MESOSCALE PRECIPITATION DISCUSSION 0776
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
112 AM EST FRI NOV 25 2016
 
AREAS AFFECTED...WESTERN OREGON/NORTHWESTERN CALIFORNIA... 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 250611Z - 251611Z
 
SUMMARY...MODERATE TO LOCALLY HEAVY RAINFALL WILL SHIFT ITS FOCUS
SOUTHWARD TOWARD SOUTHWESTERN OREGON/EXTREME NORTHWESTERN
CALIFORNIA DURING THE NEXT 12 HOURS. EXPECT HOURLY RAINFALL RATES
TO APPROACH 0.50 INCHES AT TIMES WITHIN THE STRONGER PRECIPITATION
CORES.

DISCUSSION...IN ADVANCE OF A SYNOPTIC COLD FRONT...A DECENT POOL
OF TROPOSPHERIC MOISTURE IS IN PLACE WITH SATELLITE-DERIVED PWAT
VALUES AT OR ABOVE 0.75 INCHES. SOME OF THE GPS DATA ALONG THE
NORTHWESTERN COAST OF OREGON HAVE SUPPORTED VALUES AS HIGH AS 0.87
INCHES NEAR ASTORIA. THE LATEST SOUNDING OUT OF SALEM SHOWED A
STRONG WIND FIELD BETWEEN 925 AND 700-MB WITH GENERAL
SOUTH-SOUTHWESTERLY FLOW RANGING FROM 50 TO 75 KNOTS. MODELS
DEPICT SIMILAR WIND FIELDS FARTHER SOUTH ALONG THE NOSE OF THE
NEXT SLUG OF MOISTURE TAKING AIM AT THE SOUTHWESTERN OREGON COAST. 

BASED ON THE LATEST RAP OBJECTIVE ANALYSIS FROM THE SPC MESOSCALE
PAGE...THERE IS A NON-ZERO AMOUNT OF INSTABILITY WITH 100 J/KG
MUCAPE VALUES OFF THE COAST OF OREGON. THIS IS SUPPORTED BY THE
NUMBER OF LIGHTNING STRIKES WHICH HAD OCCURRED DURING THE LAST FEW
HOURS. HOWEVER...SUCH EVENTS HAVE DECREASED MARKEDLY DURING THE
PAST HOUR. AS SUCH...THE AMSU RAINFALL RATE ALGORITHM HAS SHOWN A
DECREASE IN AMOUNTS AS THE LIGHTNING PRODUCTION HAS DIMINISHED.
HOWEVER...IN SPITE OF THE AMSU DATA SUPPORTING ONLY 0.25 INCH
HOURLY RATES...EXPECT LOCAL OROGRAPHICS TO HELP AUGMENT AMOUNTS
WITH 0.50 INCHES BEING LIKELY AT TIMES. THIS SEEMS TO BE SUPPORTED
BY MOST RECENT CAMS ALTHOUGH THE 04Z HRRR DID SHOW A NUMBER OF
REGIONS ABOVE 0.50 INCHES WHICH SEEMS POSSIBLE.


RUBIN-OSTER

ATTN...WFO...EKA...MFR...PQR...

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

LAT...LON   45822271 45782222 45472190 45072182 44582193 
            44072231 43602286 43152326 42712350 41742335 
            41232358 41022410 41172470 42022506 43112497 
            44072471 44492433 44782412 45162352 45552304