RSS Mesoscale Discussions from Storm Prediction Center
SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1115 AM CDT Thu May 21 2026
Valid 211630Z - 221200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND
EVENING OVER PARTS OF EASTERN COLORADO....
...SUMMARY...
Thunderstorms capable of producing large hail and isolated severe
gusts should occur across parts of the central/southern High Plains
this afternoon and evening. A tornado or two may also occur.
...High Plains...
Water vapor imagery shows an upper trough moving across western
WY/CO. This feature will spread weak/broad large scale forcing for
ascent across much of the High Plains from SD to NM this afternoon.
At the surface, southerly low level winds have resulted in an axis
of 40s/50s dewpoints along this corridor. Low clouds are slowly
eroding, which should result in moderate CAPE values and aid in the
development of widely scattered afternoon thunderstorms.
Isolated storms will likely form first over parts of eastern NM.
This activity will build slowly eastward toward west TX with a risk
of large hail.
By mid/late afternoon, storms will likely develop off the Raton and
Palmer ridges, spreading eastward toward western KS this evening.
Shear profiles in this area will be stronger than farther south,
supporting longer-lived storms capable of large hail, damaging
winds, and perhaps a tornado or two.
An isolated cell or two may also produce occasional severe hail over
parts of eastern WY and into the Black Hills region later this
afternoon.
...Carolinas/VA...
Clear skies are leading to strong heating over parts of southern VA
into part of NC/SC. Scattered afternoon thunderstorms are expected
to form in this zone, with steep low-level lapse rates and
sufficient CAPE supporting a risk of gusty/damaging winds in the
strongest cells.
..Hart/Lyons.. 05/21/2026
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SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1220 PM CDT Thu May 21 2026
Valid 221200Z - 231200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ...
...SUMMARY...
Scattered severe storms capable of large hail and damaging winds are
possible across western parts of Texas and Oklahoma. An isolated
hail threat may extend into central Kansas, with sporadic
occurrences of damaging wind and perhaps a few brief tornadoes from
the central Gulf Coast into the Tennessee and Ohio Valleys.
...Synopsis...
A short-wave trough over the northern and central High Plains Friday
morning will become negatively tilted while translating through the
upper MS Valley, ahead of a weaker, upstream disturbance moving
through the central Rockies into central High Plains. Meanwhile, a
series of lower-latitude disturbances will progress from the
southern Plains and lower MS Valley into the TN and OH Valleys.
At the surface, an area of low pressure will track from SD into
northwest MN with a trailing cold front advancing east/southeast
through the central Plains, and south into the southern High Plains
where it will link with a secondary low pressure. A dryline is
expected to sharpen through the afternoon from the intersection of
the cold front in the vicinity of the TX South Plains into the
Edwards Plateau. Elsewhere, a surface low is forecast to develop
from western TN into IN/OH with an associated warm front lifting
north into the OH Valley.
...Central and Southern Plains...
An axis of 50s to low 60s dewpoints is expected to reside ahead of
the cold front and dryline, with the steepest mid-level lapse rates
confined to the southern High Plains portion of the warm sector.
Resultant MLCAPE of 1500-2500 J/kg is forecast over western TX into
the southern Panhandle, with instability decreasing with
northeastward extent across KS and NE.
Showers and thunderstorms are expected to develop early in the day
along the front in NE with additional storms forming southwestward
along the boundary during the afternoon from central KS into the
southern TX Panhandle or TX South Plains, with more isolated
development possible south along the dryline. Additional storms are
possible in the immediate post-frontal environment in northeast NE.
The most favorable overlap of moderate instability and around 30 kt
of deep-layer shear is expected to reside over parts of western TX
and the Panhandle where the potential will exist for supercell storm
modes with the predominant hazard being large hail. Storms may tend
to grow upscale into an MCS with a wind and hail threat spreading
into parts of western OK and northwest TX Friday evening.
Lesser-organized multicell structures appear possible from central
KS into southeast NE. The best potential for marginally severe hail
is expected over central KS where comparably (to NE) stronger
instability will develop.
...Central Gulf Coast and Southeast into Ohio Valley...
Some enhancement of the mid-level wind field will occur in
association with the disturbances mentioned in the synopsis. Of
potentially greater importance to severe-weather potential is the
presence of a 25-40 kt low-level jet, which will persist through the
day from the central Gulf Coast north toward the OH River amidst a
moist and marginally to moderately unstable air mass with afternoon
MLCAPE of 500-1500+ J/kg.
Scattered to numerous thunderstorms are expected within the
northward-expanding warm sector, with the strongest instability
confined to cloud-free areas where greater daytime heating can
occur. Embedded strong to severe storms will be most probable in
those areas, and given the presence of 30-35 kt deep-layer shear,
some potential for storm organization will exist, despite the
existence of poor mid-level lapse rates. A corridor of stronger
low-level shear (i.e., effective SRH of 100-200 m2/s2) is forecast
from eastern MS and western AL through middle TN into OH, along the
low-level jet axis, where a few brief tornadoes appear possible.
Otherwise, locally damaging downburst winds appear to be the primary
hazard.
..Mead.. 05/21/2026
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