SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0653 AM CST Thu Mar 07 2024
Valid 071300Z - 081200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
SOUTHERN PLAINS...
...SUMMARY...
Severe hail and thunderstorm gusts are possible over parts of the
southern Plains this afternoon into tonight.
...Synopsis...
The mid/upper-level pattern will remain progressive through the
period, as a strong shortwave trough exits the northeastern CONUS,
and a series of shortwaves traverse an eastward-shifting mean trough
across the West. The most important of those shortwaves is evident
in moisture-channel imagery over the lower Colorado River Valley
region and nearby parts of southern CA. This feature should move
eastward across central/southern AZ and adjoining portions of
extreme northwestern MX through the period, reaching southern NM and
-- at its easternmost part -- the TX/NM border region of the Llano
Estacado by 12Z tomorrow. In the foregoing southwest-flow regime
aloft, several weak/subtle vorticity lobes should cross portions of
the southern Plains States through the period.
At the surface, 11Z analysis showed a low over southeastern CO, with
wavy and somewhat diffuse warm front across northern parts of the TX
Panhandle and OK, to the western Ozarks. The low is expected to
migrate across the OK Panhandle to south-central/central KS through
the day, with 00Z trailing cold-frontal position across northwestern
OK and the northern/central TX Panhandle. By 12Z, the initial low
should reach eastern KS or western MO, with cold front to another
low near SPS, then across the South Plains to southeastern NM. A
dryline should sharpen through the day with continued moist
advection to its east. By 00Z, the dryline should extend from the
eastern TX Panhandle southward then south-southwestward to northern
Coahuila. The cold front will overtake the dryline from north-south
across the eastern Panhandle and northwest TX overnight.
...Southern Plains...
Isolated, marginally severe hail may occur from elevated
thunderstorms now prevalent over portions of the Arklatex to
southern Ozarks, eastern OK, and south-central KS, and a zone of
steep lapse rates aloft, low-level warm advection and moisture
transport above the surface. However, the main severe threat will
be later today.
Isolated to scattered thunderstorms -- forming along/ahead of the
dryline this afternoon and persisting/expanding into the overnight
hours -- will be capable of large hail (some potentially 2+ inches
in diameter) and occasional damaging to severe gusts. The tornado
risk is more sparse and conditional, given a lack of more-robust
moisture. A bimodal overall severe-threat distribution still is
apparent, with the greatest cumulative convective concentrations
likely centered on western OK to southern KS, and that part of
west-central to north-central TX in and south of the ongoing
convective band. With some reservations, a relative probabilistic
minimum will be maintained over the northwest TX region, but with
the understanding that any storm forming/sustaining in the
environment just east of the dryline still may become a supercell
capable of strong-severe gusts and significant hail.
Favorable destabilization will develop over the dryline and nearby
moist sector by mid/late afternoon, but in different ways from
north-south. More sustained/direct insolation and colder air aloft
is expected over northern areas where the ongoing high-cloud plume
will be less dense, and should exit sooner. In southern areas,
shorter duration/weaker magnitude of diabatic heating will be offset
to some extent by greater ambient moisture/theta-e. Each process
will weaken MLCINH enough to support surface-based convection this
afternoon into evening. Aside from the dryline and front, foci for
development may include outflow/differential-heating boundaries from
morning activity, and a persistent low-level convergence zone
already apparent near I-20 from the Big Country into north-central
TX. While denser convection training along in that convergence zone
may disfavor sustained large-hail potential, embedded supercells are
possible, and isolated discrete supercells may offer severe to
significant hail farther south. Forecast soundings south of the
convergence zone reasonably show rich inflow-layer moisture, strong
mid/upper winds and deep shear near the subtropical jet (with 60-75
kt effective-shear magnitudes possible), and long, nearly straight,
somewhat hook-shaped hodographs. Splitting storms are possible with
severe-hail potential from left- or right-moving supercells.
Overnight, as large-scale ascent strengthens ahead of the
approaching mid/upper trough, multiple rounds of development are
possible, especially in either "slight" risk area. A large-hail and
sporadic damaging-wind threat will exist with any such convection.
..Edwards/Jewell.. 03/07/2024
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