Mesoscale Discussion 1421
NWS Storm Prediction Center Norman OK
0345 PM CDT Thu Aug 05 2021
Areas affected...southern Idaho and extreme northeast Nevada and
Concerning...Severe potential...Watch unlikely=20
Valid 052045Z - 052245Z
Probability of Watch Issuance...5 percent
SUMMARY...High-based convection may pose a risk for isolated
downburst winds this afternoon into the early evening hours. It
appears coverage of any severe events will probably remain too
sparse to warrant a WW.
DISCUSSION...This afternoon high-based convection is in the process
of developing from northeast NV through northern UT and southern ID.
Most of this activity has yet to produce lightning. Strong diabatic
heating is occurring in the wake of the morning clouds and showers,
boosting temperatures into the 90s F, but with surface dewpoints
likely to mix into the 40s and upper 30s F over much of this region.
Deeply mixed boundary layers with steep lapse rates will
characterize the atmosphere, but instability will remain marginal
with 300-600 J/kg MLCAPE. Scattered showers and thunderstorms will
continue developing within the zone of upper diffluence and ascent
downstream from a shortwave trough situated over northern CA.
High-based updrafts rooted near 600 mb atop deep inverted-V boundary
layers will promote a threat for isolated downburst winds as
activity spreads northward into the early evening.
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