SPC Dec 21, 2025 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1114 PM CST Sat Dec 20 2025

Valid 211200Z - 221200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected today.

...Pacific Northwest...

Low-amplitude short-wave trough is forecast to approach the Pacific
Northwest coast later this evening as modest midlevel height falls
spread inland across WA/OR. Latest model guidance suggests weak
buoyancy will persist much of the period, particularly near the
coast, where onshore flow will contribute to SBCAPE generally less
than 100 J/kg. As freezing levels lower, shallow convection may
penetrate levels necessary for lightning discharge. For these
reasons will maintain 10% probability for isolated thunderstorms,
primarily near the coast.

..Darrow/Squitieri.. 12/21/2025


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SPC Dec 21, 2025 0100 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 0100Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0633 PM CST Sat Dec 20 2025

Valid 210100Z - 211200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few lightning flashes may occur late tonight over southern
Louisiana; however, this activity will be very sparse.

...01z Update...

Weak surface front is expected to settle into northern LA, arcing
southwest into the Hill Country of central TX by the end of the
period. Favorable low-level trajectories will continue across the
western Gulf basin into southern LA tonight where 60s surface dew
points are expected to hold. However, large-scale forcing is not
expected to be particularly notable and a fairly strong cap is
currently noted around 2km on the 00z LCH sounding. Latest model
guidance suggests this capping will likely persist, but possibly
weaken toward 12z. If so, a few flashes of lightning may accompany
weak convection across southern LA.

..Darrow.. 12/21/2025


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SPC Dec 20, 2025 1300 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0632 AM CST Sat Dec 20 2025

Valid 201300Z - 211200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected, but a few lightning flashes
may occur today near coastal Washington.

...Discussion...
Progressive/low-amplitude flow aloft will prevail over the CONUS to
the south of an amplifying shortwave trough over the Great
Lakes/Ontario. Surface high pressure will expand eastward across the
Plains and Midwest. Some inland moistening will occur across east
Texas toward the Lower Mississippi Valley via the western Gulf, but
weak forcing/capping will hinder appreciable convective development.
In the Pacific Northwest, a marginally supportive thermodynamic
environment may allow for a few lightning flashes near the
Washington coast today and tonight.

..Guyer/Marsh.. 12/20/2025


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SPC Dec 20, 2025 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1120 PM CST Fri Dec 19 2025

Valid 201200Z - 211200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated lightning flashes may occur near coastal sections of
Washington today.

...Synopsis...
A mid-level trough will progress across the eastern CONUS while
upper ridging builds west of the Rockies, resulting in surface high
pressure overspreading the Midwest as a surface trough impinges on
the Pacific Northwest Coastline. Cooler temperatures aloft will
overspread a marine boundary layer over the Washington coast,
resulting in scant buoyancy, which may favor a few convective
updrafts that may deepen enough to produce isolated lightning
flashes. A weakening surface low will also drift southward across
the southern Plains, promoting low-level moisture return inland from
the western Gulf. However, considerable convective inhibition should
limit convective development through the Day 1 period.

..Squitieri.. 12/20/2025


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