SPC Sep 27, 2026 1630 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1630Z Day 1 Outlook


Day 1 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
1137 AM CDT Sun Sep 27 2026

Valid 271630Z - 281200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

CORRECTED TO REMOVE DUPLICATE TSTM AREA IN NEW ENGLAND

...SUMMARY...
Organized severe storms are not expected through early Monday.

...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.

..Thompson/Chalmers.. 09/27/2026


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SPC Sep 27, 2026 0100 UTC Day 1 Convective Outlook

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


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0730 PM CDT Sat Sep 26 2026

Valid 270100Z - 271200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PORTIONS OF
WESTERN OKLAHOMA AND NORTHWEST TEXAS...

...SUMMARY...
Isolated hail and strong outflow winds may accompany thunderstorms
across portions of the southern Plains this evening into the
overnight.

... Synopsis ...

Scattered thunderstorms continue to develop this evening along a
surface trough across western Oklahoma and northwest Texas, or along
a myriad of outflow boundaries from prior convection (as is the case
across southwest Oklahoma). The airmass ahead of these storms is
still quite warm, with 90F temperatures as far north as portions of
northwest Oklahoma. These warm surface temperatures are contributing
to steep low-level lapse rates conducive to downward momentum
transfer and isolated damaging thunderstorm outflows. Although the
most likely threat will be strong, gusty winds, the degree of
instability and strength of the cloud-layer vertical shear may
support a marginally severe hail threat with the strongest cores.

This activity should continue into the evening hours before
weakening low-level lapse rates and increasing surface-based
inhibition diminishes the overall severe threat.

..Marsh.. 09/27/2026


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SPC Sep 26, 2026 2000 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 2000Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0250 PM CDT Sat Sep 26 2026

Valid 262000Z - 271200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON/EVENING FROM WESTERN OKLAHOMA INTO NORTHWEST TEXAS...

...SUMMARY...
Isolated hail and strong outflow winds may accompany thunderstorms
across portions of the southern Plains late this afternoon into the
early evening.

...20z Update...
The forecast remains generally on track, with only a slight
southward expansion of the 5% wind probability area made with this
update based on latest environmental/observational trends. As of
1945 UTC, a deepening cumulus field was noted on visible satellite
imagery from West Texas into southwestern Oklahoma, with isolated
thunderstorm development ongoing across the higher terrain of
southwest Texas. Temperatures have generally warmed into the
upper-80s to mid-90s F across much of the region, with T-Td spreads
approaching 30 F in some parts of northwest Texas. Coupled with
steep low-level lapse rates, this may support isolated potential for
strong/damaging outflow wind gusts. with an instance of large hail
also possible (primarily farther north where deep-layer shear is
forecast to be marginally stronger). A lack of stronger
synoptic-scale forcing for ascent, generally weak/modest low- to
mid-tropospheric flow, and poor mid-level lapse rates are expected
to limit overall convective intensity and severe coverage, however.

..Chalmers/Thompson.. 09/26/2026

.PREV DISCUSSION... /ISSUED 1115 AM CDT Sat Sep 26 2026/

...Synopsis...
A midlevel shortwave trough over KS/OK will continue generally
eastward through the larger-scale ridge and slowly weaken by
tonight. Scattered convection and widespread clouds persist this
morning from southwest OK into KS in the primary zone of ascent
preceding the midlevel trough, though clearing from the west is
expected this afternoon. Surface heating west of the clouds and
within an axis of low-level moisture (boundary-layer dewpoints in
the low-mid 60s) along a weak surface trough could support
additional, surface-based thunderstorms this afternoon across
western OK into northwest TX. Relatively deep mixing/inverted-V
profiles appear to favor isolated strong outflow gusts as the
primary hazard late this afternoon/evening. Vertical shear will be
on the lower margins for supercells with marginally severe hail.

Elsewhere, occasional/mainly elevated thunderstorms will be possible
through tonight from northeast OK northward to IA. Other isolated
lightning flashes will remain possible through the day near the
southeast New England coast with elevated convection atop a
low-level warm advection regime.


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SPC Sep 26, 2026 1630 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1630Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1115 AM CDT Sat Sep 26 2026

Valid 261630Z - 271200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON/EVENING FROM WESTERN OKLAHOMA INTO NORTHWEST TEXAS...

...SUMMARY...
Isolated hail and strong outflow winds may accompany thunderstorms
across portions of the southern Plains late this afternoon into the
early evening.

...Synopsis...
A midlevel shortwave trough over KS/OK will continue generally
eastward through the larger-scale ridge and slowly weaken by
tonight. Scattered convection and widespread clouds persist this
morning from southwest OK into KS in the primary zone of ascent
preceding the midlevel trough, though clearing from the west is
expected this afternoon. Surface heating west of the clouds and
within an axis of low-level moisture (boundary-layer dewpoints in
the low-mid 60s) along a weak surface trough could support
additional, surface-based thunderstorms this afternoon across
western OK into northwest TX. Relatively deep mixing/inverted-V
profiles appear to favor isolated strong outflow gusts as the
primary hazard late this afternoon/evening. Vertical shear will be
on the lower margins for supercells with marginally severe hail.

Elsewhere, occasional/mainly elevated thunderstorms will be possible
through tonight from northeast OK northward to IA. Other isolated
lightning flashes will remain possible through the day near the
southeast New England coast with elevated convection atop a
low-level warm advection regime.

..Thompson/Chalmers.. 09/26/2026


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