676  
FXUS66 KPQR 260950 RRA  
AFDPQR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PORTLAND OR  
249 AM PDT WED APR 26 2017  
   
SYNOPSIS
 
ANOTHER WET DAY, WITH SNOW IN THE CASCADES. RAIN WILL  
TRANSITION TO SHOWERS LATER TODAY. BUT, SHOWERY WEATHER WILL CONTINUE  
THROUGH THU. DOES APPEAR WILL HAVE A BREAK FOR LATER FRI AND SAT,  
WITH DRY AND MILD CONDITIONS. BUT, WILL SEE THREAT OF RAIN RETURN  
LATER SAT NIGHT AND SUN. WITH ALL THESE APRIL SHOWERS, JUST IMAGINE  
THE SIZE OF THOSE COMING MAYFLOWERS.  

 
   
SHORT TERM...(TODAY THROUGH FRI)
 
RATHER ACTIVE AND MOIST JET LIES  
OFFSHORE, AND CONTINUES TO AIM ITSELF RIGHT OVER THE PAC NW TODAY  
INTO TONIGHT. NEXT BOUNDARY WILL PUSH ONSHORE AROUND MID-MORNING,  
WITH RAIN QUICKLY TRANSITIONING TO SHOWERS. WILL MAINTAIN THIS TREND,  
WITH DECREASING SHOWERS FROM WEST TO EAST ACROSS THE REGION THIS  
AFTERNOON. SHOWERS WILL PERSIST WELL INTO THIS EVENING IN THE  
CASCADES, THANKS TO FAVORABLE OROGRAPHIC FLOW.  
 
NOW, THERE IS A DEVELOPING WAVE ON THE TRAILING PART OF THE FRONT,  
BUT NOW APPEARS THAT THIS WILL PUSH INLAND OVER SOUTHWESTERN OREGON.  
MODELS AGREE FOR THE MOST PART, AS HEAVIEST RAIN ASSOCIATED WITH THIS  
WAVE MAINLY FOCUSED FROM COAST RANGE OF WEST CENTRAL OREGON EXTENDING  
INTO PARTS OF SOUTHWEST OREGON. PRECIPITABLE WATER VALUES SUPPORT  
DECENT SHOT OF RAINFALL THIS AM IN THOSE AREAS, WITH 0.50 TO 0.75  
INCH NOT OUT OF THE QUESTION. BUT, HEAVIEST PRECIPITATION MAY WIND UP  
FALLING OVER THE CASCADES FROM SANTIAM PASS SOUTHWARD TO NEAR CRATER  
LAKE. IF SO, THIS COULD BE QUITE A GOOD ACCUMULATION OF SNOWFALL FOR  
TODAY INTO EARLY THIS EVENING. CURRENT WINTER WEATHER ADVISORY FOR  
SNOW ABOVE 4500 FEET IN THE CASCADES LOOKS REASONABLE, WITH 6 TO 12  
INCHES LIKELY. AS USUAL, HEAVIEST SNOW WOULD BE ON HIGHER  
PEAKS/RIDGES, MAINLY ABOVE 5000 FEET. WILL EXTEND ADVISORY OUT TO 7  
PM TODAY, AS SHOWERS WILL PERSIST INTO EARLY EVENING.  
 
SHOWERS WILL GRADUALLY DECREASING TONIGHT. BUT NOT EXPECTING MUCH  
CHANGE IN OVERALL AIR MASS ON THU. A FEW PASSING EMBEDDED  
DISTURBANCES IN THE WESTERLY FLOW ON THU WILL BE ENOUGH TO  
DESTABILIZE AIR MASS BIT MORE, WITH SHOWERS INCREASING AGAIN LATER  
THU AM INTO THE AFTERNOON. SNOW LEVELS REMAIN BETWEEN 3500 AND 4500  
FEET, BUT WITH LESS PRECIPITATION AMOUNTS WILL RESULT IN ONLY A FEW  
INCHES OF NEW SNOW. SHOWERS WILL GRADUALLY DECREASE THU NIGHT.  
 
NOW, AFTER ALL THE RAIN, WE WILL NEED A BREAK. INDEED, IT APPEARS  
THAT BREAK ARRIVES ON FRI. STILL A MINOR THREAT OF SHOWERS, BUT THINK  
EVEN THAT THREAT WILL BE OVER THE CASCADES. OTHERWISE, WILL TREND TO  
PARTLY SUNNY SKIES WITH MILD TEMPERATURES. ROCKEY.  
 
   
LONG TERM...FRIDAY NIGHT THROUGH TUESDAY
 
SHOWERS CONTINUE TO  
FURTHER DIMINISH LATER FRIDAY THROUGH SATURDAY AS AN UPPER LEVEL  
RIDGE OVER THE EASTERN PACIFIC WILL FURTHER AMPLIFY IN BETWEEN LOW  
PRESSURE SYSTEMS BOTH UPSTREAM AND DOWNSTREAM. NOT QUITE CONFIDENT  
ENOUGH YET TO BRING SKY COVER TO MOSTLY SUNNY WORDING, BUT DID TREND  
THINGS THAT DIRECTION. MEANWHILE, TEMPERATURES WILL ALSO RESPOND  
ACCORDINGLY WITH HIGH TEMPERATURES IN THE AFTERNOON WARMING INTO THE  
MID 60S - ALL THE WAY TO AROUND SEASONAL NORMALS, AT LEAST FOR ONE  
DAY! HOWEVER, THIS WILL BE YET ANOTHER ONLY SHORT-LIVED INTERMISSION  
IN THE SEASON OF STEADY RAIN. A WEAKENING FRONTAL SYSTEM WILL BRING  
INCREASING ROUND OF CLOUDS, ANOTHER CHANCE OF RAIN, AND SLIGHTLY  
COOLER TEMPERATURES. FORECAST MODELS DO DIVERGE A BIT THE FIRST HALF  
OF NEXT WEEK, BUT AS WE TRANSITION TO MAY THERE IS SOME POTENTIAL  
FOR A BIT OF SHIFT IN THE PATTERN. AT THIS POINT, TRENDED THE  
FORECAST DRY FOR MONDAY AND TUESDAY, BUT DID SO SOMEWHAT CAUTIOUSLY  
FOR TWO REASONS - FIRST, ENSEMBLE MEMBERS CONTINUE TO SUGGEST A  
SOMEWHAT LARGE SPREAD IN POSSIBLE SOLUTIONS; SECOND, WE'VE SEEN THIS  
SORT OF PATTERN IN THE MODELS SEVERAL TIMES IN RECENT WEEKS, WHERE A  
SEEMING TREND TOWARD DRY CONDITIONS AND A BUILDING RIDGE FAILS TO  
APPEAR. THAT SAID, THIS WOULD BE CONSISTENT WITH THE LATEST CPC 6-10  
OUTLOOK OF WARMER AND DRIER THAN AVERAGE MAY 1-5 PERIOD. AN ABUNDANCE  
OF WORDS TO SAY THE FORECAST WAS TRENDED THIS DIRECTION BUT WITH  
LOWER THAN TYPICAL CONFIDENCE. CULLEN  

 
   
HYDROLOGY
 
THE LOWER COLUMBIA RIVER WILL BE RUNNING ABOVE BANKFULL  
FOR THE NEXT SEVERAL DAYS. PRIMARY AREAS OF CONCERN ARE THE COLUMBIA  
NEAR VANCOUVER AND DOWNSTREAM PAST THE COLUMBIA NEAR LONGVIEW TO THE  
MOUTH. CONTRIBUTIONS TO THE HIGH FLOW ARE COMING FROM HIGH  
ASTRONOMICAL TIDES IN ADDITION TO INCREASED RUNOFF FROM THE SNAKE  
RIVER AND WILLAMETTE RIVER BASINS. LOWER REACHES OF TRIBUTARIES  
FLOWING INTO THE COLUMBIA RIVER MAY ALSO EXPERIENCE PERIODS OF  
ELEVATED WATER DURING THE HIGH TIDE CYCLES. PLEASE CONTINUE TO  
MONITOR THE FORECASTS FOR THE NEXT SEVERAL DAYS. /JBONK  

 
   
AVIATION
 
MOIST ONSHORE FLOW CONTINUES TODAY. AN UPPER LEVEL  
SHORTWAVE WILL MOVE ACROSS THE AREA THIS MORNING, PROVIDING  
BROAD LIFT OVER THE AREA. RAIN WILL INCREASE THIS MORNING AND  
TAPER OFF LATER THIS AFTERNOON. MVFR CONDITIONS ARE LIKELY AT THE  
COAST. LOCAL IFR CIGS AND VIS ARE POSSIBLE THROUGH THE  
AFTERNOON. INLAND AREAS STARTING OFF WITH VFR AND LOCAL MVFR  
CIGS, BUT AS RAIN INCREASES WITH INCOMING SYSTEM MVFR CONDITIONS  
SHOULD BECOME MORE WIDESPREAD. RAIN TAPERS OFF MID TO LATE IN THE  
AFTERNOON WITH COOLER AIR ALOFT ARRIVING. THIS SHOULD HELP  
IMPROVE CONDITIONS TO PREDOMINANTLY VFR. MODEL OUTPUT INFO: 00Z  
MOS GUIDANCE SEEM TO HAVE CAUGHT UP ON IFR CONDITIONS FROM TUE  
EVENING AND CONTINUE WITH LOW MVFR TO IFR CONDITIONS INLAND THIS  
MORNING AND AFTERNOON FOLLOWING BY IMPROVING CONDITIONS. THIS  
SEEMS OVERDONE GIVING THE OCCLUDED FRONT YESTERDAY WAS STRONGER  
THAN WHAT MODELS ARE SUGGESTING FOR TODAY.  
 
KPDX AND APPROACHES...VFR EARLY WITH LOCAL MVFR IN THE AREA.  
SHOULD SEE MVFR CONDITIONS INCREASE AFTER 15Z OR SO AND CONTINUE  
THROUGH ABOUT 21Z WITH IMPROVING CONDITIONS FOLLOWING./MH  
 

 
   
MARINE
 
WIND SLOWLY SETTLING DOWN AND ARE MOSTLY BELOW ADVISORY  
CRITERIA. THERE ARE A FEW SPOTS GUSTING IN THE 20-25 KNOT RANGE.  
WINDS WILL CONTINUE IN THE 15 TO 20 KNOT RANGE THIS MORNING AND  
SLOWLY DECREASE IN THE AFTERNOON. SEAS RUNNING 7 FT WITH SHORT  
PERIOD WHICH WILL CREATE SOME ROUGH CONDITIONS, THIS SHOULD ABATE  
EARLY THIS MORNING.  
 
BROADER HIGH PRESSURE BUILDS OVER THE NE PAC KEEPING A RELATIVE  
LULL IN WINDS THROUGH FRIDAY. SEAS MAY NEXT REACH 10-11 FT  
THURSDAY THROUGH EARLY FRIDAY AS THE SOUTHERN END OF A SWELL  
TRAIN CLIPS THE NORTHERN WATERS FROM A SURFACE LOW CROSSING THE  
ALASKAN PANHANDLE. /MH TW  
 

 
   
PQR WATCHES/WARNINGS/ADVISORIES
 
 
OR...WINTER WEATHER ADVISORY UNTIL 7 PM TODAY FOR CASCADES IN  
LANE COUNTY AND NORTHERN OREGON CASCADES.  
 
WA...NONE.  
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 AM PDT EARLY  
THIS MORNING FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO  
FLORENCE OR OUT 60 NM.  
 
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 7 AM  
PDT THIS MORNING.  
 
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 4 PM  
THIS AFTERNOON TO 8 PM PDT THIS EVENING.  
 

 
 
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. THE AREA IS  
COMMONLY REFERRED TO AS THE FORECAST AREA.  
 
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