052
ACUS48 KWNS 210848
SWOD48
SPC AC 210846

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0346 AM CDT Fri Jun 21 2024

Valid 241200Z - 291200Z

...DISCUSSION...
...D4/Monday: Northern Plains into the upper MS Valley/Great
Lakes...
A mid/upper-level shortwave trough and deepening surface low are
forecast to move across parts of SK/MB on Monday. A surface trough
will extend southward from the low into the northern Great Plains,
with secondary surface low development possible across the Dakotas.
A warm front will move northeastward somewhere from the eastern
Dakotas into the upper MS Valley. Strong buoyancy is forecast to
develop near and to the south/west of the warm front, with favorable
deep-layer shear providing a conditionally favorable environment for
severe thunderstorms.

While some severe potential appears likely to evolve somewhere from
the northern Plains into the upper MS Valley and/or upper Great
Lakes, guidance varies regarding the position of the warm front, and
also the southern extent of height falls and large-scale ascent
attendant to the SK/MB shortwave trough. Much of the warm sector
will likely remain capped, but severe storm development will be
possible in closer proximity to the warm front and secondary surface
low, which could potentially grow upscale and move southeastward
along the instability gradient. Severe probabilities will likely be
needed once confidence increases regarding the placement of the
primary surface features.

...D5/Tuesday: Upper Midwest into the central/southern Plains...
The shortwave trough that moves across parts of SK/MB on Monday is
generally forecast to move east-southeastward on Tuesday across
parts of ON and the upper Great Lakes. Model spread regarding the
timing and track of this shortwave continues to increase at this
time range, and the potential for MCS development on D4/Monday
further reduces predictability regarding the severe threat on
Tuesday. However, some severe-thunderstorm potential may evolve
along a southeastward moving cold front from the Great Lakes/upper
Midwest into parts of the central/southern Great Plains.

...D6/Wednesday - D8/Friday...
Some threat for strong to severe thunderstorms could continue to
accompany a southeastward-moving cold front on D6/Wednesday from the
southern Plains into the Ohio Valley and Northeast, though
predictability remains low regarding the details at this time range.

By D7/Thursday into D8/Friday, extended-range guidance generally
suggests the potential for a mid/upper-level shortwave trough to
move across the northern Rockies toward the northern High Plains.
However, model spread remains rather high regarding the evolution of
moisture return and any increasing severe potential in association
with this system.

..Dean.. 06/21/2024