ACUS01 KWNS 151246
SWODY1
SPC AC 151245

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0745 AM CDT Mon Apr 15 2024

Valid 151300Z - 161200Z

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

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN MID-ATLANTIC...

...SUMMARY...
Scattered severe thunderstorms are likely across parts of the Great
Plains, beginning mainly this evening and continuing overnight.
Several tornadoes, large to very large hail, and damaging wind gusts
all appear possible. Strong tornadoes may occur this evening across
parts of Kansas and Nebraska.

...Synopsis...
A large, closed upper cyclone is present over the Great Basin this
morning. This feature will track eastward across the central
Rockies, eventually ejecting over the southern/central Plains
tonight. A strong mid/upper-level jet attendant to this upper
cyclone will overspread much of the southern/central Plains through
this evening. Pronounced large-scale ascent preceding the
upper-level trough/low will encourage additional deepening of a
surface low over the central High Plains though the day. Moisture
will continue streaming northward through the period in tandem with
a warm front and persistent low-level warm/moist advection. This
warm front should be located across NE and perhaps into far southern
SD by late this evening, as the primary surface low consolidates
over the NE Panhandle. A dryline is forecast to mix eastward across
the southern/central High Plains through peak afternoon heating,
before retreating westward this evening across parts of the TX/OK
Panhandles and western KS.

...Northern/Central Plains (Kansas/Nebraska/South Dakota)...
A cap and the late timing of large-scale ascent associated with the
ejecting upper cyclone will likely inhibit convective development
across the northern/central Plains through at least late afternoon.
Still, low-level moisture will gradually increase through the day,
with surface dewpoints of at least upper 50s to low 60s becoming
common by early this evening across the warm sector. Steep mid-level
lapse rates and cooling thermal profiles aloft are expected to
contribute to substantial MLCAPE by the peak of the diurnal heating
cycle, with values likely ranging around 2000-3000 J/kg. With
gradually strengthening mid/upper-level flow anticipated, deep-layer
shear should also become sufficiently strong to support a mix of
supercells and multicells across this region.

Convective initiation should be delayed across much of KS/NE/SD
until around 00Z as a southerly low-level jet rapidly strengthens to
50-60 kt. Very large hail (around 2-3 inches in diameter) will be a
threat with any supercells that can form along/near the warm front,
or southward along the length of the dryline into western KS.
Low-level hodographs are forecast to become enlarged/curved in the
00-06Z time frame tonight, and the threat for tornadoes is likewise
expected to increase with any supercells that can persist and remain
at least semi-discrete. Confidence has increased in a more
concentrated corridor of tornado potential across parts of
western/central KS into central NE, where supercells appear most
likely in very favorable thermodynamic and kinematic parameter
space. Given the forecast strength of the low-level shear, strong
tornadoes appear possible this evening/tonight across this area. Severe/damaging winds will also be possible as convection attempts
to grow upscale into one or more clusters overnight. Even with
nocturnal cooling, these severe/damaging winds may persist given the
ample reservoir of buoyancy available.

...Southern Plains (Oklahoma/Texas)...
The overall coverage and severity of convection across the southern
Plains is somewhat more uncertain compared to locations farther
north across the central Plains. This uncertainty is largely tied to
the influence of a sub-tropical mid/upper-level jet that will move
over the southern Plains through the period, along with associated mid/upper-level cloudiness. These clouds may tend to limit daytime
heating to some extent along the length of the dryline. Even so,
attempts at robust convective development will probably occur across
parts of northwest TX by late this afternoon. If this activity can
be sustained, then supercells appear likely given ample (50-60 kt)
deep-layer shear. Isolated large to very large hail will probably be
the main threat with this convection as it moves towards
north-central TX. But, occasional severe/damaging winds and perhaps
a couple of tornadoes may also occur through the early evening. Most
guidance indicates any supercells which develop will weaken with
eastward extent as they encounter increasing MLCIN, and become
increasingly displaced from the better large-scale ascent with the
upper trough/low ejecting over the central Plains. A highly
conditional severe threat remains apparent across OK late this
afternoon and evening, with a favorable parameter space to support
supercells capable of producing all severe hazards. But, much of OK
may have a relative minimum in convective activity until late
tonight as a Pacific cold front overtakes the dryline.

...Mid-Atlantic to the Mid Mississippi Valley...
The glancing influence and modest ascent with an upper trough across
the Northeast and eastern Canada will overspread parts of the
Mid-Atlantic by early afternoon. Weak low-level convergence along a
sagging cold front should be sufficient to support isolated to
scattered thunderstorm development through the afternoon and evening
from parts of the mid MS Valley into the OH Valley, central
Appalachians, and southern Mid-Atlantic. Ahead of the front across
the Mid-Atlantic, generally low 50s surface dewpoints and steepened
mid-level lapse rates will foster around 1000-1500 J/kg of MLCAPE
with moderately enhanced westerly mid/upper-level flow. Deep-layer
shear across this region appears strong enough to support supercells
with an associated threat for large hail. Damaging wind gusts may
also occur with multicell clusters that attempt to form as they
track generally east-southeastward through the evening hours. With
weaker deep-layer shear across the mid MS and OH Valleys, convection
should be somewhat less organized while still posing an isolated
threat for hail/wind. The overall severe threat should gradually
diminish through late evening with the loss of diurnal heating.

..Gleason/Grams.. 04/15/2024

$$
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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.

$$
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ACUS01 KWNS 261254
SWODY1
SPC AC 261253

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0753 AM CDT Fri Apr 26 2024

Valid 261300Z - 271200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS
AFTERNOON/EVENING ACROSS NORTHEAST KS/SOUTHEAST NE/NORTHWEST
MO/SOUTHWEST IA...

...SUMMARY...
A few tornadoes, including a couple of strong tornadoes, isolated
very large hail (greater than 2 inch diameter) and isolated wind
damage will be possible, mainly this afternoon/evening from
northeast Kansas/southeast Nebraska into northwest Missouri and
southwest Iowa. Occasional severe storms are expected farther south
into Arkansas, eastern Oklahoma and northeast Texas.

...Mid MO Valley to TX through tonight...
A complex surface pattern is evident this morning with a cyclone in
northern KS, a trailing dryline/Pacific front into western OK, and
the east edge of the warm sector demarcated by a warm front from
eastern OK into eastern KS. An ongoing QLCS with occasional wind
damage and tornado reports is moving across eastern OK near the warm
front, with an area of rain-cooled/overturned in OK in the wake of
these storms. Farther north, an undisturbed portion of the warm
sector extends across central KS.

The eastern OK convection will likely persist through the day toward
western AR, with additional expansion of rain/thunderstorms farther
northeast into southwest/central MO. The OK/AR portion of this
convection will be the most likely to maintain access to the surface
warm sector through the day, where a mix of bowing segments or
embedded supercells will be possible with all hazards.

The clouds/rain will slow the northeastward progress of the warm
sector, and northward advection of the overturned airmass in OK will potentially impact the breadth and quality of the unstable warm
sector this afternoon. Assuming sufficient recovery during the day,
there will be a window of opportunity for tornadic supercells along
the dryline this afternoon/evening starting in northeast
KS/southeast NE and spreading into northwest MO/southwest IA.
MLCAPE at or above 2000 J/kg, boundary-layer dewpoints in the mid
60s, and sufficiently long hodographs with low-level hodograph
curvature (effective bulk shear in excess of 50 kt, and effective
SRH of 200-300 m2/s2) suggest the potential for a couple of strong
tornadoes with any persistent, semi-discrete supercells. Isolated
very large hail (in excess of 2 inches in diameter) will also be
possible, while the potential for a few damaging gusts will
accompany any upscale growth into line segments this evening.

Additional thunderstorm development will be possible today farther
southwest into TX, in association with weak height falls on the
southern fringe of the ejecting midlevel trough. The 12z FWD
sounding showed only a weak cap, so the SLGT has been expanded some
to the southwest to account for large hail/wind damage potential
today. Storms will likely weaken by this evening as weak height
rises commence and the remnant dryline begins to retreat to the
west.

..Thompson/Guyer.. 04/26/2024

$$
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