Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0256 PM CDT Sun Apr 12 2026
Valid 122000Z - 131200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
CENTRAL TEXAS...
...SUMMARY...
Isolated to scattered severe thunderstorms remain possible today
into evening mainly across parts of Texas and perhaps other nearby
parts of the southern Plains. More isolated severe storms may occur
across portions of the Upper Great Lakes and northern Rockies.
...20z Update Central TX...
Filtered diurnal heating in the wake of earlier showers and storms
across much of central TX was supporting moderate destabilization
this afternoon. While mid-level lapse rates are generally poor,
sufficient destabilization should support a gradual uptick in
convective coverage this afternoon and evening. With moderate
deep-layer shear in place, some organization could support a risk
for damaging gusts, hail, and tornado or two.
...MN/WI...
The aforementioned warm front continues to surge north but has
slowed farther south than earlier guidance. Weak to moderate
destabilization along and just south of the boundary will remain
supportive of a conditions supercell risk this afternoon/evening.
Strong shear profiles east of the surface low and near the rapidly
modifying boundary could support a risk for hail and possibly a
tornado. Have shifted severe probabilities southward slightly to
better match the observed frontal positioning. See MCD #390 for the
latest information.
...OK/KS/TX Panhandle...
A conditional risk for a supercell or two remains evident this
afternoon across the dryline in the central and southern Plains.
Ample heating in the wake of an early morning MCS could allow for
isolated storm this afternoon or evening as the dryline is forecast
to mix eastward before eventually retreating. Forecast guidance
continues to show weak subsidence suppressing convective
development, but deepening cumulus evident over the southern TX
Panhandle could support an isolated storm this evening. All severe
hazards would be possible.
...Intermountain West...
Steep mid-level lapse rates beneath the cold core of the upper low
over the West will continue to support scattered high-based storms
this afternoon. With a relatively dry-sub cloud layer, somewhat deep
boundary-layer mixing will support strong to
severe downburst winds.
..Lyons.. 04/12/2026
.PREV DISCUSSION... /ISSUED 1129 AM CDT Sun Apr 12 2026/
...Synopsis...
Recent satellite imagery shows a pair of phased shortwave troughs
over the Plains, one moving through the Dakotas and another moving
through KS/OK. Both of these waves are forecast to continue
northeastward through the day, with the northern wave reaching
northwestern Ontario and the southern wave reaching the Great Lakes
region. This evolution will take these waves east/northeast of the
higher low-level moisture, which will remain in a corridor from the
southern Plains northeastward into the Upper Midwest. Showers and
thunderstorms are anticipated throughout much of this corridor
today, with highest thunderstorm chances across central/east TX and
from the Upper Midwest into the Great Lakes.
Farther west, an upper low is slowly drifting eastward across
northern CA. Guidance suggests this eastward drift will continue
today, with several shortwave troughs rotating quickly through the
base of this system and ejecting across the Great Basin and northern
Rockies. Large-scale ascent and modest mid-level moisture associated
with these waves will combine with cold temperatures aloft and
associated buoyancy to support thunderstorms today from northern CA
across the northern Great Basin and northern Rockies, and into the
northern Plains.
...Southern/Central Plains...
Much of this region will be displaced south and west of any notable
large-scale forcing for ascent. This limited ascent, combined with
the showers and isolated thunderstorms currently ongoing across
central and east TX, complicates the overall forecast today, with
mesoscale factors likely contributing significantly to when and
where storms develop this afternoon and evening. General expectation
is for development along the southern and western periphery on the
ongoing storms (i.e. from southeast/south-central TX into southwest
TX) later this afternoon and this evening. This redevelopment will
be supported by a combination of moist advection, modest heating,
and limited low-level convergence. Moderate to strong buoyancy amid
moderate vertical shear could support supercells if the mode remains
discrete. However, the weakness in the mid-level flow suggests
storms may tend to cluster, a scenario that is supported by most CAM
guidance. Buoyancy and shear are still strong enough to support
rotating updrafts and large hail early in the convective cycle, but
the trends towards a messy convective mode could limit the
persistence and coverage of robust updrafts. Damaging gusts are
possible even with the clustered storm mode, especially given there
is some potential for slightly more organized bowing segments over
time.
Farther west, mid-level height rises/subsidence are anticipated
coincident with the dryline from central Kansas south-southwestward
across western Oklahoma and west/southwest Texas. The environment,
characterized by 1500 to 2000 J/kg of MLCAPE and 30 to 40 kt of
westerly deep-layer shear, is conditionally supportive of supercells
capable of all severe hazards. However, the previously mentioned
height rises and subsidence, combined with modest convective
inhibition, are generally expected to preclude thunderstorm
development. Even so, given the conditional risk, Marginal risk
probabilities will be maintained.
...Minnesota/Wisconsin...
Recent surface analysis places a low just west of FAR, with a warm
front extending southwestward across central/southeast MN and
southern WI. This low is forecast to move eastward today, while the
warm front expands northward. A narrow corridor of surface-based
buoyancy could develop from north-central MN into far northwest WI
as dewpoints increase in the upper 50s (perhaps even low 60s).
Thunderstorm initiation appears possible along the cold front within
this corridor, although veered low-level flow and northward/westward
displacement of the better forcing casts doubt to whether updrafts
will be maintained. Any storms that do mature within this warm
sector should become supercells capable of all severe hazards,
including large hail and tornadoes. However, low confidence in storm
development and maturity precludes higher probabilities with this
outlook.
...Northern Rockies...
Mid-level moisture will support another day of modest surface-based
buoyancy ahead of the shortwave trough mentioned in the synopsis.
Persistent 30-40 knot flow within the CAPE-bearing layer combined
with somewhat deep boundary-layer mixing will support strong to
severe downburst winds with the more robust convective cells, mainly
this afternoon through early evening.
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