ZCZC SPCSWOMCD ALL
ACUS11 KWNS 180121 
SPC MCD 180121 
TXZ000-180245-

MESOSCALE DISCUSSION 0408
NWS STORM PREDICTION CENTER NORMAN OK
0821 PM CDT SUN APR 17 2016

AREAS AFFECTED...PORTIONS OF THE LOWER RIO GRANDE VALLEY

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 180121Z - 180245Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...A LOCALIZED LARGE-HAIL AND DAMAGING-WIND RISK WILL DEVELOP
THIS EVENING FROM AN INTENSE THUNDERSTORM CLUSTER MOVING NORTHWARD
OUT OF NORTHERN MEXICO.

DISCUSSION...AT 0115Z...AN INTENSE CLUSTER OF THUNDERSTORMS WAS
ONGOING ABOUT 30 MILES SOUTH OF RIO GRANDE CITY AND MOVING NORTHWARD
TOWARD THE INTERNATIONAL BORDER. RADAR STRONGLY SUGGESTS THAT VERY
LARGE HAIL IS CURRENTLY BEING PRODUCED BY THIS CLUSTER...WITH MRMS
MESH DATA INDICATING A MAX HAIL SIZE ABOVE TWO INCHES IN DIAMETER. 

THE THUNDERSTORM CLUSTER DEVELOPED FROM THE MERGER OF MULTIPLE
LEFT-MOVING SUPERCELLS...AND THE ENVIRONMENT SHOULD REMAIN FAVORABLE
INTO THE RIO GRANDE VALLEY...WITH 00Z RAOBS AND OBJECTIVE ANALYSIS
INDICATING THE PRESENCE OF STEEP MID-LEVEL LAPSE RATES...STRONG
BUOYANCY...AND SUFFICIENT DEEP-LAYER SHEAR FOR STORM ORGANIZATION.
THE PRIMARY UNCERTAINTY REGARDING THE LONGEVITY OF THIS CLUSTER WILL
BE THE ONSET OF DIURNAL COOLING AND RESULTING INCREASE IN CINH FOR
SURFACE-BASED PARCELS. HOWEVER...GIVEN THE CURRENT INTENSITY OF THE
SYSTEM AND THE POTENTIAL FOR SOME UPSCALE GROWTH /GIVEN THE PRESENCE
OF MULTIPLE STRONG UPDRAFTS IN CLOSE PROXIMITY/...IT APPEARS LIKELY
THAT THE SYSTEM WILL AT LEAST AFFECT PORTIONS OF STARR AND ZAPATA
COUNTIES OVER THE NEXT 1-2 HRS BEFORE WEAKENING...WITH A THREAT OF
LARGE HAIL AND LOCALLY DAMAGING WINDS. 

GIVEN THE LIMITED AREA AFFECTED...WATCH ISSUANCE IS CURRENTLY NOT
ANTICIPATED FOR THIS AREA.

..DEAN/EDWARDS.. 04/18/2016

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

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

LAT...LON   26259869 26379907 26849937 27039943 27229940 27269917
            27229902 27099889 26909882 26459867 26329863 26259869 

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