also be
possible. A brief tornado and/or strong wind gusts could accompany
any organized, more persistent storm structures.

..Mosier/Chalmers.. 09/29/2026

Day 1 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
1120 AM CDT Tue Sep 29 2026

Valid 291700Z - 301200Z

No changes were made to the existing outlook. A localized fire
weather threat within dry northerly flow will evolve across portions
of central Nevada today as a mid/upper low pushes into the
Southwest. Sustained north winds as high as 20 mph with higher gusts
will align with minimum daytime RH of around 15% in valleys by this
afternoon. However, recent but patchy rainfall across the central
Nevada Mountain ranges and marginal fuels precludes introduction of
broader Elevated highlights.

..Williams.. 09/29/2026

.PREV DISCUSSION... /ISSUED 1257 AM CDT Tue Sep 29 2026/

...Synopsis...
A closed mid-level low will continue to traverse the southwestern
CONUS today as the remnants of Hurricane Polo become entrained
within the overall flow, aiding in widespread rainfall from the
Desert Southwest into the central U.S. Meanwhile, surface high
pressure filtering into the Intermountain West will contribute to
dry northerly flow across portions of the Sacramento Valley and
southern California. Farther north, increasing westerly flow aloft
and a tightening surface pressure gradient across the northern
Rockies/High Plains will promote breezy, downslope winds in
north-central Montana.

...Sacramento Valley and Southern California...
Daytime high temperatures in the 90s and RH values of 10-15% are
expected as a strengthening thermal trough induces northerly winds
of 10-15 mph into the Sacramento Valley. Meteorological conditions
amid a drying fuelscape support an Elevated fire weather risk this
afternoon. Northerly, offshore wind trajectories and RH as low as
15% will also impact southern Santa Barbara County, and the
mountains and foothills of Ventura and Los Angeles Counties through
the early afternoon. Wind speeds in favored terrain gaps will
approach 15-20 mph with stronger gusts of 35-45 mph. Thus, Elevated
highlights have been maintained for portions of southern California.

...North-Central Montana...
A region of 50-60 kt mid-level zonal flow atop a tightening surface
pressure gradient across the northern High Plains will contribute to
dry downslope flow over portions of north-central Montana this
afternoon. Westerly surface winds of 15-25 mph and minimum RH of
20-25 percent will overlap drying fuels, promoting an Elevated fire
weather risk.

...Please see www.spc.noaa.gov/fire for graphic product...