LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1259 AM CDT Thu Mar 16 2023
Valid 161200Z - 171200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR
NORTH-CENTRAL/NORTHEAST TX...SOUTH-CENTRAL/SOUTHEAST OK...EXTREME
SOUTHWEST AR...
...SUMMARY...
Scattered severe thunderstorms capable of producing large hail,
damaging winds, and a few tornadoes appear likely Thursday afternoon
and evening across parts of the southern Plains. Some of the hail
could be very large over south-central Oklahoma and north-central
Texas.
...Synopsis...
A low-amplitude mid/upper-level shortwave trough will move quickly
from the southern Rockies across the southern Plains today, and into
the mid-MS Valley tonight. Meanwhile, a northern-stream trough will
amplify through the period as a mid/upper-level cyclone moves
southward across Manitoba. The primary surface cyclone will deepen
across the upper Great Lakes region, in response to the
northern-stream system. A strong cold front will surge southeastward
across much of the Great Plains and Midwest, reaching deep south TX
and the lower MS Valley by Friday morning.
...Southern Plains...
The environment will become quite favorable for organized severe
storms across the parts of the southern Plains into the ArkLaTex
this afternoon into tonight. Low-level moisture will stream
northward through the day, south of the surging cold front and
along/east of a weak surface trough that may effectively become a
weak dryline due to differential heating/mixing. Diurnal heating
will promote moderate to locally strong destabilization (MLCAPE of
1500-2500 J/kg) across the warm sector, in the presence of
relatively steep midlevel lapse rates. Effective shear will increase
into the 40-60 kt range as strong midlevel flow overspreads the
region.
Despite the favorable environment, some aspects of the synoptic
pattern may mitigate the threat of long-lived supercells, at least
to some extent. The primary southern-stream shortwave will emerge
rather early in the day, moving across OK in the 18-21Z time frame
and quickly moving away from the warm sector by 00Z. The low-level
jet will remain relatively veered through the day and become focused
into parts of the mid MS Valley and Midwest, in response to the
deepening cyclone over the Great Lakes. The fast-moving cold front
may tend to quickly undercut any discrete cells that develop across
the warm sector. These factors cast some uncertainty on the coverage
and duration of supercell development this afternoon and evening,
though scattered severe thunderstorms potentially capable of
producing all severe hazards are still expected this afternoon and
evening.
Surface-based storms may develop along the front as soon as 18Z
across central OK into western north TX, as the main shortwave
trough ejects eastward. Meanwhile, isolated to widely scattered
discrete storm development will be possible later this afternoon
from south-central OK into north-central TX along the pre-frontal
trough/weak dryline.
The initial frontal storms and any discrete development across the
warm sector may quickly evolve into supercells across south-central
OK and north-central TX, with a threat of very large hail and
isolated severe gusts. Also, despite somewhat veered low-level flow,
effective SRH of 200-400 m2/s2 (larger with eastward extent) will
support a tornado threat (including a conditional risk for a strong
tornado) with any sustained supercells that can avoid being undercut
by the front. Higher tornado probabilities may eventually be needed
if multiple long-lived pre-frontal supercells appear increasingly
likely.
The potential for pre-frontal storm development is more uncertain
with southwestward extent across south-central TX, with this area
being further removed from the ejecting shortwave trough. However,
any discrete supercell development along the pre-frontal trough or
the front itself would quickly pose a threat of large hail and
isolated severe gusts. Storm coverage will increase with time along
the front tonight. While there will be a tendency for storms to be
undercut by the front in this area, the strongest updrafts may still
be accompanied by hail and isolated strong gusts.
...ArkLaTex region into the lower MS Valley...
A supercell or two may develop out of initially elevated convection
across the ArkLaTex region later today. While this scenario remains
very uncertain, low-level shear/SRH will be sufficient for a tornado
or two, should any convection become surface-based in this area
during the afternoon or early evening. Later tonight, extensive
frontal convection will spread into the region, with low-level and
deep-layer shear remaining sufficient for a threat of damaging gusts
and a couple of tornadoes, especially where any embedded supercells
or bowing segments can be maintained without being undercut by the
front. A weakening trend is expected late tonight as storms move
into a less unstable environment, but some threat for locally
damaging wind and possibly a brief tornado may extend as far as the
lower MS Valley by 12Z Friday morning.
..Dean/Wendt.. 03/16/2023
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