Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0241 PM CDT Sat Sep 27 2025
Valid 272000Z - 281200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
A severe threat is not expected to develop across the continental
U.S. today and tonight.
...20z Update...
No changes were made to the outlook, severe potential is limited.
Scattered thunderstorms should continue underneath a broad upper low
over the Southwest. Modest MLCAPE, poor mid-level lapse rates and
decreasing vertical shear will limit storm intensity.
A similar situation is expected beneath the upper low over the
Southeast. Higher PWATs and some clustering of storms could promote
an occasional wet microburst. However, little storm organization and
thus low severe potential is expected. See the prior outlook for
more info.
..Lyons.. 09/27/2025
.PREV DISCUSSION... /ISSUED 1123 AM CDT Sat Sep 27 2025/
...Synopsis and Discussion...
Upper ridging currently extends from the ArkLaTex/Lower MS Valley
through the central High Plains with upper lows flanking this
ridging on each side. The western upper low is centered over
southern CA/Lower CO River Valley. This low is displaced well south
of the westerlies along the US/Canada border and is not expected to
move much throughout the day. In general, poor lapse rates should
temper the buoyancy near and downstream of this low (i.e. from the
Lower CO Valley into AZ), mitigating the overall severe potential.
The greatest buoyancy is expected across far eastern southern CA and
southwestern AZ, near the center of the upper low where mid-level
temperatures are coolest. Here, a few stronger storms are possible
during the afternoon and evening. Severe coverage is still expected
to be too low to merit any probabilities.
The eastern upper low, currently centered over the southern
Appalachians, has a more broad circulation than the southern CA low,
with most guidance suggesting it devolves and shifts northeastward
into the Mid-Atlantic throughout the period. Moderate mid-level
southwesterlies will persist within the eastern periphery of this
cyclone (i.e. from the eastern Carolinas into NJ and eastern PA)
today. Buoyancy will be modest, but the stronger shear from these
southwesterlies could help support a few stronger multicells capable
of damaging gusts. Overall severe coverage is still expected to be
too low to merit any probabilities.
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