MESOSCALE PRECIPITATION DISCUSSION 0798
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
109 PM EST THU DEC 15 2016
 
AREAS AFFECTED...COASTAL CENTRAL CA/INTERIOR NORTHERN/CENTRAL
CA... 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 151808Z - 160308Z
 
SUMMARY...AN ENHANCED SUBTROPICAL MOISTURE PLUME TO SLOWLY DRAG
SOUTHWARD SPREADING MODERATE/LOCALLY HEAVY RAINFALL DOWN INTO THE
COASTAL RANGES OF CENTRAL CA EASTWARD INTO THE NORTHERN/CENTRAL
SIERRA. HOURLY RATES HAVE EXCEEDED 0.50 INCHES WITHIN AREAS OF
UPSLOPE FLOW WHICH SUGGESTS SIMILAR AMOUNTS ARE LIKELY THROUGH THE
REMAINDER OF THE DAY.

DISCUSSION...IN ADVANCE OF A SHORTWAVE APPROACHING 130W
LONGITUDE...AMPLE MOISTURE FROM THE SUBTROPICAL PACIFIC CONTINUES
TO LIFT NORTHWARD AHEAD OF A SLOW-MOVING SYNOPTIC BOUNDARY. MUCH
OF THIS ENHANCED MOISTURE HAS WORKED ITS WAY INLAND PER 12Z RAOBS
FROM OAK/BVG WHERE PWATS WERE AROUND 1.10 INCHES. COMPARISON TO
THE SPC PWAT CLIMATOLOGY PAGE...THIS RANKS JUST SHORT OF THE DAILY
MOVING MAXIMA FOR MID-DECEMBER. FARTHER OFFSHORE...AMSU IMAGERY
DATA SUGGESTED 1.50 INCH PWATS WERE PERHAPS 100 TO 200 MILES WEST
OF THE SAN FRANCISCO BAY AREA. VAD-WIND PROFILER DATA FROM KBBX
SHOWED IMPRESSIVE LOW-LEVEL ADVECTION WITH 45 TO 50 KNOT
SOUTH-SOUTHWESTERLY FLOW SLAMMING INTO THE COASTAL RANGES. THE 16Z
RAP FORECAST SHOWS THESE ENHANCED MOISTURE FLUXES SHIFTING
SOUTHWARD IN TIME SPREADING THE HEAVY RAINFALL THREAT DOWN INTO
THE CENTRAL CA COAST. OFFSHORE HOURLY RATES PER AMSU DATA
INDICATES 0.50 INCHES APPROACHING THE COAST. ADDING THE ELEMENT OF
UPSLOPE FLOW COULD SUGGEST FURTHER INCREASES IN THESE RATES IF THE
BAND OF PRECIPITATION REMAINS ORGANIZED.

FARTHER INLAND...THERE IS ALSO A STRONG SIGNAL FOR HEAVY
PRECIPITATION ACROSS THE NORTHERN/CENTRAL SIERRA. GIVEN LOWERING
SNOW LEVELS AS THE UPPER TROUGH APPROACHES THE COAST...MUCH OF THE
HIGHER ELEVATIONS OF THE SIERRA CAN EXPECT SNOW...PARTICULARLY
OVER THE CENTRAL SECTION OF THE RANGE. A VAST MAJORITY OF THE
LATEST CAMS INDICATE 3 TO 5 INCHES OF PRECIPITATION ARE LIKELY
THROUGH 06Z OVER THIS REGION. WILL ALLOW THIS MPD TO PERSIST
THROUGH JUST AFTER 03Z AND THEN LET THE NIGHT SHIFT RE-ASSESS THE
SITUATION.


RUBIN-OSTER

ATTN...WFO...EKA...HNX...LOX...MTR...REV...STO...VEF...

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

LAT...LON   41112177 40862153 40582086 40182064 39752023 
            39371980 38811966 38401940 37851890 37401857 
            37011832 36491824 35941812 35731849 35901890 
            36411922 36981981 37352023 37712072 37882127 
            38092153 37962173 37942182 37652158 37502127 
            36982116 36702095 36432048 36082053 36502118 
            36412143 35722080 35442054 35062035 35072111 
            35812204 36542254 38442334 39112306 39272272 
            39152236 39392205 40052205 40722234 41012217