Mesoscale Discussion 1032
NWS Storm Prediction Center Norman OK
0337 PM CDT Wed Jun 14 2017
Areas affected...Portions of eastern/southern
Concerning...Severe potential...Watch possible
Valid 142037Z - 142300Z
Probability of Watch Issuance...40 percent
SUMMARY...The area is being monitored for severe-thunderstorm
potential into the evening hours. Prospects for sustained deep
convection with severe hail/wind potential are presently unclear,
but the conditional potential will exist, and Severe Thunderstorm
Watch issuance may eventually become necessary.
DISCUSSION...Amid a moist boundary layer characterized by surface
dewpoints in the middle 60s to lower 70s, diabatic surface-layer
heating has contributed to strong diurnal gains in buoyancy.
Modifications to the 17Z Lamont OK sounding for ongoing surface
conditions suggest 2500-4000 J/kg of MLCAPE across the region, with
substantial erosion to MLCINH accompanying the base of a
moist-boundary-layer-overlying EML. In fact, visible satellite
imagery is suggesting slight agitation to cumulus fields across
south-central and central KS -- i.e., near a northeast-southwest-
oriented surface front marking the west edge of the strongest
buoyancy. This boundary extends from its intersection with a
diffuse, frontolytic, west-east outflow boundary near/north of the
Topeka KS area southwestward into east-central parts of the TX
Panhandle area. Baroclinic circulations along the front and decaying
outflow boundary could be foci for surface-based convective
development during the next several hours.
However, the severe risk is conditional on surface-based convective
initiation and sustenance. Surface observations suggest only weakly
convergent wind fields accompanying the aforementioned boundaries.
Furthermore, notable midlevel drying in the wake of a shortwave
trough is evident per water vapor imagery, with ongoing midlevel
height rises. This reflects air with a history of subsidence, which
may be associated with thermodynamic conditions proving hostile for
sustained storm development -- i.e. both associated with localized
boosts in static stability in the thermal profile aloft and abundant
dry-air-entrainment potential with incipient updrafts.
If convection were to develop (perhaps following repeated and
spatially focused pulsations of shallow convective plumes), the
aforementioned substantial buoyancy may facilitate the development
of vigorous updrafts. Moreover, with 25-40 kt of effective shear,
southward- to southeastward-moving supercells and multicell clusters
could evolve through the evening hours. Severe hail/wind would be
the primary concerns with this activity. Also, the overlap of
pre-existing vertical vorticity and substantive low-level buoyancy
on either side of the outflow boundary could foster very low tornado
potential in northeast KS. Some heat-burst potential may accompany
decaying convection later this evening (accompanied by strong
surface winds and rapid warming/drying of the boundary layer) --
especially in OK where midlevel lapse rates will be steepest in
association with the largest DCAPE.
Again, any severe risk is highly conditional, and prospects for
sustained storm formation -- if any -- are highly unclear. If it
were to appear a sustained severe risk were to eventually evolve,
Watch issuance may possibly become necessary.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 34889980 35679964 38059809 39469634 39499535 38749475
36799517 34899766 34489890 34459945 34889980