170
ACUS48 KWNS 090900
SWOD48
SPC AC 090858

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0358 AM CDT Sun Aug 09 2026

Valid 121200Z - 171200Z

...DISCUSSION...
...Wednesday/Day 4 to Friday/Day 6...
From Wednesday to Friday, a broad mid-level cyclonic flow pattern is
forecast to remain in place across the Great Lakes and the
Northeast, as a ridge moves eastward from the northern Rockies into
the upper Mississippi Valley. At the surface, a cold front is
forecast to become quasi-stationary from the central and northern
Plains into the mid Missouri and Ohio Valleys. Low-level convergence
near this front will be a focus for convective development each day.


On Wednesday, model forecasts suggest that scattered thunderstorms
will most likely develop Wednesday afternoon along an axis of
moderate instability from western Nebraska into southwestern South
Dakota. The storms will be supported by a mid-level shortwave trough
moving across the north-central U.S. Moderate deep-layer shear near
the instability axis should support a severe threat during the
afternoon and evening. The models also suggest that a convective
cluster will form within a very moist and unstable airmass in the
central Appalachians Wednesday afternoon, where a wind-damage threat
will be possible.

On Thursday, the most favored corridor for convective development is
forecast from eastern Nebraska into central Illinois. However, the
models suggest that scattered convective coverage could be
concentrated overnight as low-level flow increases across the
region. A severe threat could develop during the day but would
remain relatively isolated due to a lack of storm coverage. An
isolated severe threat could also develop across parts of the
central and northern High Plains during the afternoon. However,
storms there will also likely be isolated due to a shortwave ridge
aloft.

On Friday, thunderstorm swill also be possible from the central
Plains eastward into the Ohio Valley during the afternoon and
evening. However, the most favored locations are likely to be
determined by outflow boundaries associated with the previous day`s
convection. For this reason, uncertainty is substantial on Friday.

...Saturday/Day 7 and Sunday/Day 8...
Over the weekend, a mid-level shortwave ridge is forecast to move
across the north-central U.S., as west-northwesterly flow remains in
the Northeast. An axis of instability is forecast from the central
Plains into the Ohio Valley, which will be a focus for thunderstorm
development. It appears that an isolated severe threat could develop
along and near the instability axis each afternoon and evening.
However, uncertainty is considerable concerning the details of any
potential scenario.

..Broyles.. 08/09/2026