LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1233 AM CDT Thu May 11 2023
Valid 111200Z - 121200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL AND SOUTHERN PLAINS...
...SUMMARY...
Strong/severe thunderstorms are forecast Thursday across the central
and southern Plains, where large hail and a few tornadoes can be
expected along with locally damaging winds. Isolated hail/damaging
winds are also possible across the lower Mississippi Valley into the
Southeastern states.
...Central/Southern Plains...
Latest water-vapor imagery depicts a well-defined upper low
beginning to eject northeast across northwestern NM as 500mb speed
max translates through the base of the trough. This speed max is
forecast to progress into the eastern TX Panhandle by 18z, then
gradually weaken as it shifts into northwestern OK by early evening.
Subsequent weakening is expected during the overnight hours as the
associated short-wave trough lifts into the mid-MO Valley by the end
of the period. In response to this feature, LLJ should be focused
across the High Plains from northwest TX into western KS early in
the period.
Scattered strong/severe thunderstorms are currently ongoing ahead of
the trough from the NM/TX border, north into western KS. As
large-scale ascent spreads into the High Plains this activity should
be maintained to some degree, likely continuing into the early part
of the day1 period. With more significant height falls forecast to
spread into the central High Plains, southern extent of this
activity should weaken/dissipate by mid day with only weak showers
and associated cloud debris expected to spread across portions of
the southern Plains. Of potentially more significance, cooling
mid-level temperatures and steep lapse rates will spread across
eastern CO/western KS early in the period. Strong boundary-layer
heating is expected to contribute to steep low-level lapse rates
across eastern NM into southwest KS by 18z. As a result, renewed
thunderstorm development is expected fairly early in the period
within the exit region of the aforementioned mid-level jet.
Supercells should evolve and lift north-northeast across the central
High Plains within a strongly sheared and modestly unstable
environment. Hail, wind, and tornadoes are possible with these
storms.
Farther southeast, negligible height changes will be noted across
OK/northwest TX. As a result, strong surface heating will prove
instrumental in convective development along the dryline by late
afternoon. If early-day convective debris is not that appreciable,
surface temperatures are expected to warm into the lower 90s across
northwest TX into extreme southwest OK by 22z. Convective
temperatures will be breached along the dryline with these readings
and isolated thunderstorms will likely develop soon thereafter.
While high-level flow is not forecast to be that strong, surface-6km
bulk shear will be strong and 0-3km SRH will be notable (300 m2/s2),
especially by early evening along the I-35 corridor where the LLJ is
expected to strengthen. NAM forecast sounding for OKC at 01z
exhibits 4100 J/kg MLCAPE with significant veering with height in
the lowest 5km. Any storms that develop near the dryline should
advance northeast into an environment favorable for maintaining
supercells. Very large hail, severe wind gusts and a tornado threat
will be noted with this more isolated activity.
...Gulf States...
Low-latitude trough, currently located over the lower MS Valley, is
forecast to gradually weaken as it advances into the central Gulf
States. Despite expansive cloudiness ahead of this feature,
strongest boundary-layer heating is forecast along the FL Gulf Coast
into eastern MS. Scattered robust convection should evolve ahead of
the trough and isolated gusts/hail could be noted with the strongest
storms.
..Darrow/Bentley.. 05/11/2023
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