SPC AC 250557
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1257 AM CDT Mon Oct 25 2021
Valid 261200Z - 271200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN AND CENTRAL PLAINS...
...SUMMARY...
Scattered severe thunderstorms associated with large hail, wind
damage and an isolated tornado threat are expected across parts of
the southern and central Plains from late Tuesday afternoon through
the evening into the overnight.
...Southern and Central Plains...
An upper-level trough will move eastward across the southern Rockies
on Tuesday as an associated 60 to 80 knot mid-level jet moves into
the southern and central High Plains. Southwest mid-level flow will
be in place ahead of the system across the southern and central
Plains. The approach of the system will result in strong moisture
advection across the southern and central Plains during the day with
a corridor of moderate instability developing by late afternoon from
west-central Texas northward into west-central Kansas. A capping
inversion during the day will prevent convection initiation from
taking place until late afternoon along and to the east of a
dryline. Initially, thunderstorm development is expected to be
isolated but storm coverage should steadily increase during the
evening as the low-level jet strengthens. The storms should
eventually organize into a line with MCS development possible during
the mid to late evening.
Model forecasts are in good agreement concerning the timing of the
upper-level system and position of the moist axis. During the early
evening, MLCAPE is forecast to reach the 1000 to 2000 J/kg range
along much of the instability corridor. Supercell wind profiles are
forecast in most areas with 0-6 km shear in the 35 to 45 kt range.
In addition, mid-level lapse rates are forecast to be near 7.5 C/km
in the vicinity of the dryline. This will be favorable for the
development of supercells with large hail. In areas that destabilize
the most, supercells with hailstones of greater than 2 inches in
diameter will be possible. Supercells will also be capable of
damaging wind gusts and an isolated tornado threat. A more
widespread wind-damage threat should develop as storms congeal
during the evening and move eastward across north-central Texas,
west-central Oklahoma and south-central Kansas. The severe threat
will become isolated during the early overnight period.
Further to the north across northern Kansas and central to eastern
Nebraska, a severe threat is also expected to develop. The northern
end of a convective line should be located in central or northern
Nebraska during the evening. Instability is forecast to be weaker
this far north but strong deep-layer shear will still be adequate
for severe storms. Isolated large hail and wind-damage are expected
to be the primary threats.
..Broyles.. 10/25/2021
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