spc ac 201724
day 2 convective outlook
nws storm prediction center norman ok
1224 pm cdt wed may 20 2026
valid 211200z - 221200z
...there is a slight risk of severe thunderstorms across eastern
colorado...
...summary...
widely scattered severe storms are expected to develop across
eastern colorado thursday afternoon and evening. large hail will be
the predominant hazard, with locally severe wind gusts and perhaps a
brief tornado or two also possible.
...synopsis...
a short-wave trough and associated jet streak initially over the
northern rockies thursday morning will progress southeast into the
central rockies by thursday night. farther to the south, a
short-wave trough will translate from the southern plains into lower
ms valley.
at the surface, a weak surface low is expected to develop from
southeast wy into western sd by thursday evening, along a front
advancing through the northern high plains. a lee trough will deepen
from the vicinity of low south through eastern parts of co and nm.
elsewhere, a cold front will push south from va into the carolinas
with the western extension of that boundary lifting north through
the lower ms valley thursday night in response to weak cyclogenesis
in that area.
...central high plains...
while low-level moisture will remain somewhat limited, the presence
of steep low/mid-level lapse rates will contribute to mlcape of
750-1000+ j/kg during the peak of the diurnal heating cycle.
low-level upslope flow will be augmented by increased forcing for
ascent downstream from the approaching short-wave trough to foster
widely scattered thunderstorm development along favored terrain by
mid to late afternoon.
strengthening mid-level flow coupled with the southeasterly
low-level wind component will yield effective bulk shear of 40-50
kt, supportive of supercell storm modes with the predominant hazard
being large hail. a brief tornado or two is possible, owing to
strengthening low-level shear by early evening. however, the
marginal moisture content is expected to limit a more robust threat.
...western dakotas...
at least a marginally unstable air mass is expected to develop ahead
of the front, supporting widely scattered thunderstorm development
by afternoon. stronger vertical shear is expected to reside to the
south of the area, limiting the potential for organized storm modes.
nonetheless, locally strong wind gusts and sub-severe hail appear
possible with the strongest storms.
...west texas...
there is some model signal that a broken band of thunderstorms may
evolve near the nm/tx state line by late afternoon or evening,
amidst a steep lapse rate environment. some potential will exist for
locally strong wind gusts and/or hail with that activity.
...eastern oklahoma into northeast texas...
the 12z convection-allowing models indicate a broader-scale complex
of storms evolving across the area thursday. weak vertical shear and
poor lapses are expected to limit the potential for storm
organization. however, the presence of a moist and moderately
unstable air mass will support briefly vigorous up/downdrafts
capable of locally strong wind gusts.
...deep south texas...
remnants of overnight storms may be ongoing thursday morning with
another round of thunderstorms potentially moving through the area
late thursday night into friday morning. some potential will exist
for a few strong storms capable of gusty winds and hail.
...lower ms valley...
the models suggest that low-level shear will strengthen late
thursday night into friday morning in response to weak cyclogenesis
over the area. lapse rates will be poor, limiting instability.
however, given the presence of a moist/low-lcl boundary layer, some
potential for low-level updraft rotation will exist with any deeper
convective elements, with a non-zero risk for a brief tornado.
...southern va into the carolinas....
a hot, well-mixed boundary layer is forecast ahead of the front
thursday afternoon. however, forecast soundings indicate warm
mid-level temperatures (500 mb and above), which are expected to
limit overall parcel buoyancy. nonetheless, a few locally strong
wind gusts appear possible with storms developing along and ahead of
the boundary.
..mead.. 05/20/2026
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note: the next day 2 outlook is scheduled by 0600z