Mesoscale Discussion 677

Issued

May 18, 2021, 5:39 PM CDT (22:39 UTC)

Expired

May 18, 2021, 7:45 PM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe thunderstorm watch 189

The Western Arkansas radar (KSRX), 146 km from the middle of the area, began a volume at 22:39 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

441 
ACUS11 KWNS 182240
SWOMCD
SPC MCD 182239 
ARZ000-LAZ000-TXZ000-OKZ000-190045-

Mesoscale Discussion 0677
NWS Storm Prediction Center Norman OK
0539 PM CDT Tue May 18 2021

Areas affected...Western Arkansas and the Arklatex region

Concerning...Severe Thunderstorm Watch 189...

Valid 182239Z - 190045Z

The severe weather threat for Severe Thunderstorm Watch 189
continues.

SUMMARY...Sporadic damaging winds remain possible in the near term,
but a gradual weakening trend appears likely heading through the
remainder of the evening hours.

DISCUSSION...An organized line of storms continue to propagate
east/northeastward across western AR and the Arklatex region. A
handful of wind damage reports have been noted along the leading
edge of the QLCS, and recent GOES IR imagery shows a few strong
updrafts persist within the line, suggesting damaging winds remain
likely in the near term (roughly over the next hour or so). However,
composite reflectivity and lightning trends over the past hour hint
at a gradual weakening trend as the line of storms moves further
into AR where deep-layer shear is less favorable for organized
convection. Sufficient instability with minimal inhibition across
central and southern AR should allow for additional convective
development as this line continues east, and this may pose an
isolated wind/hail threat with any stronger updrafts. But the lack
of more robust deep-layer flow will likely limit the potential for a
more organized severe threat. Trends will be monitored, but a
downstream watch is currently not anticipated.

..Moore.. 05/18/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...LZK...SHV...TSA...

LAT...LON   32599514 33239471 33889429 34629428 34979468 35329494
            35509475 35699397 35739286 35379233 34729221 34159255
            33609288 33099339 32689387 32369417 32409482 32599514

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The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.