269  
FXUS66 KPQR 162158  
AFDPQR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PORTLAND OR  
258 PM PDT MON OCT 16 2017  
   
SYNOPSIS
 
DRY WEATHER TONIGHT BEFORE A SERIES OF PROGRESSIVELY  
MOISTER FRONTS BRING A PROLONGED PERIOD OF WET WEATHER TUESDAY  
THROUGH NEXT WEEKEND. BREEZY CONDITIONS ARE EXPECTED WEDNESDAY AND  
THURSDAY AS WELL AS PERIODS OF HEAVY RAIN. SNOW LEVELS WILL LOWER TO  
NEAR THE CASCADE PASSES FRIDAY AND SATURDAY.  
 

 
   
SHORT TERM...TODAY THROUGH THURSDAY
 
A FLAT UPPER RIDGE OF HIGH  
PRESSURE SHOULD KEEP RAIN NORTH OF THE PORTLAND FORECAST AREA  
TONIGHT. CLOUDS ASSOCIATED WITH A FRONT WELL NORTH OF THE AREA WILL  
MOVE OVER EXTREME SW WASHINGTON AND NW OREGON THIS EVENING AND  
TONIGHT. SATELLITE IMAGERY ALSO SHOWS MARINE CLOUDS OFFSHORE THAT  
WILL LIKELY FILL IN ALONG THE OREGON COAST THIS EVENING AND TONIGHT.  
OTHERWISE, INLAND AREAS ESPECIALLY IN OREGON WILL HAVE MOSTLY CLEAR  
SKIES THIS EVENING AND EXPECT FOG TO FORM IN SOME OF THE INTERIOR  
VALLEYS TONIGHT. THE FOG WILL NOT LIKELY LAST LONG DUE TO INCREASED  
MIXING AND CLOUDS AHEAD OF AN APPROACHING FRONT.  
 
A SERIES OF STORMS WILL BRING A RETURN OF RAIN TO THE  
REGION BEGINNING TUESDAY AND LASTING THROUGH THE WEEK. WATER VAPOR  
IMAGERY SHOWS AN ATMOSPHERIC RIVER OF MOISTURE EXTENDING ACROSS THE  
WHOLE PACIFIC THAT THE STORMS WILL BE ABLE TO TAP INTO.  
 
THE FIRST FRONT IS EXPECTED ON TUESDAY WITH RAIN REACHING THE SW  
WASHINGTON AND NW OREGON COAST MID MORNING, AND MOVING INLAND THROUGH  
THE AFTERNOON. THE RAIN WILL BE MOSTLY CONFINED TO THE OREGON  
CASCADES TUESDAY EVENING. BESIDES THE COAST AND CASCADES, LANE COUNTY  
WILL SEE VERY LITTLE IF ANY TRAIN WITH THIS SYSTEM. THE FIRST FRONT  
EXPECTED ON TUESDAY WILL EAST RAINFALL WITH EACH RAIN TOTALS WILL BE  
GREATEST FOR THE WASHINGTON COAST, THE WILLAPA HILLS AND THE  
WASHINGTON CASCADES WHERE 0.5 TO 0.8 INCH IS EXPECTED. AROUND 0.25  
INCH OF RAIN IS LIKELY FOR FOR THE NORTH OREGON CASCADES AND COASTAL  
MOUNTAINS WITH LESS THAN 0.2 INCH EXPECTED ELSEWHERE. ONLY LIGHT RAIN  
(LESS THAN 0.05 INCH) IS EXPECTED FOR LANE COUNTY.  
 
THERE WILL BE BREAK IN THE RAIN TUESDAY NIGHT. SOME FOG MAY FORM IN  
THE IN THE INTERIOR VALLEYS AND ALONG THE COAST TUESDAY NIGHT, BUT  
ANY SKY COVER WILL LIMIT THE EXTENT OF THIS FOG.  
 
A MOIST WARM FRONT WILL START THE SECOND ROUND OF RAIN FOR THE SW  
WASHINGTON AND NW OREGON COASTS WEDNESDAY MORNING. THE EXTENT OF THE  
RAIN WILL BE SIMILAR WITH THIS FRONT WITH THE BEST CHANCE FOR RAIN  
ACROSS THE NORTH AND VERY LITTLE RAIN EXPECTED FOR LANE COUNTY. THE  
RAIN WITH THIS SYSTEM WILL HAVE A BETTER POTENTIAL TO BE HEAVY AT  
TIMES, AND RAINFALL TOTALS WILL BE HIGHER. THE SW WASHINGTON COAST AND  
WILLAPA HILLS CAN EXPECT AN ADDITIONAL 0.75 TO 1.5 INCH OF RAIN FROM  
WEDNESDAY MORNING THROUGH WEDNESDAY EVENING. THE SW WASHINGTON  
CASCADES CAN SEE ANOTHER 0.75 TO 1 INCH, WITH AROUND 0.5 INCH FOR THE  
OREGON COAST RANGE AND CASCADES AND LESS THAN 0.2 INCH FOR THE  
INTERIOR VALLEYS. AGAIN, AREAS IN LANE COUNTY CAN EXPECT LESS THAN  
0.05 INCH.  
 
THERE WILL NOT BE A BREAK WEDNESDAY NIGHT AS THE TRAILING COLD FRONT  
FRONT MOVES ACROSS THE AREA WEDNESDAY NIGHT THROUGH THURSDAY. THIS  
FRONT IS LOOKING JUICY, AND EXPECT WIDESPREAD RAIN THAT WILL BE HEAVY  
AT TIMES. AN ADDITIONAL 1.5 TO 2 INCHES OF RAIN IS EXPECTED FOR THE  
HIGHER TERRAIN OF SW WASHINGTON AND NORTH OREGON WEDNESDAY NIGHT  
THROUGH THURSDAY EVENING. OTHER AREAS (INCLUDING LANE COUNTY) CAN  
EXPECT 0.75 TO 1.5 INCH OF RAIN. DEPENDING ON THE RAIN RATES, THERE  
COULD BE LOCALIZED FLOODING CONCERNS WEDNESDAY NIGHT AND THURSDAY  
WITH THE BEST CHANCES FOR HYDROLOGIC CONCERNS IN THE WILLAPA HILLS AND  
NEAR THE FIRE BURN SCARS IN THE COLUMBIA RIVER GORGE.  
 
BESIDES RAIN, THE WEDNESDAY AND THURSDAY FRONTS WILL GENERATE WINDY  
CONDITIONS FOR THE COAST AND BREEZY CONDITIONS INLAND. SOUTH GUSTS  
UP TO 45 MPH ARE POSSIBLE FOR THE BEACHES, HEADLANDS, AND HIGHER  
TERRAIN WITH GUSTS OF 30 TO 35 MPH POSSIBLE FOR THE INTERIOR VALLEYS  
INCLUDING THE WILLAMETTE VALLEY. ~TJ  
   
LONG TERM...THURSDAY NIGHT THROUGH MONDAY.
 
LATEST MODEL CONSENSUS  
HAS THE WARM FRONT PUSHING ONSHORE ALONG THE OREGON AND SOUTHERN  
WASHINGTON COAST LATE THURSDAY NIGHT. A BAROCLINIC ZONE MOVES  
THROUGH THE REGION WITH MODEL FORECAST PW VALUES REMAINING HIGH,  
CONTINUING MODERATE TO HEAVY RAINFALL. EXPECT GUSTY WINDS ESPECIALLY  
ALONG THE COAST AND IN THE HIGHER TERRAIN OF THE COAST RANGE WITH  
THIS SYSTEM. SNOW LEVELS WILL REMAIN RATHER HIGH AROUND 5,000 FEET.  
THE COLD FRONT FINALLY PASSES ACROSS THE REGION BY LATE FRIDAY, WITH  
ONGOING SHOWERS AND LOWERING SNOW LEVELS AS THE COLDER AIR MASS  
MOVES OVER THE PACIFIC NORTHWEST.  
 
TIMING AND LOCATION OF THE HEAVIEST RAINFALL MAY CONTINUE TO CHANGE  
WITH FUTURE UPDATES, THE KEY MESSAGE IS THAT A RATHER WET WEATHER  
SYSTEM MAY BRING ABUNDANT RAINFALL TO THE AREA. EXPECT TO SEE SOME  
RISES ON AREA RIVERS, ESPECIALLY IN THE COASTAL BASINS, AND IF THE  
HEAVY RAIN SETS UP OVER URBAN AREAS, SOME LOCALIZED URBAN FLOODING  
ISSUES COULD DEVELOP. ALSO, LOCATIONS WITH SIGNIFICANT BURN SCARS  
SHOULD BE AWARE OF POSSIBLE LAND OR MUD SLIDES. BISHOP  

 
   
AVIATION
 
HIGH PRESSURE WILL BRING VFR CONDITIONS THROUGH THIS  
EVENING BEFORE FOG TRIES TO REFORM IN THE LOWEST VALLEY  
LOCATIONS LATER TONIGHT. AN INCOMING FRONT SHOULD INCREASE WINDS  
TUESDAY MORNING, WHICH SHOULD RESULT IN FOG LIFTING A LITTLE  
FASTER THAN THIS MORNING, ESPECIALLY ACROSS THE NORTH. HOWEVER,  
AN AREA OF LOW END VFR AND MVFR CONDITIONS WILL SPREAD  
SOUTHEASTWARD ACROSS THE AREA TUESDAY AS A BAND OF RAIN MOVES  
ACROSS THE AREA.  
 
KPDX AND APPROACHES...HIGH PRESSURE WILL BRING VFR CONDITIONS  
THROUGH THIS EVENING. ADDITIONAL MVFR TO LIFR CONDITIONS ARE  
POSSIBLE TOWARDS 13-15Z TUESDAY, BUT CONFIDENCE IN WHETHER THESE  
RESTRICTIONS WILL DEVELOP AT THE TERMINAL IS LOW AT THIS POINT.  
/NEUMAN  
 

 
   
MARINE
 
HIGH PRESSURE OVER THE WATERS TODAY WILL GIVE WAY TO A  
COLD FRONT MOVING SOUTHEASTWARD ACROSS THE WATERS LATE TONIGHT  
AND TUESDAY. THIS WILL LIKELY SPREAD SMALL CRAFT ADVISORY LEVEL  
WIND GUSTS OF 25 TO 30 KT ACROSS THE NORTHERN WATERS LATER  
TONIGHT AND ALLOW SEAS TO CLIMB TO NEAR 10 FT TUESDAY. HOWEVER,  
THE FRONT SHOULD WEAKEN ENOUGH TO PREVENT THESE WINDS AND HIGHER  
SEAS FROM SPREADING INTO ALL BUT THE MOST NORTHERNMOST PORTIONS  
OF THE CENTRAL OREGON WATERS ON TUESDAY.  
 
THE NEXT FRONT WILL DROP SOUTHEASTWARD ACROSS THE WATERS ON LATE  
WEDNESDAY AND EARLY THURSDAY AND APPEARS LIKELY TO SPREAD GALE  
FORCE WIND GUSTS OF 35 TO 45 KT INTO THE WATERS. A COASTAL JET  
COULD PRODUCE LOCALLY STRONGER WINDS WITHIN 10NM OF THE COAST.  
EITHER WAY, THE STRONG WINDS SHOULD ALLOW SEAS TO CLIMB INTO AT  
LEAST THE MID TO UPPER TEENS LATE WEDNESDAY. AFTER WINDS DROP OFF  
BEHIND THE FRONT WEDNESDAY AND EARLY THURSDAY, SEAS SHOULD DROP  
RATHER QUICKLY INTO THE LOW TEENS. HOWEVER, MODELS CONTINUE TO  
SUGGEST A LARGE WESTERLY SWELL AROUND 20 FT WILL MOVE INTO THE  
WATERS LATE THURSDAY AND MAY NECESSITATE A HIGH SURF ADVISORY.  
ADDITIONAL STORM SYSTEMS CAPABLE OF PRODUCING GALE FORCE WIND  
GUSTS APPEAR POSSIBLE DURING THE UPCOMING WEEKEND AS WELL. /NEUMAN  
 

 
   
PQR WATCHES/WARNINGS/ADVISORIES
 
 
OR...NONE.  
WA...NONE.  
PZ...GALE WATCH FROM LATE TUESDAY NIGHT THROUGH WEDNESDAY EVENING  
FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD  
OR OUT 60 NM.  
 
SMALL CRAFT ADVISORY FOR WINDS FROM 1 AM TO 1 PM PDT TUESDAY  
FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD  
OR OUT 60 NM.  
 
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 5 AM TO 9 PM PDT  
TUESDAY FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO  
CASCADE HEAD OR OUT 60 NM.  
 
GALE WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY MORNING  
FOR COASTAL WATERS FROM CASCADE HEAD OR TO FLORENCE OR OUT  
60 NM.  
 

 

 
 
INTERACT WITH US VIA SOCIAL MEDIA:  
WWW.FACEBOOK.COM/NWSPORTLAND  
WWW.TWITTER.COM/NWSPORTLAND  
 
THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON  
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THIS AREA IS  
COMMONLY REFERRED TO AS THE FORECAST AREA.  
 
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