MESOSCALE PRECIPITATION DISCUSSION 0045
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
420 AM EST SUN MAR 06 2016
 
AREAS AFFECTED...CENTRAL/SOUTHERN CALIFORNIA 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 060915Z - 061200Z
 
SUMMARY...ATMOSPHERIC RIVER CONDITIONS WILL BE SUBSIDING OVER THE
NEXT FEW HOURS...BUT THERE WILL STILL BE SOME POCKETS OF HEAVY
RAINFALL WITH AT LEAST ISOLATED AREAS OF ADDITIONAL RUNOFF
CONCERNS.

DISCUSSION...IR/WV SATELLITE IMAGERY SHOWS THE UPPER TROUGH THAT
HAS BEEN DRIVING THE ROBUST ATMOSPHERIC RIVER INTO CENTRAL AND
NORTHERN CA OVER THE LAST 12 TO 18 HOURS IS BEGINNING TO MOVE WELL
INLAND ACROSS THE STATE ALONG WITH AN ASSOCIATED COLD FRONT. AREA
RADARS STILL SHOW AREAS OF MODERATE TO HEAVY RAIN IMPACTING THE
FOOTHILLS OF THE CENTRAL SIERRA-NEVADA ALONG WITH SOME EMBEDDED
CONVECTIVE ELEMENTS WHICH ARE STILL PRODUCE SOME INTENSE RAINFALL
RATES. HOWEVER...THE ACTIVITY OVER THE COASTAL RANGES HAS BEEN
GRADUALLY BECOMING MORE SHOWERY WITH LESS COVERAGE AS MID LEVEL
DRY AIR MOVES INLAND AS SEEN CLEARLY IN WV IMAGERY AND THE
500/700MB LAYER PER THE CIRA LAYERED PW PRODUCT.

OVER THE NEXT FEW HOURS...THE COLD FRONT AND ASSOCIATED UPPER
TROUGH WILL CONTINUE TO MOVE INLAND...BUT THE DEEPER FETCH OF
HIGHER PWATS ALONG THE FRONT WILL BE SHIFTING FARTHER EAST WHILE
ALSO THINNING OUT. THE STRONGER UPPER JET DYNAMICS WHICH HAS
FOSTERED STRONG LARGE SCALE ASCENT OVERNIGHT WILL ALSO BE
GRADUALLY WEAKENING. THEREFORE...EXPECT THE RAINFALL RATES TO
GRADUAL SUBSIDE FROM THIS POINT FORWARD. HOWEVER...THERE IS STILL
SOME ADDITIONAL POTENTIAL FOR RAINFALL RATES OVER THE NEXT FEW
HOURS TO REACH UP TO OR EXCEED A 0.50 INCH/HR...AND THIS WILL
MAINLY BE FOR FOOTHILLS OF THE CENTRAL AND SOUTHERN SIERRA-NEVADA
AND ALSO THE COASTAL RANGES OF SOUTHERN CA WHERE THE COLD FRONT
HAS NOT YET PASSED THROUGH. SOME OF THE MORE FAVORED TERRAIN WHERE
OROGRAPHICS WILL ENHANCE RAINFALL RATES INCLUDE THE TOPATOPA/SANTA
MONICA MOUNTAINS AND INTO THE SAN GABRIEL AND SAN BERNADINO
MOUNTAINS.

ADDITIONAL RAINFALL AMOUNTS ACROSS ALL OF THESE AREAS MAY REACH 1
TO 1.5 INCHES THROUGH 12Z...WITH AGAIN THE FOCUS PRIMARILY ON THE
OROGRAPHICALLY FAVORED AREAS. THESE AMOUNTS WILL STILL BE CAPABLE
OF PRODUCING SOME RUNOFF PROBLEMS WITH CONCERNS FOR LOCALIZED
FLASH FLOODING...MUDSLIDES AND DEBRIS FLOWS IN AROUND BURN SCAR
AREAS. AFTER 12Z...CONDITIONS ARE EXPECTED TO IMPROVE STEADILY
WITH ATMOSPHERIC RIVER CONDITIONS ENDING.

ORRISON

ATTN...WFO...HNX...LOX...REV...SGX...STO...

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

LAT...LON   39582064 38191940 36621843 35601824 35061812 
            34661779 34271716 33461706 33091747 33191781 
            33871901 34121990 34602019 35072015 35802021 
            36532033 37062048 37852069 39352130