083
ACUS01 KWNS 011940
SWODY1
SPC AC 011938

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0238 PM CDT Sat Jun 01 2024

Valid 012000Z - 021200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS
SOUTHWEST KANSAS INTO THE OKLAHOMA/TEXAS PANHANDLES AND NORTHWEST
OKLAHOMA...

...SUMMARY...
Scattered severe storms, including a few supercells, are expected
across the central and southern High Plains region, including
portions of the Big Bend of Texas. This activity should evolve into
organized clusters while spreading into the adjacent Great Plains
later in the evening. Severe wind, hail, and perhaps a couple of
brief tornadoes are the expected risks.

...20z Update...

The Marginal risk (level 1 of 5) has been expanded northward across
parts of northeast TX into northern LA. A cluster of storms has
persisted through the morning and into the mid-afternoon. A likely
MCV associated with this activity and a very moist/unstable
downstream airmass will continue to support storms into early
evening. This activity may sporadically produce strong gusts and
perhaps marginally severe hail.

The Slight risk (level 2 of 5) has also been expanded across parts
of the LA coastal vicinity where Severe Thunderstorm Watch 365 is in
effect. Strong to severe thunderstorm clusters will continue to pose
a risk for locally damaging gusts the next few hours. See MCD 1108
for more details.

The Slight risk (level 2 of 5) also has been expanded across
south-central TX to the Middle TX Coast. The 12z MPAS suite of
guidance, and to a lesser degree the 18z HRRR, shows a cluster of
supercells near the Rio Grande developing eastward across the Edward
Plateau vicinity this evening into tonight. If this occurs, the
overall environment will support severe gusts and large hail.

Elsewhere, the outlook remains unchanged (including the Enhanced
risk (level 3 of 5) across parts of the western KS/OK vicinity. See
previous discussion below for more details, and latest MCDs for
short term information regarding severe potential.

..Leitman.. 06/01/2024

.PREV DISCUSSION... /ISSUED 1150 AM CDT Sat Jun 01 2024/

...Central and southern High Plains through tonight...
Morning surface analysis places a surface front draped across NE,
with weak lee troughing farther to the south across eastern CO/NM in
response to modest westerly midlevel flow.  Residual outflow
boundary intersects the lee trough/dryline over western NE.
Scattered thunderstorms are expected to form by mid afternoon along
the surface boundaries and immediately east of the higher terrain,
and then move eastward/southeastward onto the Plains through
tonight.

A few supercells may also form across eastern CO into western NE,
where large hail up to 2-2.5 inches in diameter will be possible.
Recent model guidance has shown stronger agreement in showing
scattered thunderstorms developing from southeast CO into western KS
late this afternoon into the evening.  Upscale growth into an MCS is
progged by model guidance within an environment characterized as
moderately unstable and featuring steep low to mid-level lapse
rates, and moderately strong deep flow supporting organized storms.
An intensification of low-level southerly flow during the evening
will promote additional storms/mergers into a severe cluster moving
east-southeast into parts of the TX Panhandle/northwest OK during
the evening.  Large hail will be possible with the initial storms,
but the threat should evolve more to severe outflow winds of 60-80
mph with the upscale growth.

Farther south, the environment across southwest TX will favor
splitting supercells immediately east of the mountains, where
long/straight hodographs (with effective bulk shear 40-50 kt), steep
midlevel lapse rates and MLCAPE near 3000 J/kg will support very
large hail of baseball size (2.75 inches) or larger.  Isolated
severe outflow gusts will also be possible.

...South central/southeast TX into southwest LA this afternoon...
Scattered thunderstorm development is expected this afternoon along
a stalled front extending from south central TX into southwest LA.
The boundary layer continues to destabilize (strong buoyancy as of
midday) with moderately strong westerly flow above 500 mb.  A mix of
multicell clusters and, perhaps, some weak supercell structures will
be possible, with the potential to produce isolated large hail and
wind damage.

...MS/AL/TN area today...
A midlevel trough over the middle and lower MS Valley will move
slowly eastward to the TN/OH Valleys through tonight.  A couple of
different storm clusters will be possible this afternoon near and
just east of the midlevel trough within the surface warm sector
across MS/AL/TN.  Deep-layer vertical shear is relatively weak per
regional VWPs, but there is some low-level hodograph curvature
within a warm advection regime.  Given weak-moderate buoyancy where
boundary-layer dewpoints are in the upper 60s or greater, and later
pockets of surface heating in cloud breaks, a few storm clusters may
include embedded, weakly rotating storms capable of producing a
brief tornado or two, along with isolated wind damage.

...Northern UT...
Isolated to widely scattered high-based convection is forecast to
develop this afternoon.  Ample mid- to high-level flow will aid in
some organization.  The very steep lapse rates (inverted-v profiles)
will favor evaporative cooling with the stronger cores and the
potential for isolated severe gusts.

$$