SPC Jun 21, 2025 0100 UTC Day 1 Convective Outlook

SPC 0100Z Day 1 Outlook

Day 1 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
0816 PM CDT Fri Jun 20 2025

Valid 210100Z - 211200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
NORTH DAKOTA AND MINNESOTA...

CORRECTED AREA MENTIONED IN FIRST SENTENCE OF THIRD PARAGRAPH OF
DISCUSSION

...SUMMARY...
A significant swath of severe winds is expected this evening and
tonight from the northern Plains eastward into the upper Mississippi
Valley.

...Northern Plains/Upper Mississippi Valley...
Water vapor imagery currently shows a shortwave trough moving
through the northern High Plains. Near the trough, a line of strong
to severe thunderstorms is ongoing across western North Dakota and
far northwestern South Dakota. As these storms move eastward across
the northern Plains this evening, a 60 to 70 knot mid-level jet will
move northeastward through the Dakotas. Lift associated the left
exit region of the jet, combined with a strongly unstable airmass
over the eastern Dakotas and western Minnesota will be favorable for
vigorous convective development. In response, the ongoing storms are
expected to grow upscale into a fast-moving severe MCS. The MCS is
forecast to track eastward across far northern South Dakota, North
Dakota and north-central Minnesota this evening.

At the surface, a 991 mb low will move northeastward across northern
South Dakota this evening. A tongue of very moist air with surface
dewpoints in the lower to mid 70s F will move northward into
southeastern North Dakota and central Minnesota this evening. Within
this moist airmass, strong instability is analyzed by the RAP with
MLCAPE in the 4000 to 5000 J/kg range. The ongoing line of severe
storms will move into this strong instability, and gradually
intensify over the next couple of hours. RAP forecast soundings
along the expected track of the MCS in southeastern North Dakota
this evening have moderate to strong deep-layer shear, long and
looped hodographs and steep mid-level lapse rates. This should be
favorable for supercells with large hail, wind damage and tornadoes.
A strong tornado may occur. Supercell development will be most
likely among cells that remain semi-discrete. However, a line is
expected to become more organized, which will make severe wind gusts
likely along its leading edge. Gusts above 80 mph will be possible
ahead of the more intense parts of the line. A Derecho may develop
across parts of the northern Plains and upper Mississippi Valley
this evening into tonight.

As the MCS moves into south-central North Dakota over the next few
hours, some short-term model forecasts develop discrete cells
further to the east near the moist axis in the vicinity of the
ND-SD-MN triple point. These storms are forecast to quickly expand
in coverage and move across northwest and north-central Minnesota,
ahead of the approaching MCS. These storms will likely be
supercellular, and be associated with large to very large hail, wind
damage and possible tornadoes.

A consolidation of the two areas of convection will likely take
place late this evening, with the severe MCS continuing to track
eastward across north-central Minnesota. A wind-damage swath is
expected as far east as northern Wisconsin and the western Upper
Peninsula of Michigan. Wind gusts of 85 to 105 mph will be possible
along parts of the MCS track.

...Southern Rockies/Central High Plains...
Water vapor imagery shows southwest flow over much of the
south-central U.S. A subtle shortwave trough appears to be located
in the southern Rockies, where convection has increased in coverage
over the last couple of hours. These storms will continue to move
northeastward into the High Plains this evening. Forecast soundings
from northeast New Mexico into northwest Kansas early this evening
have very steep low to mid-level lapse rates. This will likely
support a marginal threat for severe gusts, as the cells move into
the stronger instability over the High Plains.

..Broyles.. 06/21/2025

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