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ACUS11 KWNS 172150
SPC MCD 172150

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

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

...Please see for graphic product...


LAT...LON   26599901 26839945 27379960 27769992 27909970 27929897
            27709778 27479713 26839718 26349724 26389806 26599901 is the U.S. government's official web portal to all federal, state and local government web resources and services.