MESOSCALE PRECIPITATION DISCUSSION 0020
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
351 AM EST THU JAN 28 2016
 
AREAS AFFECTED...WA...OR...NORTHWEST CA 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 280900Z - 281700Z
 
SUMMARY..HOURLY RAINFALL RATES NEAR 0.50 INCHES ARE EXPECTED
ACROSS OLYMPICS AND CASCADES IN WA THROUGH 12Z. THE HIGHER
RAINFALL RATES DROP SOUTH INTO OR AND NORTHWEST CA BETWEEN 12Z AND
17Z AS THE BEST MOISTURE DROPS SOUTH. TOTAL RAINFALL AMOUNTS
THROUGH 17Z SHOULD RANGE BETWEEN 2.00 AND 2.50 INCHES. 

DISCUSSION...THE LATEST WATER VAPOR LOOP SHOWED A SHORT WAVE NEAR
43N 131W. AHEAD OF THIS FEATURE AND ITS ASSOCIATED COLD
FRONT...REGIONAL VWP SHOWED A 50 KNOT LOW LEVEL SOUTHWEST FLOW
TRANSPORTING 1.00 TO 1.25 INCH PRECIPITABLE WATER AIR (PER THE
LATEST TPW IMAGERY) INTO WA AND THE NORTHERN OR COAST. THE KLGX
RADAR SHOWED SPOTTY HOURLY RAINFALL RATES NEAR 0.50 INCHES OVER
THE OLYMPIC RANGE IN WA... THOUGH MESONET SITES HAVE SHOWN HOURLY
RATES JUST UNDER THIS VALUE. 

THE LOW LEVEL FLOW SHOULD CONTINUE TO PUSH 1.00 TO 1.25 INCH
PRECIPITABLE WATER AIR (WHICH IS BETWEEN TWO AND THREE STANDARD
DEVIATIONS ABOVE THE MEAN) TO THE WA AND OR COASTS THROUGH 12Z.
THIS SHOULD BE SUFFICIENT TO PRODUCE 0.50 INCH HOURLY RAINFALL
RATES IN WA...FOCUSED MAINLY ON THE OLYMPIC RANGE. THESE RAINFALL
RATES ARE BACKED BY THE MORE RECENT HRRR/RAP SOLUTIONS...WHICH
SHOWED 0.50 INCH HOURLY RAINFALL RATES HERE THROUGH ABOUT 12Z.

AS THE SHORT WAVE CROSSES NORTHERN WA THIS MORNING...THE LOW LEVEL
FLOW BECOMES MORE SOUTHWEST WITH TIME...FOCUSING THE DEEPER
MOISTURE FURTHER SOUTH ACROSS THE OR COASTAL RANGE...THE OR
CASCADES AND EVENTUALLY INTO NORTHWEST CA BETWEEN 12Z AND 17Z.
HIGH RESOLUTION MODELS SUGGEST THE MOISTURE BECOMES A BIT LESS
ROBUST WITH TIME AS THE LOW LEVEL FLOW BECOMES MORE
SOUTHWESTERLY...BUT THE MOISTURE AND UPSLOPE FLOW SHOULD BE ENOUGH
TO PRODUCE HOURLY RAINFALL RATES NEAR 0.50 INCHES ACROSS OR AND
NORTHWEST CA DURING THIS TIME FRAME.

DUE TO THE TRANSITORY NATURE OF THE DEEPER MOISTURE...TOTAL
RAINFALL AMOUNTS THROUGH 17Z SHOULD GENERALLY RANGE BETWEEN 2.00
AND 2.50 INCHES. THE HIGHEST AMOUNTS ARE EXPECTED ACROSS THE
OLYMPIC RANGE IN WA AND THE COASTAL RANGE IN OR.

HAYES

ATTN...WFO...EKA...MFR...OTX...PDT...PQR...SEW...

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

LAT...LON   48442085 47862056 46842093 46472101 45822124 
            45102151 44102193 42702251 41782302 41272342 
            41122365 41262406 41932431 43922419 45932390 
            47322441 47982460 48232402 47792367 47192334 
            46972300 47052203 47902153