Graphic for MPD #0002

MESOSCALE PRECIPITATION DISCUSSION 0002
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
445 AM EST TUE JAN 09 2018

AREAS AFFECTED...SOUTHERN CA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 090944Z - 091514Z

SUMMARY...ANTICIPATED HIGH IMPACT FLASH FLOOD EVENT WAS GETTING
UNDERWAY AT 0930Z. HEAVY RAIN RATES WILL PROGRESS WEST TO EAST
ALONG THE COAST AND COASTAL MOUNTAIN RANGES THROUGH EARLY MORNING.
FLASH FLOODING LIKELY...ESPECIALLY OWING TO RECENT LARGE BURN
SCARS AND ASSOCIATED DEBRIS FLOWS.

DISCUSSION...GOES-16 MESO SECTOR 1-MINUTE IMAGERY SHOWED
INCREASINGLY COLD CLOUD TOPS DOWN TO -50C APPROACHING THE COASTAL
BEND / POINT CONCEPTION...AND ASSOCIATED WITH RADAR IMAGERY FROM
KVBX OF A STRONGLY FORCED SQUALL LINE. NO RECENT AMSU PASS WAS
AVAILABLE SINCE THE DEVELOPMENT OF THE LINE...BUT DUAL-POL RADAR
ESTIMATES FROM KVBX SHOWED HOURLY RATES APPROACHING AN IMPRESSIVE
1.50 INCHES/HOUR OFFSHORE. WHEN BRINGING THIS RAIN ONSHORE FOR
OROGRAPHIC ENHANCEMENT...WITH KVBX VAD WIND INDICATING
SOUTHEASTERLY 45 KNOT 925 MB WIND...SUSPECT THAT ISOLATED
ACCUMULATIONS COULD REACH 1.75 INCHES PER HOUR...SEEMINGLY BORN
OUT IN THE 08Z HRRR HOURLY RAINFALL PROJECTION. THE HRRR AND 00Z
WRF-ARW WERE HANDLING THE TIMING AND PLACEMENT PARTICULARLY
WELL...AND WOULD INDICATE STEADY EASTWARD PROGRESSION OF THE
LEADING LINE OF CONVECTION...DISSIPATING OVER MONTEREY AND SAN
LUIS OBISPO COUNTIES BY 13Z...BUT REMAINING STRONG ACROSS SANTA
BARBARA/VENTURA COUNTIES...REACHING LOS ANGELES AROUND 13Z GIVE OR
TAKE.

THE INTENSE RATES LIKELY WILL NOT LAST MORE THAN AN HOUR AT A
GIVEN LOCATION...BUT ADDITIONAL CONVECTIVE RAINS WILL FOLLOW
BEHIND THE STRONGER INITIAL WAVE/SUPPORTED BY STRONGLY DIFLUENT
FLOW ENE OF DEVELOPING MID LEVEL CLOSED LOW AND ASSOCIATED 120
KNOT JET STREAK. EXPECT 2-4 INCH AREAL AVERAGE EVENT TOTALS...BUT
ISOLATED 6-PLUS INCH TOTALS IN FAVORED TERRAIN...MUCH OF WHICH MAY
FALL BY 15Z. GIVEN THE INTENSE FIRE SEASON WITH MANY LARGE FRESHLY
BURNED AREAS...IMPACTS FROM FLASH FLOODING... MUDSLIDES...AND
DEBRIS FLOWS ARE ANTICIPATED. 

BURKE

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

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

LAT...LON   36802098 35722031 35101952 35121915 35251844
            34991810 34751775 34441688 33771681 33351831
            33902053 36282199


Last Updated: 445 AM EST TUE JAN 09 2018