Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1025 AM CST Wed Dec 24 2025

Valid 241630Z - 251200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
COASTAL CALIFORNIA AND PORTIONS OF THE CENTRAL VALLEY...

...SUMMARY...
An isolated risk for severe/damaging gusts and perhaps a brief
tornado will exist today into tonight along much of the California
Coast and portions of the Central Valley.

...California...
A shallow band of pre-frontal convection may continue to pose a
threat for locally severe/damaging winds (especially across higher
terrain/ridgetops) and perhaps a brief tornado this morning across
parts of coastal southern CA. This activity is being supported by
strong low-level warm advection and large-scale ascent associated
with an enhanced mid/upper-level jet. Current expectations are for
this activity to continue moving eastward through the afternoon
across the remainder of coastal southern CA in a strongly sheared
environment. However, various NAM/RAP forecast soundings across this
area suggest that even with low 60s surface dewpoints and
modest/filtered daytime heating, the overall severe threat will
likely remain isolated due to poor lapse rates aloft and limited
boundary-layer instability. Reference Mesoscale Discussion 2269 for
more details on the near-term severe threat across southern CA.

Additional rounds of convection are expected later this evening and
overnight into early Thursday morning over portions of
northern/central CA, as multiple mid-level shortwave troughs
embedded within persistent large-scale upper troughing over the
eastern Pacific overspread these areas. One such shortwave trough is
forecast to advance over coastal central CA and vicinity around
25/00-06Z this evening, with cool temperatures aloft (less than -20C
at 500 mb) supporting weak MUCAPE. Both low-level and deep-layer
shear are expected to gradually increase this evening as the
shortwave trough approaches, with some updraft organization
possible. Strong to locally severe winds and a brief tornado or two
appear possible with this activity, but uncertainty is still
substantial whether sufficient instability will be present to
support surface-based thunderstorms.

A stronger mid-level shortwave trough will move east-northeastward
from the eastern Pacific and approach the northern CA Coast by 12Z
Thursday morning, along with a deepening surface low and attendant
cold front. A 70-80+ kt mid-level jet will accompany this shortwave
trough, along with a 50-60 kt south-southwesterly low-level jet. A
broken band of low-topped thunderstorms will likely develop in
association with this shortwave trough along/ahead of the front, and
overspread coastal portions of northern/central CA late tonight
through early Thursday morning (25/06-12Z). A strongly sheared
environment and weak but sufficient MLCAPE may exist to support at
least an isolated threat for severe/damaging winds and a tornado or
two as this activity spreads inland through the end of the period.
Still, the overall severe threat should be tempered by the lack of
stronger instability.

Finally, some chance for low-topped/mini supercells may exist late
this afternoon/evening across parts of the Central Valley of CA. If
these thunderstorms can develop and be sustained, they could pose a
threat for both damaging winds and a brief tornado. But, confidence
in this scenario occurring remains rather low.

..Gleason/Bunting.. 12/24/2025

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1128 AM CST Wed Dec 24 2025

Valid 251200Z - 261200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE CENTRAL CALIFORNIA COAST...

...SUMMARY...
Thunderstorms with potential to produce marginally severe wind gusts
and perhaps a brief tornado will be possible on Thursday along parts
of the central California Coast.

...Central California Coast...
A broad upper low with multiple embedded disturbances will continue
to linger over the West Coast Thursday. Ahead of the trough, a
stream of moisture associated with an ongoing atmospheric river will
continue overspreading much of California where numerous convective
showers and isolated thunderstorms are expected to develop during
the day and continuing into early Friday. Buoyancy will be weak, but
MUCAPE peaking around 400 J/kg amidst the strong westerly flow could
support a couple marginally severe storms.

One of the more intense embedded features will likely move onshore
across parts of central CA early in the period before lifting
northward across southern WA Thursday evening. A strong offshore low
and cold front will likely support a broken band of low-topped
storms moving onshore early. Beneath a 50 to 60 knot southwesterly
low-level jet, flow aloft may mix down to the surface supporting
marginally severe gusts. Additionally, moderate shear in the lowest
few km could support a brief tornado with any transiently organized
storms.

A second embedded impulse is forecast to approach the coast farther
south into early Friday. Ascent ahead of the trough and a second
weaker cold front will help support another band of low-topped
storms. Considerable uncertainty remains regarding buoyancy for this
round given the overnight timing and multiple rounds of rain prior.
Still, some CAM guidance shows a narrow frontal band of low-topped
storms capable of damaging gusts or a brief tornado moving onshore
over the central Coast before 12z Friday.

..Lyons.. 12/24/2025

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0120 PM CST Wed Dec 24 2025

Valid 261200Z - 271200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe storms are not expected across the continental U.S. Friday or
Friday night.

...Synopsis...
An expansive upper ridge centered over the Plains States will begin
to weaken as it moves eastward Friday. Flow aloft will become
increasingly zonal as broad troughing over the West Coast moves
inland. With continued moisture transport and southwesterly flow in
place over much of the West, isolated storms could be ongoing across
parts of the West Coast and southern CA early. However, little to no
severe threat is expected given the weak buoyancy. Troughing is
forecast to move farther inland quickly, limiting the thunderstorm
threat Friday and Friday night.

...Upper OH Valley...
A secondary low-amplitude upper trough will develop over the
northeastern US late Friday. As it moves southeastward, a weak,
clipper-style, surface low will deepen across the upper OH Valley
and central Appalachians. Cool mid-level temperatures and modest
low-level moisture ahead of the low and trailing cold front could
support weak elevated buoyancy into early Saturday. Isolated
thunderstorms are possible into early Saturday. However, with less
than 500 J/kg of MUCAPE, severe storms appear unlikely.

..Lyons.. 12/24/2025