000
ACUS01 KWNS 252000
SWODY1
SPC AC 251958

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0258 PM CDT Thu Apr 25 2024

Valid 252000Z - 261200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL AND SOUTHERN PLAINS...

...SUMMARY...
Very large hail up to 3 inches in diameter and a strong tornado or
two will be possible this evening across western Kansas and
vicinity. Large hail, damaging winds to 70 mph, and a few tornadoes
will be possible this evening and tonight from northwest Texas into
central Oklahoma.

...20Z Update...
The Enhanced Risk across western KS has been expanded to include
more of northwest KS, far northeast CO, and far southwest NE. Based
on recent visible satellite trends, convective initiation appears
imminent across east-central CO along/near a surface dryline.
Additional robust thunderstorm development will likely occur this
afternoon across northeast CO into northwest KS and vicinity as an
upper trough continues ejecting eastward over the central High
Plains. Given moderate buoyancy and strong deep-layer shear, very
large hail (possibly up to around 3 inches) should be the main
threat with initial supercells. By early this evening, strengthening
low-level shear should encourage a greater tornado threat with any
supercells that can persist, especially as this activity interacts
with a warm front across northwest KS. A strong tornado or two
remains a possibility across this area. See Mesoscale Discussion 513
and recently issued Tornado Watch 133 for more details on the severe
threat for this region.

No changes have been made to the separate Enhanced Risk across parts
of northwest TX into southern/central OK. It still appears likely
that convection will develop by 06Z across this region, and quickly
spread east-northeastward through early Friday morning. All severe
hazards still appear possible with this activity, including the
potential for a few nocturnal tornadoes given the forecast strength
of the low-level shear.

In between the two Enhanced Risks (OK/TX Panhandles), there is still
a fair amount of uncertainty regarding how many supercells may
develop along/east of the dryline. Some cu has recently formed over
the northwest TX Panhandle. But, a 19Z special sounding from DDC
still shows substantial capping in place. Regardless, a conditional
threat for supercells posing an isolated threat for very large hail
and perhaps a couple of tornadoes will exist through this evening
across this area.

..Gleason.. 04/25/2024

.PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Apr 25 2024/

...Synopsis...
Morning water vapor imagery shows a negatively-tilted shortwave
trough rotating across UT/AZ, with an associated 70kt mid-level jet
max moving into NM.  This system will eject into the
central/southern Plains this evening/tonight, resulting in multiple
clusters of severe thunderstorm activity.

...Western KS...
A quasi-stationary surface boundary extends from northwest CO into
northwest KS.  Visible imagery shows broken cloud cover across
western KS this morning, with dewpoints in the low 60s to the south
of the front.  Strong heating will likely ensue through the
afternoon, resulting in deepening mixing to the east of the dryline
and eventual isolated thunderstorm development.  CAM solutions
differ significantly on coverage of convection, but it appears
likely that at least isolated supercells will form along the
dryline, capable of very large hail, damaging winds, and a few
tornadoes (possibly strong).

The confidence of initiation is much higher along the warm front
from northeast CO into northwest KS, and forecast soundings along
this corridor show strong low-level vertical shear supporting
supercell structures.  It is uncertain how far north these storms
can remain surface-based, but there is an apparent tornado risk
(possibly strong) along the immediate boundary and a large hail risk
for some distance northward.  This activity will likely spread into
south-central NE after dark.

...TX Panhandle/Western OK...
As the primary upper trough ejects this evening, large-scale height
falls and forcing will overspread the dryline across the OK/TX
Panhandles.  Forecast soundings show a persistent capping inversion
along the dryline, and CAM guidance generally shows very isolated
convective initiation.  Any storm that forms will pose a risk of all
severe hazards, including very large hail.

Overnight, a strengthening low-level jet over west TX will likely
lead to a large cluster of thunderstorm.  These storms will track
northeastward across northwest TX and into western/central OK in the
pre-dawn hours.  Large hail will be likely with these storms, but
damaging winds and isolated tornadoes will also be a risk if a more
organized linear MCS can evolve.

$$