Mesoscale Discussion 0621
NWS Storm Prediction Center Norman OK
0254 PM CDT Sat May 15 2021
Areas affected...Northeastern Utah and southwestern Wyoming.
Concerning...Severe potential...Watch unlikely=20
Valid 151954Z - 152130Z
Probability of Watch Issuance...5 percent
SUMMARY...High-based thunderstorms developing near an area of low
pressure across northern Utah may produce some severe wind gusts or
large hail. A weather watch is unlikely.
DISCUSSION...As of 1930 UTC, radar and satellite observations showed
several thunderstorms developing across northern Utah and
southwestern Wyoming ahead of an upper low across the Great Basin.
Surface observations show modest low-level moisture (dewpoints in
the mid to upper 30s F) have pooled along and north of a stalled
frontal boundary along the southern Wyoming border. To the north of
the front, SPC mesoanalysis indicates around 500 J/kg of MLCAPE has
developed, owing to steep low and mid-level lapse rates near 9 C/km.
Diffluent southwesterly flow ahead of the upper low will continue to
slowly overspread the region and support between 25 and 35 kt of
effective shear. A couple of strong/severe storms capable of severe
hail, or more likely damaging outflow winds, will be possible into
early evening. Additional storm development within thermally driven
terrain circulations along the northern crest of the Uinta Range and
across the higher terrain of western Wyoming appear possible with
continued heating and the approaching mid-level diffluence. Low
confidence in convective evolution/coverage exists, suggesting a
weather watch is unlikely.
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