Graphic for MPD #0122

MESOSCALE PRECIPITATION DISCUSSION 0122
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1023 PM EDT SUN APR 16 2017

AREAS AFFECTED...SOUTH-CENTRAL TX

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 170223Z - 170753Z

SUMMARY...CONVECTION HAS BROKEN THE CAP ACROSS SOUTH-CENTRAL TX
AHEAD OF AN MCV MOVING IN FROM NORTHEAST MEXICO.  HOURLY RAIN
RATES UP TO 2", WITH LOCAL AMOUNTS OF 3-5", COULD LEAD TO FLASH
FLOODING.

DISCUSSION...A WEAK SURFACE DENSITY GRADIENT WAS BARELY
PERCEPTIBLE IN THE SURFACE OBSERVATIONS FROM EAGLE PASS
NORTHEASTWARD TO SERENEDA TX.  GPS DATA INDICATE PRECIPITABLE
WATER VALUES OF 1.25-1.5" ACROSS THE REGION.  INFLOW AT 850 HPA IS
30 KTS (NEARLY DOUBLE THE MEAN 850-400 HPA WIND) ON THE WARM SIDE
OF THE BOUNDARY PER VAD WIND PROFILES.  MUCAPES ARE 2000-3000
J/KG, WHICH DESPITE THE CIN DEVELOPING ACROSS THE REGION SHOULD
KEEP CONVECTION RELATIVELY CLOSE TO SURFACE BOUNDARIES.  BULK
SHEAR IN THE 0-6 KM LAYER IS AROUND 30 KTS, WHICH SHOULD BE
SUFFICIENT TO MAINTAIN CONVECTIVE ORGANIZATION.

THE 12Z ARW HAS DONE AN EXCELLENT JOB WITH THE FORECAST OF THE
CONVECTIVE REGIME IN WEST-CENTRAL AND SOUTH-CENTRAL TX (UNLIKE
RECENT GFS, RAP, AND HRRR RUNS WHICH HAVE BACKED OFF).  IT MOVES
CONVECTION UP THE BOUNDARY AND CONVECTION FROM WEST-CENTRAL TX IN
FROM THE NORTHWEST CREATING CELL MERGERS ALONG THE WAY.  DESPITE
ITS GOOD PERFORMANCE SO FAR, IT IS POSSIBLE THE 12Z ARW IS TOO FAR
NORTH, AS THE CONVECTION SHOULD FORM A COLD POOL WHICH WOULD
DEFLECT THE PROPAGATION TO A MORE EAST-SOUTHEAST DIRECTION FROM
ITS CURRENT LOCATION RATHER THAN NORTHEASTWARD, AT ROUGHLY 15-20
KTS.  SLIGHT VEERING IN THE LOW-LEVEL FLOW OVERNIGHT IMPLIES
FORWARD PROPAGATION AS WELL. THE AVAILABLE MOISTURE SUPPORTS
HOURLY RAIN RATES UP TO 2", WITH LOCAL AMOUNTS IN THE 3-5" RANGE,
WHICH COULD LEAD TO FLASH FLOODING, PARTICULARLY IN URBAN AREAS.

ROTH

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

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

LAT...LON   30779959 30519841 29759810 28949823 28259860
            28129993 28400037 28810064 29970082 30570039
           


Last Updated: 1023 PM EDT SUN APR 16 2017