Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0255 PM CDT Thu Oct 22 2026
Valid 222000Z - 231200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS
ARIZONA/WESTERN NEW MEXICO AND THE FOUR CORNERS...
...SUMMARY...
Scattered severe thunderstorms remain possible across the Southwest,
with the most intense cells expected across parts of Arizona and
western New Mexico this afternoon and evening. Large hail, damaging
winds, and a few tornadoes are all possible.
...20z Update...
Convective coverage has increased across portions of
eastern/northeastern Arizona over the past couple of hours, with
widely scattered supercell structures noted through the
morning/early afternoon via regional radar imagery. Expectations
remain generally unchanged regarding the evolution of this
convection and the associated severe threat across much of eastern
Arizona/western New Mexico and the Four Corners region. Thus, no
changes were made to the primary risk area.
Along the periphery, a minor eastward expansion of the existing
Level 1/Marginal Risk was made along the central CO/NM border where
some low-probability potential for mainly damaging wind gusts may
persist farther eastward. Elsewhere, only minor adjustments were
made to the General Thunder area, including some trimming along the
California coastline to the west of the mid/upper trough axis. See
the previous discussion and MCD #2399 for additional information.
..Chalmers.. 10/22/2026
.PREV DISCUSSION... /ISSUED 1141 AM CDT Thu Oct 22 2026/
...Arizona/Four Corners and Great Basin...
Another active and relatively rare setup from a climatological
perspective continues regionally, and will tend to shift
east-northeastward through the afternoon and evening. This will be
as the upper low in vicinity of the SoCal coast continues to become
more northeastward progressive today, reaching portions of the Great
Basin and lower Colorado River Valley by this evening.
Scenario will continue to favor supercells, particularly for eastern
Arizona and western New Mexico from a longer-duration and tornado
perspective, as low-level winds otherwise will tend to take on more
of a westerly component over time farther west across Arizona as the
upper trough approaches. Severe probabilities have been
increased/expanded northward toward the Four Corners/Colorado
Plateau vicinity, where an atypically rare setup of
deep-layer/low-level shear coincident with modest but adequate
severe-conducive degree of destabilization is expected.
As compared to yesterday, a greater coverage of storms will likely
exist by later today/afternoon, which may mean a less-discrete
nature of the supercells, but with more numerous
severe-caliber/supercell storms capable of large hail, damaging
winds and a tornado risk. Recent Tucson WSR-88D VWP data still
reflects strong low-level shear/SRH and (splitting)
supercell-favorable deep-layer wind profiles, with the probability
that tornado potential will probably maximize across eastern
Arizona/far western New Mexico this afternoon into evening,
especially where topography influences a low-level easterly wind
component. Large hail will be associated with both left-moving and
right-moving supercells.
Farther north-northwest into the Great Basin, both low-level
moisture and related MLCAPE are generally more limited. Even so,
multiple corridors of isolated severe hail/wind and brief tornado
potential will exist this afternoon. This will be as semi-low-topped
convection develops ahead of the eastward-translating upper
trough/low amid strong southerly flow/shear through much of the
troposphere.
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