Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0257 PM CDT Sun Sep 27 2026
Valid 272000Z - 281200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Organized severe storms are not expected through early Monday.
...20z Update...
No changes were made to the existing outlook with this update cycle.
Isolated convective development is ongoing across portions of
central/north Texas as of 1945 UTC. While an isolated
strong/damaging wind gust cannot be ruled out with this activity
owing to steep low-level lapse rates and moderate buoyancy, weak
lower tropospheric flow (as depicted by regional VWPs), limited
effective shear, and poor mid-level lapse rates should largely
temper overall convective intensity. Thus, the severe threat
continues to appear too low (less than 5%) to warrant the inclusion
of severe probabilities. See the discussion below for additional
details.
..Chalmers/Guyer.. 09/27/2026
.PREV DISCUSSION... /ISSUED 1137 AM CDT Sun Sep 27 2026/
...Synopsis...
An occluded cyclone will slowly weaken near the northern
Mid-Atlantic coast, with lingering potential for elevated convection
and isolated lightning flashes to its northeast across southeast New
England. Farther west, weak ridging aloft will extend from the
southern High Plains toward MN. A few thunderstorms will be
possible late this afternoon/evening along a diffuse surface
boundary from north TX into southern OK. The strongest storms may
produce gusty outflow winds given steep low-level lapse rates with
afternoon mixing, but the severe threat appears too low to justify
adding severe-wind probabilities.
Slightly elevated convection is ongoing across central SD in a zone
of weak low-level frontogenesis, coincident with midlevel lapse
rates near 8 C/km and MUCAPE close to 1000 J/kg. Deep-layer
vertical shear is on the lower margins for storm organization, but
it appears this convection has already peaked. Additional elevated
thunderstorms are expected overnight from western SD into ND as
low-level warm advection increases in association with embedded
speed maxima downstream from a midlevel trough moving across CA/NV.
While an isolated hail report could occur overnight as far northeast
as southwest ND, the overall threat is low and when combined with
the questionable threat for diurnal convection across the central
High Plains, the MRGL area has been removed.
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