RSS Mesoscale Discussions from Storm Prediction Center
SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0110 AM CDT Sun May 17 2026
Valid 171200Z - 181200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
CENTRAL PLAINS/MIDDLE MISSOURI VALLEY...
...SUMMARY...
Severe storms are expected this afternoon into tonight across the
central Plains to the Upper Midwest. Supercells with very large hail
and strong tornadoes are possible, before one or more linear
clusters of storms leads to an increase in wind-damage potential by
evening.
...Colorado/Central Plains to Upper Midwest...
An active severe-weather day is expected regionally. A consequential
late-evening/overnight MCS and related outflow across
Nebraska/northern Kansas to southern Iowa and northern Missouri will
likely be a lingering factor for later today. For one, this includes
some southeastward regional adjustment in severe probabilities
across areas such as eastern Nebraska/western Iowa and northeast
Kansas/far northwest Missouri.
One or more embedded disturbances will emerge this afternoon from
the central Rockies amid increasingly prevalent cyclonic flow aloft
in advance of an amplifying large-scale trough over the West. Lee
cyclogenesis will occur across the central High Plains, with a
northward advection of moisture, and post-MCS-related air mass
recovery across eastern portions of Kansas/Nebraska into Iowa
through late afternoon in association with a warm front, and ahead
of a southeast-progressing cold front across the north-central High
Plains.
Initial thunderstorm development is expected across northeast
Colorado into southwest Nebraska within a low-level upslope flow
regime ahead of the approaching synoptic cold front. These storms
will be capable of large hail given very steep lapse rates, strong
vertical shear and elongated/straight hodographs.
By late afternoon/early evening, quickly intensifying deep
convection is expected farther east within the warm sector and near
and east/northeast of a surface triple point across parts of eastern
Nebraska and far southeast South Dakota/northwest Iowa, initially
including intense supercells capable of very large hail and
tornadoes, some of which could be strong. Backed low-level winds
within the warm sector, veering with height, will contribute to
increasing low-level SRH and favorably curved low-level hodographs.
While the corridor for discrete supercells will be narrow, partly
due to capping as well as the advancing cold front resulting in
upscale growth, the expectation is for a few supercells capable of
producing strong tornadoes and large to very large hail, with a
somewhat longer duration for more discrete storms with southward
extent across eastern Nebraska into northeast Kansas.
With time, one or more linear/bowing segments is expected to develop
near the east/southeast-advancing cold front and as the low-level
jet significantly increases during the evening. An attendant risk of
severe wind gusts will accompany this activity. The severe risk will
diminish with time and eastward extent during the nighttime hours as
instability weakens and capping increases.
...Kansas/Oklahoma and North Texas...
While there are some uncertainties related to capping, particularly
with southward extent, at least isolated high-based convection is
expected regionally late in the afternoon, particularly for the
Kansas and western Oklahoma/eastern Texas Panhandle portion of the
dryline. Given very steep low to mid-level lapse rates, moderate
instability, and supercell-supportive wind profiles, large to very
large hail and strong/severe wind gusts will be possible.
...Northern Illinois and Wisconsin to Lower Michigan...
While the influences of the early morning MCS across the Corn Belt
are not certain, potentially including lingering cloud cover, there
is some potential for at least isolated strong/severe storm
development near the northward-shifting warm front. This could
potentially include a few supercells and related hazards through the
afternoon/early evening.
...Southeast/Florida Peninsula...
On the western periphery of the western Atlantic anticyclone,
diurnally maximized thunderstorm development should focus from the
southern Appalachians across Georgia and interior/western Florida
Peninsula. Thermodynamic environment should be supportive of
strong/locally severe storms capable of wind damage/downbursts, and
possibly some hail.
..Guyer/Squitieri.. 05/17/2026
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SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Sun May 17 2026
Valid 181200Z - 191200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS PORTIONS OF
CENTRAL AND NORTHEASTERN KANSAS INTO FAR SOUTHEASTERN NEBRASKA...
...SUMMARY...
Numerous severe thunderstorms are expected to develop Monday along a
cold front and dryline extending from the Great Lakes into the
central/southern Plains. Supercells capable of all hazards
(including very large hail and strong to intense tornadoes) will
likely occur across central Kansas into southeastern Nebraska.
...Synopsis...
On Monday, a mid-level trough will deepen and lift out of the Four
Corners into the central Plains as a belt of enhanced westerly flow
moves within the mean flow. As this westerly flow overspreads the
Rockies, deepening of a surface cyclone across eastern Colorado is
expected, with strengthening of southerly surface flow across the
southern/central Plains. Convection is likely to be ongoing in the
vicinity of a lead shortwave across portions of Iowa into Wisconsin
at the start of the D2/Monday period.
A front will extend from the surface low in eastern Colorado
northward across southeast NE/IA/WI. A surface dryline will be
located across central Kansas extending southward into western
Oklahoma and southwestern Texas. Mid 60s to 70s dew points will be
common east of the dryline and northward ahead of the cold front
into the Great Lakes. Numerous severe thunderstorms are expected to
develop along the cold front southward to the dryline by the
afternoon. A corridor of enhanced severe potential will exist across
central KS/southeastern NE/southwest IA/northwest MO.
...Central KS into southeast NE/southwest IA/northwest MO...
Near the triple point of the surface low/dryline/cold front across
central Kansas, a more favorable corridor of severe potential will
exist Monday afternoon. Morning cloud cover should erode across
central Kansas by the afternoon allowing for strong daytime heating
and warming. Temperatures ahead of the dryline will approach the mid
to upper 80s, with dew points in the upper 60s to 70s. This will
yield and axis of moderate to strong MLCAPE around 3500-4500 J/kg
extending from central Kansas into southeastern Nebraska. MLCIN will
erode through the afternoon by around 18-20z with initiation
expected along the dryline and cold front to the north by around
20-21z. Forecast soundings indicate favorable kinematics to support
organized supercells, given deep layer shear around 40-50 kts.
Initial supercells will be capable of large to giant hail (2-4+
inch) given steep low to mid-level lapse rates around 7-8 C/km. Hail
probabilities were increased with this outlook to support this
potential.
The southerly low-level jet is progged to increase as large scale
ascent spreads eastward through the afternoon, peaking around 40-50
kts by the 00-03z across northern OK into central KS. Strengthening
flow in the 850-700 mb layer will elongate low-level hodographs with
broad clockwise curvature in the 0-2 km layer and rapidly increasing
low-level SRH. Forecast soundings indicate 0-1 km SRH will approach
250-300 m2/s2 across portions of central/eastern KS. This in
combination with the volatile thermodynamic environment will support
an increase in tornado potential through the evening. Should
discrete supercells be maintained, strong to intense tornadoes will
be possible primarily from central to northeastern KS into
southeastern NE. Given southwesterly deep layer shear is oriented
somewhat parallel to the southwest to northeast cold front, storms
near the front may cluster and grow upscale. Better potential exists
for a more semi-discrete supercell across central Kansas ahead of
the dryline. A few HREF members do support potential for this
scenario, with long UH tracks across KS into southern Nebraska.
Tornado probabilities were increased from east-central KS into
southeastern NE/southern IA/northwestern MS.
...Central IA into portions of IL/KY/WI/IN/Lower MI...
Elevated thunderstorm activity will be likely at the beginning of
the period across portions of Iowa/Wisconsin. This will pose some
risk for a few instances of severe hail. Guidance suggests that
recovery will occur by the afternoon across this region with
thunderstorms redeveloping along the cold front and re-intensifying
of downstream convection the into the afternoon. Initial morning
convection may pose some wind/hail risk into IL/IN/western KY.
Additional development by the evening along the cold front to the
north will pose some wind/hail risk across portions of the upper
Midwest.
...OK/TX...
A more conditional severe risk exists further south across OK/TX.
Large-scale ascent will remain weaker further south. However, strong
instability within the very moist warm sector will exist. Deep layer
flow will be somewhat less compared to further north, but still
sufficient for supercells. If storms can develop, a risk for large
to very large hail and perhaps a tornado will exist.
..Thornton.. 05/17/2026
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SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 AM CDT Sun May 17 2026
Valid 191200Z - 201200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE SOUTHERN
PLAINS INTO PORTIONS OF THE MIDWEST...OHIO VALLEY...AND NORTH TO THE
GREAT LAKES...
...SUMMARY...
Widely scattered severe thunderstorms will be possible along a cold
front extending from the Great Lakes into the portions of the
Midwest and south to the Southern Plains. Storms will pose a risk
for primarily damaging wind and hail.
...Synopsis...
A cold front will extend from the Great Lakes region to the Midwest
and south into the Southern Plains D3/Tuesday. The upper-level
trough will continue lifting north and east into the Great Lakes
through the period.
...Upper Midwest to the Great Lakes...
Some remnant elevated thunderstorm activity may be ongoing toward
the start of the period D3/Tuesday across the upper Midwest. This
may pose some potential for a few instances of severe hail.
Redevelopment of thunderstorms is likely along the front by the
afternoon. Sufficient deep layer shear around 20-30 kts and moderate
instability ahead of the front may support supercells initially
capable of large hail and perhaps a tornado. Linear forcing with the
cold front will likely lead to upscale growth and potential for
damaging wind downstream into the Ohio Valley through time.
...Oklahoma/Texas...
Trends continue for more progressive movement of the cold front
through Oklahoma/north Texas Tuesday morning. As a result,
probabilities were shifted eastward again with this update. Widely
scattered thunderstorm development is expected by the afternoon
across eastern Oklahoma into north Texas. Though the better
mid-level flow will be displaced to the north, steep low to
mid-level lapse rates remaining across this region will support
potential for damaging wind and large hail given moderate
instability ahead of the front.
..Thornton.. 05/17/2026
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