Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1153 PM CST Tue Dec 23 2025
Valid 241200Z - 251200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS COASTAL
CALIFORNIA AND THE CENTRAL VALLEY...
...SUMMARY...
Thunderstorms with marginally severe wind gusts, small hail and
potentially a brief tornado will be possible from Wednesday into
Wednesday night along parts of the California coast, and inland
across the San Joaquin Valley.
... Synopsis ...
A high-amplitude midlevel pattern will persist on Wednesday,
characterized by a deep trough across the eastern Pacific and a
building ridge across the Plains. This pattern will maintain a broad
belt of intense cyclonic flow across California into the Interior
West.
Throughout the day, an initial shortwave trough will continue
lifting northeast from the eastern Pacific into the Pacific
Northwest, while the attendant surface low lifts more northward
along the coast toward Washington. Late on Wednesday a second, more
potent trough will approach central and northern California --
primarily after dark. This setup will facilitate a prolonged period
rain and embedded thunderstorms across California and portions of
the Interior West into Thursday.
... California Coast ...
Strong ascent and strengthening onshore flow will aid in modest
destabilization Wednesday morning ahead of a surface cold front. An
ongoing band of convection is expected across the central and
southern coastal areas associated with the strongly forced ascent
along the advancing cold front. Given the presence of a strong
low-level jet (locally exceeding 50 knots at 1 km AGL), there is a
risk that these strong winds will mix to the surface within the
strongest convection resulting in damaging wind gusts. Forecast
soundings across the area do maintain some low-level curvature ahead
of the convective line, such that any convective element able to
interact with true surface-based buoyancy would have the potential
for a brief tornado.
In the wake of the morning convection, a secondary surface low will
intensify during the afternoon and overnight as it approaches the
northern California coast. This will likely trigger another round or
two of broken, low-topped convection along a second cold front.
Despite weaker instability than with the morning convection, the
strength of the wind fields would suggest an ongoing risk for
isolated wind damage as this convection moves inland.
... Central Valley ...
Cold midlevel temperatures and increasing height falls will
overspread surface dewpoints in the 40s to perhaps low 50s. Although
buoyancy will remain modest (MUCAPE at or below 500 J/kg), the
presence of a powerful midlevel jet in excess of 100 knots will
support long hodographs. This combination of modest instability and
large/long hodographs may support a threat for semi-organized
convection, including some potential for supercells. The strongest
storms will be capable of producing damaging gusts, hail, and a
brief tornado before the convection shifts east into the higher
terrain and weakens.
..Marsh/Squitieri.. 12/24/2025
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