SPC AC 081957
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0257 PM CDT Mon Jun 08 2026
Valid 082000Z - 091200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF NORTHEASTERN COLORADO AND NORTHERN INTO CENTRAL AND EASTERN
KANSAS...
...SUMMARY...
Severe thunderstorms potentially capable of large to giant hail and
a couple of tornadoes are still possible over the plains of eastern
Colorado. Scattered to numerous severe thunderstorms are expected
farther east over northern Kansas late this afternoon through the
late evening. Very large to giant hail and severe gusts ranging from
60-100 mph are possible along with a risk for a couple of tornadoes.
...20Z Update...
Hail conditional intensity level 2, and tornado conditional
intensity level 1 were added to portions of northern into central
KS. Some of the latest high-resolution guidance depicts supercells
potentially remaining discrete or semi-discrete for a couple more
hours longer compared to earlier CAM runs. Given anticipated strong
low-level shear along the terminus of the low-level jet/baroclinic
boundary intersection, and over 40 kts of effective bulk shear
likely, any supercells that remain discrete could become quite
intense given strong to locally extreme buoyancy. Very large hail
approaching 4 inches in diameter may occur with longer-lived
supercells. Furthermore, RAP forecast soundings show appreciably
large and curved low-level hodographs this evening (given low-level
jet intensification). As such, a strong tornado cannot be ruled out,
either with discrete supercells or with a well-defined mesovortex as
storms merge into an intense cold-pool-driven bow echo MCS later
this evening.
A Category 4/Moderate risk was considered for this outlook. However,
it remains unclear whether supercells will rapidly grow upscale into
a bow echo, or maintain discrete structures for a longer period of
time. It therefore remains questionable whether significant-severe
hail or wind will dominate long enough to warrant Moderate risk
coverage of a specific hazard. Nonetheless, very intense and
damaging storms capable of a combination of all significant-severe
hazards are expected across portions of northern into eastern KS
this afternoon into the evening hours.
Otherwise, the rest of the previous forecast (see below) remains on
track, with only minor changes made to thunder and severe
probabilities to reflect the latest observations and guidance
consensus.
..Squitieri.. 06/08/2026
.PREV DISCUSSION... /ISSUED 1152 AM CDT Mon Jun 08 2026/
...Eastern CO into Western NE/KS...
A belt of moderate southwesterly mid-level flow will be maintained
over the central High Plains to the downstream of a western U.S.
upper trough. A surface low near Dodge City, KS and moist easterly
low-level flow to its north, will contribute to upslope flow into
eastern CO and the CO Front Range. Strong heating and 50s to lower
60s deg F dewpoints and steep 700-500 mb lapse rates will result in
moderate to large buoyancy by mid afternoon. Elongated hodographs
will favor supercells with the more intense updrafts. Some increase
in low-level hodographs towards early evening coupled with a moist
boundary layer may aid in the risk for supercell tornadoes, in
addition to the risk for hail. Some of the latest model forecast
soundings suggest giant hail (3.0-4.5 inches in diameter) with the
more intense supercells over eastern CO late this afternoon into the
early evening. Severe gusts will also be possible with the stronger
storms with this activity diminishing by late evening.
...KS vicinity...
A very moist surface was analyzed this morning across the central
Great Plains to the south of a front across central and northern KS
to the east of a triple point. Model guidance shows lowest 100-mb
mean mixing ratios of 16-18 g/kg later this afternoon. This very
rich moisture coupled with heating to the south of the front and
early day outflow from storm activity over southwest NE, will result
in a very unstable airmass by late afternoon. Model guidance has
trended towards a severe MCS developing across northern KS and
moving east-southeastward into the lower MO Valley by late evening.
Although it remains unclear exactly how this will evolve, confidence
has increased with regard to a storm cluster and upscale growth
occurring on the northern rim of very rich moisture and a modest
southerly LLJ. Some indication exists for a couple of supercells to
develop ahead of the evolving cluster and eventual squall line.
Large hail and perhaps a tornado risk could accompany this activity.
Have increased severe-wind probabilities and intensity levels, with
the most intense phase of the squall line likely where the overlap
of greater effective shear (30-35 kt) and the large buoyancy
resides. A bow potentially capable of a swath of 60-80 mph gusts
(locally peaking 80-100 mph) is forecast, along with the possibility
for a couple of mesovortices capable of these locally higher gusts
and/or tornadoes. A gradual weakening is expected as this MCS moves
into western parts of MO late.
...Southern KS/Northwest OK...
A dryline will become established this afternoon from the eastern TX
Panhandle into south-central KS. Hot conditions along/west of the
dryline will help to initiate isolated thunderstorms. These
high-based supercells could pose an occasional threat of hail and
damaging winds for a few hours.
...Southern IL/Western KY...
An upper trough continues to lift northeastward across the mid MS
valley today, with a moist/moderately unstable air mass present from
southern IL southward. Mid-level lapse rates are marginal for
severe storms, and winds aloft are modest. Nevertheless, veering
winds-with-height and sufficient CAPE will pose an occasional risk
of strong storms capable of gusty winds or a tornado today.
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
SPC AC 081736
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1236 PM CDT Mon Jun 08 2026
Valid 091200Z - 101200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF NORTH AND SOUTH DAKOTA INTO NORTHWEST MINNESOTA...
...SUMMARY...
Numerous severe thunderstorms are likely to develop across parts of
the northern Plains and Upper Mississippi Valley Tuesday afternoon
into night. Very large hail, tornadoes, a few of which could be
strong, and damaging winds with significant gusts appear likely.
...Synopsis...
A negatively tilted upper trough will be oriented from the Pacific
Northwest to the southern Great Basin Tuesday morning. This feature
will pivot east through the period, become positioned from southwest
Saskatchewan to the central High Plains. A belt of enhanced
southwesterly 500 mb flow will overspread portions of the
northern/central Plains ahead of the aforementioned trough.
Meanwhile, an intensifying low-level jet will develop during the
evening/overnight hours across much of the Plains toward the Upper
Midwest.
At the surface, low pressure over eastern MT will gradually deepen
and shift east/northeast across the northern Plains and adjacent
Canadian Prairies. A Pacific front/dryline feature will extend
southward from the low across the western Dakotas and NE. A
secondary surface low may develop in the vicinity of eastern
CO/western KS/southwest NE, where a dryline will extend from western
KS southward into northwest OK and the TX Panhandle. Further east, a
quasi-warm front feature is expected to extend northwest to
southeast from MN to the Mid-MS Valley. This boundary may gradually
lift northward through the evening/overnight in response to the
low/midlevel mass response/increasing low-level jet.
These boundaries will be a focus for severe storm development during
the afternoon into the overnight hours.
...Northern Plains vicinity...
Convection is expected to develop near the ND/MT border vicinity by
mid/late afternoon along the surface boundary. A warm front should
be well north of the Dakotas over the southern Canadian Prairies,
and increasing southerly low-level flow will transport low to mid
60s F dewpoints northward into the region. Cooling aloft will result
in steepening midlevel lapse rates atop rich boundary-layer
moisture, supporting MLCAPE increasing to 3000-4000 J/kg.
South/southwesterly low-level winds will become southwesterly in the
mid/upper levels, resulting in supercell wind profiles and 40+ kt
effective shear magnitudes. Initial supercell storms are expected,
though these storms may be somewhat higher-based within the more
modest boundary layer moisture across the western Dakotas/far
eastern MT. Large hail and damaging gusts are possible with these
storms initially.
As convection develops eastward into the axis of greater low-level
moisture and strong instability, severe potential will increase,
particularly with respect to swaths of damaging winds and tornadoes.
As the low-level jet increases during the evening, and given
mid/upper flow oriented parallel to the surface boundary, upscale
growth into one or more linear segments is expected. As cold pool
consolidation occurs, potential for significant wind gusts (greater
than 65 kt) is expected to increase across parts of central ND.
Low-level shear will also support tornado potential, whether
semi-discrete supercells can be maintained, or with mesovortex
generation within linear bands. As such, have left tornado
probabilities similar to the prior forecast. Given the expectation
that storm mode will become more linear with time, hail
probabilities have been lowered (removed 45 percent). Nevertheless,
large to very large hail will be possible with any discrete
supercells that can be maintained or are embedded within linear
segments.
...NE/SD/Mid-MO Valley vicinity...
Convection emanating northeast from NE may eventually grow upscale
into an MCS during the nighttime hours and spread into eastern SD
and the Mid-MO Valley area. This scenario is uncertain. However,
given ample deep-layer flow, extreme instability and at least subtle
large-scale ascent over the region as the low-level jet overspreads
this area overnight, this scenario seems plausible. If this occurs,
damaging wind potential will be possible, and severe probabilities
have been expanded eastward across portions of the region.
...KS into the OK/TX Panhandles and northeast NM...
High-based convection is expected to develop along the surface
dryline during the late afternoon. Deep boundary layer mixing will
support steep low-level lapse rates. 500 mb temperatures around -10
C also will support steep midlevel lapse rates near 8-8.5 C/km per
regional forecast soundings. Deep layer shear will not be as strong
as further north, but strong instability and inverted-v sub-cloud
thermodynamic profiles will support severe wind gusts. There is some
potential that if storms can be maintained further east toward
better low-level moisture as the low-level jet increases during the
evening, a swath of significant wind gusts could occur across the
southwest KS vicinity. Severe probabilities have been increased
across portions of the area given a favorable environment and strong
signal within most forecast guidance.
...Mid-MS Valley into Lower OH Valley...
A quasi-warm front/moisture boundary will overlap the region from
northwest to southeast, and is likely to lift northward toward Lake
MI overnight. Large-scale ascent will remain weak until late in the
period. Nevertheless, strong instability within a very moist and
unstable airmass will support isolated severe wind gusts potential
through peak heating with any storms that develop. Additional storms
may develop overnight from WI into northern IL as the low-level jet
noses into the region resulting in strong warm advection atop the
surface boundary. While this activity may remain elevated above the
nocturnal stable layer, some potential for strong gusts or marginal
hail is possible.
..Leitman.. 06/08/2026
WUUS02 PTSDY2
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
SPC AC 081921
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0221 PM CDT Mon Jun 08 2026
Valid 101200Z - 111200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF EASTERN MINNESOTA...WISCONSIN...EASTERN IOWA...AND NORTHERN
ILLINOIS...
...SUMMARY...
Scattered to numerous severe thunderstorms capable of large to very
large hail, tornadoes, and damaging winds with significant gusts
appear likely across portions of the upper Mississippi Valley and
Midwest Wednesday afternoon into night. More sporadic occurrences of
large hail and damaging winds are possible into the central Plains.
...Synopsis...
An upper low is forecast over southern Alberta/Saskatchewan and
northern MT Wednesday morning. One upper shortwave trough associated
with this system will be oriented over the northern High Plains
Wednesday morning, and will spread eastward through the period into
the Upper Midwest/Great Lakes vicinity. A second upper shortwave
trough will deepen and develop southeast from the northern Rockies
to the central High Plains by Thursday morning.
At the surface, a cold front will initially be located from eastern
ND toward the central High Plains. The northern portion of this
front will develop east across the Upper Midwest, while the
southwestern extension of the front stalls from the Mid-MO Valley
into the southern High Plains as a surface low deepens over NE/KS
overnight.
...Upper MS Valley/Great Lakes toward the Mid/Lower MO Valley
vicinity...
Remnant convection from the Day 2/Tuesday period may be
ongoing/decaying across parts of the region Wednesday morning.
Furthermore, convective outflow could be positioned somewhere across
the Upper Midwest. As a result, evolution of convection from the Day
2 period will likely have some impact on where corridors of greater
severe potential develop on Wednesday. Regardless, rich boundary
layer moisture will spread across parts of MN/WI/IA/IL as a warm
front retreats northward across the Great Lakes and ahead of the
advancing surface cold front. This will foster strong
destabilization across the region as vertical shear increases with
time. Numerous organized severe thunderstorms, possibly both
supercells and bowing segments, are expected with an accompany
all-hazards severe risk, particularly across parts of MN/WI and
possibly IA into northern IL.
With southwest extent into the Mid/Lower MO Valley, effective shear
magnitudes will decrease. However, a very moist and strongly
unstable airmass will be in place ahead of the stalled surface
boundary across KS to western IA. A dryline will also extend into
the southern High Plains, though boundary layer moisture will also
become more modest with southwest extent. Both of these boundaries
will serve as a focus for a second area of severe thunderstorm
potential during the late afternoon/evening, with both large hail
and damaging gusts possible. Additional severe thunderstorms may
develop overnight as a low-level jet strengthens and overspreads the
stalled surface boundary across KS. Large hail could accompany this
activity later in the forecast period.
..Leitman.. 06/08/2026
WUUS03 PTSDY3
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z
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