998  
FXUS66 KPQR 182200  
AFDPQR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PORTLAND OR  
300 PM PDT FRI JUL 18 2025  
   
SYNOPSIS
 
STRENGTHENING ONSHORE FLOW WILL BRING CONTINUED  
COOLING THROUGH THE WEEKEND WITH TEMPERATURES FALLING BEFORE  
NORMAL TO BEGIN THE NEXT WORKWEEK. AN UPPER LOW PASSING OVERHEAD  
SUNDAY NIGHT INTO MONDAY MAY BRING THE BEST CHANCES FOR RAIN SO  
FAR THIS MONTH, ALTHOUGH ODDS FOR ACCUMULATING PRECIPITATION  
REMAIN FAIRLY LOW. FORECAST CONFIDENCE DECREASES MIDWEEK,  
ALTHOUGH A RETURN TO WARMER TEMPERATURES IS MOST LIKELY.  
 

 
   
SHORT TERM...NOW THROUGH SUNDAY
 
ANOTHER UPPER-LEVEL SHORTWAVE  
PASSING OVER OR JUST NORTH OF THE REGION THIS AFTERNOON AND  
EVENING WILL USHER IN INTENSIFIED ONSHORE FLOW, CONTINUING THE  
COOLING TREND THROUGH THE WEEKEND. MID-LEVEL TEMPERATURES AROUND  
15C AT 850 HPA TODAY WILL FALL TO 10-11C BY SUNDAY AFTERNOON,  
PUSHING SURFACE TEMPERATURES BELOW SEASONAL NORMALS, WITH  
AFTERNOON HIGHS FALLING TO THE 60S ALONG THE COAST AND IN  
TERRAIN, AND MID 70S TO LOW 80S ALONG THE I-5/I-84 CORRIDORS.  
THE STRONGER ONSHORE PUSH WILL ALSO FAVOR INCREASED LOW CLOUD  
COVER, ESPECIALLY ALONG THE COAST AND INTO COAST RANGE GAPS,  
INCLUDING UP THE COLUMBIA RIVER INTO THE PORTLAND/VANCOUVER  
METRO. COASTAL MIST AND FOG ARE ALSO MOST LIKELY SUNDAY MORNING  
REACHING INTO WEST-FACING COAST RANGE VALLEYS. WEST TO NORTHWEST  
WINDS WILL ALSO STRENGTHEN MODESTLY, WITH GUSTS AS HIGH AS  
30-35 MPH THROUGH THE COLUMBIA GORGE EACH AFTERNOON. -PICARD  
 
   
LONG TERM...SUNDAY NIGHT THROUGH FRIDAY
 
BY SUNDAY NIGHT INTO  
MONDAY, THERE IS INCREASING CONSENSUS THAT A VIGOROUS UPPER  
SHORTWAVE WILL DIVE SOUTHWARD OVER THE HAIDA GWAII AND  
VANCOUVER ISLAND, RESULTING IN ELONGATED UPPER TROUGHING OR EVEN  
A CUTOFF LOW CENTERED DEVELOPING OVER THE PACIFIC NW. WHILE  
THIS WAVE MAY SUPPORT LIGHT RAIN REACHING INTO THE REGION TO  
START THE WORKWEEK, CHANCES REMAIN FAIRLY LOW, ONLY 15-25% ALONG  
THE COAST AND IN THE COAST RANGE, AND SLIGHTLY LOWER IN THE  
CASCADES AND FOOTHILLS. IT'S WORTH NOTING THAT AN INCREASED  
NUMBER OF GLOBAL ENSEMBLE MEMBERS ARE SHOWING ACCUMULATING RAIN  
AS WELL AS ANOMALOUSLY HIGH VALUES OF PRECIPITABLE WATER,  
GENERALLY 1-1.25" ACROSS THE FORECAST AREA, WHICH WOULD BE ABOVE  
THE 90TH CLIMATOLOGICAL PERCENTILE OF KSLE SOUNDING OBSERVATIONS.  
WITH LIGHT MEAN CLOUD-LEVEL WINDS, AROUND 5 KT, SLOW-MOVING  
CONVECTIVE SHOWERS WHICH COULD WRING OUT A TRUE WETTING RAIN IN  
SOME AREAS CANNOT BE RULED OUT.  
 
NUMERICAL GUIDANCE THEN DIVERGES TOWARD THE MIDDLE OF THE WEEK  
AS THE EVOLUTION OF THE TROUGH OR CUTOFF LOW REMAINS SOMEWHAT  
LOW CONFIDENCE. MANY ENSEMBLE MEMBERS ARE CONTINUING TO FAVOR  
ANOTHER CUTOFF UPPER LOW DEVELOPING NEAR CAPE MENDOCINO WHILE  
THE MEAN FLOW TO THE NORTH RETURNS TO A MORE ZONAL PATTERN. IN  
THIS SCENARIO, HEIGHTS RISING ALOFT AND MODERATING MID-LEVEL  
TEMPERATURES WOULD FAVOR A WARMING TREND AT THE SURFACE, WHILE  
SOUTHERLY TO SOUTHEASTERLY FLOW ABOUT THE EASTERN FLANK OF THE  
UPPER LOW COULD GENERATE CONVECTION OVER THE CASCADES. -PICARD  
 

 
   
AVIATION
 
INLAND, VFR CONDITIONS ARE EXPECTED BENEATH  
INCREASING CIRRUS CLOUDS AT OR ABOVE 25 KFT THROUGH THIS  
EVENING. A STRONGER MARINE PUSH MAY RESULT IN FEW-SCT LOW  
STRATUS REACHING UP THE COLUMBIA RIVER TO PORTLAND-AREA  
TERMINALS (KPDX, KHIO, KVUO, KTTD), BUT SUFFICIENT COVERAGE TO  
YIELD MVFR CIGS IS UNLIKELY, ONLY A 10-20% CHANCE AFTER 12-15Z  
SAT. AT THE COAST, EXPECT LOW MARINE STRATUS WITH HIGH-END IFR  
TO LOW-END MVFR CIGS TO PERSIST AT KAST THROUGH 00Z SUNDAY.  
FORECAST CIGS ARE A BIT MORE UNCERTAIN AT KONP. ALTHOUGH KONP  
WAS MOSTLY CLEAR AS OF 2130Z FRIDAY, LOW MARINE STRATUS WILL  
EVENTUALLY MOVE BACK IN THIS EVENING, HOWEVER THE EXACT ONSET  
TIMING IS UNCERTAIN AND COULD OCCUR ANYWHERE BETWEEN 00-05Z  
SATURDAY. GIVEN THE STRONGER MARINE PUSH THIS EVENING, SUSPECT  
TIMING WILL BE CLOSER TO 00Z RATHER THAN TO 05Z.  
 
DIURNAL WEST TO NORTHWEST WINDS BUILD TO 5-10 KT WITH OCCASIONAL  
GUSTS OF 15-20 KT THIS AFTERNOON, THEN DIMINISH TO 5 KT OR LESS  
TONIGHT.  
 
PDX AND APPROACHES...CONTINUED VFR CONDITIONS EXPECTED THROUGH  
THE PERIOD. HIGH CIRRUS COVERAGE INCREASES THROUGH THIS  
AFTERNOON, THEN SCATTERED LOW CLOUDS DEVELOP OVERNIGHT AS A  
STRONGER MARINE PUSH TAKES PLACE. THERE IS A 10-20% CHANCE FOR  
SUFFICIENT STRATUS COVERAGE TO YIELD MVFR CIGS AFTER 12-15Z SAT  
BEFORE STRATUS MIXES OUT BY 18Z SAT. NORTHWEST WINDS REMAIN  
AROUND 10 KT THIS AFTERNOON WITH GUSTS UP TO 15-20 KT, BEFORE  
EASING TO 5 KT OR LESS AFTER 06Z SAT. -TK/PICARD  
 

 
   
MARINE
 
WHILE WINDS REMAIN WEAK ACROSS THE WATERS, HIGH  
PRESSURE WILL MAINTAIN NORTHERLY TO NORTHWESTERLY WINDS THROUGH  
NEXT WEEK, HOWEVER WINDS WILL REMAIN RELATIVELY WEAK AND SHOULD  
STAY UNDER 10-15 KT. SEAS SHOULD SUBSIDE TO 5 TO 6 FT FRIDAY  
EVENING AND THEN STAY AT OR BELOW 5 FT THROUGH THE UPCOMING  
WEEK. THERE ARE NO SIGNS CONDITIONS WILL MEET SMALL CRAFT  
ADVISORY CRITERIA OVER THE COASTAL WATERS AT THIS TIME. -TK  
 

 
   
PQR WATCHES/WARNINGS/ADVISORIES
 
 
OR...NONE.  
WA...NONE.  
PZ...NONE.  
 

 
 

 
 
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