MESOSCALE PRECIPITATION DISCUSSION 0576
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
212 PM EDT THU AUG 18 2016
 
AREAS AFFECTED...TEXAS BIG BEND 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 181815Z - 182315Z
 
SUMMARY...SLOW MOVING HIGHLY EFFICIENT CONVECTION MAY POSE FLASH
FLOODING CONCERNS.

DISCUSSION...GOES VISIBLE LOOP MOSAIC DENOTES NORTHERN OUTER
CONVERGENCE BAND OF DEEP CYCLONIC CIRCULATION OVER WESTERN MEXICO
LIFTING NORTHWARD ACROSS N MEXICO TOWARD THE BIG BEND OF TEXAS. 
WV LOOP ALSO DENOTES A HIGHLY SHEARED VORT CENTER ACROSS NW
CHIHUAHUA WITH A MODERATELY STRONG (30 KT) OUTFLOW CHANNEL TOWARD
THE NORTHWEST PROVIDING SOLID UPPER LEVEL SUPPORT FOR BROAD UVVS. 
THIS IS COINCIDENT WITH TAIL END OF DEEP MOISTURE/CONFLUENCE
CHANNEL WITH ANOMALOUSLY HIGH TPWS.  LOW LEVEL (SFC-800MB) WIND
FIELDS PER THE RAP SHOW A BROAD CYCLONIC SELY TO NELY TURNING OF
LIGHT TO MODERATE WINDS CONTINUING TO ADVECT HIGHER MOISTURE
TOWARD THE BIG BEND AROUND THE HIGHER TERRAIN OF THE SIERRA
MADRE...PROVIDING SOME MST CONVERGENCE BUT ALSO INCREASING TPWS IN
THE 1.75" AND HIGHER RANGE.  INSOLATION HAS PROVIDED MODERATE SFC
T INCREASE SUPPORTING AN INCREASE OF SBCAPES TO 2000-2500 J/KG
RANGE PER THE RAP...FUELING STRENGTHENING CORES AS WELL.  

CURRENT VIS SHOWS HIGHLY SHEARED TCU CONTINUING TO DEVELOP ALONG
HIGH TERRAIN...GIVEN MOISTURE PROFILE AND MST FLUX CELLS SHOULD BE
QUITE EFFICIENT RAINFALL PRODUCERS AND REMAIN FAIRLY TERRAIN
LOCKED AS THE OUTER BAND INFLUENCES LIFT NORTHWARD LIKELY WITH
STRENGTHENING CONVECTION/CLUSTER EXPECTED PARTICULARLY NEAR THE
NATIONAL PARK.  RATES UP TO 1.5"/HR ARE PROBABLE...LEADING TO
LOCAL RUNOFF ISSUES WITH SOME ISOLATED FLASH FLOODING POSSIBLE
GIVEN HARD-PAN GROUND CONDITIONS. HRRR/ARW/NMMB ALL SUPPORT THIS
IDEA OF HIGHER RATES CAPABLE OF EXCEEDING THE LOW FFG VALUES IN
THE VICINITY (BELOW 1.5"/1HR).  

GALLINA

ATTN...WFO...EPZ...MAF...

ATTN...RFC...WGRFC...

LAT...LON   31210444 31090347 30570258 29810216 29540244 
            28870301 29030357 29410437 29720470 30140487 
            30570524 30880524 31060501