MESOSCALE PRECIPITATION DISCUSSION 0001
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
544 AM EST TUE JAN 05 2016
 
AREAS AFFECTED...CENTRAL CA COAST...SRN CA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 051043Z - 051643Z
 
SUMMARY...RAIN RATES WILL INCREASE ALONG THE CENTRAL AND SOUTHERN
CALIFORNIA COAST EARLY THIS MORNING...AND HEAVIER RAIN WILL BEGIN
TO SPREAD INTO THE L.A. BASIN AROUND 15Z. FLASH FLOODING IS
POSSIBLE.

DISCUSSION...STRONG ASCENT WILL ACCOMPANY AN OCCLUDED FRONT COMING
ONSHORE ALONG THE LENGTH OF THE CA COAST...AND ASSOCIATED POSITIVE
TILT UPPER TROUGH...WITH LATER EMPHASIS FOR HEIGHT FALLS IN THE
BASE OF THE TROUGH ALONG THE SOUTHERN CALIFORNIA COAST. ALTHOUGH
LIGHTNING HAD NOT BEEN DETECTED AS OF 1030Z...RADAR AND SATELLITE
PRESENTATION WAS IMPRESSIVE NEAR AND OFFSHORE OF MONTEREY...WHERE
CLOUD TOPS HAD COOLED TO -40C...AND CONVECTIVE RADAR ELEMENTS WERE
TRACKABLE...NOT SIMPLY HIGH REFLECTIVITY DUE TO BRIGHT BANDING.
SURFACE OBSERVATIONS HAD BEGUN TO SAMPLE HEAVY RAIN AND
ACCUMULATIONS EXCEEDING A HALF INCH PER HOUR IN THE BAY AREA.

A FRONTAL PRECIPITATION BAND WILL PROGRESS STEADILY
EASTWARD...WITH THE BACK EDGE COMING SOUTH ALONG THE COAST THIS
MORNING. EXPECTATIONS PER THE HIGH RESOLUTION MODELS ARE FAIRLY
UNIFORM...WITH AREAL AVERAGE 0.50 TO 1.0 INCHES OF RAIN THROUGH
18Z...BUT LOCALLY GREATER THAN 1.5. TOTALS MAY BE ESPECIALLY
ENHANCED IN THE SOUTHWARD FACING MOUNTAINS OF SOUTHERN
CALIFORNIA...OWING TO S/SW LOW LEVEL FLOW...LONGER DURATION OF
BROAD HEIGHT FALLS...AND PROXIMITY TO GREATER PW VALUES NEAR 1.00
INCH ALONG WITH ENOUGH INSTABILITY FOR THE HRRR TO PICK UP ON 250
J/KG. THE HEAVIER RAIN RATES SHOULD REACH LOS ANGELES BY
15-17Z...AND THE EVENT IS EXPECTED TO CONTINUE INTO THE AFTERNOON
FROM THERE SOUTHWARD...WITH MAXIMUM HOURLY RATES APPROACHING 0.75
INCHES. THIS WOULD BE VERY CLOSE TO FLASH FLOOD GUIDANCE
VALUES...AND WOULD BE MORE THAN ENOUGH TO CAUSE FLASH FLOODING IN
THE MORE SUSCEPTIBLE BURN SCAR AREAS.

BURKE

ATTN...WFO...HNX...LOX...MTR...SGX...

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

LAT...LON   37502223 36982159 36182100 35532038 34991960 
            34501826 34091761 33811897 34132032 34592104 
            37072251