095
ACUS48 KWNS 180843
SWOD48
SPC AC 180842

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0342 AM CDT Wed Jun 18 2025

Valid 211200Z - 261200Z

...DISCUSSION...
...D4/Saturday...
An amplified upper-level pattern will continue into Saturday, with a
prominent ridge extending from the Southeast into the Midwest and
Ohio Valley, and a deep trough over much of the West. Large to
extreme buoyancy will again develop across parts of the
central/northern Plains and Upper Midwest, but the influence of the
ridge will tend to suppress storm development across the warm
sector.

While differing in the details, some extended-range guidance
suggests that an MCS (or at least its remnant MCV) that develops
late on D3/Friday will move across the far northern Great Lakes and
adjacent parts of Ontario on Saturday, and potentially into parts of
the lower Great Lakes by Saturday evening. Should such an evolution
occur, some severe threat could accompany this system, but
predictability for such a scenario at this range is inherently low.

Farther west, there is substantial spread in guidance regarding the
magnitude of low-level moisture and instability across parts of MT
and northern WY into western ND on Saturday. However, if stronger
flow associated with the western trough can impinge upon favorable
instability, then an organized severe threat could evolve during the
afternoon and evening.

...D5/Sunday...
The western trough is generally forecast to take on more of a
positive tilt and eventually deamplify on Sunday, as a substantial
shortwave and midlevel jet maximum eject across parts of the
northern High Plains. As this occurs, a cold front will move across
parts of the northern/central Plains. At this time, it appears the
organized severe threat may be limited by very warm temperatures
aloft and a tendency for stronger deep-layer flow to lag behind the
front.

Strong buoyancy may spread into parts of the Ohio Valley and
Northeast on Sunday. Some organized severe potential could develop
within the instability gradient along the periphery of the ridge,
though mesoscale details remain highly uncertain at this time.

...D6/Monday - D8/Wednesday...
Uncertainty increases into early next week regarding evolution of
the synoptic pattern, though guidance generally suggests that an
upper ridge will remain prominent across parts of the eastern CONUS,
while a weak upper trough will persist across parts of the West into
the northern and central Plains. While some severe potential could
evolve across parts of the Great Plains, Great Lakes, and Northeast
along the periphery of the ridge, details regarding favored days and
locations remain highly uncertain.

..Dean.. 06/18/2025