RSS Mesoscale Discussions from Storm Prediction Center
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0258 PM CDT Fri May 15 2026
Valid 152000Z - 161200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF IOWA...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE UPPER
MIDWEST AND CENTRAL/SOUTHERN PLAINS....
...SUMMARY...
Severe thunderstorms capable of producing severe/damaging winds and
large to very large hail are likely late this afternoon and evening
centered across much of Iowa. Isolated to scattered severe hail and
damaging winds are possible over a broader area from parts of the
southern High Plains to the Upper Midwest.
...20z Update Central Plains...
Several areas of thunderstorm development are expected this
afternoon and evening across the central Plains and Midwest.
Moderate instability beneath 40+ kt of mid-level flow will promote a
mixed mode of supercells and eventually linear clusters. Hail (some
2+ inches) along with damaging gusts appear likely with the more
robust supercells initially along the cold front across NE/northern
KS, and farther north along the warm front into southern MN.
Eventual upscale growth into one or more linear clusters should
favor an increase in the threat for damaging gust and a couple
tornadoes over parts of IA, IL and southern WI this evening.
...Eastern NM/CO and the TX/OK Panhandles...
Initial high-based shower and thunderstorm development is underway
coincident with very strong heating and the arrival of a weak
upper-level shortwave trough atop the well-mixed air mass west of
the dryline. With mixing depths of 4-5 km below modest buoyancy,
strong to severe gusts are possible with these showers and
thunderstorms across the southern High Plains. Wind probabilities
were shifted slightly west. See MCDs #723 and #724 for short term
information.
..Lyons.. 05/15/2026
.PREV DISCUSSION... /ISSUED 1129 AM CDT Fri May 15 2026/
...Central Plains into the Upper Midwest including Iowa...
A cyclonically influenced moderately strong belt of westerlies will
exist over the northern Plains to Upper Midwest and upper Great
Lakes. The primary surface low will remain in northern Ontario, with
a trailing cold front extending southward into the Upper Midwest and
northern/central Plains. A secondary surface low will exist across
southwest Kansas and northwest Oklahoma around peak afternoon
heating, with a dryline extending south-southwestward from this low
across much of the southern High Plains.
Continued expectations are for robust thunderstorm development along
the cold front/surface trough from eastern Nebraska into Iowa to be
delayed until late afternoon or early evening (around 22-00Z), as
large-scale ascent will remain weak until a low-amplitude shortwave
trough embedded within the westerly mid-level flow eventually
overspreads the surface warm sector. Continued low-level warm/moist
advection through the day and diurnal heating will contribute to the
development of moderate to locally strong instability (2500+ J/kg
MLCAPE) across this region by early evening. While low-level winds
are forecast to remain fairly modest, enhanced mid/upper-level flow
will support sufficient (35-50 kt) deep-layer shear for updraft
organization.
Initial supercells should pose a threat for large to isolated very
large hail (2+ inches in diameter), before likely quick upscale
growth this evening across Iowa with an increasing potential for
scattered severe/damaging winds. Some of these gusts could exceed 75
mph on a localized basis given the expectation for an organized
cluster and ample instability. A tornado or two could also occur
this evening as low-level shear gradually increases with a
strengthening low-level jet.
...Southern High Plains...
While clouds linger at midday, particularly with southward extent
across west/southwest Texas, robust daytime heating will yield a
very well-mixed/deep boundary layer near/south of the secondary
surface low over southwest Kansas/northwest Oklahoma. Mid-level
temperatures will remain cool enough to support at least weak
instability, even with modest low-level moisture/surface dewpoints.
A weak mid-level shortwave trough moving from the southern Rockies
into the southern High Plains will enhance large-scale ascent late
in the day. This should support the development of high-based
thunderstorms, with occasional strong to severe wind gusts expected.
Latest short-term guidance suggests a more probable zone of
thunderstorm-related gust potential may focus across the Texas South
Plains and Low Rolling Plains. Isolated gusts of 70+ mph may occur
given the very deeply mixed boundary layer extending up to around
500 mb. Cells that develop in west/southwest Texas may also contain
some hail, with elongated hodographs in mid/upper levels.
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SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1227 PM CDT Fri May 15 2026
Valid 161200Z - 171200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM EXTREME
NORTHEAST COLORADO INTO SOUTHWEST NEBRASKA AND NORTHWEST KANSAS...
...SUMMARY...
Severe storms capable of large to very large hail, wind damage and
perhaps a couple of tornadoes will be possible Saturday afternoon
and evening across parts of the central Plains. Scattered
thunderstorms will also pose potential for strong to severe winds
across the lower to mid- Missouri Valley.
...Central Plains to the OH Valley...
Amplification of the pattern will occur this weekend as a midlevel
trough digs south-southeastward over the northern Rockies/Great
Basin, with downstream lee cyclogenesis expected in the vicinity of
southeast CO. Within the warm sector of the cyclone, an influx of
mid-upper 60s boundary-layer dewpoints will persist from OK/KS into
the lower MO Valley and the OH Valley. Remnants of D1 convection
could be ongoing at the start of the period across parts of MO/IL,
with the possibility of an MCV moving eastward during the day across
the OH Valley. Isolated wind damage and large hail will be possible
with loosely organized clusters during the day into the OH Valley.
Isolated severe storms will also be possible during the afternoon
along the outflow-reinforced front across northern MO.
The primary severe threat is expected to increase Saturday
afternoon/evening, starting in northeast CO and spreading eastward
into NE and adjacent areas of northwest KS. Upslope flow north of
the lee cyclone and westward advection of low-level moisture beneath
steep midlevel lapse rates will result in moderate-large buoyancy
near the warm front. Storm initiation is probable by mid-late
afternoon in northeast CO, and storms will subsequently spread
eastward toward southwest NE/northwest KS. Wind profiles with long
hodographs will favor supercells capable of producing very large
hail (up to 3 inches in diameter). Low-level shear and moisture
will become sufficient for a few tornadoes as the storms move
farther east toward the CO/KS/NE border region. Upscale growth into
a cluster/MCS will also be possible Saturday evening, with an
increase in the potential for severe outflow gusts of 65-80 mph.
Farther south, thunderstorm development along the dryline is more
questionable given a warm elevated mixed layer and (at best) weak
forcing for ascent. Still, hot temperatures/deep mixing could
support isolated, high-based storms with the conditional threat for
large hail and strong outflow gusts.
..Thompson.. 05/15/2026
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SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0229 PM CDT Fri May 15 2026
Valid 171200Z - 181200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
NEBRASKA TO SOUTHWEST MINNESOTA...
...SUMMARY...
Severe storms are expected Sunday afternoon into Sunday night from
portions of the central Plains into the Upper Midwest. Supercells
with very large hail and tornadoes are possible, before upscale
storm growth leads to an increase in the wind damage threat.
...Synopsis...
The primary midlevel trough over the northern Great Basin Sunday
morning will progress to the Four Corners by Monday morning. A
subtle, lead shortwave trough (now over northern CA) will eject
northeastward during the day from NM to western KS/central NE, and
it will reach MN by early Monday. A weak reflection of the initial
lee cyclone will likewise move north-northeastward across NE to MN,
along a pre-existing baroclinic zone. The boundary layer will
consist mostly of roughly mid 60s dewpoints east of the dryline and
south of the warm front Sunday, while the fully modified (maritime
tropical) air mass will return to TX through Sunday night.
...NE to MN...
The elevated remnants of overnight convection across NE/IA, and an
associated MCV, should move northeastward toward the upper MS Valley
and weaken. In the wake of the early convection, surface heating in
cloud breaks will contribute to destabilization and storm
development will become probable by Sunday afternoon/evening along
the stalled front in NE, in advance of the weak surface cyclone and
subtle/ejecting midlevel trough. Mesoscale details are fairly
uncertain this far in advance. Still, the forecast environment
appears favorable for initial supercells with very large hail and
tornadoes, and some increase in the threat for damaging winds as
convection grows upscale along the front and spreads northeastward
into southeast SD, northwest IA and southwest MN through Sunday
night.
...Western KS to TX Panhandle dryline...
A relatively warm elevated mixed layer and no obvious forcing for
ascent both suggest that storm initiation will rely on sufficiently
deep mixing along the dryline, and that storm formation is very much
in question. If a storm or two forms late afternoon/evening before
the dryline retreats overnight, there be a conditional threat for
supercells with large hail.
..Thompson.. 05/15/2026
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