MESOSCALE PRECIPITATION DISCUSSION 0646
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1035 AM EST MON NOV 16 2015
 
AREAS AFFECTED...WESTERN WA 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 161532Z - 162100Z
 
SUMMARY...STRONG EASTERN PACIFIC JET AND WARM ADVECTION WILL BRING
MODERATE TO HEAVY RAINS INTO WESTERN WA BY EARLY TO MID-AFTERNOON.

DISCUSSION...WV IMAGERY THIS MORNING SHOWS A POWERFUL WEST/EAST
ORIENTED H25 JET OF 190 TO 200 KTS FOCUSED JUST SOUTH OF AN
AMPLIFYING SHORTWAVE AND ASSOCIATED LOW CENTER WEST OF BRITISH
COLUMBIA AND NEAR THE GULF OF AK. MEANWHILE...THE DEEPENING LOW
CENTER IS FOCUSING VERY STRONG WARM ADVECTION OFFSHORE AND THIS IS
RAPIDLY APPROACHING WESTERN WA THIS MORNING.

THE 06Z GFS AND 00Z ECMWF SHOW A 50 TO 60 KT WESTERLY LOW LEVEL
ARRIVING ACROSS THE WA COASTAL RANGES BY AROUND 21Z...WITH A POOL
OF 1.0 TO 1.2 INCH PWATS. THIS WILL DRAMATICALLY ENHANCE THE
ARRIVAL OF HEAVIER WARM ADVECTION RAINS ACROSS THE ALREADY
SATURATED TERRAIN OF WESTERN WA.

A 1320Z AMSU PASS ALREADY INDICATES OFFSHORE RAINFALL RATES OF
0.25 TO 0.40 INCHES/HR JUST AHEAD A WARM FRONT...AND THE 00Z ARW
AND 00Z NMMB SUGGEST THESE RAINFALL RATES ARRIVING BY
MID-AFTERNOON ACROSS THE OLYMPIC PENINSULA AND ADJACENT COASTAL
RANGES JUST TO THE SOUTH DOWN TO NEAR THE WA/OR BORDER.

DEEP LAYER WESTERLY ONSHORE FLOW WILL STRENGTHEN FURTHER JUST
BEYOND THIS PERIOD TOWARD 00Z AND WILL FOSTER EVEN HEAVIER
RAINFALL RATES GIVEN ENHANCED OROGRAPHIC FORCING. WILL CONTINUE TO
MONITOR.

ORRISON

ATTN...WFO...PQR...SEW...

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

LAT...LON   49302327 48752195 47792184 45932238 46012381 
            46782454 48792466 49262400