spc ac 151728
day 2 convective outlook
nws storm prediction center norman ok
1228 pm cdt mon jun 15 2026
valid 161200z - 171200z
...there is a marginal risk of severe thunderstorms for portions of
the northern plains into the upper midwest...the great lakes to the
central plains...and the western/central gulf coast....
...summary...
isolated to scattered strong to severe thunderstorms are possible
tuesday afternoon and evening across parts of the midwest into lower
michigan. additional strong to severe storms are possible across the
northern plains into the upper midwest tuesday night.
...synopsis...
a belt of moderate to strong mid-level flow will extend from the
northwest to the northern plains and the midwest and to the
mid-atlantic on tuesday. within this flow, a mid-level shortwave
trough will move through the great lakes. an additional, stronger
shortwave trough will amplify across the northern plains toward the
end of the period. a weak surface low will move through the northern
great lakes through the day and weaken while an associated cold
front moves across the midwest and eventually stalls toward the end
of the period. a stronger surface low will develop across the
northern plains tuesday night and will be located somewhere near
eastern south dakota by the end of the period.
...midwest to the central plains...
strengthening lower tropospheric flow will transport moisture
northward ahead of a cold front tomorrow morning/afternoon with weak
to potentially moderate instability expected. an initial line of
storms will likely develop on the leading edge of the returning
moisture in a more well-mixed and uncapped environment. this
activity will likely stay sub-severe, but a few isolated damaging
wind gusts will be possible given the steep low-level lapse rates
and strengthening flow. the greater severe weather potential is
expected along the cold front during the afternoon where upper 50s
to low 60s dewpoints should be present. cloud-cover from initial
activity should limit overall instability (and a more substantial
threat), but cooling temperatures aloft should provide adequate
instability for strong to severe storms along the front. the strong
shear across the region will support the potential for rotating
updrafts capable of isolated large hail, damaging wind gusts, and
perhaps a tornado. if instability trends increase, an upgrade to
slight risk (level 2/5) may be necessary in later outlooks across
northern indiana, southern michigan and northwest ohio.
...northern plains to the upper midwest...
tuesday night, as the mid-level trough amplifies across the northern
plains, the frontal zone across the northern plains will tighten.
instability is forecast to be relatively weak initially, but strong
forcing from dcva across the region, strengthening isentropic ascent
due to the strengthening cyclone, and strong shear beneath the 100+
knot 300mb jet streak will provide an environment that supports
isolated strong to severe storms along the frontal zone despite the
weak instability.
within this larger marginal risk region, a greater severe threat may
exist shortly before 12z across northern iowa and vicinity. here
richer 850 moisture, advected by the strengthening low-level jet,
will yield greater elevated instability (1500 to 2000 j/kg mucape).
this will provide an environment featuring moderate instability and
strong shear amid strengthening isentropic ascent.
...gulf coast...
most guidance shows a mcv developing across northern mexico/south
texas today, which is already somewhat apparent across the region.
this feature is forecast to move into the western gulf on tuesday.
strengthening flow associated with this mcv will overspread the
texas and louisiana coast tomorrow. a tropical environment will be
present with weak mid-level lapse rates. however, this strengthening
flow may support an isolated tornado threat from the central texas
coast to the eastern louisiana coast.
..bentley.. 06/15/2026
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note: the next day 2 outlook is scheduled by 0600z