604
ACUS01 KWNS 021951
SWODY1
SPC AC 021949

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0249 PM CDT Sun Jun 02 2024

Valid 022000Z - 031200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF NEBRASKA AND NORTHERN KANSAS...

...SUMMARY...
Scattered severe thunderstorms are forecast across much of the
Plains region this afternoon and evening, especially across the
central Plains of Nebraska and northwest Kansas. Very large hail of
2-3 inches in diameter, severe gusts of 60-80 mph, and a couple of
tornadoes are expected.

...OK/TX...

The Slight (level 2 of 5) and Marginal (level 1 of 5) risk areas
have been expanded to the east and south of an ongoing bowing
cluster of storms near the Red River and western north TX. These
storms are expected to continue shifting east/southeast along an
instability gradient amid 35-45 kt 0-6 km west/northwesterly flow.
Damaging gusts will be the main hazard with this activity, though
large hail is also possible within strongest cells.

Tornado probabilities have also been adjusted a small amount in the
TX Panhandle based on the 18z AMA RAOB, and across southwest TX
based on latest surface observations.

...Northern/Central Plains...

No changes have been made to the ongoing outlook. See previous
outlook for more details, and latest MCDs for short term severe
potential.

..Leitman.. 06/02/2024

.PREV DISCUSSION... /ISSUED 1142 AM CDT Sun Jun 02 2024/

...Central Plains through tonight...
Considerable uncertainty is apparent in this forecast update due in
part to mesoscale-driven convective outflow and its effects on
destabilization and quality of the warm sector for later this
afternoon and tonight.  Within generally zonal flow aloft, a low
amplitude shortwave trough will progress eastward from the northern
Rockies to the northern Plains through tonight.  Lee cyclogenesis is
expected across western NE/northeast CO near the southern influence
of this midlevel trough, with a weak cold front farther north into
the Dakotas.  The surface front/cyclone, as well as a lee trough
farther to the south will help focus thunderstorm development this
afternoon and storms will spread eastward through tonight.

Late this morning, several thunderstorm clusters have moved east and
weakened across the eastern half of NE and central KS.  To the west
of the outflow/residual cold pools from this early-day activity,
surface temperatures will warm into the 80s with boundary-layer
dewpoints mainly in the upper 50s to lower 60s, beneath steep
midlevel lapse rates.  The net result will be a narrow corridor of
large buoyancy (MLCAPE of 2500-4000 J/kg) and minimal convective
inhibition by mid afternoon from west TX to NE to the east of the
lee trough/dryline, when thunderstorm development is expected.

The initial storms in western NE into northwest KS could be
supercells capable of producing isolated very large hail (2-3 inches
in diameter) and any tornado threat will be tied to the more
discrete initial supercells.  Eventual upscale growth during the
evening will lead to an increasing threat for severe gusts 60-80 mph
as this activity develops and moves eastward as a southerly LLJ
intensifies.

...Southern High Plains this afternoon into tonight...
Similar to the central High Plains, appreciable uncertainty in this
forecast due to an ongoing midday thunderstorm cluster over southern
OK/north TX (reference MCD #1124 and associated Severe Thunderstorm
Watch #372) and its stabilizing influence and ability to focus storm
development later this afternoon and tonight.  If fresh outflow is
able to be reduced and/or become much more displaced from the
dryline by mid-late afternoon, it seems plausible the deleterious
effects will be minimal from the western TX Panhandle southward
along/east of the dryline.  At least widely scattered storms are
expected by mid-late afternoon along the dryline from the TX
Panhandle into west central TX, potentially aided by a mid-level
shortwave trough moving east across NM late this morning.  Elongated
hodographs will favor supercells capable of producing isolated very
large hail (2-3 inches in diameter).  Any mature supercell able to
interact in the vicinity of the modified outflow boundary or within
richer low-level moisture over the TX South Plains, will potentially
yield a tornado risk.  Though storm coverage will be a primary
driver of any damaging-wind threat, thermodynamic profiles will
favor intense downdrafts capable of producing isolated significant
outflow gusts of 75-80 mph.  A coalescing of storms during the
evening into the overnight may eventually move into northwest
TX/western OK before weakening late tonight.

...Northern Plains this afternoon/evening...
Not much change from previous forecast thinking in that the warm
sector will narrow and buoyancy will weaken with northward
extent from SD into ND, ahead of the surface cold front.  This
front, and ascent related to the approaching midlevel trough, will
help focus a line of thunderstorms along the front in central ND by
early-mid afternoon (possibly evolving from the ongoing storms near
the southwest ND border), and storms will subsequently spread
eastward toward western MN in the evening and develop southward into
SD.  The initial storms, or any embedded supercells, will pose a
threat for large hail of 1-1.75 inches in diameter, while damaging
gusts of 60-70 mph will become the more common threat once a linear
mode is established (and before the storms move too far east of the
primary buoyancy corridor).

...Southern LA to central/north TX this afternoon...
Scattered thunderstorm development will be possible in a loosely
focused corridor from southern LA into parts of southeast, central
and north TX along a remnant outflow/returning moisture gradient.
Though storm development in any particular area is low confidence, a
few storms in this area could pose a threat for isolated large
hail/wind damage given large CAPE and sufficient deep-layer
shear/hodograph length for at least some supercell potential.

$$