MESOSCALE PRECIPITATION DISCUSSION 0031
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 PM EST SUN FEB 14 2016
 
AREAS AFFECTED...WA CASCADES AND OLYMPIC PENINSULA 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 141940Z - 150600Z
 
SUMMARY...AN OCCLUDED CYCLONE APPROACHING BRITISH COLUMBIA SHOULD
CHANNEL THE BEST LOW-LEVEL INFLOW AND MOISTURE INTO WA WITH TIME,
WHICH IS EXPECTED TO INCREASE RAIN RATES TO 0.50"-0.75" AN HOUR
LOCALLY, PRIMARILY PAST 01Z.

DISCUSSION...AN ATMOSPHERIC RIVER, IN THE FORM OF A PINEAPPLE
CONNECTION MOVING THROUGH THE PAPAHANAUMOKUAKEA MARINE NATIONAL
MONUMENT IN HAWAI'I, IS FOCUSING A NARROWING CHANNEL OF MOISTURE
TOWARDS THE WA/OR BORDER AT THE PRESENT TIME WITH VALUES DOUBLE
WHAT IS NORMAL FOR MID-FEBRUARY, PER A BRIEFING FROM SAB/NESDIS. 
HOURLY RAIN RATES TODAY HAVE BEEN IN THE 0.2-0.3" RANGE.  GPS
INFORMATION COMBINED WITH SATELLITE ESTIMATES INDICATE THAT
PRECIPITABLE WATER VALUES OF ~1.1" INHABIT THE COASTLINE, WITH
VALUES CLOSER TO 0.75" NEAR THE CASCADES.  UNIDIRECTIONAL FLOW OUT
OF THE WEST IS FOCUSED ON THE PACIFIC NORTHWEST, WITH LOW-LEVEL
INFLOW RUNNING 35 KTS PER RECENT VAD WIND PROFILES FROM PORTLAND
OR.

AMSU ESTIMATES OF RAIN RATES NEAR 45N 145W ARE CURRENTLY IN THE
0.1-0.2" RANGE AND HEADING IN THE DIRECTION OF THE PACIFIC
NORTHWEST, BUT THESE RATES SHOULD INCREASE WITH TIME.  RAP
FORECASTS INDICATE THAT AS THE OCCLUDED CYCLONE AND PARENT 500 HPA
SHORTWAVE MOVE INTO BRITISH COLUMBIA AND A RIDGE BUILDS ACROSS THE
WEST COAST, LOW-LEVEL INFLOW BECOMES MORE FOCUSED INTO WA STATE BY
01Z.  LOW-LEVEL INFLOW AT 850/700 HPA NEARLY DOUBLES, RISING TO
65-75 KTS BY 06Z.  CAM GUIDANCE INDICATES LOCAL AMOUNTS OF 2-3"
ARE POSSIBLE IN THE TERRAIN OF THE OLYMPIC PENINSULA AND WA
CASCADES BETWEEN 00-06Z, WHICH USUALLY LEADS TO HOURLY RAIN RATES
IN THE 0.5-0.75" RANGE.  PER THE 12Z SSEO NEIGHBORHOOD
PROBABILITIES, THESE SORT OF RAIN RATES ARE MOST LIKELY PAST 01Z. 
 

ROTH

ATTN...WFO...OTX...PDT...PQR...SEW...

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

LAT...LON   49082009 48951982 47742031 47242020 46772062 
            46162144 46232166 46732166 46862195 47892180 
            48502198 48102265 48012293 47482320 47262354 
            47632411 48102429 48252308 48952210