SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1139 PM CST Sun Nov 17 2024
Valid 181200Z - 191200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
OKLAHOMA INTO NORTH TEXAS...
...SUMMARY...
Thunderstorms associated with isolated severe gusts and perhaps a
few tornadoes will be possible across parts of north Texas into
central Oklahoma this morning. A marginal risk for severe gusts is
expected across a relatively large area during the afternoon and
evening from the eastern parts of the southern and central Plains
into the Ozarks and lower Mississippi Valley.
...Synopsis...
An upper trough over the southern Plains this morning will lift
northeast across the Mid-MO Valley toward the upper Midwest today
and tonight. Strong southwesterly deep-layer flow will overspread
the southern Plains to the Mid/Lower MS Valley. An 80-100 kt 500 mb
jet over the southern Plains this morning will shift northeast
toward the Ozark Plateau through 00z, before weakening overnight.
Further southeast, 40-50 kt southwesterly midlevel flow will
overspread the central Gulf Coast vicinity overnight, though
large-scale ascent will become increasing displaced to the north as
the upper trough approaches the Upper Midwest/Great Lakes after 00z.
At the surface, low pressure is expected to be oriented over
southwest OK/northwest TX at 12z this morning. The low will deepen
as it lifts northeast in tandem with the upper trough, located near
southeast NE by 00z this evening, and over southeast MN by 12z
Tuesday. A cold front will sweep eastward across the southern Plains
today, becoming oriented from the Mid-MS Valley to the northwest
Gulf of Mexico by early Tuesday morning.
...Southern Plains to the Ozark Plateau...
A QLCS will be ongoing this morning from central OK into central TX
ahead of an eastward-advancing surface cold front. Southerly
low-level flow will transport Gulf moisture north and east from the
southern Plains into KS/MO. Instability is expected to remain modest
with northward extent despite low to mid 60s F dewpoints, partly due
to poor lapse rates and layers of modest inhibition. Nevertheless,
strong forcing along the cold front, and in association with the
northeast ejecting upper trough, in combination with strong
deep-layer flow, will support a risk for strong to severe gusts
during the morning hours across parts of OK and north TX. Where
pockets of low-level instability are maximized, particularly
near/east of the I-35 corridor in OK/TX, a risk for a few tornadoes
is expected through midday.
As the upper trough lifts northeast during the afternoon/evening,
stronger forcing will become displaced to the north, and instability
will be scant with eastward extent from eastern OK/TX into parts of
AR/MO. Nevertheless, moderate to strong vertical shear will be
present and a risk for isolated strong gusts and perhaps a tornado
may persist across the Ozark Plateau.
...Central/Eastern KS Vicinity...
A secondary area of thunderstorms may develop closer to the surface
low and behind the initial QLCS from north-central OK into eastern
KS. These storms may develop in a modestly steep midlevel lapse rate
environment amid more unidirectional southwesterly deep-layer flow
near the exit region of the midlevel jet streak. A couple of severe
storms may develop, posing an isolated risk for strong gusts, a
tornado and perhaps small hail.
...Southeast TX to Lower MS Valley Vicinity...
The trailing cold front and QLCS associated with the cyclone
ejecting over the Mid/Upper MS Valley during the evening/overnight
will move into an increasingly moist airmass over the Sabine and
Lower MS Valleys. Forecast soundings suggest surface-based
instability will remain scant, through MLCAPE to around 500-750 J/kg
is possible. A robust low-level jet is forecast to overspread the
region ahead of eastward-advancing line segments/clusters. This will
result in enlarged, curved low-level hodographs, and increasing 0-1
km SRH during the late afternoon into overnight. At least an
isolated risk for strong gusts and perhaps a tornado or two will
accompany thunderstorm activity through the nighttime hours. If
forecast trends become more favorable modest surface-based
destabilization, an upgrade to severe probabilities may become
necessary in subsequent outlooks.
..Leitman/Wendt.. 11/18/2024
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