RSS Mesoscale Discussions from Storm Prediction Center
SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1252 AM CDT Thu May 21 2026
Valid 211200Z - 221200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
EASTERN COLORADO...
...SUMMARY...
Thunderstorms with a threat for large hail, isolated severe gusts
and possibly a tornado are expected in parts of eastern Colorado
from mid afternoon to early evening. Isolated large hail will also
be possible in parts of the southern High Plains this afternoon.
...Central and Southern High Plains...
An upper-level trough will move eastward into the central Rockies
today. Ahead of the trough, a lee surface low will form over eastern
Colorado. As surface temperatures warm, convection will initiate in
the higher terrain near Denver and Colorado Springs. From this
convection, storms will develop and move eastward into the central
High Plains during the afternoon. In eastern Colorado, a
north-to-south axis of instability will be in place by afternoon,
where model forecasts have MLCAPE peaking around 1500 J/kg. In
addition, late afternoon RAP forecast soundings in eastern Colorado
have 0-6 km shear in the 45 to 55 knot range with 700-500 mb lapse
rates near 8 C/km. This will be favorable for supercells with large
hail and isolated severe gusts. If a supercell can become locally
dominant, then a tornado will also be possible. The severe threat
will likely persist into early evening.
Further south into the southern High Plains, an axis of instability
will be in place by afternoon. The strongest instability is forecast
on the Caprock of west Texas, where 0-6 km shear is forecast to be
around 30 knots. This, along with 700-500 mb lapse rates near 7
C/km, may be enough for an isolated large hail threat.
..Broyles/Squitieri.. 05/21/2026
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SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1250 AM CDT Thu May 21 2026
Valid 221200Z - 231200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF THE
SOUTHERN PLAINS...
...SUMMARY...
Scattered strong to severe storms will be possible across portions
of the southern Plains with potential for large hail and damaging
wind.
...Synopsis...
Two weak shortwaves, with one wave in central Plains and a secondary
wave into the Tennessee/Ohio Valleys, are forecast within the
broader Northern Rockies trough through afternoon on D2/Friday. A
surface low will be located across eastern New Mexico/southeastern
Colorado with a front lifting northward into Kansas and a dryline
extending southward into southwestern Texas. Another surface low
will develop across the Mississippi and Ohio Valleys with a warm
front lifting northward across Kentucky. These features will be the
focus for scattered thunderstorm development in both regions by the
afternoon/evening.
...Southern and Central Plains...
Scattered thunderstorm development is expected across the Cap Rock
near the dryline in Texas and back into eastern New Mexico along the
high terrain Friday afternoon and evening. Steep low to mid-level
lapse rates will be in place across much of the region from eastern
New Mexico into western Texas. Dew points in the mid 50s to low 60s
and daytime heating will yield moderate instability amid deep layer
shear around 30-40 kts. This will promote initial supercells across
the high terrain with potential for additional multi-cell clusters
through time. These may grow upscale into an MCS into western
Oklahoma by the evening. The primary risk will be for large hail
before the damaging wind risk increases into the evening.
A few additional strong thunderstorms may extend into portions of
southern Kansas. The thermodynamic environment becomes less
favorable with northern extent due to widespread cloud cover and
morning precipitation. However, increasing mid-level flow and shear
may allow for a few organized cells with potential for large hail
and strong to severe wind further north.
...Tennessee and Ohio Valleys...
A warm front will lift across northern Tennessee into Kentucky
through the afternoon on Friday, with 60-70s dew points streaming
northward ahead of the approaching mid-level wave. Modest height
falls are expected across western Kentucky into the Ohio Valley,
with an increase in 850-700 mb flow. Widely scattered thunderstorms
are expected overnight into Friday morning. An increase in this
activity can be expected as a vorticity maxima and increasing large
scale ascent into the afternoon occurs. Though instability will be
marginal, guidance does suggest a plume of higher theta-e air may
advect into western/central Kentucky by the afternoon. In addition,
guidance suggests a few transient supercells will be possible with
potential for damaging winds and perhaps a tornado.
..Thornton.. 05/21/2026
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SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0229 AM CDT Thu May 21 2026
Valid 231200Z - 241200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Widely scattered thunderstorms are expected from the
central/southern Plains into the lower Mississippi Valley and
southeastern US. A few stronger storms may be possible across the
southern Plains, particularly near the Texas and Oklahoma
Panhandles.
...Synopsis...
A weak impulse will rotate across the central Plains on D3/Saturday
as a surface low moves northward across the Ohio Valley. A trailing
cold front will extend from the surface low back into the southern
Plains. Widely scattered thunderstorm activity will be possible
from the central/southern Plains into the lower Mississippi Valley
and across the Southeast. A few stronger storms may be possible
across the Texas/Oklahoma Panhandles.
...TX/OK Panhandles...
Weak forcing for ascent and easterly upslope flow across the Caprock
will produce scattered thunderstorm activity Saturday afternoon.
Forecast soundings suggest a plume of steep to low mid-level lapse
rates will still reside across the OK/TX Panhandles with mid 50s to
60s dew points and moderate instability by the afternoon. Shear
profiles will be fairly weak, with deep layer shear around 25 kts. A
few stronger storms may produce gusty winds and hail. Overall, weak
deep layer shear for organization may limit the severe threat.
..Thornton.. 05/21/2026
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Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0347 AM CDT Thu May 21 2026
Valid 241200Z - 291200Z
...DISCUSSION...
Severe potential will remain low through the beginning of the
extended period. Weak troughing will continue across the central
Plains D4/Sunday before height rises begin across the central US
with a high amplitude ridge settling in from the west D5/Monday.
This pattern will remain in place through early next week. Slow
moisture return will be ongoing across much of the Plains into the
Midwest with occasional rounds of widespread rainfall and
thunderstorms, but generally weak flow and subsidence will keep
organized storm potential low.
By the midweek, a trough is progged to begin deepening across the
Pacific Northwest. As the upper low slowly shifts eastward, stronger
flow will overspread the Intermountain West into the Northern
Rockies, resulting in strengthening lee troughing across the
central/northern Plains D6/Tuesday and D7/Wednesday. Moisture
advection will spread northward amid strengthening southerly flow
across the central/northern Plains. While there are some differences
in the placement of upper-level and surface features, it is possible
that severe chances will return across portions of northern High
Plains. For now, confidence in exact corridors remains low given
model guidance differences.
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