spc ac 260543
day 2 convective outlook
nws storm prediction center norman ok
1243 am cdt sun apr 26 2026
valid 271200z - 281200z
...there is an enhanced risk of severe thunderstorms monday
afternoon through monday evening across much of the middle
mississippi valley...including portions of southeastern
iowa...southern wisconsin..eastern missouri...much of illinois...and
portions of northeastern arkansas...northwestern tennessee and
western indiana...
...summary...
widespread strong to severe thunderstorm development appears
probable across the middle mississippi into lower ohio valleys
monday afternoon through monday evening, accompanied by potential
for a few strong tornadoes, damaging wind gusts and large hail.
...discussion...
models suggest that the northern periphery of a prominent
subtropical high, centered near the mexican gulf coast, may build a
bit further northward through the southern great plains and
gulf coast states through this period. this is forecast to occur
downstream of a digging mid/upper trough and embedded low across the
southern mid- to subtropical latitudes of the eastern pacific, while
broad, larger-scale troughing to its north progresses eastward
through much of the interior of north america.
near the leading edge of the latter regime, it appears that a
significant short wave perturbation will accelerate northeast of the
lower missouri valley through the upper midwest/great lakes region,
accompanied by a notable (sub-1000 mb) deepening surface cyclone. a
trailing low may migrate from east central kansas through eastern
iowa during the day monday, trailed by a dryline just ahead of a
cold front, which may gradually overtake the dryline across eastern
iowa through southwestern missouri late monday afternoon into
evening. it appears that this may be preceded by one or two
clusters of storms maintained by forcing for ascent associated with
lower/mid-tropospheric warm advection, which may still be ongoing
across northern missouri/southern iowa into parts of northern and
central illinois at the outset of the period, before shifting
eastward into the ohio valley during the day.
the impacts of this potential activity on subsequent destabilization
and convective development remains unclear, and a significant source
of lingering forecast uncertainty. however, most guidance continues
to indicate moderate to strong warm sector boundary-layer
destabilization will occur with low-level moisture return and
insolation beneath an initially northeastward advecting plume of
capping elevated mixed-layer air, ahead of the dryline. substantive
destabilization still appears possible to the cool side of an
outflow boundary generated by the early day convection, which may
retreat northward through parts of southeastern iowa and central
through northern illinois by late afternoon, as an effective warm
frontal zone to the east of the southern surface low.
...middle mississippi into lower ohio valleys...
aided by mid/upper forcing for ascent to the poleward side of a 70+
kt southwesterly, cyclonic 500 mb jet streak, it appears that the
triple point low/dryline may become the focus for strongest storm
development by late monday afternoon across parts of northeastern
missouri/southeastern iowa into northwestern illinois. given the
environment, including sizable clockwise-curved low-level hodographs
beneath 40-50 kt southerly 850 mb flow, this probably will include
discrete supercells initially, with potential to produce large hail
and strong tornadoes. gradually, it is probable that this will grow
upscale along the remnant outflow boundary and along the dryline as
it begins to be overtaken by the southward surging cold front, into
the lower ohio valley by late monday evening. as this occurs,
embedded supercell structures may continue to pose a risk for strong
tornadoes, with evolving meso-vortices along developing gust fronts
of convective outflow also posing a risk for brief tornadoes and/or
damaging wind gusts.
the extent of the tornadic threat remains a bit unclear, and will
probably be dependent on how long discrete supercells are maintained
along/ahead of the dryline. however, depending on how the modifying
initial convective outflow evolves across southeastern iowa into
central illinois, this boundary could become a focus for heightened
tornado potential, with a few strong, and particularly damaging,
tornadoes possible. categorical and severe probabilities could
still be upgraded further in later outlooks for this period.
..kerr.. 04/26/2026
click to get wuus02 ptsdy2 product
note: the next day 2 outlook is scheduled by 1730z