Mesoscale Discussion 0536
NWS Storm Prediction Center Norman OK
0112 PM CDT Fri Apr 21 2017
Areas affected...Far eastern OK...AR...Western TN...Northern MS
Concerning...Severe Thunderstorm Watch 154...
Valid 211812Z - 211945Z
The severe weather threat for Severe Thunderstorm Watch 154
continues.
SUMMARY...A risk of locally damaging wind continues with the
long-lived convective system moving into western AR. The longevity
of this system is somewhat uncertain, but a local watch areal
extension or new watch issuance may be required to cover the threat.
DISCUSSION...At 1800Z, a well-organized, long-lived MCS is moving
quickly eastward into western AR. The system continues to be
primarily north of an outflow-reinforced frontal boundary, but a
well-defined surface pressure perturbation associated with the MCS
continues to support sporadic strong wind gusts along the line,
though recent observed gusts have not been as strong as noted
earlier.
A modest southwesterly low-level jet may continue to support renewed
convection atop the shallow cold outflow across portions of AR,
which could help to maintain the convective system into the
afternoon. The damaging wind potential is uncertain given the
cool/stable airmass present north of the boundary, though at least
sporadic strong wind gusts are likely to continue, with perhaps a
somewhat greater chance of damaging winds along and just north of
the frontal boundary, where greater buoyancy is available. The
maintenance of this system may necessitate local areal extensions of
WW 154, with new watch issuance downstream possible later this
afternoon if the system exhibits renewed intensity.
Further to the east across western TN and northern MS, loosely
organized convection is underway. Some of these cells could briefly
exhibit supercell characteristics as they interact with the frontal
boundary, though any severe threat with this activity is expected to
remain isolated at best.
..Dean/Goss.. 04/21/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MEG...LZK...SHV...TSA...
LAT...LON 35779402 35699310 35649203 35659102 35609019 35648808
34338836 34039212 34149312 34269483 34499527 34949511
35369480 35789453 35779402
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