RSS Mesoscale Discussions from Storm Prediction Center
SPC 1200Z Day 1 Outlook
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
Read more
SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1256 AM CST Wed Dec 24 2025
Valid 251200Z - 261200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS 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.
...California Coast...
A mid-level low and an associated trough over the eastern Pacific
will gradually approach the West Coast on Thursday. Ahead of the
trough, a stream of moisture will feed into California, where
scattered thunderstorms are expected to develop during the day. At
the surface, a front is forecast to move southward along the central
California coast. To the south of the front near the coast, surface
dewpoints will be in the 50s F. In addition, a 50 to 60 knot
low-level jet is forecast to be in proximity to the higher surface
dewpoints. This feature will create strong low-level shear along the
central California coast, where some forecast soundings have curved
hodographs and 0-3 km storm-relative helicity above 250 m2/s2. This
could support a marginal severe threat, with cells that rotate
within short line segments. A brief tornado or isolated severe wind
gust will be possible.
..Broyles.. 12/24/2025
Read more
SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 AM CST Wed Dec 24 2025
Valid 261200Z - 271200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
No severe storms are expected to develop across the continental U.S.
on Friday or Friday night.
...DISCUSSION...
At mid-levels, a ridge will move eastward across the central U.S. on
Friday, as a subtle shortwave trough moves into the Northeast. A few
storms may form ahead of the trough Friday afternoon and evening
across parts of the central Appalachians. Out west, a trough will
move inland across the Pacific Northwest, with southwesterly flow
being in place across the Intermountain West. Isolated storms will
be possible across parts of California and in the Intermountain
West. No severe threat is expected to develop Friday or Friday
night.
..Broyles.. 12/24/2025
Read more
