MESOSCALE PRECIPITATION DISCUSSION 0664
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
313 PM EST SAT DEC 05 2015
 
AREAS AFFECTED...W WASHINGTON/FAR NW OREGON 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 052015Z - 060315Z
 
SUMMARY...ENHANCING RAINFALL RATES TO COMPOUND PRECURSORY TOTALS
ACROSS OLYMPICS AND WA/NW OR COASTAL RANGE

DISCUSSION...PERSISTENT SW TO NE MOISTURE CONVERGENCE PLUME FROM
TRAILING EDGE OF PRIOR SHORTWAVE CONTINUES TO BE WELL DEFINED
WITHIN RAP ANALYSIS FOCUSED ON THE OLYMPICS BACK ACROSS THE MOUTH
OF THE COLUMBIA RIVER TOWARD THE APPROACHING SHORTWAVE/INFLECTION
SEEN IN 15Z 89GHZ AMSU NEAR 45.5N128.5W WHICH MATCHES UP WITH
ENHANCED RAIN RATES NEAR .25"/HR.  BLENDED TPW ANALYSIS INDICATES
INCREASING VALUES TO 1.0-1.2" IN THE NEAR OFFSHORE OF WA/OR.  THIS
INCREASING MOISTURE AND MST CONVERGENCE CONTINUE TO INCREASE
HOURLY RATES TO THE .2-.3"/HR RANGE ACROSS THE SW FACING OROGRAPHY
ALONG THE MOISTURE CONVERGENCE ZONE.   THESE RATES HAVE PROVIDED
TOTALS IN EXCESS OF 2" OVER THE PAST DAY WHICH HAVE SET THE STAGE
FOR THE APPROACHING INCREASE/THREAT OF ENHANCED RAINFALL.

WITH THE SHORTWAVE/INFLECTION POINT APPROACHING...WINDS INCREASE
TO 60-70KTS AT 850MB FOR MUCH HIGHER MOISTURE FLUX JUST AHEAD OF
THE COLD FRONT.  THE .25"/HR RATES SEEN IN BLENDED RR IMAGERY WILL
ASCEND ALONG OROGRAPHY WITH THESE WINDS TO PRESS .5-.6"/HR RATES
WITH SOLID SUPPORT OF AN ADDITIONAL 2-2.5" OVER THE NEXT 6-9HRS
BEFORE THE FRONTAL PASSAGE OCCURS.  ANY FLOODING THREAT WILL BE
LIMITED TO THOSE AREAS IMPACTED BY THE PERSISTENT PRECURSORY
MOISTURE CONVERGENCE BAND PARTICULARLY SW FACING OROGRAPHY IN THE
OLYMPIC CHAIN.  THE EVOLUTION/PROGRESSION OF THE WAVE SEEMS TO BE
A SHADE FASTER THAN MUCH OF THE HI-RES MODELS ARE INDICATING WITH
SATELLITE TRENDS TO MAKE LANDFALL NEAR SW WA AROUND 23-00Z WHILE
MODELS ARE IN THE 02Z RANGE.  STILL HI-RES MODELS DO APPEAR TO
HAVE A STRONG HANDLE ON THE ORIENTATION AND RAINFALL MAGNITUDES
PARTICULARLY THE 12Z ARW/NMMB/NSSL-WRF.

GALLINA

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

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

LAT...LON   48442460 48162284 47072294 45682325 45252370 
            45482408 46832424 47812481 48412474