666
ACUS01 KWNS 160601
SWODY1
SPC AC 160559

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1259 AM CDT Mon Jun 16 2025

Valid 161200Z - 171200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
THE UPPER MIDWEST AND THE CENTRAL PLAINS...

...SUMMARY...
Scattered severe thunderstorms capable of producing severe gusts,
large hail, and perhaps a couple tornadoes are forecast today from
the north-central High Plains into the Upper Mississippi Valley.

...Synopsis...
Within a belt of zonal midlevel flow extending from the northern
Rockies/High Plains into the Upper MS Valley, a convectively
augmented midlevel impulse/MCV will track eastward across the
Dakotas into MN through the afternoon. In response to this feature,
a weak frontal-wave low will migrate eastward from the eastern
Dakotas into MN -- along a surface boundary extending southwestward
through the central Plains. Farther west, an additional
low-amplitude impulse accompanied by strong westerly flow aloft will
emerge over the northern/central High Plains during the late
afternoon/early evening.

...Upper MS Valley into the central Plains...
Scattered thunderstorms should generally be focused along/ahead of
the frontal-wave low and remnant MCV as it moves into MN during the
afternoon, with additional trailing development possible along the
surface boundary into NE. Here, rich boundary-layer moisture and
modestly steep midlevel lapse rates will contribute to a strongly
unstable air mass, while the enhanced midlevel westerly flow yields
around 40 kt of effective shear. This should support a risk of a
couple supercells and organized clusters capable of producing large
hail, damaging winds, and a couple tornadoes.

...Southeast MT into the central High Plains...
As low-level lapse rates diurnally steepen amid
recycled/post-frontal boundary-layer moisture over the
northern/central High Plains, scattered thunderstorms should evolve
eastward from southeast MT/eastern WY into the central Plains --
aided by the emerging midlevel impulse. Upwards of 40-50 kt of
effective shear and steepening deep-layer lapse rates will favor
large hail and locally severe wind gusts with initial
discrete/semi-discrete supercell structures and organized clusters.
As these storms track east-southeastward into the evening,
additional storms may be developing farther south along the
southwestward-extending surface boundary over western/central
NE/northeastern CO/northwest KS. While the overall convective
evolution is unclear, current thinking is that multiple
opportunities for upscale growth into one or more MCSs will exist in
the NE/KS vicinity into the evening/overnight hours. A swath of
severe wind will be possible where this evolution occurs.

..Weinman/Leitman.. 06/16/2025

$$