006  
FXUS66 KPQR 201044  
AFDPQR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PORTLAND OR  
245 AM PST MON NOV 20 2017  
   
SYNOPSIS
 
WET AND UNSETTLED WEATHER THIS WEEK. A COLD FRONT WILL  
MOVE SOUTHEAST ACROSS THE AREA TODAY. THE FRONT RETURNS TONIGHT AND  
TUE, LIFTING NORTH AS A WARM FRONT. A COLD FRONT WILL PUSH INTO THE  
REGION OFF THE PACIFIC TUESDAY NIGHT AND WEDNESDAY. ANOTHER COLD  
FRONT WILL MOVE THROUGH ON THANKSGIVING, WITH SHOWERS LINGERING INTO  
FRIDAY. ANOTHER FRONT IS EXPECTED FOR THE WEEKEND.  

 
   
SHORT TERM...TONIGHT THROUGH WEDNESDAY
 
A FINE LINE ON KLGX  
RADAR, AND BUOYS SHOWED THE COLD FRONT FINALLY APPROACHING THE COAST  
EARLY THIS MORNING, WITH COASTAL SURFACE PRES GRADIENTS BEGINNING TO  
WEAKEN. EXPECT THE WINDS TO DIMINISH ONCE THE FRONT MOVES ONSHORE  
DURING THE EARLY MORNING HOURS. HEAVIEST PRECIPITATION WAS OUT IN  
FRONT OF THE FRONT, WHERE SW 850 MB WINDS FROM 50 TO 60 KT WERE  
COUPLED WITH PRECIPITABLE WATER VALUES OF 1.1 TO 1.2 INCHES. THE  
FOCUS OF THE HEAVIEST RAINS WILL SHIFT SOUTH AHEAD OF THE FRONT  
TODAY, WITH THE FRONT ULTIMATELY EXPECTED TO DROP DOWN INTO SW  
OREGON. SURFACE OBSERVATIONS IN THE SOUTH WA CASCADES WERE WARMING,  
REFLECTING RISING SNOW LEVELS. EXPECT TO BE ABLE TO DROP THE WINTER  
STORM WARNING A LITTLE EARLY THERE WITH THE NEW FORECAST, AS  
PRECIPITATION TURNS OVER TO RAIN OVER ALL BUT THE HIGHEST  
ELEVATIONS.  
 
MODELS CONTINUE TO SHOW THE UPPER LEVEL RIDGE QUICKLY REBUILDING  
OVER THE PACIFIC NW TONIGHT AND TUE, ONCE THE SHORTWAVE MOVING  
ACROSS WA HEADS OFF TO THE EAST. THIS BRINGS THE OLD FRONTAL  
BOUNDARY OVER SW OR BACK NORTH TONIGHT AND TUE, LIFTING THE FRONT  
BACK UP INTO WA. GOOD MOIST ISENTRPIC LIFT IS NOTED INI THE LOWER  
LEVELS, SEEN ALONG THE 290K ISENTROPE TONIGHT, SO WILL SEE  
CATEGORICAL POPS SPREAD BACK TO THE NORTH OVERNIGHT INTO EARLY TUE.  
DEEP MOISTURE IS NOTED WITH THE AIR MASS SOUTH THE OF THE FRONT AND  
FEEDING UP OVER THE FRONT, WITH PRECIPITABLE WATER VALUES AROUND 1.3  
INCHES. THE FRONT MOVES UP PRETTY QUICKLY HOWEVER, SHIFTING THE  
FOCUS FOR THE HEAVIEST RAINS BACK NORTH INTO WA BY TUE. A MILD AND  
VERY MOIST AIR MASS HOWEVER REMAINS OVER THE REGION INTO WED.  
DYNAMICS HOWEVER ARE RATHER WEAK, AS A RATHER AMORPHOUS-LOOKING OLD  
BAROCLINIC ZONE DRIFTS IN FROM THE WEST. WITH THE DEEP MOISTURE,  
WILL NEED KEEP A DECENT CHANCE FOR POPS GOING THROUGH WED, BUT NOT  
ENOUGH CONFIDENCE TO KEEP CATEGORICAL POPS EVERYWHERE, SO WLLL BACK  
OFF ON POPS A BIT FOR TUE NIGHT AND WED. SOUTH OF THE WARM FRONT TUE  
THROUGH WED, WILL SEE TEMPS ABOVE NORMAL WITH SNOW LEVELS WELL ABOVE  
PASS LEVELS.  
   
LONG TERM
 
WEDNESDAY NIGHT THROUGH SUNDAY. NO CHANGES.  
PREVIOUS DISCUSSION FOLLOWS. EXPECT STEADY RAIN ACROSS THE REGION  
DURING ANY PRE-HOLIDAY TRAVEL. FOR THANKSGIVING, A FRONT CROSSING  
THE AREA WILL BRING RAIN TO SOUTHWEST WASHINGTON AND NORTHWEST  
OREGON, BUT EXPECT TEMPERATURES TO BE SEVERAL DEGREES ABOVE SEASONAL  
NORMALS, WITH AFTERNOON HIGHS IN THE MID TO UPPER 50S. SNOW LEVELS  
LOOK TO REMAIN WELL ABOVE THE CASCADE PASSES. THERE MIGHT BE A  
SLIGHT BREAK IN PRECIPITATION AT THE START OF NEXT WEEKEND, BUT IT'S  
LOOKING MORE UNLIKELY AS A NEW SYSTEM ENTERS INTO THE AREA DURING  
THE WEEKEND. BISHOP/TOLLESON
 
   
AVIATION
 
COLD FRONT SLOWLY WORKING SOUTH ALONG THE WA COAST.  
FRONT IS MOVING ASHORE ON THE SOUTH WA COAST AS OF 2 AM AND WILL  
CONTINUE TO SLOWLY DROP SOUTH AND EAST THIS MORNING. AHEAD OF  
THE FRONT MAINLY MVFR CIGS WITH OCCASIONAL IFR CIGS AND VIS AT  
THE COAST AND NORTH OF KSLE INLAND. LOWER CONDITIONS WILL FILL IN  
SOUTH OF KSLE AS THE FRONT NEARS. MODEL SOUNDINGS SUGGEST BETTER  
MIXING AFTER 18Z MON FOR IMPROVEMENT TO AN MVFR TO VFR MIX.  
CASCADES AND HIGHER TERRAIN BECOME FREQUENTLY OBSCURED. A WARM  
FRONT LIFTS FROM SOUTH TO NORTH TONIGHT INTO TUE MORNING. EXPECT  
MVFR OR LOWER CONDITIONS WITH THIS SYSTEM.  
 
KPDX AND APPROACHES...MODERATE RAIN IN THE AREA BUT GENERALLY  
MVFR, BUT MAY SEE IFR CIGS THROUGH 18Z AS THE FRONT MOVES  
THROUGH. LOW-LEVEL INSTABILITY AFTER 18Z WILL HELP TO IMPROVE  
FLIGHT CONDITIONS TO AN MVFR TO VFR MIX. /MH WEISHAAR  
 

 
   
MARINE
 
FRONT IS SLOW TO DROP SOUTH ALONG THE COAST. IT APPEARS  
TO HAVE MADE LANDFALL NEAR WILLAPA BAY AS OF 2 AM. IT APPEARS TO  
BE WEAKENING AS WELL ALTHOUGH SLOWLY. WILL CONTINUE GALE WARNING  
THROUGH EARLY MORNING. THERE SHOULD BE A SHORT PERIOD OF SMALL  
CRAFT ADVISORY WINDS AND SEAS LATER IN THE MORNING THEN EASE  
QUICKLY AS WEAK HIGH PRESSURE BUILD OVER THE WATERS. THIS QUIET  
PERIOD WILL BE BENIGN AS THE FRONT RETURNS AS A WARM FRONT  
TONIGHT INTO TUE. THIS SYSTEM WILL PROBABLY BRING GALE FORCE  
WINDS, ESPECIALLY TO THE OUTER ZONES LATER TONIGHT INTO TUE.  
A SERIES OF SYSTEMS MOVE SOUTH TO NORTH OFFSHORE WED AND MAY  
BRING S WINDS 20 TO 30 KT AT TIMES THROUGH THU.  
 
WITH THE SLOWER MOVEMENT OF THE FRONT, COMBINED SEAS REMAIN NEAR  
20 FT AND REMAINS 3 TO 4 FT ABOVE SPECTRAL BULLETIN FORECAST. SEAS  
FORECAST TO DROP TO NEAR 10 FT OR LESS LATER THIS AFTERNOON. SEAS  
CLIMB BACK WELL INTO THE TEENS TUE AND LOOK TO REMAIN AT THAT  
LEVEL THROUGH THANKSGIVING. /MH WEISHAAR  
 

 
   
PQR WATCHES/WARNINGS/ADVISORIES
 
 
OR...NONE.  
WA...NONE.  
PZ...GALE WARNING UNTIL 5 AM PST EARLY THIS MORNING FOR COASTAL  
WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR OUT 60  
NM.  
 
GALE WARNING UNTIL 7 AM PST THIS MORNING FOR COASTAL WATERS  
FROM CASCADE HEAD OR TO FLORENCE OR OUT 60 NM.  
 
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 9 AM  
PST THIS MORNING.  

 
 

 
 
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 CWA, OR FORECAST AREA.  
 
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