zczc spcswod48 all
acus48 kwns 200958
spc ac 200958
day 4-8 convective outlook
nws storm prediction center norman ok
0358 am cst wed feb 20 2019
valid 231200z - 281200z
...discussion...
medium-range model output continues to indicate strong cyclogenesis
will commence across the southern plains by 12z saturday, before
continuing northeastward through the great lakes region by 12z
sunday. guidance indicates that the rapid evolution of a broad and
deep cyclone is likely, aided by a vigorous short wave impulse
emerging from the southwest. it appears that this will be
accompanied by an intensifying cyclonic mid-level jet, including in
excess of 100 kt at 500 mb by midday saturday across the southern
plains red river valley, and 50-80+ kt south/southwesterly 850-700
mb flow across the destabilizing warm sector. this environment may
become conducive to the evolution of a significant organized
mesoscale convective system, potentially accompanied by considerable
damaging wind gusts.
highest severe probabilities appear focused in a swath across parts
of the ozark plateau and lower mississippi valley into the tennessee
and lower ohio valleys. a warm front may initially be located along
a corridor near or just south of the ohio river, west southwestward
into northwestern arkansas, near the northern periphery of the
currently depicted 15 percent severe probabilities. while the
influence of current snow and ice cover near and northwest of this
region remains uncertain, this boundary may ultimately remain the
focus for the track of the northern flank of an evolving squall
line. however, based on the track of the low, aided by strong
dynamic forcing, destabilization supportive of severe thunderstorm
potential could develop northward into southern portions of the
great lakes region saturday night.
the southern edge of the 15 percent probabilities is based on the
model consensus of the southern periphery of the deeper surface
cyclone. the southern flank of an evolving squall line may extend
this far south, where boundary-layer moistening and destabilization
will likely be most favorable. this environment may also support
discrete supercell development in advance of the squall line. in
addition to the risk for damaging convective gusts, there appears
potential for tornadoes, including some strong.
..kerr.. 02/20/2019
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