MESOSCALE PRECIPITATION DISCUSSION 0575
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
728 PM EDT THU OCT 15 2015
 
AREAS AFFECTED...PORTIONS OF SOUTHERN CA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 152330Z - 160430Z
 
SUMMARY...CONVECTION TRAINING ACROSS PORTIONS OF SOUTHERN CA COULD
RESULT IN FLASH FLOODING THROUGH THE MID EVENING HOURS.

DISCUSSION...SCATTERED CONVECTION CONTINUES TO TRACK NORTHWARD
FROM TIJUANA TO NEAR KRIV. THUS FAR...CIN HAS KEPT THE CONVECTIVE
DEVELOPMENT TO A RELATIVE MINIMUM. HOWEVER...NEW CONVECTION NEAR
THE MEXICAN BORDER MAY BE UTILIZING THE 1000-1500 J/KG OF MLCAPE
IN PLACE...OVERCOMING THE CIN IN PLACE. THE CONVECTION IS ALSO
FORMING IN AN AXIS OF 1.5O INCH PRECIPITABLE WATER AIR (WHICH IS
ABOUT FOUR STANDARD DEVIATIONS ABOVE THE MEAN). CONVECTION TAPPING
INTO THE RIBBON OF MOISTURE RICH AIR HAS LED TO FLASH FLOODING IN
PORTIONS OF SAN BERNARDINO COUNTY IN THE PAST HOUR.

INSTABILITY COULD END UP BEING THE LIMITING FACTOR FOR CONVECTION
BECOMING MORE WIDESPREAD DURING THE LATE AFTERNOON AND EARLY
EVENING HOURS. HOWEVER...ADDITIONAL CONVECTION THAT DEVELOPS WILL
TEND TO TRACK OVER THE SAME LOCATIONS AS EARLIER
CONVECTION...SINCE THE MID LEVEL FLOW AND CORFIDI VECTORS BECOME
BETTER ALIGNED DUE TO EASTWARD MOVEMENT OF A CLOSED MID LEVEL LOW
OFF THE SOUTHERN CA COAST.

TRAINING CELLS COULD RESULT IN LOCAL 2 INCH RAINFALL AMOUNTS...AND
THESE AMOUNTS ARE SUPPORTED BY THE 21Z HRRR. ONE HOUR FLASH FLOOD
GUIDANCE VALUES ARE AS LOW AS AN INCH...WITH TRAINING CELLS POSE
THE GREATEST THREAT FOR FLASH FLOODING INTO THE MID EVENING HOURS.
AS THE INSTABILITY STARTS DIMINISHING AFTER 16/04Z...THE
CONVECTIVE COVERAGE SHOULD WANE...ALONG WITH THE FLASH FLOOD
THREAT.

HAYES

ATTN...WFO...PSR...SGX...VEF...

ATTN...RFC...CNRFC...

LAT...LON   34891662 34081591 33551590 33121596 32801612 
            32651633 32661653 32981669 33441687 33621694 
            34781743