SPC Sep 20, 2026 1630 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1630Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1126 AM CDT Sun Sep 20 2026

Valid 201630Z - 211200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
CENTRAL AND EASTERN OKLAHOMA...AND FROM EASTERN COLORADO INTO FAR
WESTERN KANSAS...

...SUMMARY...
Thunderstorms with severe wind gusts and large hail will be possible
this afternoon and evening across parts of Oklahoma and from eastern
Colorado into far western Kansas. Isolated severe gusts and hail
will also be possible in parts of the southern Plains, and from the
Ozarks eastward into the Ohio Valley.

...Central/North TX into central/eastern OK...
Surface analysis places a low over central OK, along a cold front
that arcs from northeast OK into southwest OK and then back up
through the central TX Panhandle. This low also precedes a shortwave
trough moving into western OK. The cold front is forecast to shift
southward/southeastward today as the shortwave continues eastward.
The airmass ahead of this front will be warm, moist, and moderately
buoyant, and thunderstorm development is expected from
central/eastern OK into central TX. Mid-level flow is slightly
stronger across OK, supporting a greater potential for strong to
severe storms. A more isolated severe risk exists across TX where a
more disorganized storm mode is likely. Primary threat is damaging
gusts from 55 to 65 mph.

...Central High Plains...
An easterly component to low-level flow north of the surface front
will maintain a fetch of moisture (50s deg F surface dewpoints)
across eastern CO this afternoon. This moisture, combined with
heating and cool temperatures aloft, will enable moderate
destabilization by afternoon. Thunderstorm development is expected
as ascent attendant to the mid-level cyclone over WY persists across
the region. Moderate mid-level westerly flow will also persist
throughout the base of this cyclone, resulting in moderate to strong
vertical shear across the region this afternoon and evening. Storm
coverage is expected to remain isolated to widely scattered (largely
due to cooler surface temperatures and some lingering convective
inhibition), but any storms that do form and mature will likely be
supercellular. Primary severe hazard is large hail (1 to 2.5 inches
in diameter), but isolated severe gusts are possible as well. Some
lingering severe risk may eventually develop over southeast CO late
this evening and spread into the OK Panhandle overnight.

...Ozarks into the Mid Mississippi and Ohio Valleys...
Recent surface analysis places lows over central PA, central IL,
central MO, and central OK. An arcing stationary boundary extends
between these features, with this boundary largely demarcated by a
subtle wind shift. Current water vapor satellite imagery shows
several convectively augmented vorticity maxima within this corridor
as well. These vorticity maxima are forecast to progress
eastward/northeastward along the northern periphery of a weakened
mid-level anticyclone centered over the northwest Gulf Coast,
augmenting low-level convergence and helping to support
afternoon/evening thunderstorms from the OH Valley into
central/southern MO.

Despite ample low-level moisture, relatively warm temperatures aloft
will likely mitigate the overall buoyancy. Even so, steep low-level
lapse rates and moderate mid-level flow could still support some
bowing line segments capable of damaging gusts. Highest thunderstorm
coverage this afternoon and evening is expected from
central/southern IN into southern OH, with another corridor of
relatively higher coverage developing across central MO later this
evening as well. Both of these corridors are downstream of a
previously mentioned vorticity max, and represent areas of greater
severe potential.

..Mosier/Chalmers.. 09/20/2026


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SPC Sep 20, 2026 1300 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0727 AM CDT Sun Sep 20 2026

Valid 201300Z - 211200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
OKLAHOMA AND FROM EASTERN COLORADO INTO FAR WESTERN KANSAS...

...SUMMARY...
Thunderstorms with severe wind gusts and large hail will be possible
this afternoon and evening across parts of Oklahoma and from eastern
Colorado into far western Kansas. Isolated severe gusts and hail
will also be possible in parts of the southern Plains, and from the
Ozarks eastward into the Ohio Valley.

...OK and TX...
Southwesterly upper-level flow over the southern Great Plains will
be downstream of an eastward-migrating upper trough moving into the
central and southern High Plains by early evening. A frontal zone
modulated by convection overnight over the eastern part of the TX
Panhandle and OK will sag southward through tonight. A moist
airmass will undergo appreciable heating amidst surface dewpoints
in the mid to upper 60s F, resulting in moderate buoyancy by mid
afternoon. Sufficient deep-layer shear for storm organization is
expected across OK, where a risk for severe wind gusts and some hail
is expected to evolve during the afternoon into the early evening.
The 20/00z HREF/REFS ensemble guidance showed agreement in
delineating the strongest explicit 10-m wind gusts across parts of
southern OK within a corridor characterized by very steep 0-3 km
lapse rates. Have introduced an intensity level-1 area where
confidence in 60-80 mph gusts is greatest.

...Central High Plains...
A mid-level shortwave trough will move into the central High Plains
today. An easterly component to low-level flow north of the surface
front will maintain a fetch of moisture (50s deg F surface
dewpoints), and this moisture combined with heating will enable
moderate destabilization by afternoon. As surface temperatures warm
and convective inhibition erodes, scattered storms are forecast by
mid-late afternoon. Model forecast soundings show straight
hodographs with sizable CAPE in the -10 to -30 deg C layer. As a
result, a few supercells are probable with the primary severe hazard
being large hail (1 to 2.5 inches in diameter) along with isolated
severe gusts. Some lingering severe risk may eventually develop
over southeast CO late this evening and spread into the OK Panhandle
overnight.

...Ozarks/Mid Mississippi and Ohio Valleys...
A series of low-amplitude perturbations will move generally east
across the Ozarks and OH Valley to the north of a weakened mid-level
anticyclone centered over the northwest Gulf Coast. A reservoir of
seasonally rich low-level moisture (mid 60s to low 70s deg F surface
dewpoints) will exist south a cold front that was analyzed near the
I-70 corridor this morning. This frontal zone is forecast to
gradually push southward during the period and serve as the northern
delimiter of strong/severe thunderstorm activity.

As the boundary layer heats through the mid afternoon to the south
of more extensive cloud cover with north extent, moderate buoyancy
will likely develop. Some modest enhancement to mid-level flow will
probably accompany the aforementioned convectively augmented
mid-level features. Portions of eastern IL into IN could perhaps
yield a slightly more favorable environment for severe storms due to
hodograph structure. Yet, it remains uncertain whether some
strengthening of low-level flow in vicinity of the effective frontal
zone occurs later today. The 19/06z NAM differed substantially
versus recent RAP model runs. Regardless, a few clusters of strong
to severe thunderstorms will probably evolve, posing mainly an
isolated threat for wind damage.

..Smith/Mead.. 09/20/2026


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SPC Sep 20, 2026 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1219 AM CDT Sun Sep 20 2026

Valid 201200Z - 211200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
OKLAHOMA AND FROM EASTERN COLORADO INTO FAR WESTERN KANSAS...

...SUMMARY...
Thunderstorms with severe wind gusts and large hail will be possible
this afternoon and evening across parts of Oklahoma and from eastern
Colorado into far western Kansas. Isolated severe gusts and hail
will also be possible in parts of the southern Plains, and from the
Ozarks eastward into the Ohio Valley.

...Southern Plains...
At mid-levels, southwesterly flow will be in place today over much
of the central U.S. A shortwave trough is forecast to move into
Kansas and Oklahoma this afternoon. At the surface, a low will
deepen over southwest Oklahoma today, as a cold front advances
southward into central Oklahoma. Near the front, surface dewpoints
will be in the mid to upper 60s F, which will allow moderate
instability to develop by afternoon. MLCAPE is forecast to peak in
the 2000 to 3000 J/kg range in much of central and eastern Oklahoma.
As surface temperatures warm and low-level convergence increases,
scattered thunderstorms are expected to develop in the afternoon,
with storms moving from the Low Rolling Plains and Red River Valley
northeastward into central and eastern Oklahoma.

RAP forecast soundings at 00Z near the instability axis in central
Oklahoma have MLCAPE around 3000 J/kg with 0-6 km shear near 30
knots, and 700-500 mb lapse rates in the 7 to 7.5 C/km range.
Although a mixed mode is expected, the environment will likely
support supercell development in areas that become locally
favorable. Large hail and severe wind gusts will be possible with
supercells. The potential for supercells may continue into the early
evening over east-central Oklahoma, but a gradual transition to
linear mode is expected to take place. The wind-damage threat could
become maximized in the early evening, if an organized line segment
can develop.

...Central High Plains...
A mid-level shortwave trough will move into the central High Plains
today. Ahead of this feature, a lee surface trough will deepen
during the day from northeast New Mexico into eastern Colorado.
Surface dewpoints near the surface trough will be in the 50s F,
which will enable moderate destabilization by afternoon. As surface
temperatures warm, convection will initiate in the higher terrain
during the early afternoon and move eastward into the lower
elevations. A small complex of storms will likely develop from this
convection over the central High Plains. RAP forecast soundings near
the instability axis in eastern Colorado at 00Z have MLCAPE near
1500 J/kg with 0-6 km around 40 knots, and 700-500 mb lapse rates
near 7.5 C/km. This environment should be capable of producing
supercells with large hail and severe wind gusts.

...Ozarks/Mid Mississippi and Ohio Valleys...
At mid-levels, a subtle anticyclonic flow pattern will be in place
from the Ozarks eastward into the Ohio Valley. At the surface, an
axis of moisture and instability will be located from central
Missouri eastward into southern Indiana and southern Ohio, along
which surface dewpoints will be in the 70s F. By mid to late
afternoon, MLCAPE is forecast to peak in the 2000 to 3000 J/kg range
along much of this corridor. Although large-scale ascent will remain
relatively limited, increasing low-level convergence near the moist
axis will result in isolated convective initiation. Any small
cluster that can develop and persist in the late afternoon and early
evening could produce isolated severe wind gusts.

..Broyles/Thornton.. 09/20/2026


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SPC Sep 20, 2026 0100 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 0100Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0757 PM CDT Sat Sep 19 2026

Valid 200100Z - 201200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTH-CENTRAL
KANSAS TO NORTHWEST MISSOURI...AND IN FAR WESTERN KANSAS...

...SUMMARY...
Thunderstorms with scattered severe wind gusts and large hail are
possible this evening across parts of the central Plains and Lower
Missouri Valley.

...Southern and Central Plains/Lower Missouri Valley...
The latest water vapor imagery shows a mid-level trough over the
Intermountain West, with southwesterly flow aloft from the southern
and central Rockies eastward into much of the Great Plains. A
shortwave trough appears to be located in central Kansas, close to
the position of a front oriented from southwest to northeast across
the central Plains. Near and to the southeast of the boundary,
surface dewpoints are in the 60s and lower 70s F, which is
contributing to moderate instability. The RAP shows an axis of
MLCAPE in the 1500 to 2500 J/kg range from central Kansas
northeastward into northwest Missouri and southern Iowa...see MCD
2312. Scattered strong to severe storms are ongoing along the
southwestern part of this corridor of moderate instability...see MCD
2311.

The 00Z sounding at Topeka has MLCAPE near 2000 J/kg with 0-6 km
shear around 20 knots, and a 0-3 km lapse rate just above 7.5 C/km.
RAP analysis suggests that deep-layer shear is stronger near the
front. The environment will support a continued severe threat this
evening. Severe wind gusts and isolated large hail will be the
primary threats. The line that is currently developing in northeast
Kansas may continue to have a severe threat later this evening as it
tracks northeastward into northwest Missouri and far southern Iowa.
A marginal wind-damage threat will extend southwestward along a
surface trough into parts of west Texas.

In the central High Plains, the western edge of moderate instability
extends westward into far western Kansas. Scattered strong storms
are ongoing near the Colorado-Kansas state line where the RAP has
MLCAPE around 1500 J/kg. The Goodland WSR-88D VWP has 0-6 km shear
around 50 knots, and the RAP has 700-500 mb lapse rates in western
Kansas near 7.5 C/km. This will support a supercell threat this
evening with a potential for isolated large hail. Severe wind gusts
will also be possible...see MCD 2313.

..Broyles.. 09/20/2026


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