SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 PM CDT Fri Apr 29 2022
Valid 292000Z - 301200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
AND EVENING OVER PORTIONS OF SOUTHEAST NEBRASKA AND NORTHEAST
KANSAS...
...SUMMARY...
A complex and significant severe weather episode is forecast this
afternoon into tonight across the central Great Plains vicinity.
...Discussion...
Only two minor changes were made to the previous convective outlook.
1) Made slight adjustments by sharpening the severe probability
gradient for parts of the dryline to reflect dryline position and
developing high-based cumulus.
2) Added low hail probabilities for parts of eastern CO.
For short-term details regarding expected thunderstorm development
and associated severe hazards, reference MCDs 580-582.
..Smith.. 04/29/2022
.PREV DISCUSSION... /ISSUED 1119 AM CDT Fri Apr 29 2022/
...Southeast NE/Northeast KS...
Morning water vapor imagery shows a negatively tilted upper trough
over the central Rockies emerging into the High Plains. An
associated 60+ knot mid-level jet will move across KS this
afternoon, aiding surface cyclogenesis and resulting in a favorable
setup for severe storm development. Backed low-level winds to the
north/east of the surface low and warm front, along with persistent
moisture convergence and mid-level capping through the early
afternoon will result in a corridor of boundary layer moisture
"pooling" roughly along the KS/NE border. Forecast soundings in
this corridor show very favorable parameters for tornadic
supercells, but given the strong forcing that will overspread the
area, it is uncertain how long supercells can be maintained before
linear structures develop. Regardless, significant tornadoes,
destructive wind gusts, and very large hail are possible with the
storms that move across southeast NE and far northeast KS this
afternoon and evening.
...Eastern KS along the dryline...
By late afternoon, the surface dryline is expected to extend from
the surface low over north-central KS to near ICT. Temperatures
west of the dryline will warm to near 90F, while mid 60s dewpoints
are maintained to the east. While there is still uncertainty
whether many storms form along this axis, most of the 12z CAM
guidance now shows at least isolated supercell development over
parts of this area. Strengthening southerly low-level flow/shear by
early evening would support the potential for strong tornadoes,
along with very large hail and damaging winds from the most intense
storms. By mid-evening, the surface cold front will overtake the
dryline, leading to widespread thunderstorms capable of large hail
and damaging winds. The MDT risk area has been expanded slightly
southward to include parts of this area, and a 15% tornado risk area
has been added.
...Central OK along the dryline...
The uncertainty of convective initiation increases south of the
KS/OK border, but most CAM guidance shows one or more isolated
supercells forming along the dryline somewhere over OK by late
afternoon/early evening. Forecast soundings show an uncapped air
mass along a somewhat convergent dryline, underscoring the potential
for development. Have maintained the SLGT/ENH risk areas across
this region with a conditional risk of very large hail and tornadoes
from any supercell that can form on the dryline today.
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