Mesoscale Discussion 1212
NWS Storm Prediction Center Norman OK
0211 PM CDT Sat Jun 20 2026
Areas affected...parts of eastern Colorado...southwestern
Nebraska...western Kansas
Concerning...Severe potential...Watch likely
Valid 201911Z - 202115Z
Probability of Watch Issuance...80 percent
SUMMARY...Intensifying scattered thunderstorm development
increasingly probable by 2-4 PM MDT, with a few supercells evolving
thereafter. This may be accompanied by increasing potential for a
couple of strong tornadoes, mainly in a corridor west through south
of the Imperial, NE vicinity toward early evening.
DISCUSSION...Beneath a plume of very warm (including 14-16 C+
temperatures around 700 mb) elevated mixed-layer advecting east of
the southern Rockies, a surface low is beginning to develop within
rapidly deepening surface troughing across eastern Colorado. This
is coinciding with strong boundary heating and deep mixing, to the
south of a zone of strengthening differential surface heating
evolving to the north of the developing low, across parts of
northwestern Kansas into the southern slopes of the Cheyenne Ridge.
Along and to the cooler side of this boundary, higher boundary-layer
moisture content and potential instability (including CAPE exceeding
2000 J/kg) are forecast to be maintained through the afternoon.
Even to the south of this boundary, the more deeply mixed
boundary-layer is forecast to become characterized by modest (but
increasing across the plains toward the Kansas state border) CAPE,
as convective temperatures are approached later this afternoon.
Inhibition may remain strong along the zone of differential heating,
but forcing for ascent associated with focused low-level convergence
and warm advection may eventually contribute to isolated supercell
development. In the presence of strengthening deep-layer and
low-level shear, this may be accompanied by increasing potential for
a strong tornado or two, in addition to large hail, by early
evening, if not earlier.
Otherwise, high-based convective development now underway across and
to the east of the higher terrain is expected to continue to spread
eastward across the plains and intensify, with scattered
thunderstorms increasingly probable by 20-22Z. This will be
accompanied by increasing potential for large hail, locally damaging
wind gusts, and perhaps at least some risk for a couple of tornadoes
as well.
..Kerr/Hart.. 06/20/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LBF...DDC...GLD...PUB...BOU...CYS...
LAT...LON 41060388 41090243 40420074 39400063 38270150 37160181
37170326 37510356 38450320 39330408 40290403 41060388
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