SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1237 AM CDT Mon Mar 21 2022
Valid 211200Z - 221200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS CENTRAL
AND EASTERN TEXAS INTO EXTREME WESTERN LOUISIANA...
...SUMMARY...
Severe thunderstorms capable of producing very large hail, damaging
wind gusts, and several tornadoes are likely across portions of
central and eastern Texas, starting this afternoon and lasting
through much of the night. A couple of strong tornadoes are
possible.
...Synopsis...
A neutral-tilted trough will gradually traverse the southern Plains
today as a surface cyclone gradually intensifies across northwestern
Texas and propagates east-northeast. An embedded 500 mb impulse will
pivot around the upper trough during the afternoon/early evening
hours across Texas, encouraging the eastward shunting of a dryline
across the Texas Hill Country while a warm front gradually drifts
northward towards the Red River through the afternoon. Given
prolonged deep-layer ascent from the approaching upper trough,
coupled with a continuous feed of moist, buoyant air from the south,
multiple rounds of strong to severe storms are expected across
central/eastern Texas and surrounding areas this afternoon to 12Z
Tuesday. All facets of severe will be possible.
...Central and eastern Texas into far southern Oklahoma today...
The mid-level impulse embedded within the upper trough will
overspread central and eastern TX by noon, accompanied by an 80+ kt
500 mb speed max, which will in turn encourage the development of a
60 kt 850 mb jet across central and eastern TX this afternoon.
Deep-moisture/warm-air advection associated with the low-level jet
will support widespread showers and elevated thunderstorms, starting
in the morning. These preceding showers and storms complicate the
forecast somewhat as they may impede the northward speed of surface
airmass recovery. Nonetheless, latest guidance consensus shows 64 F
dewpoints and surface-based buoyancy in far northeast TX by 00Z.
Some marginally severe hail may accompany the initial WAA-driven
elevated storms in northern TX/far southern OK. Later in the
afternoon, semi-discrete supercells and small bowing-segments are
expected to develop ahead of the dryline, given the presence of
1000-2000 J/kg MLCAPE and 50+ kts of effective bulk shear. 8 C/km
mid-level lapse rates closer to the dryline, along with
unidirectional deep-layer shear, suggests that large hail will be
the initial main threat across central into northern Texas, with
some significant severe hail possible. As storms advance eastward
into the moister environment and approach the low-level jet axis,
storms may acquire stronger low-level rotation and produce
tornadoes. A strong tornado may accompany any sustained, discrete
supercell. Meanwhile, the linear segments may produce damaging gusts
in addition to some severe hail.
...Eastern Texas into the Arklatex later tonight...
As the main upper trough continues to advance towards the lower
Mississippi Valley, earlier day storms may coalesce into more linear
segments capable of several damaging gusts and at least a couple of
tornadoes given the strong low-level shear. Several CAM guidance
members depict the initiation of a second line of storms across
eastern TX, which will advance towards Louisiana in the 09-12Z
period. Given adequate buoyancy and long, curved hodographs,
stronger segments/cells within the broader line may acquire strong
rotation, capable of producing damaging gusts and tornadoes. A
strong tornado is also possible with the more intense QLCS
circulations given the magnitude of strong low-level shear.
...Portions of northwest Texas into southwest Oklahoma this
afternoon...
Modest low-level moisture will wrap around the eastern/northern
portion of the surface low across northwest TX this afternoon,
overspread by -20C 500 mb temperatures and steep mid-level lapse
rates. Semi-discrete supercells will develop near the triple point
along the northwest TX/southwest OK border by early afternoon. The
cold temperatures aloft suggest that severe hail will be the main
threat, with an instance of 2+ inch hail possible, though a couple
damaging gusts and perhaps a tornado also cannot be ruled out.
..Squitieri/Broyles.. 03/21/2022
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