LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1147 PM CST Tue Feb 14 2023
Valid 151200Z - 161200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE LOWER MISSISSIPPI VALLEY AND WESTERN TENNESSEE VALLEY...
...SUMMARY...
Widely scattered severe thunderstorms are possible over parts of
Texas and Oklahoma beginning late in the day and into the evening on
Wednesday. A severe threat will also develop overnight over the
lower Mississippi Valley/Mid-South region, with a tornado risk.
...Eastern OK/North-Central TX to the Mid-South...
Late-evening satellite imagery depicts a well-defined upper low
digging southeast into northern AZ. This feature is forecast to
shift into the southern Rockies by mid day as a 110kt 500mb jet
translates across the desert southwest toward the southern High
Plains. With time this feature will advance into eastern KS allowing
the trough to become more positive tilted as it moves into the
central Plains. This evolution will maintain broad southwesterly
flow across lower latitudes, including the Mid-South region. Of
particular concern will be the development of a pronounced LLJ
across the lower MS/TN Valley, especially during the latter half of
the period when a marked increase is expected (in excess of 60kt).
More appreciable mid-level height falls will remain north of the
higher-buoyancy air mass, thus low-level warm advection will likely
prove instrumental in the majority of supercell development through
the period.
At 05z, a narrow band of strongly-forced convection is observed
along the front over AZ. Otherwise, most of the southern states are
convective free with strong capping. Low-level trajectories favor
Gulf air mass advancing inland across the lower MS Valley, and mid
60s surface dew points are well established at this time over much
of the upper TX Coast and LA. Latest guidance suggests this air mass
will easily advance north into AR/western TN Valley later today;
however, convective development will likely remain suppressed until
the latter half of the period when the LLJ intensifies in response
to the approaching short wave.
Upstream, strong boundary-layer heating across the southern High
Plains will result in very steep surface-3km lapse rates from the
southern TX Panhandle into western OK/northwest TX. It appears this
steep lapse rate plume will overspread the northwestern portions of
return moisture across south-central OK/north-central TX, just ahead
of the front/dry line. As temperatures warm into the lower 70s
capping should weaken and scattered convection is expected to
develop. Forecast soundings favor supercell development and this
activity should spread east during the evening hours with an
attendant threat for all hazards.
Downstream, LLJ will increase across LA into western TN from late
afternoon into the evening. Steep mid-level lapse rates will
overspread this region as 3km capping gradually weakens. As the cap
weakens, isolated discrete supercells are expected to evolve within
a moistening, warm advection regime. ESRH values in excess of 300
m2/s2, along with steep lapse rates, and modest instability favor
severe supercells capable of producing tornadoes, possibly strong. A
corridor of supercells may ultimately evolve along an axis from
southeast AR into western TN, during the latter half of the period,
as the cold front will not advance east of the MS River prior to
sunrise. Warm advection should be the primary forcing mechanism for
this activity, thus episodic bouts of severe are possible.
..Darrow/Thornton.. 02/15/2023
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