Severe Storm Outlook Narrative (AC)
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117
ACUS11 KWNS 211744
SWOMCD
SPC MCD 211744
TXZ000-211915-

Mesoscale Discussion 0805
NWS Storm Prediction Center Norman OK
1244 PM CDT Sun May 21 2017

Areas affected...Middle/Upper Rio Grande Valley

Concerning...Severe potential...Watch possible

Valid 211744Z - 211915Z

Probability of Watch Issuance...40 percent

SUMMARY...Strong thunderstorms are expected across the middle-upper
Rio Grande Valley region.  Large hail is the primary risk, though
gusty winds may also accompany this activity.

DISCUSSION...Latest satellite/model data suggest a mid-level
short-wave trough has migrated across northern Mexico and is
approaching the middle-upper Rio Grande Valley region.  Over the
last several hours, numerous thunderstorms have developed over the
higher terrain of northern Mexico and these storms are gradually
evolving into a larger complex.  With time an MCS should develop and
turn southeast along the Rio Grande River Valley such that strong
storms could bleed across the international border.  This is
supported by an expected increase in southeasterly LLJ across the
Rio Grande Valley.  Radar algorithms suggest large hail accompanies
the strongest activity, primarily west of the border.  However,
severe threat should increase along the immediate US side as this
maturing complex of storms turns southeast.  WW may be warranted for
this activity.

..Darrow/Weiss.. 05/21/2017

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

ATTN...WFO...CRP...EWX...SJT...MAF...

LAT...LON   27340058 28690222 30310171 29920024 27729894 27340058




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