301  
FXUS66 KPQR 180405  
AFDPQR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PORTLAND OR  
902 PM PDT SUN JUN 17 2018  
   
SYNOPSIS
 
A CHANCE FOR SHOWERS AND THUNDERSTORMS WILL CONTINUE  
OVER THE CASCADES THROUGH WEDNESDAY AS AN UPPER LOW MOVES SLOWLY EAST  
INTO IDAHO AND THEN MONTANA. OTHERWISE DRY AND WARMER WEATHER THROUGH  
MIDWEEK AS A RIDGE OF HIGH PRESSURE MOVES OVER THE REGION.  
 

 
   
SHORT TERM
 
UPDATE FOR THIS EVENING. CONVECTIVE LINE OF SHOWERS AND  
ISOLATED THUNDERSTORMS MOVED OFF THE CASCADES AND INTO THE VALLEY  
THIS EVENING BRINGING SOME LOCALLY HEAVY RAIN AND GUSTY WINDS.  
NUMEROUS REPORTS THIS EVENING OF HEAVY RAINFALL AND GUSTY WINDS THAT  
BROKE TREE BRANCHES. RAIN GAGES SHOW ABOUT 0.1 TO 0.4 INCH OF  
RAINFALL THE PAST 3 OR 4 HOURS. THE BROKEN TREE BRANCHES APPEAR TO  
HAVE FALLEN ON A FEW POWER LINES CAUSING SOME ISOLATED POWER OUTAGES  
IN THE PORTLAND METRO AREA SOUTHWARD INTO MARION AND YAMHILL  
COUNTIES. THE SHOWERS AND THUNDERSTORM ACTIVITY WILL WANE AS WE GO  
INTO THE OVERNIGHT HOURS. TW  
 
THE REST OF THE AFTERNOON DISCUSSION FOLLOWS. AS THE UPPER LOW  
CONTINUES TO MOVE SLOWLY EAST AND THEN NE THROUGH WEDNESDAY, THE  
PRIMARY THREAT FOR WRAP-AROUND SHOWERS AND THUNDERSTORMS WILL REMAIN  
IN THE CASCADES. BUT LOCALLY THE CASCADES WILL REMAIN IN N/NE FLOW,  
WHICH WILL CONTINUE TO BE FAVORABLE FOR SOME SHOWER AND  
THUNDERSTORM DEVELOPMENT. IN FACT, MODELS ARE WETTER IN THE CASCADES  
TUESDAY AND WEDNESDAY AFTERNOONS THAN THEY HAVE BEEN, SO ADDED  
SLIGHT CHANCE POPS EACH DAY.  
 
LATE TONIGHT AND MONDAY, MODELS CONTINUE TO INDICATE A SOUTHERLY  
PUSH, BRINGING CLOUDS AND POSSIBLY FOG UP THE COAST. COULD EVEN SEE  
SOME CLOUDS AT EUGENE ON THE SOUTH END AND KELSO ON THE NORTH END  
INLAND. THIS WILL KEEP TEMPERATURES MUCH COOLER MONDAY AT LEAST ALONG  
THE COAST, AND ANYWHERE INLAND WHICH SEES CLOUDS MONDAY MORNING WILL  
LIKELY ALSO BE COOLER THAN TODAY. OTHERWISE, MODEL 850 MB TEMPS  
SUGGEST LITTLE CHANGE TO TEMPS FROM TODAY TO MONDAY. MARINE CLOUDS  
WILL LIKELY PUSH ONTO THE COAST AGAIN MONDAY AND TUESDAY NIGHTS, BUT  
MOST INLAND AREAS SHOULD REMAIN CLEAR OTHER THAN ANY DEBRIS FROM  
CASCADE SHOWERS. ON TUESDAY, THE LOW LEVEL WIND FIELD BECOMES RATHER  
FLAT, WHILE 850 MB TEMPS WARM SLIGHTLY, WHICH SHOULD BE ENOUGH TO  
PUSH HIGH TEMPS CLOSE TO THE 90F MARK IN SOME OF THE LOW INLAND  
VALLEYS. HIGH PRESSURE BECOMES A LITTLE BIT MORE DOMINANT ON  
WEDNESDAY, ALLOWING FOR ADDITIONAL HEATING COMPARED EVEN TO TUESDAY,  
SO MAY SEE SOME LOW OR EVEN MID 90S INLAND ON WEDNESDAY.  
 

 
   
LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS
 
WEDNESDAY  
NIGHT THROUGH SUNDAY. IT LOOKS LIKE THE MODELS HAVE CHANGED AGAIN FOR  
THE LATTER PART OF THE WEEK. THE 12Z GFS AND THE 12Z EURO BOTH ARE  
SHOWING A TROUGH MOVING INTO THE AREA. HOWEVER, THEY DIFFER IN  
POSITIONING AND ORIENTATION. THE GFS SHOWS A FAIRLY DEEP TROUGH  
ENTERING INTO THE AREA, BUT KEEPING THE AREA DRY THROUGH THE END OF  
THE WEEK. THE EURO SHOWS A NEGATIVELY TILTED SHALLOW TROUGH, BUT  
INCREASING POPS FOR THE MAJORITY OF THE AREA THROUGH FRI MORNING. THE  
MODELS BOTH HAVE ONSHORE FLOW STAYING CONSTANT, WHICH LOOKS TO COOL  
DOWN THE AREA FOR THE LATTER PART OF THE WEEK INTO THE WEEKEND.  
 
FOR THE WEEKEND BOTH MODELS SEE A RIDGE DEVELOPING TOWARDS THE START  
OF SAT, AND BECOMING THE DOMINATE FEATURE FOR THE REST OF THE  
WEEKEND, KEEPING THE AREA ON THE COOLER AND DRIER SIDE. THE GFS IS  
SHOWING A FAIRLY STRONG RIDGE BECOMING ESTABLISHED FROM A HIGH  
PRESSURE SYSTEM LOCATED NEAR THE CENTRAL CALIFORNIA COAST. THE EURO  
ON THE OTHER HAND HAS A SHORTWAVE RIDGE SLIDING IN FROM A MUDDLED  
HIGH LOCATED FARTHER OFF THE CALIFORNIA COAST.  
 
ONE THING TO NOTE IS THAT THE START OF NEXT WEEK, BOTH MODELS ARE  
SHOWING A LOW ORIGINATING FROM THE GULF OF ALASKA. THIS HAS THE  
POTENTIAL TO BRING SOME PRECIP INTO THE AREA, BUT CURRENTLY IT IS  
HARD TO SAY IF THIS WILL HAPPEN. /42  
 

 
   
AVIATION
 
MAJORITY OF THUNDERSTORMS AND SHOWERS HAVE  
DIMINISHED AND SHOULD END BY 06Z. AREAS OF CONCERN AS OF 04Z IS  
ISOLATED THUNDERSTORMS OVER NE OF KTTD THAT MAY AFFECT THE KPDX  
AREA THROUGH 05Z. THE OTHER AREA IS NEAR KEUG WHERE SHOWERS ARE  
JUST ABOUT TO DEPART TO THE SOUTH. VFR SHOULD PERSIST AT THE  
INTERIOR TAF SITES THROUGH THE NEXT 24 HRS WITH SOME MID-LEVEL  
CONVECTIVE DEBRIS CLOUDS THIS EVENING. THE KEUG AREA MAY SEE LOW  
MVFR CIGS LATE TONIGHT AND EARLY MONDAY FROM RESIDUAL MOISTURE  
FROM SHOWERS AS WELL AS MARINE AIR INFILTRATING INTO THE AREA.  
 
A THIN STRIP OF LOW STRATUS CLOUDS IS CLINGING TO THE PART OF THE  
COAST. KONP NOW HAS IFR CONDITIONS AND SHOULD CONTINUE INTO MON.  
THERE WILL ALSO BE A SOUTHERLY MARINE SURGE MOVING UP THE COAST  
OVERNIGHT INTO MON MORNING. THIS SHOULD RESULT IN IFR CONDITIONS  
SPREADING ALONG THE ENTIRE COAST BY LATE MON MORNING.  
 
KPDX AND APPROACHES...VFR CONDITIONS TO PERSIST THROUGH THE NEXT  
24 HOURS. THERE IS A SLIGHT CHANCE OF A SHOWER OR THUNDERSTORM  
EAST OF KPDX THROUGH 05Z MON. /MH  
 

 
   
MARINE
 
NORTHERLY WINDS CONTINUING AS HIGH PRESSURE RESIDES  
OVER THE NE PAC AND THERMAL LOW PRESSURE ALONG THE NORTHERN  
CALIFORNIA AND SOUTHERN OREGON COAST. TOMORROW THE PRESSURE  
GRADIENT LOOKS TO WEAKEN AS WEAK LOW PRESSURE STARTS TO SAG SOUTH  
FROM VANCOUVER ISLAND. THIS MEANS NORTHERLY WINDS SHOULD STAY  
BELOW 20 KT TONIGHT. A SOUTHERLY FLOW REVERSAL WILL MOVE UP THE  
COAST OVERNIGHT AND MON MORNING. WE WILL RETURN TO THE TYPICAL  
NORTHERLY FLOW PATTERN WED, WITH HIGH PRES OVER THE NE PAC HIGH  
AND THERMAL LOW OVER NORTHERN CALIF. THIS CONTINUES INTO NEXT  
WEEKEND.  
 
SEAS WILL HOVER AROUND 6 TO 8 FT THROUGH MONDAY, BUT SHOULD  
SUBSIDE TO AROUND 5 FT BY TUE AND REMAIN THERE THROUGH THE END  
OF THE WEEK. PYLE  
 

 
   
PQR WATCHES/WARNINGS/ADVISORIES
 
 
OR...NONE.  
WA...NONE.  
PZ...SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 7 AM TO  
11 AM PDT MONDAY.  

 
 

 
 
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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