MESOSCALE PRECIPITATION DISCUSSION 0121
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
123 AM EDT SUN APR 17 2016
 
AREAS AFFECTED...CENTRAL TEXAS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 170522Z - 171052Z
 
SUMMARY...SLOW EASTWARD MOVING WEDGE OF CONVECTION TO PRODUCE
ADDITIONAL 1-3" TOTALS WITH SOME ISOLATED FLASH FLOODING POSSIBLE.

DISCUSSION...IR LOOP AND RADAR MOSAIC INDICATE A MATURE MCS
EXTENDING FROM N PECOS TO JONES COUNTY TX...PRESENTED AS A DEEP
WEDGE ON IR WITH A SOLID LINE OF OVERSHOOTING TOPS TO -70C.  UPPER
LEVEL JET STRUCTURE IS QUITE FAVORABLE FOR THIS WEDGE AS IT IS
QUITE DIFFLUENT THROUGHOUT THE LENGTH OF THE MCS.  IN THE LOW
LEVELS BROAD SELY BOUNDARY LAYER FLOW FOCUSED NEARLY PERPENDICULAR
TO THE LINE EXCEPT NEAR THE NORTHERN EDGE WHERE FLOW AS VEERED A
BIT...SUPPORTING STRONG CONVERGENCE.  HOWEVER...BOTH BLENDED AND
LAYER BLENDED TPW AND RAP ANALYSIS INDICATE THE MST TRANSPORT IS
REDUCED ACROSS THE HILL COUNTY INTO THE EDWARDS PLATEAU GIVEN THE
BEST CHANNEL OF RETURN MOISTURE IS FOCUSED FURTHER NORTH.  ONLY
DEEPER MOISTURE CHANNELED THROUGH THE RIO GRANDE WITH 850 TDS TO
16C PROVIDES BEST MST FLUX.  HOWEVER...700-500MB LAYER IS MUCH
DRIER AS THE BEST PACIFIC MST AS LIFTED NORTH AND SO PROFILES ARE
A BIT DRIER ALOFT WITH 7-8C LAPSE RATES.  THIS SUPPORTS HIGHER
INSTABILITIES TO MAINTAIN CONVECTION BUT WILL ALSO SUPPORT
GENERATION OF COLD POOLS AND WITH STRONG SELY FLOW...QUICKER
PROPAGATION.  

BY 10Z REMAINING INSTABILITY BEGINS TO WANE AS WELL...AN THE
SOUTHERN PORTION OF THE LINE WITH BEST MOISTURE AVAILABILITY (TPWS
UP TO 1.25") SHOULD WEAKEN CONSIDERABLY.  STILL IN THE SHORT
TERM...RATES UP TO 2"/HR ALONG WITH SOME POTENTIAL TRAINING HAS
SOME OF THE BETTER PERFORMING HI-RES CAMS (EXPERMINAL ESRL HRRR)
OUTPUT STILL PROVIDING 1-3" OF ADDITIONAL QPF ALONG THE N CROCKETT
TO COLEMAN LINE...POSING ISOLATED FLASH FLOODING THREAT IN THE
NEXT 3-4HRS. 

GALLINA

ATTN...WFO...EWX...FWD...MAF...SJT...

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

LAT...LON   32389973 32189849 31569847 31049869 30489963 
            30200046 30140099 30200221 30570197 31360108 
            32020049 32320017