Mesoscale Discussion 0393
NWS Storm Prediction Center Norman OK
0554 PM CDT Sat Apr 01 2017
Areas affected...Portions of the Texas Big Country and Edwards
Plateau
Concerning...Severe Thunderstorm Watch 106...
Valid 012254Z - 020030Z
The severe weather threat for Severe Thunderstorm Watch 106
continues.
SUMMARY...Strong/severe thunderstorms will persist across primarily
central and southern portions of Watch 106 this evening.
Additionally, a southward expansion may be necessary if convective
trends warrant.
DISCUSSION...Through 22Z, the severe threat in Watch 106 has been
confined to a supercell that formed near a triple point near the
I-20 corridor this afternoon. However, this storm has become rooted
above a shallow surface stable layer, as a cold front steadily
pushes southeast across the Big Country. With this cell becoming
progressively displaced from warm/moist surface air, continued
weakening is probable. However, persistent large-scale ascent and
considerable effective shear may maintain some threat for large hail
with any cell that develops across northern portions of the watch.
Farther south, convection has attempted to organize from the
dryline/cold front intersection to points southeastward along a
remnant boundary extending towards Llano, TX. Overall, weak surface
convergence and mid-level flow perpendicular to this initiating
boundary have given cells a rather elongated, marginal structure.
While the cold front will gradually undercut the northwestern extent
of these cells, a band of ascent aloft (noted in water vapor
imagery) may yield a few stronger cells near/south of the ongoing
watch (either along the dryline/cold front or the remnant boundary).
Here, steep mid-level lapse rates and ample effective shear would
yield a threat for both large hail and damaging winds with more
robust cells. As such, southward expansion of the ongoing watch may
be needed if convective trends warrant.
..Picca.. 04/01/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FWD...SJT...LUB...MAF...
LAT...LON 31550119 32830030 33369928 33289862 31709871 30559922
30389959 30370112 30660143 31550119
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