Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS11 KWNS 220916
SPC MCD 220916
Mesoscale Discussion 0544
NWS Storm Prediction Center Norman OK
0416 AM CDT Sat Apr 22 2017
Areas affected...Northeast Texas...northern Louisiana...southern
Arkansas...and part of northwest Mississippi
Concerning...Severe Thunderstorm Watch 156...
Valid 220916Z - 221045Z
The severe weather threat for Severe Thunderstorm Watch 156
SUMMARY...The overall severe weather threat should continue to
diminish gradually into the early morning from northeast TX to
northwest MS. Isolated strong winds and/or a hail threat will be
the primary threats, with any of the remaining stronger storms.
DISCUSSION...A convectively reinforced surface boundary has
continued to advance southward across much of far northwest MS and
into southern AR, while the TX portion of this wind shift spreads
east/southeast across northeast and central TX. Vertically veering
winds exist across much of the pre-frontal environment with strong
effective bulk shear sufficient for storm organization. The
strongest instability remains across central and east TX into
western/northern LA and southern AR that would support a
severe-weather threat. However, weakening trends in mid-level CAPPI
data and warming cloud tops suggest storms in the TX/LA portion of
WW 156 are gradually diminishing in intensity.
Meanwhile, the leading edge of a cluster of storms located across
south-central and southeast AR may remain capable of producing
locally strong wind gusts and/or hail in the short term, as this
activity moves from southeast AR into the adjacent portion of MS.
Pre-frontal VWP data indicated southwesterly 40-45 kt winds from
around 0.5 km to around 1 km above ground level. These wind speeds
plus an eastward storm motion at 35 kt could result in stronger
winds to reach the surface. However, the downstream environment is
more stable and could inhibit the severe-weather threat with
eastward extent into MS.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 32049546 32699455 33019392 33679291 33829216 33969149
34079107 34039078 33799045 33249064 32559176 32089282
31549382 31199402 31059452 31329503 32049546