MESOSCALE PRECIPITATION DISCUSSION 0037
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
933 PM EDT SAT APR 11 2015
 
AREAS AFFECTED......SOUTH TEXAS... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 120133Z - 120733Z
 
SUMMARY...FLASH FLOODING INCREASINGLY POSSIBLE IN VICINITY OF
STATIONARY BOUNDARY OVERNIGHT AS A MESOLOW AND LARGER SCALE MCV
CONVERGE UPON THE BOUNDARY.

DISCUSSION...A WEAKLY-ORGANIZED MESOLOW NEAR WEBB COUNTY AND A
LARGER-SCALE MVC OVER NORTH TEXAS DUE TO EARLIER CONVECTION WILL
TRANSLATE STEADILY EASTWARD THROUGH THE NIGHT AND ALONG OR NEAR A
STATIONARY BOUNDARY EXTENDING ALONG THE BORDER SEPARATING THE CRP
AND BRO COUNTY WARNING AREAS.

SOUTHEASTERLY STORM INFLOW NEAR THE GROUND IS HELPING TO OFFSET AN
OTHERWISE MODEST WESTERLY MOTION...WITH CELL MOTIONS AVERAGING
LESS THAN 20 KNOTS ALONG THE BOUNDARY.  GIVEN PW VALUES NEAR 1.8
INCHES AND MIXED LAYER TO MOST UNSTABLE CAPES OF 1000-2000
J/KG...RAIN RATES OF 1.5 TO PERHAPS 2 INCHES PER HOUR HAVE
OCCURRED...AND WITH THE STATIONARY BOUNDARY EXPECTED TO MOVE VERY
LITTLE OVERNIGHT DUE TO ITS ORIENTATION PARALLEL TO THE DEEP LAYER
FLOW...THESE RAIN RATES MAY EXIST FOR 2 HOURS OR MORE...WHICH
COULD RESULT IN FLASH FLOODING.  HI RES GUIDANCE SUPPORTS THIS
NOTION WITH A LOW LEVEL JET OF 25 TO 30 KNOTS FORMING
OVERNIGHT...WHICH MAY BE LOCALLY ENHANCED ON THE MESOSCALE AS THE
MESOLOW AND MCV ENTER THE REGION.

JAMES

ATTN...WFO...BRO...CRP...

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

LAT...LON   27789844 27309689 26299721 26639865 27199937 
            27639936