MESOSCALE PRECIPITATION DISCUSSION 0794
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
307 AM EST WED DEC 14 2016
 
AREAS AFFECTED...NW CALIFORNIA AND SW CALIFORNIA 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 140806Z - 142006Z
 
SUMMARY...AN ATMOSPHERIC RIVER OVER THE EASTERN PACIFIC WILL
INCREASE RAINFALL COVERAGE AND INTENSITY ACROSS SOUTHWESTERN
OREGON AND NORTHWESTERN CALIFORNIA THROUGH MIDDAY WEDNESDAY. 
RAINFALL AMOUNTS OF 2 TO LOCALLY 4 INCHES CAN BE EXPECTED THROUGH
20Z, ESPECIALLY ALONG SOUTHWEST-FACING TERRAIN.

DISCUSSION...RECENT GOES-15 WATER VAPOR IMAGERY INDICATES A DEEP
FLOW OF MOISTURE FROM THE SOUTHWEST, ORIGINATING EAST OF HAWAII. 
A MID-LEVEL VORTICITY MAX AT 08Z WAS LOCATED IN THE VICINITY OF
40N AND 130W, AND A 250MB JET STREAK OF 130-150KTS AIMED TOWARDS
THE OREGON COAST.  AN AXIS OF 1.3 TO 1.5 INCH PWS WAS NOTED ON THE
LATEST RAP ANALYSIS TO THE SOUTH OF THIS JET STREAK IN THE RIGHT
ENTRANCE REGION.  

THE LATEST RAP MODEL PROJECTION INDICATES THAT THE AXIS OF HIGHEST
MOISTURE WILL REMAIN IN PLACE OVER THE NEXT 12 HOURS.  A 40 TO 50
KNOT SOUTHWESTERLY LOW LEVEL JET WILL INCREASE THE MOISTURE
CONVERGENCE OVER THIS REGION LATER IN THE MORNING HOURS.  THE HRRR
SUGGESTS THAT THE HEAVIEST RAINFALL RATES WILL LIKELY ARRIVE BY
15Z WITH HOURLY RAINFALL RATES ON THE ORDER OF A HALF INCH PER
HOUR AS A SURFACE LOW OFFSHORE APPROACHES THE COAST.  THIS IS ALSO
SUPPORTED BY THE 00Z ARW, WITH THE HEAVIEST RAINFALL FIRST
AFFECTING EXTREME NORTHWEST CALIFORNIA AND THEN EDGING NORTHWARD
OVER SOUTHWEST OREGON.  ADDITIONAL HEAVY RAINFALL IS LIKELY AFTER
20Z.

HAMRICK

ATTN...WFO...EKA...MFR...REV...STO...

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

LAT...LON   43662419 43642345 43292266 43022245 42172179 
            41782139 41112133 40162129 40002204 39792247 
            39482280 39252318 39172396 39752411 40452461 
            41412434 42712465 43312465