Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 172150
SWOMCD
SPC MCD 172150
TXZ000-172345-

Mesoscale Discussion 0515
NWS Storm Prediction Center Norman OK
0450 PM CDT Mon Apr 17 2017

Areas affected...Portions of south TX

Concerning...Severe potential...Watch unlikely

Valid 172150Z - 172345Z

Probability of Watch Issuance...5 percent

SUMMARY...An isolated large hail/gusty wind risk may develop for
several hours. Watch issuance is not anticipated due to the marginal
nature of the threat.

DISCUSSION...The atmosphere has been able to re-destabilize this
afternoon across parts of south TX behind a morning MCS that
traversed this area. Convection has recently intensified from Zapata
to Brooks County TX along an instability gradient/possible outflow
boundary from earlier storms. A warm and moist low-level airmass
resides across deep south TX, with surface temperatures in the mid
80s to around 90, and dewpoints in the mid 60s to around 70.
Although low-level winds remain modest, they do veer some with
height, and northwesterly mid-level winds across this region are
being slightly enhanced by an MCV centered over Gonzales County TX
as of 2145Z. Resultant effective bulk shear values of 35-40 kt
should allow for updrafts to maintain some organization/strength.
Steep mid-level lapse rates suggest isolated instances of large hail
may occur, and convective downdrafts may pose a gusty wind threat as
well while low-level lapse rates remain steep due to a well-mixed
boundary layer. Any strong/severe storm should weaken by mid evening
with the loss of daytime heating and related reduction in
instability.

..Gleason/Peters.. 04/17/2017

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

ATTN...WFO...CRP...BRO...

LAT...LON   26599901 26839945 27379960 27769992 27909970 27929897
            27709778 27479713 26839718 26349724 26389806 26599901




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