spc ac 201930
day 3 convective outlook
nws storm prediction center norman ok
0230 pm cdt sat jun 20 2026
valid 221200z - 231200z
...there is a slight risk of severe thunderstorms across a part of
the mid-atlantic...
...summary...
widely scattered severe storms appear possible across portions of
the mid-atlantic monday afternoon and evening. more isolated severe
weather is expected along a frontal zone that will extend from the
southern appalachians to the mid-south and southern plains, as well
as across the central and northern high plains monday afternoon and
evening.
...synopsis...
a series of mid-level disturbances initially from the great lakes
and oh valley into the mid-south monday morning are expected to
translate east toward the atlantic coast during the forecast period.
a belt of stronger mid-level flow will coincide with a more
prominent short-wave trough translating through the mid-atlantic
during the day. elsewhere, mid-level flow is forecast to strengthen
across the northern and central high plains, downstream from a
short-wave trough moving through the northern high plains.
at the surface, an area of low pressure over the upper oh valley at
12z monday is forecast to develop toward the mid-atlantic coast by
evening with a trailing cold front advancing through the central
appalachians and tn valley into the southeast and central gulf coast
states. the western extension of the boundary will extend through
the southern plains into eastern nm with a strengthening upslope
flow regime developing within the post-frontal environment across
the central and northern high plains.
...mid-atlantic...
areas of showers and thunderstorms are expected to be ongoing monday
morning across the lower great lakes/upper oh valley region. ahead
of that convection, a southwesterly low-level jet is forecast to
migrate through the mid-atlantic, enhancing the poleward transport
of an increasingly moist and unstable boundary layer. increasing
height falls/forcing for ascent coupled with convergence near and
ahead of the surface low, cold front, and any existing outflow
boundaries are expected to foster an increase in storm coverage and
intensity by afternoon. strengthening mid-level flow aloft will
combine with backed, near-ground winds ahead of the surface low to
enhance vertical shear across the delmarva region, supporting the
potential for supercell storm modes capable of all severe-weather
hazards.
...northern and central high plains into the southern plains...
there is some model signal for a weak mid-level disturbance to
overspread the northern and central high plains monday, ahead of a
stronger short-wave trough, which will remain well upstream through
the peak of the diurnal heating cycle. forcing for ascent remains
much more nebulous across the southern plains. thunderstorms appear
possible during the afternoon within the upslope flow regime across
the northern and central high plains, as well as along the stalled
synoptic front in tx and ok. storm coverage remains uncertain, which
precludes higher probabilities at this time. however, given the
presence of moderate to strong instability and more-than-sufficient
vertical shear for supercells, a conditional intensity group one
contour has been added to the forecast.
...southern appalachians into the mid-south and lower mississippi
valley...
multiple, larger-scale storm clusters may be ongoing monday morning
across the ozark plateau into the mid-south. daytime heating coupled
with the presence of a very moist low-level air mass is expected to
yield moderate to strong instability by afternoon ahead of the
early-day storms. as such, any storms that linger through the
morning may intensify by afternoon, with additional storms
developing along the synoptic front and any remnant outflow
boundaries. generally weak vertical shear is expected to limit
organized, severe-storm potential; however, the magnitude of
instability and presence of steep low-level lapse rates will be
supportive of damaging downburst winds.
..mead.. 06/20/2026
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note: the next day 3 outlook is scheduled by 0730z