MESOSCALE PRECIPITATION DISCUSSION 0010
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
643 AM EST SUN JAN 17 2016
 
AREAS AFFECTED...SOUTHWEST OR & NORTHWEST CA 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 171142Z - 171742Z
 
SUMMARY...AN ATMOSPHERIC RIVER IS APPROACHING THE COASTS OF
SOUTHWEST OR AND NORTHWEST CA.  HOURLY RAIN RATES ARE EXPECTED TO
PEAK IN THE 0.5-1" RANGE AFTER ~13Z.

DISCUSSION...WATER VAPOR IMAGERY SHOWS AN ATMOSPHERIC RIVER
APPROACHING SOUTHWEST OR AND NORTHWEST CA.  PRECIPITABLE WATER
VALUES ALONG THE COAST HAVE RISEN TO 0.8-1" ACROSS SOUTHWEST OR
AND NORTHWEST CA PER THE LATEST GPS INFORMATION.  A BRIEFING FROM
SAB/NESDIS INDICATED HOURLY RAIN RATES PEAKING IN THE 0.5-0.75"
RANGE WELL OFFSHORE THE CA COAST PER THE AMSU MICROWAVE PASS FROM
0554Z.  LOW-LEVEL INFLOW HAS REACHED 50 KTS OUT OF THE SOUTH AT
ARCATA PER VAD WIND PROFILES.  MUCAPES OFFSHORE ARE IN THE 100-200
J/KG RANGE, PER RECENT SPC MESOANALYSES.

INFLOW IS EXPECTED TO BECOME MORE SOUTHWESTERLY WITH TIME AS THE
CYCLONE'S WARM CONVEYOR BELT/FRONTAL ZONE MOVES SLOWLY INLAND AND
A SHORTWAVE CURRENTLY NEAR 39N 134.5W APPROACHES THE AREA. 
LOW-LEVEL INFLOW INCREASES TOWARDS 65 KTS BETWEEN 13-14Z PER
RECENT RAP GUIDANCE.  PRECIPITABLE WATER VALUES NEAR THE COAST ARE
EXPECTED TO RISE TO NEAR 1.25", WHICH IS AROUND TWO SIGMAS ABOVE
THE MEAN FOR MID-JANUARY.  THE CAM GUIDANCE INDICATES LOCAL
AMOUNTS IN THE 2-4" RANGE THROUGH 18Z, WITH THE HEAVIEST RAINFALL
EXPECTED AFTER 13Z IN SOUTHWEST OREGON WHILE THE INTENSITY SLOWLY
RAMPS UP ACROSS NORTHWEST CA PER THE 06Z SSEO NEIGHBORHOOD
PROBABILITIES.  THESE LOCAL TOTALS USUALLY TRANSLATE INTO HOURLY
RAIN RATES IN THE 0.5-1" RANGE, WHICH ARE EXPECTED IN AREAS BELOW
~6500 FOOT ELEVATION.  

ROTH

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

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

LAT...LON   42872449 42872341 42402342 41962307 41632295 
            41612226 41392189 41102180 40572219 40402273 
            39792279 39222310 38752368 39332400 39952421 
            40382457 41272425 42142452