478  
FXUS66 KPQR 222210  
AFDPQR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PORTLAND OR  
304 PM PDT SAT JUL 22 2017  
   
SYNOPSIS
 
A WEAK UPPER TROUGH WILL PASS OVER WASHINGTON ON SUNDAY  
FOR A SLIGHT INCREASE IN ONSHORE FLOW BRINGING A BIT OF COOLING TO  
TO THE COAST AND WILLAMETTE VALLEY. AN UPPER RIDGE WILL BUILD OVER  
OUR AREA ON MONDAY AND TUESDAY FOR A WARNING TREND. AN UPPER LEVEL  
LOW TO OUR SOUTHWEST MAY PRODUCE SOME THUNDERSTORMS IN THE  
LANE COUNTY CASCADES SUNDAY THROUGH TUESDAY AFTERNOON AND EVENING.  
INCREASED ONSHORE FLOW AND COOLER CONDITIONS ARE EXPECTED FOR THE  
SECOND HALF OF NEXT WEEK BRINGING TEMPERATURES BACK TO NEAR NORMAL.  
 

 
   
SHORT TERM...SATURDAY NIGHT THROUGH TUESDAY
 
UPPER TROUGH PASSING  
BY TO THE NORTH ON SUNDAY WILL RESULT IN SOME COOLING OF THE AIR MASS  
OVER THE REGION. ONSHORE FLOW WILL LIKELY PUSH MARINE STRATUS INTO  
THE WILLAMETTE VALLEY AND SOUTHWEST WASHINGTON INTERIOR DURING THE  
EARLY MORNING HOURS ON SUNDAY. THIS AFTERNOON TEMPERATURES SHOULD  
REACH THE LOWER 90S IN MOST VALLEY LOCATIONS BUT THE UPPER TROUGH  
WILL RESULT IN TEMPERATURES AROUND 5 DEGREES COOLER SUNDAY.  
 
THERE IS A DEVELOPING UPPER LOW OFF THE COAST OF CALIFORNIA WHICH  
WILL MOVE TO THE N CALIFORNIA COAST AND LINGER THROUGH TUESDAY.  
SOUTHERLY FLOW DEVELOPS ALOFT AHEAD OF THE LOW AND WILL LIKELY RESULT  
IN INCREASING MOISTURE AT MID AND HIGH LEVELS OVER THE SOUTHERN  
PORTION OF OUR FORECAST AREA. CHANCE OF THUNDERSTORMS IN THE LANE  
COUNTY CASCADES SUNDAY THROUGH TUESDAY DURING HEATING IN THE  
AFTERNOON AND EVENING HOURS. THIS APPEARS TO BE THE MOST SIGNIFICANT  
CHANCE OF LIGHTNING WITH THE POTENTIAL FOR FIRE STARTS IN THE  
CASCADES SO FAR THIS SUMMER. MODELS SHOW THAT ANY MOISTURE THAT DOES  
FORM WILL BE HIGH LEVEL AND NOT LIKELY TO SEE ANY SIGNIFICANT  
PERCIPITATION FROM THIS SYSTEM. THE SOUTHERLY FLOW COMBINES WITH THE  
UPPER RIDGE TO THE NORTH OF THE LOW FOR WARMING ON TUESDAY...LIKELY  
SHOOTING BACK IN THE THE LOWER 90S IN THE VALLEYS.  
 
   
LONG TERM...TUESDAY NIGHT THROUGH SATURDAY
 
MODELS ARE IN GOOD  
AGREEMENT KICKING OUT THE UPPER LOW OVER NORTHERN CALIFORNIA T MOVING  
IT NORTHWEST DURING THE DAY ON WEDNESDAY. WEAK WESTERLY FLOW DEVELOPS  
AT 700MB AS THE LOW MOVES OUT IT LOOKS LIKE THE THREAT OF  
THUNDERSTORMS WILL BE GREATLY REDUCED. HOWEVER, THIS COULD CHANGE IF  
THE UPPER LOW LINGERS...WHICH THEY ARE NOTORIOUS FOR DOING THIS TIME  
OF YEAR. THAT COULD PROLONG CONVECTION FOR ANOTHER AFTERNOON AND  
EVENING HEATING CYCLE.  
 
MODELS SHOW A UPPER TROUGH APPROACHING FROM THE NORTHWEST BY THURSDAY  
WHICH PUTS US BACK IN WSW FLOW ALOFT AND DRYS OUT THE CASCADES ENDING  
ANY THUNDERSTORM THREAT. NIGHT AND MORNING LOW CLOUDS MAY BECOME MORE  
EXTENSIVE THURSDAY THROUGH SATURDAY WITH TEMPERATURES RETURNING TO  
NEAR NORMAL.  
SCHNEIDER  
 

 
   
AVIATION
 
EXPECT PREDOMINATELY VFR CONDITIONS UNDER MOSTLY  
CLEAR SKIES THROUGH TONIGHT. WINDS WILL CONTINUE TO INCREASE  
ALONG THE COAST THIS AFTERNOON WITH GUSTS TO 25 KT POSSIBLE AT  
KONP AND GUSTS TO 20 KT AT KAST. GUSTY WINDS IN THE INTERIOR,  
WITH GUSTS 15-20 KT, WILL CONTINUE THROUGH THIS EVENING BEFORE  
SUBSIDING BY 06Z TONIGHT. MVFR CONDITIONS LOOK TO REDEVELOP ALONG  
THE COAST AFTER 06Z TONIGHT. BRIEF PERIODS OF LOCALIZED IFR FOG  
IS POSSIBLE EARLY SUNDAY MORNING IN SOME OF THE MORE SHELTERED  
VALLEYS ALONG THE COAST. CONDITIONS IN THE INTERIOR WILL LIKELY  
REMAIN VFR THE NEXT 24 HOURS. HOWEVER, GUIDANCE CONTINUES TO SHOW  
SOME MVFR CIGS DEVELOPING ALONG THE COLUMBIA RIVER EARLY SUNDAY  
MORNING WHICH COULD BRING A BRIEF PERIOD OF REDUCED CIGS TO THE  
METRO TERMINALS BETWEEN 12-18Z, BUT CONFIDENCE IS LOW ON WHETHER  
THESE CIGS WILL IMPACT THE TERMINAL. KTTD HAS THE BEST CHANCE OF  
MVFR CIGS AS LOW STRATUS DEVELOPS ALONG THE CASCADE FOOTHILLS  
OVERNIGHT. EXPECT ANY LOW CIGS THAT DO DEVELOP TO BE BRIEF AND  
LIFT BY LATE SUNDAY MORNING.  
 
KPDX AND APPROACHES...PREDOMINATELY VFR THE NEXT 24 HOURS. GUSTY  
WINDS TO 15 KT POSSIBLE THROUGH AROUND MIDNIGHT TONIGHT. THERE  
IS A CHANCE THAT MVFR CIGS AROUND 2000 FT WILL BRIEFLY IMPACT THE  
TERMINAL BETWEEN 13-17Z SUNDAY, BUT CONFIDENCE IS LOW. /64  
 

 
   
MARINE
 
HIGH PRESSURE WILL CONTINUE TO STRENGTHEN OVER THE NE  
PACIFIC THIS AFTERNOON, WHILE HOT WEATHER OVER SW OREGON AND NW  
CALIFORNIA WILL HELP TO STRENGTHEN A THERMAL TROUGH OVER THOSE  
AREAS. THIS WILL BRING AN INCREASE IN NORTHERLY WINDS, WITH GUSTS  
25-30 KT EXPECTED ACROSS OUR SOUTHERN WATERS BY SUNSET AND  
SPREADING NORTH INTO OUR NORTHERN WATERS LATER TONIGHT. THE  
INCREASING WINDS WILL RESULT IN STEEP WIND-DRIVEN SEAS. WINDS  
WILL CONTINUE TO INCREASE ON SUNDAY. MODELS CONTINUE TO SUGGEST  
THAT GALE FORCE WINDS ARE POSSIBLE OVER OUR SOUTHERN WATERS.  
HOWEVER, NORTHERLY GALES OVER OUR WATERS ARE RELATIVELY RARE, SO  
GIVEN THAT THE STRONGER MODELS CONTINUE TO ONLY SHOW MARGINAL  
GALES WILL STICK WITH OUR CURRENT SMALL CRAFT ADVISORIES FOR  
WINDS AND HAZARDOUS SEAS, BUT WOULD NOT BE SURPRISED LOCAL GUSTS  
TO 35 KT. SCA CONDITIONS LOOK TO PERSIST INTO TUESDAY SO THE  
CURRENT ADVISORIES WILL LIKELY NEED TO BE EXTENDED. MODELS THEN  
SHOW AN UPPER TROUGH FROM THE GULF OF ALASKA MOVING CLOSER TO OUR  
WATERS WHICH WILL LIKELY BRING A DECREASE IN WINDS/SEAS TOWARDS  
THE MIDDLE OF NEXT WEEK. /64  
 

 
   
PQR WATCHES/WARNINGS/ADVISORIES
 
 
OR...NONE.  
WA...NONE.  
PZ...SMALL CRAFT ADVISORY FOR WINDS AND HAZARDOUS SEAS FROM 8 PM  
THIS EVENING TO 6 AM PDT MONDAY FOR COASTAL WATERS FROM  
CAPE SHOALWATER WA TO CASCADE HEAD OR OUT 60 NM.  
 
SMALL CRAFT ADVISORY FOR WINDS AND HAZARDOUS SEAS UNTIL  
6 AM PDT MONDAY FOR COASTAL WATERS FROM CASCADE HEAD OR  
TO FLORENCE OR OUT 60 NM.  
 
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 3 AM  
TO 7 AM PDT SUNDAY.  
 

 
 

 
 
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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