Mesoscale Discussion 0981
NWS Storm Prediction Center Norman OK
0944 PM CDT Sat Jun 10 2017
Areas affected...Northeast WY into western and central SD
Concerning...Severe potential...Watch likely
Valid 110244Z - 110445Z
Probability of Watch Issuance...80 percent
SUMMARY...The potential for storms to increase in coverage,
intensity and severe-weather threat is becoming more likely across
far northeast Wyoming into western South Dakota. WW issuance will
be coordinated soon for parts of western and central South Dakota
for this evening into the overnight.
DISCUSSION...Trends in mosaic radar imagery indicated an increase in
storm development and intensity since 0120-0140Z across northeast WY
and adjacent western SD where both low-level convergence and upslope
flow into the Black Hills is indicating an increase in moisture/
destabilization. Further strengthening of southerly low-level winds
into tonight from the central Plains into SD will support additional
theta-e advection. This combined with a plume of steepening
700-500-mb layer lapse rates of 7.5-8.5 C/km spreading across the
low-level moistening will support moderate instability. Vertically
veering winds from southerly at low-levels to 500-mb southwesterly
winds of 55-75 kt will contribute to quite favorable bulk shear for
storms to organize.
Given cooling surface temperatures, new storm development should be
primarily elevated within a strengthening low-level warm air
advection regime as a warm front advances poleward toward the NE/SD
border overnight. Despite the elevated nature of these storms,
sufficient dry air in the lower troposphere per 00Z RAP sounding
should allow for a damaging-wind threat, in addition to large hail.
..Peters/Edwards.. 06/11/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FSD...ABR...UNR...
LAT...LON 44420415 45060368 45450118 45459985 45069834 44109799
43689794 43419952 43300139 43410249 43490370 44420415
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