RSS Mesoscale Discussions from Storm Prediction Center
SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0653 AM CST Sun Dec 21 2025
Valid 211300Z - 221200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Severe thunderstorms are not expected today.
...Discussion...
A progressive/zonal upper-flow pattern will continue over the CONUS.
A low-amplitude shortwave trough will move inland across the Pacific
Northwest by tonight. Weak buoyancy and cooling temperatures aloft
may become sufficient for isolated lightning flashes, particularly
near the Washington coast. Farther south, a moisture-rich plume and
a marginally favorable thermodynamic environment may allow for some
lighting flashes across northern California.
Elsewhere, a relatively moist airmass near/south of a
southward-moving front, along with continued weak warm/moist
advection, will probably be conducive for isolated thunderstorms
mainly across southern portions of Louisiana and Mississippi today.
..Guyer/Marsh.. 12/21/2025
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Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0320 AM CST Sun Dec 21 2025
Valid 241200Z - 291200Z
...DISCUSSION...
Medium-range model guidance initially shows a pattern featuring an
upper ridge over the central CONUS and trough along the West Coast,
transitioning to a more progressive flow regime and lowering heights
across the Great Plains during the Thursday-Saturday (D5-D7) period.
The inland-moving West Coast trough will potentially yield isolated
to scattered thunderstorms on Wednesday into early Thursday over
portions of southern and central CA and perhaps a localized risk for
a couple of stronger thunderstorms. Details concerning this
convective scenario and overall magnitude of severe risk preclude
severe highlights. Farther east, some moisture return northward
into the southern Great Plains and MS Valley through Friday will
likely be modulated by frontal advancements during the latter part
of extended period.
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