MESOSCALE PRECIPITATION DISCUSSION 0698
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
510 PM EDT TUE AUG 15 2017

AREAS AFFECTED...WEST-CENTRAL TX

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

VALID 152109Z - 160118Z

SUMMARY...THUNDERSTORMS ARE INCREASING IN COVERAGE AND ATTEMPTING
TO ORGANIZE ACROSS THE REGION.  HOURLY RAIN TOTALS TO 2.5" WITH
LOCAL AMOUNTS TO 4" ARE EXPECTED.

DISCUSSION...RADAR AND SATELLITE IMAGERY HAVE SHOWN A SLOW GROWTH
TO CONVECTIVE ACTIVITY IN TWO DISTINCT BANDS AS CIN ERODES ACROSS
THE TRANS PECOS AND CONCHO VALLEY/HILL COUNTRY OF TX.  THIS IS
OCCURRING NEAR AN OUTFLOW BOUNDARY LEFT OVER FROM MORNING
CONVECTION.  PRECIPITABLE WATER VALUES OF 1.7-2" WERE OBSERVED
HERE AT 16Z PER GPS DATA.  A WEAK SHORTWAVE MOVING BY TO THE NORTH
NEAR THE TX PANHANDLE AND A STRONGER SHORTWAVE APPROACHING FROM
SOUTHERN NM ARE ENHANCING UPPER LEVEL DIVERGENCE.  INFLOW AT 850
HPA IS SOUTHEAST AT 15-20 KTS, SLIGHTLY EXCEEDING THE MEAN 850-400
HPA WIND, AND THERE ARE SOME INITIAL SIGNS OF CONVECTION
BACKBUILDING TOWARDS THE INSTABILITY POOL, WHICH HAS ML CAPE
VALUES OF 3000+ J/KG.  EFFECTIVE BULK SHEAR IN THE REGION IS 20-25
KTS.

THE EXPECTATION IS FOR THE CONVECTION TO GROW IN SCALE FOR A FEW
MORE HOURS, PERHAPS AS LATE AS 01Z WITH SOME SLIGHT SOUTHWARD
SHIFT AS THE OUTFLOW BOUNDARY CONTINUES TO CREEP IN THAT
DIRECTION.  THE 12Z ARW AND 15-17Z HRRR EXPERIMENTAL RUNS APPEAR
TO HAVE THE BEST GRASP OF CURRENT CONVECTIVE TRENDS, THOUGH THEIR
LOCAL AMOUNTS APPEAR A TOUCH LIGHT.  THE CURRENT BANDS ARE
ALIGNING WITH THE MEAN 850-400 HPA FLOW, WHICH SHOULD ALLOW FOR
SOME CELL TRAINING IN THE NEAR FUTURE.  WITHIN AREAS OF CELL
BACKBUILDING AND TRAINING, HOURLY RAIN TOTALS UP TO 2.5" WITH
LOCAL AMOUNTS TO 4" ARE EXPECTED.  THIS COULD BE A PROBLEM AS
SOILS ARE PARTIALLY SATURATED ACROSS THE REGION DUE TO RECENT
RAINS.

ROTH

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

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

LAT...LON   32510061 31809903 30220020 29930264 30860391
            32130255