RSS Mesoscale Discussions from Storm Prediction Center
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0123 PM CST Tue Dec 30 2025
Valid 302000Z - 311200Z
...NO THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Thunderstorms are not forecast through tonight.
...Synopsis...
No changes are needed with the 20z Day 1 Update. Thunderstorm
activity is not expected through tonight/early Wednesday.
..Leitman.. 12/30/2025
.PREV DISCUSSION... /ISSUED 1000 AM CST Tue Dec 30 2025/
...Synopsis and Discussion...
With cool/stable conditions prevalent behind a cold front across a
large portion of the CONUS, thunderstorms are not forecast today.
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SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0129 PM CST Tue Dec 30 2025
Valid 011200Z - 021200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Isolated thunderstorms are possible on New Year's Day across parts
of southern California and Arizona.
...Southern CA to AZ...
A mid/upper-level shortwave trough will move across parts of
southern CA Thursday morning, before dampening as it shifts eastward
across parts of the Desert Southwest and Four Corners region later
in the period. Cooling aloft atop modestly increasing low-level
moisture will support some early-day thunderstorm potential across
coastal southern CA.
Guidance continues to vary regarding the strength, trajectory, and
magnitude of attendant flow fields of this system as it approaches
the coast. The somewhat stronger and farther south solutions (such
as the 12Z NAM/RRFS) depict potential for strong storm development
offshore, which could affect near-coastal areas of southern CA
during the morning before weakening. Other guidance (such as the 12Z
ECMWF) has trended northward, bringing stronger midlevel flow across
southern CA, but also greater displacement between substantial
cooling aloft and the more favorable low-level moisture. In general,
confidence in sufficient strengthening of flow within this weak
buoyancy regime remains too low to include severe probabilities.
Uncertainty regarding the evolution of the shortwave extends
downstream into parts of the Desert Southwest, but an area of
modestly enhanced low-level moisture across southwest AZ could
support isolated storm development later in the day into the
evening, as some cooling aloft overspreads the region.
..Dean.. 12/30/2025
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