Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS11 KWNS 290839
SPC MCD 290839
Mesoscale Discussion 0588
NWS Storm Prediction Center Norman OK
0339 AM CDT Sat Apr 29 2017
Areas affected...Eastern Oklahoma...northwest Arkansas...southern
Missouri...and far southern Illinois
Concerning...Severe Thunderstorm Watch 172...
Valid 290839Z - 291015Z
The severe weather threat for Severe Thunderstorm Watch 172
SUMMARY...Severe storms persist across WW 172 during the overnight.
Trends in radar imagery and recent HRRR suggest the severe-weather
threat will persist from northeast OK through southern MO to far
southern IL. Local WFO temporal extension of WW 172 may be needed
beyond 10Z. Meanwhile, counties south of these areas within 172
(east-central OK and much of AR) should have a continued lull in
storm potential and may be removed early from this watch.
DISCUSSION...08Z surface analysis showed a boundary extending
eastward from central OK (just south of CHK and OUN) to west-central
AR (near FSM), then northeast through north-central AR into the MO
Bootheel and PAH eastward through northern KY. Trends in mosaic
radar imagery indicated ongoing strong to severe storms extending
from far northeast OK and far northwest AR into south-central MO,
with additional strong to severe storms in far southern IL.
Meanwhile, strong to severe storms moving through central OK will
move into northeast OK (western extent of 172) by 09Z maintaining
the valid portion of this watch.
A 50-60 kt south-southwesterly low-level jet extending from
northwest LA into AR, maintaining strong warm air advection and
isentropic ascent north of the surface boundary, will continue to
support additional storm development into early Saturday morning.
MUCAPE of 2000-3000 J/kg and effective bulk shear exceeding 50 kt
extending from northeast OK through southern MO to southern IL will
allow for additional organized storms producing large hail and
strong wind gusts.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 36479219 35969384 35579495 35399628 35549654 36129655
36559588 36969489 37309360 37549259 37789144 37869011
38168884 38228795 37498815 37138857 37078993 36589158