254
ACUS02 KWNS 171732
SWODY2
SPC AC 171730

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Sun May 17 2026

Valid 181200Z - 191200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
KANSAS TO SOUTHEAST NEBRASKA...

...SUMMARY...
Numerous severe thunderstorms are expected to develop Monday along a
cold front and dryline extending from the Great Lakes into the
central/southern Plains. Supercells capable of very large hail and
strong to intense tornadoes are most likely from central Kansas into
southeast Nebraska.

...Synopsis...
A midlevel shortwave trough, now approaching the northern Great
Basin, will move to near the Four Corners by Monday morning and then
eject northeastward over northwest KS/NE during the afternoon and to
the upper MS Valley by early Tuesday.  This path will be along and
just northwest of a stalled baroclinic zone from the central Plains
into the upper MS Valley, such that the primary height falls and
forcing for ascent will brush the northwest side of the surface warm
sector from KS to IA.  A remnant lee cyclone will persist through
the afternoon near the southwest KS/OK Panhandle border, prior to a
surge of the cold front in the immediate wake of the midlevel
trough.  Downstream from the ejecting trough, surface cyclogenesis
is expected Monday night from IA into WI along a stalled front.

...KS to IA...
There are a few questions surrounding the forecast for Monday
afternoon/night.  The northeast extent of the unstable warm sector
will depend on the persistence of rain-cooled air with morning
convection across IA/northern MO/northwest IL.  This convection and
an associated MCV could continue eastward through the day across
central/northern IL, northern IN, northwest OH and Lower MI with the
potential for occasional wind damage and isolated large hail.  The
west edge of the remnant cold pool should modify by
afternoon/evening from the MO/KS/NE border area into IA, prior to
thunderstorm development along the stalled front (and immediately in
advance of glancing influence of the ejecting midlevel trough)
21-00z from central KS into southeast NE and western IA.

Rich low-level moisture (boundary-layer dewpoints 68-72 F) is
spreading northward now from TX to OK and will be established in the
warm sector Monday.  The moisture will reside beneath an elevated
mixed layer with 8-9 C/km midlevel lapse rates and will combine with
daytime heating to drive MLCAPE of 3000-4000 J/kg.  Mass response to
the ejecting wave and the typical evening ramp up of a low-level jet
will result in favorable wind profiles/hodographs for supercells
capable of producing strong-intense tornadoes and very large hail.
The duration of a semi-discrete storm mode is another question,
given the parallel orientation of the stalled front and the
deep-layer shear vectors, in combination with focused ascent.  Thus,
the strong tornado threat will peak prior to upscale growth into
line segments along the front, with severe outflow gusts and
embedded circulations becoming the main concerns into Monday night.

...OK/northwest TX...
Storm development along the dryline to the south in OK/northwest TX
is more uncertain given little forcing for ascent.  If storms do
form, there will be a conditional threat for tornadoes and very
large hail.  A consistent forecast weakness in the flow above 500 mb
by late afternoon/evening does not appear favorable for particularly
long-lived storms if they do form.  The more probable scenario
remains a back-building line of storms along the cold front with
occasional hail/wind Monday night.

..Thompson.. 05/17/2026

$$