ACUS03 KWNS 020719
SWODY3
SPC AC 020718
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0218 AM CDT Thu Oct 02 2025
Valid 041200Z - 051200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SATURDAY
AFTERNOON AND EVENING ACROSS PARTS OF WEST CENTRAL
NEBRASKA...CENTRAL AND EASTERN SOUTH DAKOTA...SOUTHEASTERN NORTH
DAKOTA...AND NORTHWESTERN MINNESOTA...
...SUMMARY...
Strong thunderstorms may impact a corridor across parts of the
northern Great Plains late Saturday afternoon or evening,
accompanied by at least some risk for severe wind and hail.
...Discussion...
Downstream of building mid/upper ridging, perhaps including an
evolving high across the northeastern Pacific, large-scale mid/upper
troughing is likely to be maintained across the Southwest through
Great Basin vicinity. However, a notable short wave impulse
pivoting across the Great Basin at the outset of the period is
forecast to accelerate across the Rockies toward the northern Great
Plains Red River Valley, as mid-level troughing digs across the
Canadian Prairies. The lead impulse may tend to weaken as mid-level
flow trends more confluent near the central international border
vicinity Saturday night. However, models suggest that substantive
further deepening of surface troughing is probable northeast of the
Front Range into far northwestern Ontario before this occurs. It
appears that this might include the evolution of a compact embedded
surface cyclone across parts of central South Dakota toward
southeastern North Dakota late Saturday through Saturday night, but
there remains substantive spread within/among the model output
concerning this and other developments.
...Northern Great Plains...
Beneath a plume of initially warm and capping elevated mixed-layer
air, a narrow corridor of stronger surface heating and deeper
boundary-layer mixing along/ahead of the surface trough probably
will provide the primary focus for thunderstorm development with the
most appreciable severe weather potential. Although models suggest
that CAPE will be more marginal northeast of the Front Range through
central South Dakota than farther to the northeast, due to lower boundary-layer moisture content, thermodynamic profiles along the
entire corridor are forecast to become characterized by steep lower/mid-tropospheric lapse rates with sizable temperature/dew
point spreads by late afternoon. Subsequent south-southwesterly
low-level jet intensification (including 50-60+ kt around 850 mb
through mid to late evening) will support potential for severe
surface gusts, as convection develops in response to forcing for
ascent and contributes to downward momentum transport. The extent
to which this potential may be maintained beyond a couple of hours
window remains unclear, as a cold front surging out of the high
plains and overtaking the surface trough might quickly undercut the
stronger late afternoon/early evening thunderstorm development.
..Kerr.. 10/02/2025
$$
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