Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1242 AM CDT Sat Apr 11 2026
Valid 111200Z - 121200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE SOUTHERN HIGH PLAINS...
...SUMMARY...
Scattered thunderstorms producing hail and strong wind gusts will be
possible across portions of the southern High Plains this afternoon
and evening. More isolated strong to severe thunderstorms are
expected across parts of the central Rockies, central Plains, upper
Mississippi Valley, and portions of the California coast.
...Synopsis...
An upper trough is evident in early-morning water-vapor imagery off
the California Coast. This wave will gradually de-amplify over the
next 24 hours as it progresses northeastward into the northern
Rockies. Further south, a lower-amplitude upper disturbance is noted
off the coast of Baja CA, and will migrate northeast into southwest
TX through this evening. Ahead of these features, modest lee
troughing along the High Plains and the southeastward shift of
surface high from the Midwest into the upper OH Valley will yield an
extended fetch of southerly low-level flow from the TX coast into
the upper MS Valley, resulting in northward moisture return as well
as a broad zone of isentropic ascent from the Plains into the upper
MS Valley.
...Southern High Plains...
Thunderstorm development appears likely by mid-afternoon across
southwest TX as ascent associated with the upper disturbance off the
coast of Baja CA migrates out of northern Mexico and overspreads
returning moisture. Initially discrete cells are likely and will
pose a threat for large hail given adequate deep-layer wind shear.
However, weak capping and strong ascent should promote upscale
growth by early evening into one or more convective lines. As this
transition occurs, strong to severe wind gusts will become the
predominant hazard, though an embedded circulation or two may be
possible. Based on latest guidance, the wind/tornado threat may be
maximized along and south of the I-20 corridor where the signal for
clustering/banding is greatest in latest CAM and ensemble guidance.
...Central Plains to the Upper MS Valley...
Low-level warm air advection will likely become increasingly focused
through the day and into the overnight hours from the central Plains
into the upper MS Valley. 850 mb winds are forecast to strengthen to
40-50 knots by this evening and will support steady moistening in
the lowest 1-2 km under a plume of 7-7.5 C/km mid-level lapse rates.
Forecast soundings suggest that this environment will be weakly
capped and should support isolated to scattered thunderstorms during
the afternoon hours across the central Plains before
spreading/re-developing northeastward into the upper MS Valley late
tonight. While deep-layer wind shear will not be overly strong
(around 30 knots), it should be sufficient for a few transient
organized cells capable of large hail.
A more conditional supercell threat may materialize across portions
of the lower MO valley where some CAM guidance depicts convection
developing late afternoon along the surface warm front. Forecast
soundings from this region suggest a weakly capped, but moderately
buoyant and strongly sheared environment may be in place that could
support a well-organized supercell. However, poor ensemble consensus
limits confidence in this scenario.
...Central to northern Rockies...
00z RAOBs from the Great Basin/Four Corners region sampled steep
mid-level lapse rates with modest mid-level moisture. While fairly
dry, this environment was sufficient for convection yesterday and
will likely support additional thunderstorms across the central to
northern Rockies this afternoon as diurnal heating erodes inhibition
and maximizes surface-based buoyancy. Ascent ahead of the decaying
upper wave will likely support isolated to scattered thunderstorms,
and a combination of modest deep-layer wind shear and deep,
well-mixed boundary layers will promote strong to severe downburst
winds. A fairly strong wind signal in latest HREF guidance
co-located with transient UH streaks lent enough confidence to
expand 5% wind probabilities northwestward to address this concern.
...CA Coast...
A progressive upper wave will move into northern CA late this
afternoon into the overnight hours. As this occurs, ascent within
the left-exit region of an attendant upper jet, coupled with cool
mid-level temperatures near the center of the upper low, should
support isolated thunderstorms across northern CA. Winds within the
lowest 1-2 km should increase to around 40 knots as the wave moves
onshore, which may be augmented by convective downdrafts to yield a
few damaging gusts along the coast.
..Moore/Halbert.. 04/11/2026
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