Mesoscale Discussion 1512
NWS Storm Prediction Center Norman OK
1224 PM CDT Fri Aug 13 2021
Areas affected...Western Arkansas to Western Tennessee
Concerning...Severe potential...Watch unlikely=20
Valid 131724Z - 131930Z
Probability of Watch Issuance...20 percent
SUMMARY...Thunderstorms will continue to increase in coverage
through the mid afternoon hours as storms develop within the terrain
of the Ouachita/Ozark mountains and along an outflow boundary.
Isolated wind damage and severe hail is possible, but the organized
severe threat will remain limited.
DISCUSSION...Recent thunderstorm activity noted across AR and
western TN is being driven by a combination of diurnal
heating/orographic ascent and forcing along an outflow boundary from early-morning convection in southeast MO. Rich boundary-layer
moisture (denoted by dewpoints in the low to mid 70s) is
contributing to moderate to high instability (2000-3000 MLCAPE per
recent RAP mesoanalysis), limited inhibition, and low surface-parcel
convective temperatures. Recent GOES imagery shows numerous
convective towers within the region, suggesting that additional
storms are likely in the coming hours roughly along the I-40
corridor in AR into TN. While IR imagery shows vigorous cloud-top
cooling with some storms, weak deep-layer shear will favor
transient, poorly organized convection and a limited severe threat.
This precludes the need for a watch, though given the ample
instability damaging downburst winds and a few instances of severe
hail will be possible with any stronger storm.
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