Mesoscale Discussion 1016
NWS Storm Prediction Center Norman OK
0349 PM CDT Tue Jun 13 2017
Areas affected...Portions of Kansas
Concerning...Severe potential...Watch possible
Valid 132049Z - 132315Z
Probability of Watch Issuance...40 percent
SUMMARY...Isolated to widely scattered thunderstorms with a severe
hail/wind risk may develop in the 2130-0000Z time frame and continue
into the evening. The area is being monitored for possible Severe
Thunderstorm Watch issuance.
DISCUSSION...The air mass east of a composite surface trough/dryline
analyzed from the Hill City KS area southward to near Dodge City KS
and farther south into the OK/TX Panhandles continues to undergo
strong destabilization, owing to widespread insolation amid surface
dewpoints holding in the lower/middle 60s. Diabatic-surface-heating-
bolstered baroclinic circulations along the aforementioned composite
boundary may support isolated to widely scattered surface-based
convective initiation in the 2130-0000Z time frame, as lapse rates
are approaching dry adiabatic in the lowest 3 km above ground west
of this feature. The severe risk could also spread into the region
from recently issued Watch 324 into the evening hours. Storm
development may also be aided by modest large-scale ascent/midlevel
cooling accompanying the southern extension of a speed maximum
crossing the area, as implied by water vapor imagery.
With 8.5-9.5 C/km midlevel lapse rates overlying the aforementioned
moisture, SBCAPE of 3000-4000 J/kg will support robust upward
convective-scale accelerations. Meanwhile, effective shear of 25-35
kt could support organized convective structures, with possible
supercells. Forecast hodographs across the region are modestly long
in the mid/high levels, with geometries of either straight or with
one or two inflections. Resultant, storm-scale, upward perturbation
pressure gradient forces could favor both left and right members of
supercell splits, along with small convective clusters following
potential mergers of initial cells. In addition to severe hail,
amalgamating cold pools amid 1000-1700 J/kg of DCAPE may foster
isolated to widely scattered severe wind gusts.
Given the modest magnitude of large-scale ascent and somewhat modest
deep shear magnitude, severe coverage may be limited, but may be
sufficient for Severe Thunderstorm Watch issuance by this evening.
Convective and environmental trends will continue to be monitored.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 38349893 38659903 38849949 39419953 39899926 39979857
39879803 39289781 38549789 38329845 38349893