Mesoscale Discussion 1436
NWS Storm Prediction Center Norman OK
0611 PM CDT Sat Aug 07 2021
Areas affected...Parts of southeastern Nebraska...western and
central Kansas and adjacent portions of the Oklahoma
Concerning...Severe Thunderstorm Watch 412...
Valid 072311Z - 080115Z
The severe weather threat for Severe Thunderstorm Watch 412
SUMMARY...An eastward advancing corridor of increasingly widespread thunderstorm development is expected through 7-9 PM CDT, with strong
to locally severe wind gusts becoming an increasing hazard. Trends
are being monitored for the possibility of one or two additional
severe weather watches.
DISCUSSION...Stronger surface heating and deeper boundary-layer
mixing is focused near the pre-frontal surface trough axis across
the Texas/Oklahoma Panhandle vicinity through the Garden City/Dodge
City areas, into north central Kansas northeast of Hayes and
Russell. However, the bulk of ongoing thunderstorm development has
been occurring ahead of the cold front through areas west of the
surface trough axis, where higher surface dew points and cooling
aloft ahead an approaching short wave trough area contributing to
greater CAPE (in excess of 1500 J/kg). Beneath 30-40 kt
southwesterly mid-level flow, deep-layer shear is also strong,
contributing to supercell structures north of Garden City.
However, deepening convective development is evident near the
immediate vicinity of the surface trough, and models suggest that a
combination of consolidating convectively generated cold pools and
the cold front will overtake the surface trough during the next few
hours. Aided by forcing for ascent and cooling aloft associated
with the eastward progressing short wave trough, it appears that destabilization along the surface trough may support increasingly
widespread thunderstorm development during the next few hours. By
01-02Z, there is some consensus among the various model output that
this probably will extend from southeast of Dodge City through the
Concordia and Hastings/Grand Island vicinities.
Coinciding with nocturnal southerly low-level jet strengthening
along this corridor (including 30-40+ kt at 850 mb), strong surface
gusts approaching and occasionally exceeding severe limits will
likely become the most prominent severe hazard.
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