418
ACUS03 KWNS 181922
SWODY3
SPC AC 181920

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0220 PM CDT Wed Jun 18 2025

Valid 201200Z - 211200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF THE
NORTHERN PLAINS AND UPPER MIDWEST/GREAT LAKES...

...SUMMARY...
Severe thunderstorms may develop Friday into Friday night across
parts of the northern Plains and upper Midwest.

...Synopsis...
Mid-level ridging will be centered over the northern Plains on
Friday. There is considerable uncertainty regarding evolution of the
ridge with some potential for a mid-level shortwave trough to eject
from a western CONUS trough. The exact evolution of this mid-level
pattern and embedded shortwave troughs will significantly impact
severe weather potential on Friday.

...Northern Great Plains into the Upper Midwest/Great Lakes...
Guidance is in agreement regarding low to mid 70s dewpoints into the
northern Plains by Friday afternoon/evening. As temperatures warm
well into the 90s, very strong to extreme instability is forecast to
develop across much of the northern Plains and Upper Midwest. Storm
coverage/location is the primary question given the strong ridging
and strong 700mb temperatures across the region. A surface low is
forecast to develop somewhere near the Black Hills with a warm
frontal zone extending eastward from this surface low. This warm
front will likely be the focus for the most intense severe storm
potential on Friday. A stronger mid-level shortwave trough, as
indicated by the 12Z ECMWF, would likely be a scenario with the
greatest severe weather threat. This would involve supercell
development near the surface low/triple point and extending eastward
along the warm front. Eventual upscale growth into a forward
propagating MCS would be likely during the evening with a track
along this frontal zone. This scenario could have the potential for
an intense MCS capable of significant severe wind gusts.

However, if the mid-level shortwave trough is weaker, storm coverage
may be more isolated as warmer mid-level temperatures prevail. In
this scenario, the environment would still support the potential for
intense storms, but storm coverage would remain questionable.

Regardless of the diurnal threat, the risk will likely persist into
the overnight period across northern Minnesota and northern
Wisconsin as a broad low-level jet strengthens across the Plains and
Upper Midwest. This isentropic ascent, combined with a reservoir of
very strong instability and steep lapse rates will support a severe
weather threat through the overnight period.

..Bentley.. 06/18/2025

$$