SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 PM CDT Mon Mar 21 2022
Valid 212000Z - 221200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF CENTRAL/EAST TEXAS...
...SUMMARY...
Several tornadoes, including the potential for a few strong
tornadoes, along with very large hail and damaging winds are
expected this afternoon through tonight, especially across parts of
central/east Texas into western Louisiana.
...20Z Update...
Severe probabilities have been trimmed on the western edge of the
risk area, based on the eastward progression of the Pacific cold
front/effective dryline. Otherwise, no major changes have been made
to the outlook. Thunderstorm coverage and intensity is expected to
increase through the remainder of the afternoon into the early
evening, from northwest into central TX, with all severe hazards
possible.
A couple of longer-track supercells may initiate across parts of
central TX late this afternoon and move northeastward, posing a
threat of tornadoes and very large hail, with a couple of strong
tornadoes possible. Storm modes are expected to become more linear
late tonight, but a threat of damaging winds and a few tornadoes
will likely persist into the Ark-La-Tex and southeast TX into
Tuesday morning. See the previous outlook discussion, MCD 291, and
MCD 292 for more information.
..Dean.. 03/21/2022
.PREV DISCUSSION... /ISSUED 1147 AM CDT Mon Mar 21 2022/
...Northwest to south-central/east TX into southern OK...
Have introduced a Moderate Risk (Category 4 of 5) for portions of
central/east-central Texas centered on late this afternoon and
evening, including parts of the Interstates 35/45 corridors.
Expectations are for an initially semi-discrete supercellular mode
with very large hail and some tornado potential, transitioning by
evening to potential for large hail/damaging winds and tornadoes as
storms spread east-northeastward with a more complex convective mode
gradually evolving.
At midday, a closed upper trough continues to pivot eastward,
centered over southern New Mexico and nearby far northern Mexico,
with the exit region of a strong mid/upper-level jet (90+ kt at 500
mb) beginning to overspread central/east Texas. Cloud cover remains
rather persistent at midday within the warm sector, but this
sheltering/inhibited mixing is a contributing factor to the quick
north/northwestward advection of a moist air mass (70F surface
dewpoints) that is already becoming increasing well-established
across south-central/southeast Texas.
As robust mid-level DCVA occurs with a shortwave impulse ejecting
out of the basal portion of an amplified trough, surface-based
thunderstorm development is initially anticipated early to
mid-afternoon near the triple-point cyclone and arcing south along
the dryline during the late afternoon across portions of central to
south-central Texas. Cooling 500-mb temperatures and steep mid-level
lapse rates should foster potential for a few semi-discrete
supercells along this upper portion of the Red River Valley. Severe
hail and brief tornadoes will probably be the main hazards as
convection likely spreads into a less favorable environment with
northern extent in Oklahoma.
Convection farther southeast and south from north-central to
south-central TX will have a progressively larger warm/moist sector
ahead of the dryline. With MLCAPE likely to reach 1500-2000 J/kg in
conjunction with an approaching 80-kt 500-mb speed max, several
supercells should develop with a primary initial threat of very
large hail. The bulk of guidance suggests the low-level jet will
shift east-northeast during the evening which suggests that
low-level hodograph curvature and attendant SRH, while adequate for
tornadoes, may not be particularly large for the supercells
initiating along the dryline. Nevertheless, potential remains
apparently for a couple long-tracked supercells emanating from near
the I-35 corridor in central/south-central Texas east-northeastward
into parts of east Texas.
...Ark-La-Tex to southeast Texas...
With time this evening, one or more linear clusters with embedded
supercells and bowing structures should evolve from a combination of
initial dryline storms and regenerative convection within the warm
conveyor. A rather messy mode of severe hazards is expected to
accompany this evolution with an elongated slow-moving QLCS
anticipated overnight, as the primary shortwave impulse shifts
towards the Lower Missouri Valley and a secondary lobe hangs back
near the Texas/Mexico border. Amid an expansive swath of 50-60 kt
low-level flow and rich western Gulf boundary-layer moisture, all
severe hazards will remain possible through the overnight, although
probably on a more isolated basis in terms of coverage.
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