299 

ACUS48 KWNS 060845

SWOD48

SPC AC 060843



Day 4-8 Convective Outlook  

NWS Storm Prediction Center Norman OK

0343 AM CDT Sat Jun 06 2026



Valid 091200Z - 141200Z



...DISCUSSION...

...Day4/Tuesday...



Latest model guidance remains in good agreement in depicting the

progression of a short-wave trough and associated mid/upper-level

jet streaks into the northern High Plains Tuesday afternoon and

evening, with downstream height falls overspreading the Dakotas. At

the surface, a lee cyclone over eastern MT Tuesday afternoon is

expected to develop north-northeast through western ND, while a

trailing cold front edges east into the western Dakotas.



Steep low/mid-level lapse rates coupled with boundary-layer

dewpoints in the 60s are expected to contribute to moderate to

strong instability across the warm sector, supporting vigorous

thunderstorm development by late afternoon into evening as the

mid-level height falls overspread the region. Strengthening vertical

shear with the arrival of the jet streaks will favor supercells

capable of large to very large hail and severe wind gusts. Some

tornado threat could materialize across central ND during the

evening hours as low-level shear strengths in response to an

intensifying low-level jet.  





...Day5/Wednesday...



The ensembles depict the elongation of a prominent, western U.S.

trough into the northern Plains, with an associated jet extension

stretching into the upper MS Valley. That notion is confirmed by the

majority of deterministic models, which indicate a significant

short-wave trough and associated mid/upper-level jets moving through

the northern and central Plains. At the surface, there is good

agreement between the deterministic models and ensemble member

clustering that the primary surface low initially over central SD

Wednesday morning will develop north-northeast through the ND-MN Red

River Valley into southeast Manitoba, while a trailing cold front

advances through the eastern Dakotas into the upper MS Valley, mid

MO Valley, and central High Plains.



Steep lapse rates and a very moist boundary layer will contribute to

moderate to strong instability across the warm sector by mid

afternoon, with initial thunderstorm development anticipated along

the front from the eastern Dakotas into western MN. Subsequent storm

initiation appears likely southwestward along the front through the

mid MO Valley into the central Plains. While there is some model

signal that the deep-layer shear vectors may only cross the surface

frontal zone at a small angle, sufficient bulk shear magnitudes will

exist to support supercells and bowing structures amidst potentially

more complex/messy storm modes. All severe-weather hazards are

possible, with that threat quickly spreading through the upper MS

Valley into the upper Midwest Wednesday evening into night. 



Should subsequent model runs remain consistent with current trends,

a 30% unconditional probability contour may be included in the next

forecast update.





...Day 6/Thursday...



Both the ensemble mean and deterministic models indicate the

development of a prominent mid-level low over Manitoba or northwest

Ontario, with a belt of unseasonably strong mid-level flow

stretching from the northern or central Plains into the Great Lakes.

At the surface, ensemble member clustering and the deterministic

models indicate the primary low pressure over northwest Ontario with

a trailing cold front stretching from the upper Midwest through the

mid MS Valley into southern Plains.



While mid-level lapse rates are forecast to be weaker than in

previous days, the presence of a moist air mass will contribute to

moderate instability by afternoon within the warm sector. Strong to

potentially severe storms appear possible from the upper Midwest

into Great Lakes southwest into the OH and mid MS Valleys during the

afternoon and evening hours. The models suggest that the strongest

deep-layer shear may lag the surface warm sector to the immediate

west, which casts some uncertainty on the extent of the

severe-weather threat. As such, no area will be delineated in this

forecast.





...Days 7-8/Friday and Saturday...



The ensemble mean solutions suggest a gradual deamplification of the

north-central CONUS trough, with a belt of stronger mid-level flow

stretching from the northern Plains through the Great Lakes.  At the

surface, there is considerable variability in the position of any

relevant frontal systems that might focus strong to severe storm

development.



..Mead.. 06/06/2026