836  
FXUS66 KPQR 130950  
AFDPQR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PORTLAND OR  
250 AM PDT TUE APR 13 2021  
   
SYNOPSIS
 
HIGH PRESSURE OVER THE REGION WILL MAINTAIN CLEAR SKIES  
AND DRY WEATHER THROUGH THE COMING WEEKEND, WITH GRADUAL WARMING  
TREND. COMBINATION OF HIGH PRESSURE EAST OF THE CASCADES, AND THERMAL  
TROUGH WEST OF THE CASCADES WILL MAINTAIN LIGHT TO MODERATE OFFSHORE  
FLOW. THIS WILL BRING BREEZY EAST TO NORTHEAST WINDS TODAY INTO  
TONIGHT, ALONG WITH RATHER LOW HUMIDITY.  

 
   
SHORT TERM...TODAY THROUGH THURSDAY
 
HIGH PRESSURE OVER THE REGION  
WILL MAINTAIN MOSTLY CLEAR SKIES UNDER A DRY AIR MASS. SURFACE HIGH  
PRESSURE EAST OF THE CASCADES WILL INTERACT WITH THE THERMAL TROUGH  
ALONG THE OREGON/WASHINGTON COAST TO BRING BREEZY EAST TO NORTHEAST  
WINDS TO THE REGION TODAY INTO TONIGHT. PRESSURE GRADIENTS WILL  
GENERALLY BE THE TIGHTEST THIS AFTERNOON INTO THIS EVENING. WOULD  
EXPECT TO SEE STRONGEST WINDS IN THE AFTERNOON INTO TONIGHT, WITH  
GUSTS 25 TO 40 MPH OVER THE HIGHER TERRAIN, AS WELL AS AREAS OF THE  
PORTLAND/VANCOUVER METRO AS MOVE CLOSER TO THE COLUMBIA GORGE.  
THERMAL TROUGH WILL GRADUALLY SHIFT BACK INLAND ON WED, WEAKENING  
PRESSURE GRADIENTS AND RESULTING LESS WIND.  
 
STILL HAVE SOMEWHAT COOLER TEMPERATURES ALOFT, WHICH WILL COUNTERACT  
THE DOWNSLOPE COMPRESSION WARMING DUE TO OFFSHORE FLOW. SO, WILL  
GENERALLY SEE 60S ACROSS REGION, RATHER THAN THE FULL POTENTIAL OF  
REACHING THE 70S. BUT, THAT SAID, A FEW SPOTS ALONG THE COAST COULD  
GET CLOSER TO OR EVEN CRACK 70 DEG TODAY. BUT, WILL DEFINITELY BE A  
DRY DAY, WITH UNSEASONABLY LOW HUMIDITY ACROSS REGION. LIKELY TO SEE  
MINIMUM HUMIDITY OF 15 TO 25 PERCENT TODAY AND LIKELY AGAIN WED.  
 
NOW, ON THURSDAY, THE OFFSHORE GRADIENTS ARE STILL IN PLAY, BUT NOT  
ALL THAT STRONG. AIR MASS ALOFT WILL BE WARMER, THANKS TO RIDGE  
WORKING FURTHER INTO THE PAC NW. ALL AND ALL, WILL SEE TEMPERATURES  
INLAND PUSHING INTO THE 70S, AND WELL INTO THE 60S ALONG THE COAST.  
 
GIVEN THE WARM AFTERNOON TEMPERATURES, BREEZY OFFSHORE WINDS, AND  
VERY DRY AIR MASS, FIRE DANGER WILL BE UNSEASONABLY HIGH AS FINE  
FUELS CONTINUE TO DRY OUT IN WHAT HAS BEEN A VERY DRY APRIL.  
FORTUNATELY, HEAVIER FUELS REMAIN SEASONALLY MOIST AND THERE IS  
PLENTY OF SNOWPACK AT ELEVATIONS ABOVE 2500-3000 FEET. BUT ANYONE  
PLANNING TO BURN SLASH PILES OR YARD DEBRIS SHOULD BE ESPECIALLY  
CAREFUL THROUGH AT LEAST MIDWEEK, AS THESE CONDITIONS DO MAKE IT  
POSSIBLE FOR FINER FUELS TO CARRY FIRE DESPITE IT BEING WELL BEFORE  
OUR TYPICAL FIRE SEASON.  
   
LONG TERM...FRIDAY THROUGH SUNDAY
 
PACIFIC NW WILL REMAIN DRY  
THROUGHOUT THE WEEK AND INTO THE WEEKEND. THE LOW THAT MOVED SOUTH  
TUESDAY WILL CONTINUE TO MOVE SOUTHEAST INTO THE GREAT BASIN,  
MAINTAINING LIGHT TO MODERATE OFFSHORE FLOW THURSDAY. UPPER LEVEL  
HIGH PRESSURE WILL BUILD IN BEHIND THE LOW MAINTAINING DRY CONDITIONS  
AS WELL AS ALLOWING THE THERMAL LOW TO BUILD TO THE SOUTH CONTINUING  
THE OFFSHORE FLOW INTO THE WEEKEND. WITH CONDITIONS REMAINING DRY,  
EXPECT COOL NIGHTS AND WARM AFTERNOONS TO CONTINUE. LONGER RANGE NBM  
GUIDANCE SUGGESTS WE COULD PUSH 80 DEGREES AS WE HEAD INTO THE  
WEEKEND. WEAGLE/BKP  
 

 
   
AVIATION
 
UPPER LEVEL HIGH PRESSURE OFFSHORE AND ACROSS WESTERN  
CANADA DRIVING SYNOPTIC OFFSHORE FLOW EVENT ACROSS THE PACIFIC  
NORTHWEST. WITH HIGHER PRESSURE WELL INLAND AND A THERMALLY  
INDUCED LOWER PRESSURE ALONG THE NORTHERN CALIFORNIA AND SOUTHERN  
OREGON COAST. MODEL SOUNDINGS SHOW GOOD POTENTIAL FOR LLWS FOR  
AREAS NEAR THE GORGE THROUGH ABOUT MIDDAY, THEN WINDS ARE  
EXPECTED TO MIX DOWN TO THE SURFACE. EXPECT NORTH TO  
NORTHEASTERLY WIND GUSTS OF 15 TO 25 KT TO DEVELOP IN THE  
LATER IN THE MORNING THROUGH THE EARLY EVENING HOURS, PARTICULARLY  
ALONG THE COAST AND IN THE WILLAMETTE VALLEY.  
 
FOR DETAILED REGIONAL PAC NW AVIATION WEATHER INFORMATION, GO  
ONLINE TO: HTTPS://WEATHER.GOV/ZSE  
 
KPDX AND APPROACHES...VFR EXPECTED NEXT 24 HOURS. MAIN CONCERN IS  
EASTERLY WINDS TODAY ALONG WITH LLWS. MODEL SOUNDINGS SHOW GOOD  
POTENTIAL FOR LLWS NEAR THE GORGE THROUGH ABOUT MIDDAY, THEN  
WINDS ARE EXPECTED TO MIX DOWN TO THE SURFACE. EXPECT EAST TO  
NORTHEASTERLY WIND GUSTS OF 15 TO 25 KT TO DEVELOP IN THE LATER  
IN THE MORNING THROUGH THE EARLY EVENING HOURS.  
 

 
   
MARINE
 
HIGH PRESSURE CURRENTLY OVER THE NORTHEAST PACIFIC IS  
EXPECTED TO REMAIN IN PLACE FOR MUCH OF THE NEXT WEEK. THERMALLY  
INDUCED LOWER PRESSURE ALONG THE SOUTHERN OREGON COAST WILL  
GRADUALLY SPREAD NORTHWARD RESULTING IN A SUMMER-LIKE GUSTY  
NORTHERLY WIND PATTERN ACROSS THE COASTAL WATERS THROUGH TONIGHT.  
SMALL CRAFT ADVISORIES ARE OUT TODAY FOR ALL ZONES EXCEPT THE  
NEARSHORE ZONE NORTH OF CASCADE HEAD BUT LOCAL GUSTS TO 20-25 KT  
ARE POSSIBLE. THE PATTERN WEAKENS ON WEDNESDAY AS THE THERMALLY  
INDUCED LOWER PRESSURE ALONG THE COAST SHIFTS INLAND THEREBY  
EASING WINDS SOME. HOWEVER, NORTHERLY WINDS CONTINUE THROUGH LATE  
IN THE WEEK AS SURFACE HIGH PRESSURE REMAINS OFFSHORE AND THE  
THERMALLY INDUCED LOWER PRESSURE REBUILDS ALONG THE COAST. THERE  
IS A CHANCE A SOUTHERLY WIND REVERSAL COULD BRING A BRIEF BOUT OF  
GUSTY SOUTHERLY WINDS AND FOG TO THE WATERS OVER THE WEEKEND,  
BUT PLENTY OF UNCERTAINTY EXISTS AT THIS POINT IF IT WILL OCCUR  
AND HOW PRONOUNCED IT WILL BE IF IT DOES.  
 
SEAS ARE CURRENTLY HOVERING AROUND 6 TO 8 FT RANGE ACROSS THE  
WATERS, PRIMARILY SHORT PERIOD WIND WAVES/FRESH SWELL. STRENGTHENING  
NORTHERLY WINDS TODAY WILL BRING AN INCREASING WIND WAVE  
COMPONENT TO THE SEAS. AS A RESULT, SEAS MAY BECOME PARTICULARLY  
STEEP AND HAZARDOUS AS DOMINANT WAVE PERIODS FALL INTO THE 6 TO 8  
SECOND RANGE ACROSS THE WATERS. SEAS SHOULD GENERALLY BE 5 FT OR  
LESS BEGINNING DURING WEDNESDAY AND CONTINUING THROUGH AT LEAST  
THE WEEKEND. /MH  
 

 
   
PQR WATCHES/WARNINGS/ADVISORIES
 
 
OR...NONE.  
WA...NONE.  
PZ...SMALL CRAFT ADVISORY UNTIL 6 AM PDT WEDNESDAY FOR COASTAL  
WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR FROM 10 TO  
60 NM.  
 
SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO 11 PM PDT THIS  
EVENING FOR COASTAL WATERS FROM CASCADE HEAD TO FLORENCE  
OR OUT 10 NM.  
 

 
 

 
 
INTERACT WITH US VIA SOCIAL MEDIA:  
WWW.FACEBOOK.COM/NWSPORTLAND  
WWW.TWITTER.COM/NWSPORTLAND  
 
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