SPC Mar 27, 2020 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook
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Day 1 Convective Outlook NWS Storm Prediction Center Norman OK
Widespread thunderstorms capable of producing mainly isolated large
hail are expected from eastern Kansas into the Midwest today. A few
locally strong wind gusts and perhaps a tornado or two are also
possible. ...Synopsis... Upper trough currently situated over southern CA will advance east
northeast along the northwestern periphery of a subtropical ridge,
reaching the southern and central Plains later Friday night.
Preceding this feature, weaker vorticity maxima embedded within a
broad corridor of southwesterly winds aloft will advance northeast
through the central Plains and Midwest region. At the surface a lee
cyclone will develop over the High Plains of CO or western KS by
late today, and advance into northeastern KS overnight within the
exit region of a strong jet streak rotating through the base of the
upper trough. At the start of this period a stalled front should be
situated from the OH Valley westward through southern KS/northern OK
where it will intersect a dryline that will extend through western
TX. The stalled front will lift northward as a warm front, likely
reaching southern IA by the end of the period. A Pacific front will
merge with the dryline and advance east. By 12Z Saturday this front
should extend from a surface low in southern IA southward through
eastern OK and eastern TX. ...Kansas through the Midwest... The 00Z RAOBs indicate warm air at the base of an elevated mixed
layer has already spread across the central and southern Plains and
will serve to limit surface-based thunderstorm development in most
of the moderately unstable warm sector today. A few-high based
storms might initiate by late afternoon across southwest into
central KS along the dryline/front intersection, but these may
subsequently become elevated as they advance northeast. The more
substantial thunderstorm development will likely wait until at least
Friday evening when a strengthening, broad low-level jet will
continue to transport moisture northward, contributing to moderate
instability above the frontal zone (1500-2500 J/kg MUCAPE). Initial
storm development could occur anywhere from central MO eastward
through IL and IN. These storms will likely be elevated, but
effective bulk shear will support potential for supercell structures
with large hail the main threat. Late Friday night, deeper forcing
for ascent within the approaching upper jet exit region will
contribute to additional thunderstorm development ahead of the
advancing cold front from eastern KS into western MO. At least a
couple of these storms might be close to surface based and evolve
into supercell structures given favorable vertical shear, posing a
threat for large hail and perhaps a couple of tornadoes. However,
limiting factors are remnant convective inhibition and at least a
shallow near-surface stable layer. ...Southern Plains region... The moderately unstable warm sector in this region will likely
remain capped to surface-based storms during the day, though some
mid-level convection will be possible supported by steep lapse rates
and mid-level ascent attending progressive vorticity maximma
embedded within the southwesterly flow regime. Later Friday night,
additional storms will probably develop along the cold front and in
association with stronger forcing for ascent accompanying the
primary upper jet. It is probably unlikely these storms can root in
the boundary layer. However, at least a marginal risk for hail will
accompany the stronger updrafts. ..Dial/Dean.. 03/27/2020 

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