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WPC Met Watch

 
Mesoscale Precipitation Discussion: #0128 (2016)
(Issued at 459 AM EDT MON APR 18 2016 )

MPD Selection
 


Graphic for MPD #0128
MESOSCALE PRECIPITATION DISCUSSION 0128
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
459 AM EDT MON APR 18 2016
 
AREAS AFFECTED...SOUTH TEXAS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 180900Z - 181500Z
 
SUMMARY...ONGOING LIFE THREATENING FLASH FLOODING EVENT OVER SE
TEXAS TO CONTINUE WITH RAINFALL RATES OF 3-4"/HR  AND ADDITIONAL
4-8" 6HR TOTALS PSBL.

DISCUSSION...MATURE MCS WAS DRIVING EXTREME RAIN RATES BETWEEN
AUSTIN AND HOUSTON.  THIS MCS WILL LIKELY PERSIST UNTIL OVERTAKEN
FROM THE WEST AFTER 15Z...

WV LOOP INDICATES A WEAK DARKENING SHIFTING ENE ACROSS NUEVO LEON
AND IS AN INDICATOR OF SHORTWAVE FORCING COMING THROUGH THE RIO
GRADE VALLEY.  MOISTURE POOLED WITHIN THE RIO GRANDE VALLEY WITH
TPWS TO 1.5" WITH SURFACE NELY/ELY FLOW DUE TO ISALLOBARIC
COMPONENT OVER THE HIGH SIERRA MADRE...IS PROVIDING STRONG MST
CONVERGENCE TO INITIATE/MAINTAIN CONVECTION. AS THE S/W
PASSES...SPEED MAX MOVES THROUGH THE BASE OF THE TROF OVER BY
09-10Z WITH 3H WINDS INCREASING FROM 40 TO 70 KTS LEAVING
EXCELLENT UPPER LEVEL DIVERGENCE FOR THE SCATTERED CONVECTION TO
GROW UPSCALE. CAMS PARTICULARLY THE NSSL-WRF AND SPC-WRF INDICATE
THIS UPPER LEVEL DIVERGENCE/PVA WILL SUFFICE THOUGH LOW LEVEL
FORCING BECOMES DECOUPLED WHILE THE COMPLEX MOVES EAST...AS SUCH
CONVECTION WITH RATES UP TO 2.0"/HR HAVE A SHORT WINDOW AS THE
COMPLEX DEVELOPS IN THE NEXT 1-2 HOURS WITHIN THE RIO GRANDE
VALLEY.  CONFIDENCE IN HOW WELL THE CONVECTIVE COMPLEX MAINTAINS
RAINFALL EFFICIENCY SHIFTING EAST THROUGH THE SAN ANTONIO VICINITY
IS LOW GIVEN THE LIMITED LL MST FLUX/JET SUPPORT UNTIL ABOUT 98W.

FURTHER EAST...SOUTHERLY LLJ PARALLEL TO THE SOUTH TX COAST IS
CONFLUENT WITH DEEP SELY CHANNEL OF RETURN FLOW FROM THE
NORTHERN/EASTERN GULF...PROVIDING STRONG DEEP MST CONVERGENCE/FLUX
TOWARD THE WEAK SURFACE FRONT NEAR AUS/BAZ.  THIS SUPPORTS
CONTINUED CONVECTIVE DEVELOPMENT OVER SOUTH CENTRAL TX...PRIMARILY
ALONG THE WESTERN EXTENT OF THE CONVECTIVELY REINFORCED BOUNDARY
JUST NORTH OF I-10 TOWARD THE MCV NEAR POLK COUNTY.  CLOUD BEARING
FLOW IS GENERALLY EASTWARD ALLOWING FOR MERGERS ON THE WESTERN
SIDE OF THE LINE MAKING RAIN RATES GREATER THAN 4"/HR.  THIS IS
CONCURRENT WITH 20 KT SFC AND 40KT 850MB ONSHORE FLOW PROVIDING
ADDITIONAL MOISTURE FLUX TO THE STATIONARY LINE FROM COLORADO
COUNTY TO MONTGOMERY COUNTY.  LOCALLY AN ADDITIONAL 4-8" CAN BE
EXPECTED AND IN SOME CASES THIS WILL LEAD TO EVENT TOTAL IN EXCESS
OF 12".  THIS AMOUNT OF RAINFALL IN SUCH A SHORT TIME REPRESENTS A
PARTICULARLY LIFE-THREATENING SITUATION.
 
GALLINA

ATTN...WFO...EWX...FWD...HGX...LCH...MAF...SHV...SJT...

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

LAT...LON   31119541 31089453 30779408 29959399 29409522 
            29299594 29009766 29019848 28590044 29050070 
            29500114 30330172 30370055 30039933 30499739 
            30859581 


Last Updated: 459 AM EDT MON APR 18 2016
 

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