RSS Mesoscale Discussions from Storm Prediction Center
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0151 PM CST Wed Nov 12 2025
Valid 122000Z - 131200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Isolated thunderstorms remain possible along the coast of northern
California late tonight/early tomorrow. No severe threat is forecast
across the U.S. today or tonight.
...20z Update...
No changes were made to the current outlook. Isolated thunderstorms
remain possible late tonight ahead of an upper trough moving onshore
over northern CA near 12z. Severe potential is low, see the prior
outlook for more info.
..Lyons.. 11/12/2025
.PREV DISCUSSION... /ISSUED 1027 AM CST Wed Nov 12 2025/
...Synopsis...
An amplified upper pattern will persist across the CONUS
today/tonight, characterized by a trough across the eastern states
and an upper ridge over the West. At the surface, a mostly
dry/stable airmass will be in place, precluding thunderstorm
activity for most of the forecast period.
Late tonight, an upper low will progress eastward eastern Pacific,
approaching the offshore waters near northern CA. As height falls
overspread the Pacific coast, a surface low will deepen offshore. A
line of elevated convection is expected to develop ahead of a cold
front and move onshore in the 08-12z time frame. Cooling aloft will
support weak elevated instability, and isolated thunderstorms will
be possible. Severe storms are not expected.
Read more
SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
1256 PM CST Wed Nov 12 2025
Valid 141200Z - 151200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
The risk for thunderstorms appears negligible across the U.S. Friday
through Friday night.
...Discussion...
As blocking mid/upper ridging remains centered offshore of
southeastern Greenland, models indicate that a broad cyclonic regime
will be maintained to its southwest, centered near the Canadian
Maritimes. Some amplification of large-scale troughing extending
southward offshore of the remainder of the North American Atlantic
coast is forecast, downstream of a significant mid-level trough and
embedded cyclone migrating northeast and east of the Canadian
Prairies, on the leading edge of a more progressive regime.
Upstream, ridging ahead of another short wave trough appears likely
to spread across and inland of the British Columbia/adjacent Pacific
Northwest coast, to the north of an increasingly cut-off low
centered offshore of the central/southern California coast.
...Southern California...
Models indicate that the modifying mid-level cold core (including
coldest 500 mb temperatures warming above -24 C) will generally
remain offshore through this period, tending to pivot away from
central coastal areas while perhaps slowly toward southern coastal
areas late Friday night. While a corridor of continued
low/mid-level moistening along a slow moving, occluded frontal zone
may compensate and contribute to layers of weak conditional
instability inland of southern California coastal into the southern
Sierra Nevada/Mojave Desert vicinity, 10 percent or greater
probabilities for thunderstorms appear generally focused offshore.
Forcing for ascent associated with a weak developing frontal wave
late Friday night might provide support for the best potential for
thunderstorm development closest to coastal areas.
..Kerr.. 11/12/2025
Read more
