ACUS48 KWNS 190902
SWOD48
SPC AC 190900
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CDT Sun Apr 19 2026
Valid 221200Z - 271200Z
...DISCUSSION...
A western trough will take hold in the days preceding this
convective period. Ahead of this trough moisture will return
northward through the central Plains, with 50F dewpoints reaching
perhaps as far north as the Canadian border during Wednesday/Day-4.
This return flow setup and western trough will set the stage for
multiple days of severe weather potential.
On Wednesday/Day-4, a lobe of vorticity will eject northeast out of
the western longwave trough across the central and northern Plains.
As this occurs, surface cyclogenesis should take place across the
far northern Plains. To the south of this surface low, a dryline
should sharpen across western Nebraska and Kansas. At the same time,
vertical shear should strengthen as the shortwave moves northeast
across the region. The kinematic profiles will support supercells
initiating along the dryline. However, concerns remain about the
quality of the moisture to the east of the dryline and subsequently
as to the number of potential thunderstorms that may develop. This
uncertainty precluded the introduction of unconditional 15%
probabilities at this time.
On Thursday/Day-5, the shortwave trough/midlevel low will deepen as
it slowly moves north-northeast during the day. This will help
maintain a strong surface cyclone across the northern Plains, with
strong southerly winds advecting Gulf moisture northward to the east
of the north-south oriented frontal boundary. Showers and
thunderstorms will be possible along and east of the aforementioned
frontal boundary across a large portion of the central US. Strong
vertical wind shear across this frontal boundary will promote severe
potential from Oklahoma northward to perhaps as far north as
Minnesota. The northern extent of the severe potential will be
delimited by the degree of moisture return, and have expanded the
unconditional 15% probability area northward into Iowa to account
for the increasing confidence in severe thunderstorm potential.
Overnight Thursday/Day-5, a surface cold front, augmented by
convective outflow, should push east across the northern and central
Plains and south-southeast across the southern Plains. Another round
of severe thunderstorms will be possible on Friday/Day-6 across
portions of northeast Texas/northern Louisiana and much of Arkansas
as diurnal heating of a moist airmass results in MUCAPE values
between 1000-2000 J/kg beneath modest vertical shear associated
persistent southwest midlevel flow.
The severe potential will likely persist into Saturday/Day-7 and
Sunday/Day-8 across portions of the southern Plains and northern
Gulf Coast states. Here, persistent western troughing will maintain
an increasingly moist airmass along and south of the aforementioned
frontal boundary. The location of this frontal boundary will likely
be significantly impacted by the repeated rounds of thunderstorms in
the prior days. Model guidance is in general agreement that at least
modest westerly/southwesterly flow will persist across the southern
Plains, with episodic perturbations traversing this flow field
downstream of the broader large-scale western trough. However,
significant differences remain with respect to the timing, strength,
and location of any of these perturbations to attempt to highlight unconditional severe probabilities.
..Marsh.. 04/19/2026
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