408  
FXUS66 KPQR 261532  
AFDPQR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PORTLAND OR  
830 AM PDT SUN MAR 26 2017  
   
SYNOPSIS
 
AND THE WET WEATHER CONTINUES. RAINY TODAY, BUT FRONT  
WILL PUSH ONSHORE LATER THIS AFTERNOON WITH TRANSITION TO SHOWERS.  
SNOW IN THE CASCADES, ESPECIALLY ABOVE THE PASSES. SHOWERS CONTINUE  
ON MON, BUT WILL SEE BRIEF BREAK IN RAIN ON TUE. BUT, THAT SHORT  
LIVED AS ANOTHER ROUND OF RAIN WILL SPREAD INTO THE REGION TUE NIGHT.  
STILL LOOKS GOOD FOR A BREAK WITH DRY AND MILD CONDITIONS AS WE  
PREPARE TO CLOSE MARCH LATER THIS WEEK.  
 

 
 
   
SHORT TERM...(TODAY THROUGH TUESDAY)
 
NO CHANGES IN FORECASTS.  
VERY ACTIVE AND PROGRESSIVE PATTERN CONTINUES ACROSS THE NORTH  
PACIFIC TODAY, WITH THE LATEST IN THE SERIES OF FRONTS APPROACHING  
THE PAC NW COAST EARLY THIS MORNING. SIMILAR TO OUR LAST COUPLE OF  
SYSTEMS, THIS FRONT IS OCCLUDING WHILE MOVING ONSHORE. THIS WILL  
ALLOW COOLER AIR TO LINGER OVER THE CASCADES AS PRECIPITATION  
DEVELOPS, ESPECIALLY MOUNT JEFFERSON NORTHWARD. AS A RESULT, SNOW  
LEVELS ARE LIKELY TO START OFF BELOW PASS LEVEL THIS MORNING. THE  
OREGON CASCADES MAY BRIEFLY GET INTO THE WARM SECTOR FOR A FEW HOURS  
THIS AFTERNOON; THE COMBINATION OF THAT AND STRONGER LATE MARCH SOLAR  
HEATING (DESPITE BEING BEHIND CLOUDS) MAY BE ENOUGH TO ALLOW THE  
PASSES TO BE WET OR SLUSHY THIS AFTERNOON. THE HIGHER SKI RESORT  
ELEVATIONS WILL SEE PRIMARILY SNOW FROM THIS SYSTEM, AND WITH OVERALL  
QPF POSSIBLY OVER AN INCH IN THE CASCADES THROUGH MONDAY, THE HIGHER  
CASCADES COULD SEE UP TO A FOOT OF SNOW BY THE TIME SNOW SHOWERS  
TAPER OFF MON NIGHT.  
 
FOR THE LOWER ELEVATIONS, THIS WILL BE ANOTHER MODEST RAINFALL WITH  
AROUND 0.25 TO 0.50" FOR THE INLAND VALLEYS, 0.50 TO 1.00" FOR THE  
COAST, AND 1 TO 2 INCHES FOR THE COAST RANGE.  
 
THE OCCLUDING FRONT WILL PUSH EAST OF THE CASCADES LATE THIS  
AFTERNOON AND EVENING, WITH COOLER AIR ALOFT PUSHING IN BEHIND THE  
FRONT WITH THE PARENT UPPER TROUGH. IT APPEARS THE CORE OF COLDEST  
AIR ALOFT WILL MOVE THROUGH WELL BEFORE PEAK HEATING MONDAY, SO THE  
THUNDER/CONVECTION THREAT IS NOT QUITE WHAT IT WAS LAST FRIDAY.  
NONETHELESS, WITH THE 00Z GFS SHOWING 500 MB TEMPS AS LOW AS -30 DEG  
C OVER THE COASTAL WATERS LATE TONIGHT AND EARLY MON, WE DECIDED IT  
WOULD BE PRUDENT TO MENTION A SLIGHT CHANCE OF THUNDER ALONG THE  
COAST AND OVER THE COASTAL WATERS. 00Z GFS 1000-700 MB LIFTED INDICES  
REMAIN BELOW ZERO DEG C THROUGH MONDAY, SO SHOWERS WILL LIKELY BE  
NUMEROUS ACROSS THE FORECAST AREA MONDAY. HOWEVER, A STRENGTHENING  
CAP JUST BELOW 500 MB WILL PROBABLY KEEP CONVECTION SHALLOW ENOUGH TO  
MITIGATE THE THREAT OF THUNDER.  
 
SHOWERS DECREASE MONDAY NIGHT AS THE ONSHORE FLOW DECREASES,  
SUBSIDENCE ASSOCIATED WITH HIGH PRESSURE INCREASES, AND WARM  
ADVECTION ALOFT STABILIZES THE ATMOSPHERE. BASED ON LATEST GUIDANCE,  
FLAT UPPER LEVEL RIDGING WILL PROBABLY SUCCEED IN BUILDING ACROSS  
OREGON, SHOVING THE JET STREAM A LITTLE FURTHER NORTH INTO WASHINGTON  
AS THE NEXT SYSTEM MOVES TOWARD THE COAST TUESDAY. THE RESULT WILL  
LIKELY BE A MOSTLY DRY AND MILD DAY SALEM SOUTHWARD, WITH MORE IN THE  
WAY OF CLOUDINESS FOR THE PDX METRO AND A CONTINUED CHANCE OF RAIN  
ACROSS MUCH OF SW WASHINGTON TUESDAY. WEAGLE  
   
LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
 
UPPER-LEVEL PATTERN  
BECOMES MORE AMPLIFIED LATER NEXT WEEK, BEHIND A TROUGH THAT WILL  
BRING MORE RAIN TUESDAY NIGHT INTO WEDNESDAY, TRANSITIONING TO  
SHOWERS ON THURSDAY. THIS MEANS A RIDGE BUILDS UP OVER THE PACIFIC  
NORTHWEST FRIDAY FOR A DRY AND MILD DAY. MODELS ARE IN REMARKABLY  
GOOD AGREEMENT WITH THIS RIDGE FOR HOW FAR OUT IT IS IN THE FORECAST  
PERIOD, INCREASING CONFIDENCE. MODELS HOWEVER HAVE THE RIDGE  
FLATTENING WITH AN APPROACHING BROAD TROUGH, WITH SIGNIFICANT  
DIFFERENCES IN TIMING BETWEEN THE ECMWF (SATURDAY) AND THE GFS  
(MONDAY). EITHER SCENARIO WILL BRING RAIN BACK TO THE AREA WITH THE  
FLATTENING OF THIS RIDGE. SNOW LEVELS GENERALLY HOVER AROUND 4000 TO  
5000 FEET, EXCEPT FOR WEDNESDAY AND FRIDAY WHEN THEY GO UP TO 6-8000  
FEET. TEMPERATURES GENERALLY REMAIN WITHIN A FEW DEGREES OF LATE  
MARCH NORMALS THROUGH THE EXTENDED PERIOD, WITH WEDNESDAY BEING THE  
COOLEST DAY AS THE UPPER TROUGH SWINGS THROUGH. -MCCOY/WEAGLE  
 

 
 
   
AVIATION
 
PREDOMINANT VFR CONDITIONS THIS MORNING AS RAIN  
SPREADS ACROSS THE AREA. SOME MVFR CIGS AND VISIBILITIES ARE  
MIXING IN AT TIMES, BUT DO NOT EXPECT MVFR CONDITIONS TO BECOME  
MORE WIDESPREAD UNTIL THIS AFTERNOON WHEN THE FRONT MOVES  
THROUGH. ALONG AND AHEAD OF THE FRONT, EXPECT A BRIEF PERIOD OF  
MVFR VISIBILITIES AND POSSIBLY CEILINGS THAT WILL QUICKLY IMPROVE  
ONCE AGAIN BEHIND THE FRONT. BEHIND THE FRONT THIS  
EVENING/OVERNIGHT, CONDITIONS WILL BE MOSTLY VFR WITH OCCASIONAL  
MVFR CONDITIONS IN THE HEAVIEST RAIN SHOWERS.  
 
KPDX AND APPROACHES...MOSTLY VFR CONDITIONS EXCEPT FOR A BRIEF  
SEVERAL HOUR WINDOW THIS AFTERNOON ALONG AND AHEAD OF THE FRONT  
WHEN MVFR VISIBILITIES AND POSSIBLY CIGS WILL MOVE THROUGH.  
CONDITIONS WILL IMPROVE AFTER THIS WITH VFR CONDITIONS EXCEPT  
FOR ANY OCCASIONAL DETERIORATING CONDITIONS IN HEAVIER SHOWERS.  
/BENTLEY  
 

 
   
MARINE
 
A STRONG FRONTAL SYSTEM WILL PASS THROUGH THE COASTAL  
WATERS TODAY, BRINGING A PERIOD OF SOLID GALE FORCE SOUTHERLY WINDS.  
THE STRONGEST WINDS WILL BE OVER THE OUTER WATERS, WHERE GALE  
GUSTS SHOULD BEGIN BY AROUND SUNRISE. WINDS WILL HAVE AN OFFSHORE  
COMPONENT, SO THE EFFECTS WILL BE LIMITED SOMEWHAT OVER THE  
NEARSHORE WATERS. HOWEVER, STILL THINK THERE WILL BE SOME GUSTS  
TO 35 KT FOR A BRIEF PERIOD RIGHT AHEAD OF THE COLD FRONT, WHICH  
WILL MOVE ONSHORE DURING THE EARLY TO MID AFTERNOON TIME FRAME.  
SEAS WILL SEE A SHARP INCREASE THIS LATER THIS MORNING AND THIS  
AFTERNOON IN RESPONSE TO THE GUSTY WINDS. EXPECT THEM TO TOP OUT  
IN THE 13 TO 15 FT RANGE. WINDS WILL SUBSIDE AND VEER TO THE  
WEST LATER THIS AFTERNOON AND THIS EVENING. SEAS WILL ALSO DROP  
FAIRLY QUICKLY TONIGHT, LIKELY FALLING BELOW 10 FT BY AROUND  
MIDNIGHT.  
 
THERE WILL BE A LULL IN THE WEATHER LATER TONIGHT AND MON AS  
WEAK HIGH PRES BUILDS OVER THE WATERS. HOWEVER, A LONGER PERIOD  
WESTERLY SWELL WILL ARRIVE MON NIGHT, PUSHING SEAS BACK INTO THE  
TEENS. THEN ANOTHER LOW PRES SYSTEM WILL AFFECT THE PAC NW TUE  
AND WED. THIS WILL BRING A PERIOD OF WINDS GUSTING 25 TO 30 KT,  
WITH POTENTIAL FOR SOME LOW-END GALES TUE NIGHT INTO WED MORNING.  
HIGHER PRES IS THEN EXPECTED FOR THU AND FRI, BRINGING A PERIOD  
OF MORE BENIGN CONDITIONS TO THE WATERS. PYLE  
 

 
   
PQR WATCHES/WARNINGS/ADVISORIES
 
 
OR...WINTER WEATHER ADVISORY UNTIL 4 PM PDT MONDAY FOR CASCADES IN  
LANE COUNTY-NORTHERN OREGON CASCADES.  
 
WA...WINTER WEATHER ADVISORY UNTIL 4 PM PDT MONDAY FOR SOUTH  
WASHINGTON CASCADES.  
 
PZ...GALE WARNING UNTIL 4 PM PDT THIS AFTERNOON FOR COASTAL WATERS  
FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 10 NM.  
 
GALE WARNING UNTIL 3 PM PDT THIS AFTERNOON FOR WATERS FROM CAPE  
SHOALWATER WA TO FLORENCE OR FROM 10 TO 60 NM.  
 
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 1 PM  
THIS AFTERNOON TO 7 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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