SPC AC 130057
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0657 PM CST Wed Nov 12 2025
Valid 130100Z - 131200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Minimal chances of isolated thunderstorms remain possible along the
coast of northern California late tonight/early tomorrow. Severe
weather is unlikely.
...Synopsis...
A deep upper low will approach the West Coast tonight and into
Thursday, with gradual cooling aloft as well as midlevel moistening
and lift. Minimal elevated instability of perhaps 100-200 J/kg may
develop, supporting sporadic lightning flashes as precipitation
develops ahead of the wave overnight into coastal northern
California. Despite strong wind fields, surface-based CAPE will
remain near zero, and as such severe storms are not forecast.
..Jewell.. 11/13/2025
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z
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
WUUS02 PTSDY2
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0700Z
SPC AC 121856
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
1256 PM CST Wed Nov 12 2025
Valid 141200Z - 151200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
The risk for thunderstorms appears negligible across the U.S. Friday
through Friday night.
...Discussion...
As blocking mid/upper ridging remains centered offshore of
southeastern Greenland, models indicate that a broad cyclonic regime
will be maintained to its southwest, centered near the Canadian
Maritimes. Some amplification of large-scale troughing extending
southward offshore of the remainder of the North American Atlantic
coast is forecast, downstream of a significant mid-level trough and
embedded cyclone migrating northeast and east of the Canadian
Prairies, on the leading edge of a more progressive regime.
Upstream, ridging ahead of another short wave trough appears likely
to spread across and inland of the British Columbia/adjacent Pacific
Northwest coast, to the north of an increasingly cut-off low
centered offshore of the central/southern California coast.
...Southern California...
Models indicate that the modifying mid-level cold core (including
coldest 500 mb temperatures warming above -24 C) will generally
remain offshore through this period, tending to pivot away from
central coastal areas while perhaps slowly toward southern coastal
areas late Friday night. While a corridor of continued
low/mid-level moistening along a slow moving, occluded frontal zone
may compensate and contribute to layers of weak conditional
instability inland of southern California coastal into the southern
Sierra Nevada/Mojave Desert vicinity, 10 percent or greater
probabilities for thunderstorms appear generally focused offshore.
Forcing for ascent associated with a weak developing frontal wave
late Friday night might provide support for the best potential for
thunderstorm development closest to coastal areas.
..Kerr.. 11/12/2025
WUUS03 PTSDY3
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0830Z
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