SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0300 PM CDT Wed Jun 21 2023
Valid 212000Z - 221200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
EASTERN COLORADO...SOUTHEAST WYOMING...AND THE NEBRASKA
PANHANDLE...AND FROM THE EASTERN TEXAS PANHANDLE AND WESTERN
OKLAHOMA INTO CENTRAL TEXAS...
...SUMMARY...
Intense severe thunderstorms are expected late this afternoon into
this evening over parts of the central and southern Plains, where
severe gusts, very large hail, and a few tornadoes are possible.
...20Z Update...
The Marginal and Slight Risks have been trimmed over parts of OK, in
the wake of an earlier storm cluster that has since weakened.
Otherwise, the previous forecast reasoning remains valid.
...Eastern CO/Southeast WY
Intense supercell development is underway across northeast CO into
the NE Panhandle, with additional supercells expected later this
afternoon into this evening farther west toward the CO Front Range
and southeast WY. Very large hail, severe gusts, and a few tornadoes
will be possible in this area. See MCD 1188, WW 349, and WW 350 for
more information regarding the threats in this area.
...Extreme southwest KS into the TX/OK Panhandles and northwest
TX...
A separate zone of intense supercell development is expected late
this afternoon from extreme southwest KS into the TX/OK Panhandles,
within a region of very rich low-level moisture, steep midlevel
lapse rates, and strong to extreme buoyancy. Very large hail, severe
wind gusts, and a couple of tornadoes will be possible with initial
supercells. Some upscale growth is possible this evening, which may
result in a larger swath of destructive wind gusts as storms move
southeastward, though the areal extent of MCS development remains
somewhat uncertain, as a westward-moving outflow may result in a
narrowing of the instability axis with time. See MCD 1189 and WW 351
for more information regarding the short-term threat in this area.
..Dean.. 06/21/2023
.PREV DISCUSSION... /ISSUED 1123 AM CDT Wed Jun 21 2023/
...TX/OK...
Morning water vapor imagery shows a large upper trough over the
western states, with moderately strong southwesterly mid-level winds
across much of the central and southern High Plains. At the
surface, an extremely moist and potentially unstable air mass
(dewpoints in the mid 70s) is present from the eastern TX Panhandle
eastward into western OK, and extending southeastward into central
TX. Full heating will lead to afternoon MLCAPE values of 5000-6000
J/kg and minimal cap. Large scale forcing is weak, but circulations
along the surface dryline will lead to rapidly thunderstorm
development from extreme southwest KS into the eastern TX Panhandle.
These storms are likely to be supercells capable of very large hail
and a few tornadoes.
These storms are likely to slowly congeal into one or more bowing
complexes by mid evening, tracking southeastward into northwest and
central TX. Several morning CAM solutions suggest the potential for
a corridor of significant wind damage if this scenario unfolds.
...Eastern CO/Southeast WY...
An extremely moist and unstable low-level air mass is streaming into
the central High Plains, with dewpoints in the 70s being transported
westward into the higher elevations of the eastern CO/southeast WY
plains. Strong daytime heating and steep mid-level lapse rates will
yield afternoon MLCAPE values over 3000 J/kg. All morning CAM
solutions agree on the development of scattered thunderstorms by
mid-afternoon along the front range and foothills, as well as the
DCVZ along the Palmer Ridge. A combination of backed low-level
winds and 30+ knots of southwesterly flow aloft will promote
supercell structures capable of very large hail and a few tornadoes.
The threat of severe storms may persist much of the evening,
building southward along the Front Range into southeast CO.
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