SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1258 AM CDT Sat Jun 15 2024
Valid 151200Z - 161200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR EASTERN
NE/WESTERN IA AND ADJACENT PARTS OF NORTHEAST KS...NORTHWEST
MO...SOUTHEAST SD...SOUTHERN MN...AND ALSO FROM EASTERN MT INTO THE
WESTERN DAKOTAS...
...SUMMARY...
Scattered severe thunderstorms with damaging winds and large hail
are possible from the late afternoon into the evening, both across
the Mid-Missouri Valley and also from eastern Montana to central
North Dakota. A couple of tornadic storms may occur in eastern
Nebraska and western Iowa, with isolated significant severe hail and
wind possible across parts of the northern Great Plains.
...Eastern NE/northeast KS into western IA...
A weakening or decayed MCS will likely be ongoing at the start of
the period somewhere from extreme eastern NE into western IA. In the
wake of this feature, an outflow-reinforced front will likely begin
lifting northward across some part of eastern NE into western IA
through the day. Diurnal heating will support moderate to strong
destabilization, both within a richly moist environment near/north
of the front, and within a somewhat hotter and more well-mixed
environment south of the front. As a mid/upper-level trough (with
multiple embedded vorticity maxima) approaches the mid MO Valley,
and MLCINH diminishes during the afternoon, isolated to widely
scattered thunderstorm development will be possible.
Along and immediately north of the front, favorable instability,
seasonably strong low-level flow, and a favorably veered wind
profile in the lowest 3 km will be favorable for tornadic
supercells, though rather modest flow above 3 km may result in a
tendency for a cluster or complex storm mode with time. Any
supercells that can be sustained within this regime would pose a
tornado threat, in addition to hail and damaging-wind potential.
However, considerable uncertainty remains, both regarding the
frontal position during the time of storm initiation, and also the
longevity of a more discrete supercell mode. The 5% tornado area has
been expanded somewhat to account for the spatial uncertainty.
Some modest upscale growth will be possible later in the storm
evolution, which could result in a threat for damaging wind and
possibly a line-embedded tornado or two spreading east-northeastward
into parts of central IA and southern MN during the evening.
...Northern Great Plains...
A rather strong mid/upper-level shortwave trough will move across
the Northwest and northern Rockies later today, and begin
approaching the northern High Plains tonight. A surface cyclone is
forecast to deepen near the MT/WY border during the day, and then
move northeastward across the western Dakotas vicinity this evening.
Near and east of the surface cyclone, MLCAPE is forecast to increase
into the 1500-2500 J/kg range from parts of eastern MT into the
Dakotas, while stronger deep-layer flow/shear attendant to the
approaching shortwave will begin impinging on the warm sector by
late afternoon into the evening.
Storm development is expected by late afternoon from eastern MT/WY
into the western Dakotas, with development of one or more intense
storm clusters possible by early evening. Large to very large hail
could accompany any sustained supercells within this regime,
especially from eastern MT into western ND. Isolated significant
severe gusts will also be possible, especially in areas where
stronger heating/mixing occurs, and also in association with any
more organized upscale growth. A tornado or two will also be
possible, especially if any supercell across western ND can be
sustained into the evening, when a notable increase in low-level
flow/shear will be possible.
...Southern High Plains vicinity...
Isolated to widely scattered thunderstorms will be possible this
afternoon and evening across parts of the southern High Plains, and
also across the higher terrain of southwest TX. Moderate buoyancy
and marginally favorable deep-layer shear could support a couple of
modestly organized storms. Isolated severe gusts will be possible
within a generally hot and well-mixed environment, along with some
potential for hail.
..Dean/Thornton.. 06/15/2024
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