576
ACUS02 KWNS 121649
SWODY2
SPC AC 121648

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1048 AM CST Wed Nov 12 2025

Valid 131200Z - 141200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The risk for thunderstorms appears negligible across much of the
U.S. Thursday through Thursday night.

...Discussion...
With a blocking high likely to be maintained near/offshore of the
Greenland Atlantic coast, there likely will be little change to the
large-scale pattern across eastern North America into the Atlantic
through this period.  Upstream, flow is forecast to remain more
progressive, at least across the northern mid-latitudes of the
Pacific into North America.

Within the latter regime, models continue to indicate that the
northern portion of a splitting trough will advance inland of the
British Columbia and adjacent Pacific Northwest coast, providing
support for significant surface cyclogenesis across the Canadian
Prairies Thursday through Thursday night.  Some deepening of surface
troughing to the lee of the Rockies appears possible as far south as
southern portions of the high plains.  However, guidance suggests
that boundary-layer modification across the northwestern Gulf Basin
is not likely to yield a sufficiently moist return flow to support
destabilization conducive to thunderstorm development, beneath a
warming mid-level environment across the southern Rockies through
Great Plains.

Across the southern mid-latitudes of the eastern Pacific, there
remains more notable spread within/among the model output concerning
the evolution of smaller-scale developments within the southern
portion of the splitting mid/upper troughing.  However, it still
appears that an initially deep associated surface cyclone will
undergo rapid weakening offshore of the southern Oregon/northern
California coast, while the gradually warming mid-level cold core
continues to dig well offshore of the central/southern California
coast.

...California...
With the modifying and increasingly modest mid-level cold core
forecast to dig offshore, the development of thermodynamic profiles
potentially conducive to an appreciable risk for convection capable
of producing lightning (i.e., 10 percent or greater probabilities)
remains unclear.  However, high resolution, convection allowing
ensemble output and related guidance suggest at least minimal,
though diminishing, probabilities for a few pre-frontal
thunderstorms may be maintained across and just inland of the
northern/central California coast at the outset of the period.

Despite the modest mid-level cooling, a narrow plume of better
low-level moisture return ahead of the occluding, inland advancing
frontal zone may contribute to weak CAPE and thermodynamic profiles
marginally conducive to charge separation in the more vigorous
convective development.  Given the modest to weak mid/upper forcing
for ascent, and elevated nature of the potentially unstable
low-level moisture return above at least a shallow residual surface
stable layer across the interior valleys, HREF calibrated
thunderstorm probabilities appear overdone for Thursday afternoon
into Thursday night.  However, orographic forcing, aided by strong
southerly to southwesterly low-level flow impinging on the higher
terrain of the Siskiyous/Mount Shasta vicinity into the Sierra
Nevada, might contribute to convective development occasionally
becoming capable of producing lightning, perhaps most concentrated
west/northwest of Lake Tahoe into the Yosemite vicinity.

..Kerr.. 11/12/2025

$$