382  
FXUS66 KPQR 142223  
AFDPQR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PORTLAND OR  
323 PM PDT SAT SEP 14 2024  
   
SYNOPSIS
 
A FALL-LIKE WEATHER PATTERN WILL CONTINUE OVER THE  
NEXT WEEK. CHANCES FOR LIGHT SHOWERS THIS WEEKEND, HOWEVER MOST  
LOCATIONS WILL BE DRY. DRY AND MILD CONDITIONS ON MONDAY WILL  
GIVE WAY TO COOL AND WET CONDITIONS TUESDAY INTO WEDNESDAY AS A  
STRONG FRONTAL SYSTEM BRINGS WIDESPREAD RAIN TO THE AREA. DRIER  
AND WARMER CONDITIONS RETURN AGAIN LATE IN THE WEEK.  
 

 
   
SHORT TERM...NOW THROUGH MONDAY NIGHT
 
RADAR, SATELLITE, AND  
SURFACE OBSERVATIONS AS OF 230 PM PDT DEPICT BROKEN CLOUD COVER  
ACROSS THE AREA WITH SCATTERED SHOWERS ALONG THE NORTH OR/SOUTH  
WA COAST AS A BROAD UPPER LEVEL TROUGH DIPS SOUTHWARD FROM  
BRITISH COLUMBIA. AS THIS TROUGH CONTINUES TO MOVE SOUTH, EXPECT  
CHANCES (15-40%) FOR LIGHT SHOWERS TO CONTINUE ACROSS NORTHWEST  
OREGON AND SOUTHWEST WASHINGTON. ANY ADDITIONAL PRECIPITATION  
THROUGH TOMORROW MORNING WILL LIKELY AMOUNT TO LESS THAN A  
TENTH OF AN INCH, WITH MOST LOCATIONS REMAINING COMPLETELY DRY.  
 
TONIGHT INTO TOMORROW (SUNDAY), THE UPPER LEVEL TROUGH WILL  
CONTINUE TO ELONGATE AND MOVE FURTHER SOUTH TOWARD CALIFORNIA.  
AT THIS POINT, IT ALMOST BECOMES A CLOSED LOW. CONDITIONS WILL  
STILL REMAIN MOSTLY DRY FOR US, THOUGH THERE WILL BE SOME  
SPOTTY CHANCES (15-40%) FOR SHOWERS TOMORROW. THE HIGHEST  
CHANCES OF SHOWERS WILL BE SOUTH OF SALEM AND ALONG HIGHER  
TERRAIN OF THE CENTRAL OREGON COAST RANGE AND CASCADES GIVEN  
THE TRACK OF THIS LOW. AFTERNOON HIGHS ARE FORECAST TO REMAIN  
SLIGHTLY BELOW NORMAL, WITH LOW 70S FOR INTERIOR LOWLANDS, LOW  
TO MID 60S ALONG THE COAST, AND 50S IN THE CASCADES. BY SUNDAY  
EVENING/NIGHT, PRECIPITATION CHANCES DIMINISH AS THE UPPER  
LOW COMPLETELY EXITS THE AREA.  
 
EXPECT WIDESPREAD DRY CONDITIONS MONDAY THROUGH MONDAY NIGHT AS  
DRY NORTHEAST FLOW ALOFT DEVELOPS ON THE BACKSIDE OF THE  
AFOREMENTIONED LOW. MONDAY IS SHAPING UP TO BE THE SUNNIEST AND  
WARMEST DAY OF THE WEEK WITH HIGH TEMPS MOST LIKELY IN THE MID  
TO UPPER 70S FOR INTERIOR LOWLANDS AND MID TO UPPER 60S ALONG  
THE COAST. THAT SAID, CANNOT RULE OUT TEMPS A BIT WARMER THAN  
THAT AS THE NBM IS SHOWING A 10-20% CHANCE FOR HIGH TEMPS OF 80  
DEGREES OR WARMER WITHIN THE WILLAMETTE VALLEY. MONDAY WILL BE  
AN EXCELLENT DAY FOR OUTDOOR ACTIVITIES, ESPECIALLY GIVEN THE  
RAPID CHANGE TO COOL AND WET WEATHER EXPECTED THE FOLLOWING DAY.  
THIS SYSTEM IS DISCUSSED BELOW IN THE LONG TERM DISCUSSION.  
-ALVIZ/TK  

 
   
LONG TERM...TUESDAY THROUGH FRIDAY
 
CONDITIONS WILL DETERIORATE  
QUICKLY ON TUESDAY AS A STRONGER FRONTAL SYSTEM BRINGS MORE  
SIGNIFICANT MOISTURE INTO THE REGION. THERE IS HIGH CONFIDENCE  
FOR WIDESPREAD RAIN, AS EVERY SINGLE MEMBER FROM THE GEFS/GEPS/ENS  
ARE SHOWING QPF AND NBM POPS ARE OVER 90%. IN TERMS OF TIMING,  
EXPECT RAIN TO BEGIN EARLY TUESDAY MORNING AND LAST THROUGH  
EARLY WEDNESDAY MORNING BEFORE BECOMING MORE SHOWERY.  
 
DESPITE THE HIGH CONFIDENCE IN RAIN OCCURRING, THERE IS STILL  
UNCERTAINTY WITH EXACT RAIN AMOUNTS. THE "DRIEST" SCENARIO  
DEPICTED BY THE 10TH PERCENTILE NBM SHOWS 24 HR QPF AMOUNTS  
OF 0.30-0.40 INCH ALONG THE COAST/COAST RANGE AND 0.10-0.20 INCH  
EAST OF THE COAST RANGE, ENDING 5 AM WEDNESDAY. THE "WETTEST"  
SCENARIO DEPICTED BY THE 90TH PERCENTILE NBM SHOWS 1.25-1.75  
INCHES ALONG THE COAST AND MOUNTAINS, AND 0.75-1.25 INCHES FOR  
INTERIOR LOWLAND VALLEYS. FOR NOW, THE CURRENT FORECAST CALLS  
FOR 0.40-0.60 INCH IN THE WILLAMETTE VALLEY AND 0.50-0.75 ALONG  
THE COAST AND MOUNTAINS.  
 
NBM PROBABILITIES FOR A WETTING RAIN (0.25 INCH/12 HOURS) IS  
HIGH (70-90%) ACROSS THE REGION, SO THIS SYSTEM IS CAPABLE OF  
PUTTING A SIGNIFICANT DAMPER ON WILDFIRE ACTIVITY REGARDLESS OF  
UNCERTAINTY ON EXACT RAIN AMOUNTS. THIS SYSTEM WILL ALSO BRING  
TEMPS AROUND 10-15 DEGREES BELOW NORMAL FOR THIS TIME OF YEAR  
WITH HIGHS LIKELY IN THE LOW TO MID 60S ON TUESDAY.  
 
EXPECT POST-FRONTAL SHOWERS ON WEDNESDAY WITH CONDITIONS DRYING  
OUT WEDNESDAY NIGHT INTO THURSDAY. TEMPERATURES WILL REBOUND TO  
NEAR SEASONAL AVERAGES FOR INTERIOR LOWLAND VALLEYS HEADING  
INTO NEXT WEEKEND. -ALVIZ/TK  
 

 
   
AVIATION
 
WEST TO NORTHWEST FLOW ALOFT, WITH CONSIDERABLE LOWER  
AND MID-LEVEL CLOUDS TODAY. MIX BAG ALONG THE COAST INTO COAST  
RANGE, WITH WIDESPREAD MVFR AND IFR POCKETS. AS WEAK FRONT ALONG THE  
COAST MOVES FURTHER INLAND, WILL SEE SLIGHT IMPROVEMENT ALONG THE  
COAST, WITH MIX OF MVFR AND VFR CIGS.  
 
FARTHER INLAND, SHOULD REMAIN VFR, WITH CIGS 4000 TO 5500 FT. LOWEST  
CIGS EXPECTED TO FROM PORTLAND NORTHWARD, AND AGAINST THE CASCADES  
LATER THIS EVENING. SHOWERS END OVERNIGHT, BUT WILL SEE CIGS REFORM  
AT 3000 TO 4000 FT. LITTLE IMPROVEMENT EARLY SUN AM.  
 
PDX APPROACHES...LITTLE CHANGE INTO THIS EVENING, WITH CIGS 3500 TO  
4500 AND FEW LIGHT SHOWERS OR DRIZZLE AT TIMES.CLOUDS BREAK APART A  
BIT OVERNIGHT, BUT THE 3000 TO 4000 FT CIGS WILL REFORM OVERNIGHT,  
PERSISTING INTO SUNDAY AM. /ROCKEY  
 

 
   
MARINE
 
HIGH PRESSURE OVER THE OUTER WATERS WILL BUILD TONIGHT  
INTO SUNDAY. AS SUCH, WILL MAINTAIN THE NORTHERLY PRESSURE  
GRADIENTS, WITH GUSTY NORTH WINDS SUNDAY NIGHT. WILL MAINTAIN  
CURRENT SMALL CRAFT ADVISORY FOR LATE SUN AFTERNOON INTO MONDAY AM,  
WHERE HAVE GUSTS 20 TO 25 KT. DOES APPEAR WILL GET SOME GUSTS IN  
SIMILAR RANGE CLOSER TO SHORE, BUT SUSPECT MOST OF THESE WILL BE  
STAY JUST OFFSHORE. WILL EXPAND SMALL CRAFT ADVISORY TO INCLUDE THE  
NEARSHORE WATERS (0-10 NM OFFSHORE), FOR SUNDAY NIGHT. SEEMS  
GRADIENTS RELAX EARLY MONDAY AM, WITH LESS WINDS AT THAT TIME.  
OVERALL, SEAS STAY IN 5 TO 8 FT THROUGH MONDAY, WITH HIGHEST SEAS  
WELL OFFSHORE.  
 
THEN, A TASTE OF FALL. A STRONG FRONT WILL PUSH ACROSS THE WATERS  
TUESDAY AS IT ELONGATES/WEAKENS OVER THE COASTAL WATERS. WINDS NOT  
REALLY TURNING TO SOUTHERLY (AS DO WITH MOST FRONTS), BUT MAY  
BRIEFLY GET BURST OF WEST TO SOUTHWEST WINDS OF 20 TO 25 KT WITH THE  
FRONTAL PASSAGE. MODELS VARY SOME ON THE TIMING/STRENGTH OF THIS  
SYSTEM, SO WILL SEE HOW THINGS SHAPE UP AS GET CLOSER IN TIME TO  
NEXT TUE.  
 

 
   
PQR WATCHES/WARNINGS/ADVISORIES
 
 
OR...NONE.  
WA...NONE.  
PZ...SMALL CRAFT ADVISORY FROM 5 PM SUNDAY TO 5 AM PDT MONDAY FOR  
PZZ252-253.  
 
SMALL CRAFT ADVISORY FROM 5 PM SUNDAY TO 11 AM PDT MONDAY FOR  
PZZ272-273.  

 
 

 
 
WWW.WEATHER.GOV/PORTLAND  
 
INTERACT WITH US VIA SOCIAL MEDIA:  
WWW.FACEBOOK.COM/NWSPORTLAND  
X.COM/NWSPORTLAND  
 
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