RSS Mesoscale Discussions from Storm Prediction Center
SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0132 AM CST Thu Dec 11 2025
Valid 131200Z - 141200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Scattered, mostly weak, thunderstorm activity is possible across the
Gulf Coast states Saturday into Saturday night.
...Discussion...
Models indicate that the blocking high will generally maintain
strength just to the north of Aleutians through this period. The
evolution of a lower/mid-tropospheric cyclone to its east, across
the northeastern Pacific, is more unclear, but guidance indicates
that a downstream ridge will broaden eastward, inland of the British
Columbia/Pacific Northwest coast through the southern Canadian
Prairies and northern U.S. Great Plains. Farther east, it still
appears that a vigorous digging short wave trough will once again
contribute to larger-scale mid-level trough amplification across the
Upper Midwest into Great Lakes and Ohio Valley Saturday through
Saturday night.
An increasingly confluent mid-level regime, in the wake of the
amplifying trough, is forecast to support the southeastward
development of an expanding cold surface ridge to the east of the
Rockies, across much of the Great Plains and Mississippi Valley
through western slopes of the Appalachians. By late Saturday night,
a strengthening low-level baroclinic zone, near the leading edge of
the colder air, is forecast to approach southern Mid Atlantic
through Gulf coastal areas.
In lower latitudes, beneath a weak branch of westerlies emanating
from the subtropical eastern Pacific, a remnant preceding surface
frontal zone may shift northward across the Florida Keys and
southern peninsula by 12Z Sunday, downstream of broad mid-level
troughing overspreading the Gulf Basin.
...Gulf Coast states...
Although weak lapse rates and rather weak lower/mid-tropospheric
wind fields seem likely to minimize the risk for severe weather, a
substantive increase in boundary-layer moisture, in the presence of
increasing large-scale forcing for ascent, may support increasing
scattered thunderstorm development along the front, near the Florida
Keys and southern peninsula, by late Saturday night.
Elsewhere, guidance suggests that scattered thunderstorm development
is possible near/offshore of lower through middle Texas coastal
areas, at least early Saturday. Farther northeast, a narrow plume
of elevated moisture return, off the modifying northwestern Gulf
boundary layer, might contribute to weak destabilization sufficient
for convection capable of producing lightning, mainly just ahead of
the front as it approaches the Gulf coast late Saturday night.
..Kerr.. 12/11/2025
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Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0328 AM CST Thu Dec 11 2025
Valid 141200Z - 191200Z
...DISCUSSION...
Latest medium-range model output indicates that the amplified
trough, likely digging through the lower Great Lakes and Ohio Valley
at the outset of the period, will continue rapidly digging across
the U.S. Atlantic Seaboard, before pivoting offshore and supporting
strong cyclogenesis through the northwestern Atlantic into early
next week. In its wake, an initially expansive cold surface ridge,
centered near the mid/lower Missouri Valley, may gradually weaken,
but is forecast to continue southeastward into and across the
offshore Atlantic, Florida Peninsula and much of the northern Gulf
Basin.
Thereafter, it still appears that mid/upper flow may trend more
zonal, particularly across the northern U.S. and southern Canada,
downstream of a blocking high that is forecast to be maintained, but
become suppressed to the south of the Aleutians. Short wave
developments embedded within this regime remain uncertain, but there
is still at least some signal that a developing southerly return
flow may support a modest influx of moisture off the northwestern
Gulf by the middle of next week. This could contribute to
thunderstorm development across parts of the Mid South through
portions of the lower Ohio and Tennessee Valleys Wednesday into
Thursday, ahead of a modest cold front. However, at this time, it
appears that some combination of weak/limited destabilization and
modest shear/forcing for ascent will tend to minimize the risk for
severe storms.
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