MESOSCALE PRECIPITATION DISCUSSION 0652
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1206 PM EST TUE NOV 17 2015
 
AREAS AFFECTED...WESTERN WA/NORHWEST OR 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 171704Z - 180100Z
 
SUMMARY...AN APPROACHING SHORTWAVE INTO SRN BRITISH COLUMBIA IS
EXPECTED TO BRING ABOUT RAINFALL RATES UP TO 0.75 IN/HR FROM THE
OLYMPICS AND WASHINGTON COASTAL RANGES/CASCADES BEFORE SUBSIDING
AFTER 00Z.

DISCUSSION...WATER VAPOR IMAGERY CONFIRMED THE PRESENCE OF AN
EMBEDDED SHORTWAVE IMPULSE ABOUT TO CLIP NRN VANCOUVER ISLAND AT
16Z...PRECEDED BY COOLING TOPS ON INFRARED SATELLITE IMAGERY.
RAINFALL RATES ARE CURRENTLY 1 TO 1.5 INCHES IN 3 HOURS AS
MEASURED BY RECENT 3 HOURLY GAUGE REPORT OF 1.36 INCHES NEAR
QUINAULT IN OLYMPIC NATIONAL PARK AT 1605Z. AN AMSU PASS FROM
1126Z SHOWED 0.35 IN/HR RATES OFFSHORE NRN VANCOUVER
ISLAND...WHICH WHEN ACCOUNTING FOR OROGRAPHIC ENHANCEMENT FROM
ONSHORE FLOW...COULD DOUBLE TO NEAR 0.75 IN/HR. AHEAD OF THE
AFOREMENTIONED SHORTWAVE...700 MB FLOW HAS INCREASED TO 70 KTS PER
KATX VAD WIND PROFILE WHICH IS A BIT AHEAD OF RECENT MODEL
FORECASTS FROM THE RAP/12Z GFS BUT ON PAR FROM THE 12Z NAM.

AS ENHANCED 850-700 MB WLY ONSHORE FLOW OF 60-70 KTS SLOWLY SINKS
SOUTH ACROSS WRN WASHINGTON THROUGH THE REST OF THE DAY...HRLY
RAINFALL RATES OF 0.50 TO 0.75 INCHES ARE EXPECTED TO IMPACT THE
OLYMPICS AND THE MORE FAVORED PEAKS OF THE WASHINGTON CASCADES.
WHAT HAD BEEN THE NEARLY STATIONARY PLUME OF PRECIPITABLE WATER
AHEAD OF THE ASSOCIATED COLD FRONT WITH 1.1 TO 1.2 INCHES ALONG
THE WASHINGTON COAST AND NEAR 1.0 INCH ALONG THE WINDWARD SIDE OF
THE CASCADES...WILL BEGIN TO SAG SOUTH WITH THE PASSAGE OF THE
SHORTWAVE TO THE NORTH. RAINFALL RATES WILL LIKELY INCREASE A BIT
THIS AFTERNOON BEFORE SUBSIDING WHILE THE AXIS OF HEAVIEST
RAINFALL MOVES INTO NRN OREGON.

OTTO

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

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

LAT...LON   49002112 48672055 47482058 45762140 44952180 
            44792254 44932376 46172408 47792438 48202404 
            48982212