ACUS48 KWNS 080847
SWOD48
SPC AC 080845

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0345 AM CDT Mon Jun 08 2026

Valid 111200Z - 161200Z

...DISCUSSION...
...Day 4/Thursday...

An active period of severe weather is expected from the upper Great
Lakes into Ozark Plateau, with the most concentrated and potentially
most significant severe storms affecting parts of the Midwest.

Within the base of an upper low centered over Manitoba and northwest
Ontario, the models are in good agreement in depicting the
progression of a potent short-wave trough and attending
mid/upper-level jet streaks through the upper Midwest and upper
Great Lakes. There is some model signal that a trailing perturbation
on the immediate cyclonic side of the mid-level jet will overspread
the mid MS Valley Thursday night.

At the surface, a deepening surface low/frontal wave is expected to
develop from central IA into the southern UP of MI during the day,
along a cold front advancing through the upper Midwest and into the
upper Great Lakes. The southwest extension of that boundary will
progress southeast through the lower MO and Mid MS Valleys, while
becoming quasi-stationary across the southern Plains. The specific
boundary location across the Midwest may be modified to some extent
from a thunderstorm complex moving through the area Wednesday
night/early Thursday.

A very moist air mass is expected to reside to the south of the
surface front, which coupled with modestly steep mid-level lapse
rates is expected to yield moderate to strong instability. The
presence of a 50-70 kt mid-level jet streak attending the short-wave
trough will result in relatively strong deep-layer shear along the
frontal zone, with vector orientation becoming increasingly parallel
to the boundary with southward extent. The overall pattern appears
supportive of an organized severe-weather episode from the upper
Great Lakes into mid MS Valley. There is some model signal that a
corridor of enhanced tornado potential could develop along and south
of the surface low track from eastern IA and northern IL into
central and southern WI. That potential scenario will be dictated by
the location of the effective surface boundary.

Additional, more isolated severe storms appear possible across parts
of the Northeast.


...Day 5/Friday...

A number of the 00z models progress a lower-latitude short-wave
trough through the upper OH Valley and lower Great Lakes, which is a
departure from previous model runs. That scenario would increase
severe-weather potential across those areas into New England, and
perhaps the Mid-Atlantic, given the potential for a moderately
unstable air mass across the pre-frontal warm sector. Should
subsequent model runs remain consistent with this recent trend, an unconditional 15% probability contour may be needed in the next
forecast update.

Elsewhere, Isolated severe storms appear possible across portions of
the southern High Plains.


...Day 6/Saturday...

The ensemble mean solutions are in good agreement in depicting a mid/upper-level low over Hudson Bay with a belt of strong mid-level
flow extending from slight troughing over the northern High Plains
into the Great Lakes and Northeast. There is more spread across the deterministic models with respect to the longitudinal position of
that trough, and the position of the associated frontal system. In
general, it appears some severe weather threat could materialize
across the central Plains. However, confidence in that scenario is
low.


...Days 7 and 8/Sunday and Monday...

The ensembles indicate a gradual amplification of the large-scale
pattern, featuring troughing from Hudson Bay into the MS Valley, and
upstream ridging across western Canada and the Pacific Northwest.
The location of any relevant surface frontal systems remains highly
uncertain, as does the location(s) of any severe-weather threat.

..Mead.. 06/08/2026

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ACUS48 KWNS 090841
SWOD48
SPC AC 090838

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0338 AM CDT Tue Jun 09 2026

Valid 121200Z - 171200Z

...DISCUSSION...
...Day 4/Friday...

The last several deterministic model runs have consistently shown
the progression of a short-wave trough and associated 50 kt jet
streak from the OH Valley into the St. Lawrence Valley, with
meaningful height falls as far south as the Mid-Atlantic. At the
surface, the northern portion of a cold front initially from
southwest Ontario to near the confluence of the MS and OH Rivers and
into the southern Plains will progress southeast and eventually
merge with a trough stretching from southern New England to the
Carolina Piedmont. Ahead of the front, boundary-layer dewpoints in
the 60s to low/mid 70s will combine with modestly steep mid-level
lapse rates, especially across the lower Great lakes, to yield a
moderately unstable air mass by afternoon.

Initial storms are anticipated across the lower Great Lakes into
upper OH Valley by early afternoon, with activity advancing east
toward the Hudson Valley, and southeast into the central
Appalachians and Mid-Atlantic through the remainder of the afternoon
into evening. The strongest vertical shear is forecast from the
lower OH Valley to the lee of the lower Great Lakes, where organized
storm modes capable of damaging winds and large hail appear most
probable.

Elsewhere, a more isolated severe-weather threat may materialize
within a low-level upslope regime in eastern NM.


...Day 5/Saturday...

The models are in generally good agreement in depicting a
mid/upper-level low over Ontario, and a positively tilted trough
from the northern Plains into the northern Rockies. A belt of
enhanced, westerly winds in the mid levels will reside to the south
of those features, from the northern and central Plains through the
Great Lakes. At the surface, the various ensemble members
consistently show the clustering of low centers over the central
High Plains with an associated surface front extending into the
upper Great Lakes.

Moderate to strong instability is forecast ahead of the surface
front from the central Plains into upper Great Lakes with more than
sufficient deep-layer to support higher-order storm modes. Highest
confidence in storm development Saturday afternoon and evening is
across the central Plains into mid/lower MO Valley from the vicinity
of the surface low northeast along the surface front.

Other more isolated severe storms appear possible along a weakening
front in the Carolinas.


...Day 6/Sunday...

The ensemble mean solutions depict lowering mid-level heights from
the central Plains into Great Lakes and OH Valley, in conjunction
with the gradual amplification of a long-wave trough located east of
the North American Rockies. More specifically, a number of the
deterministic models suggest a short-wave trough moving from the
northern into central Rockies, with another potentially more intense
mid-level system moving through the Northeast. An associated
surface front preceding both features may serve as the focus for
some severe-weather threat from the Northeast through the OH Valley
into the Southern Plains. However, there is considerable uncertainty
in finer-scale details, so no area will be highlighted.


...Days 7-8/Monday and Tuesday...

Further amplification of the long-wave trough is forecast with an
associated belt of mid-level flow extending from the central Plains
through the mid MS Valley into New England and the Mid-Atlantic.
Despite growing spread across the deterministic models, there is a
modest signal that the Day 6/Sunday central Rockies short-wave
trough will progress through the central Plains into mid MS Valley.
Some severe-weather threat could develop ahead of that disturbance
in the vicinity of the surface frontal system, should that scenario
unfold as advertised.

..Mead.. 06/09/2026

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ACUS48 KWNS 100828
SWOD48
SPC AC 100826

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0326 AM CDT Wed Jun 10 2026

Valid 131200Z - 181200Z

...DISCUSSION...
...Day 4/Saturday...

The models are in generally good agreement in depicting a prominent, mid/upper-level low over Ontario with a secondary, weaker low or
short-wave trough across the northern Rockies. A belt of enhanced,
westerly winds in the mid levels will reside to the south of those
features from the northern Plains through the Great Lakes. At the
surface, an area of low pressure is forecast across the central
Plains with an associated front extending northeast into the upper
Great Lakes.

A strongly unstable air mass is forecast ahead of the front across
portions of the mid/lower MO Valley into Ozark Plateau with
instability decreasing with northeastward extent into the upper
Great Lakes. The models indicate sufficiently strong deep-layer
shear across the frontal zone to support organized storm modes,
including supercells. Highest confidence in greater storm coverage
and an associated severe-weather threat remains centered on the
mid/lower MO Valleys. Severe-weather probabilities may need to be
extended into the upper Great Lakes in subsequent outlooks.


...Day 5/Sunday...

A number of the deterministic models indicate a short-wave trough
and associated jet streak moving through the Great Lakes into
Northeast, within the base of the Ontario upper low. Farther west,
the northern Rockies short-wave trough will advance toward the
central Rockies. At the surface, a cold front associated with the
former disturbance mentioned above will progress through the
Northeast and OH Valley, with the western extension of the boundary
stalling across the southern Plains.

The models indicate a narrow axis of modest instability developing
by afternoon ahead of the front from the northern New England to the
upper OH Valley, where the strongest vertical shear is forecast.
Some severe weather appears possible in those areas; however, the
limited extent of the warm sector leads to uncertainty in the
coverage and duration of any threat.

Greater instability and a wider warm sector are forecast with
southwestward extent from the OH River and TN Valley into southern
Plains. Generally weak vertical shear is forecast across the frontal
zone, which should limit the degree of storm organization. A
possible exception is across the southern and central High Plains,
where an easterly low-level wind component will boost deep-layer
shear to some extent. Model trends will be monitored for the
possible inclusion of severe-weather probabilities in that area.


...Day 6/Monday...

The deterministic models are in reasonably good agreement in
amplifying the aforementioned short-wave trough over the central
Plains with an associated belt of enhanced mid-level flow extending
through the OH Valley into Northeast. At the surface, there is some
signal that an area of low pressure could develop along a front
across the southern Plains into Ozark Plateau. Some severe-weather
threat appears possible in that area, as well as along the front
that is expected to stretch east through the TN Valley into the
Carolinas. Predictability in the specific details are too low to
include an area.


...Days 7-8/Tuesday and Wednesday...

The ensemble mean solutions are in relatively good agreement in
suggesting the central Plains short-wave trough will become absorbed
into broader-scale trough amplification east of the MS Valley. At
the surface, it appears that a frontal wave will move from the TN
Valley toward the Mid-Atlantic coast, while a trailing cold front
advances into the Gulf Coast states. While areas of severe weather
are possible during this time frame, predictability in their
location is low.

..Mead.. 06/10/2026

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ACUS48 KWNS 110854
SWOD48
SPC AC 110852

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0352 AM CDT Thu Jun 11 2026

Valid 141200Z - 191200Z

...DISCUSSION...
...Day 4/Sunday...

The 00z models have trended toward a much stronger short-wave trough
and associated mid-level jet, which will progress from the Great
Lakes and OH Valley into the Northeast. Elsewhere, a short-wave
trough is forecast to move from the northern Rockies into the
central Plains. At the surface, a cold front attendant to the
Northeast short-wave trough will move through that region with the
trailing extension of the boundary pushing south through the OH and
TN Valleys into the Gulf Coast states.

A much stronger low-level jet is now forecast ahead of the cold
front across the Northeast, which will aid in greater air mass
destabilization than indicated in previous model runs. When coupled
with notably stronger vertical shear, the setup appears favorable
for organized severe storms across the Mid-Atlantic, potentially
into southern New England Sunday afternoon and evening.


...Day 5/Monday...

The models suggest the Sunday/central Plains short-wave trough will
progress through the mid MS into OH Valleys with an associated belt
of enhanced mid-level flow stretching from the central Plains into Mid-Atlantic. At the surface, there is good model agreement that the
primary synoptic front and associated warm sector will lie across TX
and the Gulf Coast states, to the south of the stronger mid-level
winds and forcing for ascent. Some severe-weather threat may develop
along and south of the front; however, the marginal vertical shear
is expected to limit the overall severe-weather threat.

Slightly stronger vertical shear is forecast across the central and
southern High Plains, due to an easterly upslope regime in the
low-levels. While the potential for more organized storms will exist
in that region, severe-weather coverage may only be isolated.


...Day 6/Tuesday...

The ensemble mean and deterministic models are suggestive that a
mid-level disturbance will track from the central Plains into the
lower OH and TN Valleys, contributing to overall amplification of
the long-wave trough in place east of the Rockies. The primary
surface front is expected to remain in place across the Gulf Coast
states, to the immediate south of the stronger forcing for ascent
and mid-level flow. While isolated occurrences of severe weather
appear possible from the southern High Plains into Southeast, the
potential for an organized severe-weather event remains in question.



...Days 7-8/Wednesday and Thursday...

The ensemble means indicate the progression of a strong mid-level
jet streak into the northern and central Plains Wednesday with that
feature moving through the OH Valley into Mid-Atlantic Thursday. At
the surface, the ensemble member low positions indicate clustering
across the northern Plains and upper MS Valley Wednesday, and across
the Great Lakes into Ontario on Thursday. The rapid poleward return
of a moist and unstable air mass is expected to occur ahead of the
surface low and associated frontal system. As such, some severe
weather appears possible across parts of the Midwest Wednesday, and
perhaps OH Valley into Mid-Atlantic Thursday.

..Mead.. 06/11/2026

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ACUS48 KWNS 120738
SWOD48
SPC AC 120736

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0236 AM CDT Fri Jun 12 2026

Valid 151200Z - 201200Z

...DISCUSSION...
...Days 4-5/Mon-Tue...

A surface front will remain across south TX and the Gulf Coast
vicinity while broad upper troughing persists east of the Rockies.
As a result, severe potential is expected to remain limited as any
deep Gulf moisture and stronger instability will remain well removed
from any stronger mid/upper flow associated with the upper trough.

...Days 6-7/Wed-Thu - Southern Plains to Midwest...

A mid/upper shortwave trough will move from the northern Rockies to
the MS Valley on Wednesday, and the OH Valley to the Northeast on
Thursday. Deepening surface low pressure will shift from the central
Plains to the Northeast and southwesterly deep-layer flow increases.
This will result in northward transport of Gulf moisture into the Plains/Midwest on Wednesday, and the Northeast by Thursday. This
could result in increasing severe potential for portions of these
regions. Currently, capping across the Plains my limit storm
coverage across that region on Wednesday. Furthermore, timing of
greater moisture return across the Midwest ahead of a surface cold
front is uncertain. Severe probabilities may be needed eventually,
but uncertainty remains too high to introduce unconditional
probabilities at this time.

...Day 8/Fri...

Upper ridging is expected to develop over the Rockies into the
Plains by the end of the forecast period. Meanwhile, upper troughing
will pivot northeast across New England. Some guidance suggests a
shortwave impulse could eject from the Rockies into the central
Plains within the broader scale upper ridging. This could support
some severe potential, but overall predictability is low given large
model spread.

..Leitman.. 06/12/2026

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