664  
FXUS66 KPQR 210316  
AFDPQR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PORTLAND OR  
815 PM PDT WED SEP 20 2017  
   
SYNOPSIS
 
AFTER ANOTHER BUSY WEATHER DAY, WEATHER STARTING TO GET  
QUIET. STILL SHOWERS AROUND REGION TONIGHT INTO THU THANKS TO COOL  
AIR MASS STILL OVER THE REGION. BUT, OVERALL TREND OF DECREASING  
SHOWERS STILL EXPECTED FOR THU. HIGH PRESSURE BUILDS IN OVER THE  
WEEKEND AND CONTINUES INTO EARLY NEXT WEEK FOR SOME GREAT LATE  
SEPTEMBER WEATHER IN STORE FOR THE REGION, WITH COOL NIGHTS WITH  
PATCHY FOG AND MILD MOSTLY SUNNY DAYS.  

 
   
SHORT TERM...TONIGHT THROUGH SATURDAY
 
THE DEFORMATION BAND THAT  
WAS OVER SOUTHWEST WASHINGTON THIS MORNING, AND OVER THE  
PORTLAND/VANCOUVER METRO AND COLUMBIA GORGE THIS AFTERNOON IS NOW  
FROM MT JEFFERSON TO CORVALLIS. MANY AREAS QUICKLY RECEIVED A QUARTER  
TO TWO-THIRDS OF INCH OF RAIN UNDER THIS BAND. SHOWERS ARE NOW  
DECREASING. BUT AIR MASS REMAINS COOL AND SOMEWHAT UNSTABLE  
OVERNIGHT. SO, WILL STILL HAVE SCATTERED SHOWERS TONIGHT INTO THU.  
BUT, PRECIPITATION AMOUNTS WILL BE MUCH LIGHTER THAN EARLIER TODAY.  
 
SNOW HAS BEEN FALLING IN THE CASCADES, BUT GENERALLY HARD TO GET MUCH  
IN WAY OF ACCUMULATIONS ON THE MAJOR PASSES, MOSTLY IN PART TO GROUND  
STILL BEING TOO WARM TO SUPPORT MUCH IN WAY OF ACCUMULATION. STILL,  
SAW AN INCH OR TWO AT SANTIAM PASS. BUT WITH MUCH COLDER AIR HIGHER  
UP, THEN HIGHER PEAKS GOT DECENT SHOT OF SNOW, WITH 12 TO 16 INCHES  
IN LAST 24 HRS, WITH 8 INCHES SINCE 5 AM TODAY REPORTED AROUND  
TIMBERLINE LODGE, OR NEAR 6000 FEET. BUT NOT QUITE AS MUCH FARTHER  
SOUTH, MAINLY DUE TO LESS PRECIPITATION. HAVE ENDED THE WINTER  
WEATHER ADVISORY FOR THE CASCADES, AS NOT EXPECTING MUCH IN WAY OF  
SNOW AT THE PASSES TONIGHT.  
 
NORTHERLY FLOW ALOFT WILL BE OVER THE AREA THURSDAY AND FRIDAY WITH  
PRECIPITATION MOSTLY ENDING OVER THE VALLEYS ON THURSDAY NIGHT.  
HOWEVER THERE COULD BE SOME SHOWERS OVER THE CASCADES AS MOISTURE  
MOVES SOUTH IN THE NORTHERLY FLOW ALOFT. SOME AREAS OF FOG ARE  
EXPECTED TO DEVELOP FRIDAY MORNING IF WE GET SOME CLEARING,  
ESPECIALLY WITH ALL THE MOISTURE AROUND. THERE IS A CHANCE OF FOG  
AGAIN SATURDAY MORNING WITH A SLOW WARMING TREND BEGINNING SATURDAY  
AFTERNOON.  
   
LONG TERM...SUNDAY NIGHT THROUGH WEDNESDAY
 
HIGH PRESSURE WILL  
BUILD INTO THE AREA. SNOW LEVELS WILL CONTINUE TO RISE INTO EARLY  
NEXT WEEK. WEAK OFFSHORE WINDS WILL PROBABLY KEEP THE COAST MOSTLY  
CLEAR. HOWEVER, TEMPERATURES WILL ALSO START WARMING BACK UP NEAR  
NORMAL INTO THE START OF NEXT WEEK. -BISHOP  

 
   
AVIATION
 
VFR CONDITIONS WITH A FEW AREAS OF MVFR CONDITIONS  
THIS EVENING AS SHOWERS DECREASE. LIKELY TO SEE MVFR CIGS EXPAND IN  
COVERAGE BETWEEN 12Z AND 18Z THURSDAY WITH MORNING STRATUS. A RETURN  
TO PREDOMINANTLY VFR CONDITIONS AFTER 18Z THU.  
 
KPDX AND APPROACHES...A MIX OF VFR AND MVFR CONDITIONS THROUGH 18Z  
THU, WITH MVFR CIGS BECOMING PREVAILING BETWEEN 12Z AND 18Z.  
GENERALLY VFR CONDITIONS AGAIN AFTER 18Z THU.  
 

 
   
MARINE
 
SEAS AND WINDS EXPECTED TO CONTINUE TO SLOWLY SUBSIDE  
OVERNIGHT AS A VERY WEAK LOW PRESSURE SYSTEM MOVES SOUTH INTO THE  
COASTAL WATERS TONIGHT AND THU. EXPECT TO BE ABLE TO ALLOW THE SMALL  
CRAFT FOR HAZARDOUS SEAS TO EXPIRE LATE TONIGHT. QUIET MARINE  
WEATHER IS EXPECTED THROUGH THE REST OF THE WEEK AND INTO THE  
WEEKEND AS TYPICAL SUMMERTIME NORTHERLIES RETURN TO THE AREA.  
 

 
   
PQR WATCHES/WARNINGS/ADVISORIES
 
 
OR...NONE.  
WA...NONE.  
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 AM PDT THURSDAY  
FOR COASTAL WATERS FROM CASCADE HEAD TO FLORENCE OR OUT 10  
NM-WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR FROM  
10 TO 60 NM-WATERS FROM CASCADE HEAD TO FLORENCE OR FROM  
10 TO 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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