RSS Mesoscale Discussions from Storm Prediction Center
SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0628 AM CST Sat Dec 27 2025
Valid 271300Z - 281200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Severe thunderstorms are not forecast through tonight across the
contiguous United States.
...Synopsis...
Water-vapor imagery this morning shows an upper trough over the
West. This upper feature will move east and reach the Dakotas and
central Rockies by early Sunday morning. Ahead of this trough,
upper ridging will occur over the MS/OH Valleys with a warm conveyor
focused over the lower MO Valley. Low 60s F dewpoints will stream
north out of the southern Plains and lower MS Valley toward the
lower MO/Mid MS Valley late and ahead of an approaching cold front
pushing southeast into the KS/IA vicinity.
Weak instability is forecast to gradually develop tonight over the
lower MO/mid MS Valley with an increase in showers and isolated
thunderstorms evolving primarily after midnight. Despite strong
effective shear, current thinking is storm intensity will be limited
with the elevated storm activity and hail potential will remain sub
severe.
..Smith/Weinman.. 12/27/2025
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SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0145 AM CST Sat Dec 27 2025
Valid 291200Z - 301200Z
...NO THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Thunderstorms are not expected on Monday or Monday night.
...Discussion...
A deep surface cyclone over Lake Huron at 12Z Monday should
gradually fill as it occludes and tracks into southern QC. Secondary
cyclogenesis should occur over ME into the Canadian Maritimes. The
surface warm-moist sector will be confined to the Southeast, up to
near the VA Tidewater, ahead of a progressive cold front. Guidance
is consistent with negligible instability along/ahead of the front,
which should clear all but the FL Peninsula by late afternoon and
then shift entirely offshore Monday night. Shallow convection is
possible along portions of the front, with thunderstorm
probabilities appearing to be less than 10 percent.
..Grams.. 12/27/2025
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Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0242 AM CST Sat Dec 27 2025
Valid 301200Z - 041200Z
...DISCUSSION...
A quiescent pattern is expected mid-week, in the wake of a D2-3
continental air mass intrusion across much of the Gulf. Return flow
and air mass modification will ensue late week into next weekend.
Run-to-run predictability remains low by this time frame, but some
models suggest a southern-stream shortwave trough could interact
with this moistening plume. This may support non-negligible severe
potential over the western Gulf States towards D8. Even this
scenario appears to be of sufficiently marginal amplitude, outside
of a singular 00Z CMC outlier, to likely yield low severe
probabilities through next Saturday. GEFS-based SPC-CSU and NSSL ML
guidance are in alignment with sub-5 percent severe probs on D8.
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