ACUS01 KWNS 251950
SWODY1
SPC AC 251948

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0248 PM CDT Sat Apr 25 2026

Valid 252000Z - 261200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
CENTRAL AND SOUTHEASTERN OKLAHOMA INTO FAR NORTHERN TEXAS...

...SUMMARY...
Severe thunderstorms with very large to giant hail (2 to 4+ inches
in diameter), tornadoes (some EF2+), and scattered damaging winds
are expected late this afternoon through tonight across parts of the
southern Plains and ArkLaTex.

...20Z Update...

The previous forecast (see below) remains on track. The main
adjustments made to the outlook (albeit minor) were to slightly
extend the moderate risk-driven hail probabilities to the southwest
to align with the current position of the surface boundary. The
latest high-resolution guidance consensus has consistently depicted
some of the most robust storms to form and anchor along this
boundary. With current mesoanalysis already showing 4000+ J/kg
MLCAPE colocated across far south-central OK, the current thinking
is that intense supercells traversing this boundary will produce
severe hail in the 3-4 inch range, and a couple of stones above 4
inches in diameter cannot be completely ruled out. Tornadoes may
also occur, with the best chance of a strong to intense tornado
being with a boundary-anchoring supercell that can remain discrete
and dominant.

..Squitieri.. 04/25/2026

.PREV DISCUSSION... /ISSUED 1131 AM CDT Sat Apr 25 2026/

...Southern Plains and ArkLaTex...

While stratus remains semi-prevalent this morning along/north of the near-stationary front, strong to locally extreme instability (MLCAPE
2500-4000+ J/kg) is expected to develop along/east of the dryline in
Texas and Red River-vicinity triple point, and to the south of slow-northward-shifting warm front in Oklahoma by peak afternoon
heating. The presence of seasonably cool temperatures aloft and
7.5-8.5 C/km mid-level lapse rates will also support this very
unstable thermodynamic environment. While large-scale ascent
associated with the ejecting mid-level shortwave trough is not
expected to be overly robust, the arrival of a shortwave
trough/mid-level speed max will be favorably timed atop the warm
sector. At least widely scattered thunderstorm initiation is
expected by mid/late afternoon to early evening (around 20-23Z),
especially near the warm front/dryline intersection and a bit north
across south-central/east-central Oklahoma.

40-50 kt of generally westerly effective bulk shear will support
intense supercells, with multiple right/left splits expected. This
activity will quickly intensify shortly after convective initiation,
and very large to giant hail appears likely (2-4+ inches in
diameter). The potential exists for multiple intense supercells to
track east-southeastward along/near the warm front. A conditional
risk for supercells remains apparent farther south along the length
of the dryline in TX, although confidence in convective initiation
remains low, but at least isolated but intense deep convective
development is plausible, especially in closer proximity to the
surface triple point across North Texas.

Modest southerly low-level winds (around 20-30 kt at 850 mb) will be
present through this evening across the southern Plains. Locally
enhanced 0-1 km SRH will exist near the warm front with backed
near-surface winds. This will support a threat for tornadoes with
any right-split supercells that remain surface based. A slight
increase in the low-level jet this evening and presence of very
strong to locally extreme buoyancy also suggests some threat for a
few EF-2+ tornadoes. With time this evening, convection may
grow upscale and pose a threat for scattered severe/damaging winds
as storm clusters move southeastward across the Red River toward and
across the ArkLaTex.

...Central Plains including Kansas/Nebraska...

Farther north, instability and low-level moisture is expected to
remain weaker/more limited. But, some supercells/small clusters are
expected to develop this afternoon and move east-northeastward given
sufficient deep-layer shear for updraft organization. Isolated to
scattered severe hail and damaging winds should be the main threat
with this activity through mid-evening before eventually weakening.

...Lower Mississippi Valley/Middle Gulf Coast...

Strong to locally severe storms may redevelop later today as outflow
modifies in the wake of the early morning MCS, with the potential
that additional storms, potentially in the form of another MCS,
approach the region from the northwest late tonight.

$$


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ACUS01 KWNS 182006
SWODY1
SPC AC 182005

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0305 PM CDT Mon May 18 2026

Valid 182000Z - 191200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
CENTRAL AND NORTHEASTERN KANSAS...FAR SOUTHEASTERN
NEBRASKA...NORTHWESTERN MISSOURI...AND FAR SOUTHWESTERN IOWA....

...SUMMARY...
Numerous severe thunderstorms are expected this afternoon and
evening across the south-central Plains and mid Missouri Valley.
Supercells capable of producing very large to giant hail and
multiple strong to intense tornadoes remain likely from central
Kansas and southeast Nebraska into Iowa and northwest Missouri.

...20z Update Midwest Lower Great Lakes...

An expansive MCS remains ongoing over portions of the lower Great
Lakes this afternoon. The environment ahead of the complex is
unstable, but with gradually decreasing moisture/buoyancy farther
east. An isolated severe risk likely exists ahead of the line across
OH and lower MI through this evening.

A large cold pool behind the complex has overturned the air mass
across much of northern IL, southern WI and eastern IA. This should
greatly limit air mass recovery this afternoon and evening.
Additional convection originating from the central Plains and mid MO
valley may continue eastward, but is forecasted to weaken as it
encounters the cooler air mass tonight. Isolated storms, likely
elevated, could persist with a risk for hail, but the severe
potential has decreased such that, probabilities were lowered.

...Central Plains and Mid MO Valley...

Several supercells and organized clusters have emerged across parts
of KS and southern NE. A very unstable and strongly sheared
environment remains in place ahead of these storms. This should
support a risk for all hazards, include strong tornadoes, very large
hail, and significant damaging winds. Current expectations are for
the individual supercells to grow upscale into one or more clusters
as they interact with a modifying outflow boundary across northeast
KS and northwestern MO. While the environment becomes gradually less
unstable farther north and east, very strong shear will likely
support a continued risk for all hazards this evening. The western
portions of the risk area has been trimmed in parts of central KS
where the cold front has sagged southward.

...Southwest TX..

Strong diurnal heating along southern portions of the dryline has
resulted in isolated storm development this afternoon. Very large
buoyancy (MLCAPE 3000-4000 J/kg) and steep lapse rates will likely
continue to support high-based isolated storms. Vertical shear is
marginal, but sufficient for supercells with hail and damaging wind
potential. Have extended severe probabilities southward along the dryline.

..Lyons.. 05/18/2026

.PREV DISCUSSION... /ISSUED 1125 AM CDT Mon May 18 2026/

...Central Plains...

Morning water vapor loop shows a potent shortwave trough rotating
across the central Rockies into western KS. The primary surface
boundary extends from western IA into central KS, with a pronounced
outflow boundary associated with overnight convection extending from
southeast KS into southern MO. The outflow boundary will lift
northward today, allowing a very moist and extremely unstable air
mass to spread into eastern KS/northwest MO/extreme southeast
NE/southwest IA. This is the area most concerning for intense
supercells later today.

Initial storms are expected to develop by early afternoon near the
triple point of the retreating outflow boundary and cold front.
These storms will track northeastward through the afternoon and
early evening in a strongly sheared environment favorable for
tornadoes, very large hail, and damaging winds. It remains unclear
how stormscale interactions will impact discrete supercell mode, but
strong tornadoes are a concern in this region.

Farther southwest, thunderstorms will develop in vicinity of the
cold front across south-central KS by late afternoon. Recent CAM
solutions suggest these storms may be affected by the linear frontal
forcing, and may be slightly anafrontal. This would lessen the
tornado risk, but very large hail and damaging winds would remain a
concern. No changes have been made to the Moderate Risk area due to conflicting model signals.

...Western OK/Northwest TX...

Full sunshine will lead to hot temperatures along the dryline over
western OK into northwest TX. At least isolated thunderstorms are
expected to form in this area, with a risk of large hail and
damaging winds. Weak large scale forcing may limit storm duration
and intensity.

...OH Valley/Great Lakes...

A line of thunderstorms along the IL/IN border is tracking
northeastward into a warm/moist air mass. Relatively strong
low-level wind fields and steep low-level lapse rates suggest a
continued risk of scattered wind damage with the strongest storms as
they track across parts of IN/Lower MI/Northwest OH.

$$


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* Origin: Project Scorpio TEST (618:250/6)