853  
FXUS66 KPQR 300425  
AFDPQR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PORTLAND OR  
925 PM PDT SAT APR 29 2017  
   
SYNOPSIS
 
LOW PRESSURE MOVING INTO BRITISH COLUMBIA WILL BRING A  
FRONTAL SYSTEM AND SOME RAIN THROUGH THE REGION TONIGHT. THERE WILL  
BE POST-COLD FRONTAL SHOWERS EARLY SUNDAY, WITH SHOWERS DECREASING  
THROUGH THE DAY. ANOTHER WEAK SYSTEM WILL LIKELY BRING LIGHT RAIN  
MONDAY INTO MONDAY NIGHT. HIGHER PRESSURE WILL BRING DRY AND MUCH  
WARMER WEATHER TO THE AREA DURING THE MID WEEK PERIOD, THOUGH A WARM  
FRONT MIGHT GET CLOSE TO BRUSHING THE FAR NORTH COAST TUESDAY. AN  
UPPER LEVEL TROUGH IS MODELED TO APPROACH THE PAC NW LATE THURSDAY  
INTO FRI AND MAY LINGER INTO THE WEEKEND. THIS WILL BRING INCREASING  
PRECIP CHANCES AND COOLER WEATHER.  
 

 
   
SHORT TERM...TONIGHT THROUGH TUESDAY
 
RADAR AND SURFACE  
OBSERVATIONS SHOWED A FAIRLY SOLID AREA OF MOSTLY LIGHT RAIN  
SPREADING STEADILY SE ACROSS THE FORECAST AREA EARLY THIS EVENING.  
RAIN PRECEDES A WARM FRONT THAT WAS WORKING ITS WAY SE DOWN THE WA  
COAST, AND IS EXPECTED TO BE FAIRLY QUICKLY FOLLOWD BY A COLD FRONT.  
MODELS CONSISTENT IN SHOWING THE COLD FRONT PUSHING INLAND LATER  
TONIGHT, WITH THE RAIN TRANSITIONING TO SHOWERS OVERNIGHT OVER THE  
NW PART OF THE FORECAST AREA.  
 
REMAINDER OF SHORT TERM DISCUSSION UNCHANGED...THERE WILL BE SOME  
POST-FRONTAL SHOWERS AROUND SUNDAY. THERE IS NOT MUCH COLD AIR ALOFT  
MOVING IN BEHIND THIS FRONT, SO INSTABILITY WILL BE LIMITED AND  
SHOWERS SHOULD BE PRETTY WEAK. THE BEST SHOWERS SHOULD BE IN THE  
MORNING, WITH DECREASING ACTIVITY IN THE AFTERNOON. THE AIRMASS WILL  
BE COOLER, WITH 850 TEMPS MODELED TO DROP BACK BELOW 0C.  
THIS SHOULD LIMIT HIGH TEMPS IN THE UPPER 50S FOR THE LOWLANDS.  
 
THERE WILL BE A BREAK LATER SUN INTO EARLY MON. THEN THE FCST MODELS  
IN DECENT AGREEMENT THAT ANOTHER WEAK LOW WILL FORM OFFSHORE ALONG  
THE STALLED BAROCLINIC ZONE FROM TONIGHT'S SYSTEM, BRINGING THE FRONT  
BACK NORTH AS A WARM FRONT DURING THE DAY MON. EXPECT RAIN CHANCES TO  
INCREASE MON AFTERNOON AND MON NIGHT. THE SYSTEM IS WEAK ENOUGH THAT  
CONFIDENCE IS NOT ALL THAT HIGH THAT ALL LOCATIONS WILL SEE  
MEASURABLE RAINFALL.  
 
THE NE PAC UPPER LEVEL RIDGE WILL STRENGTHEN SIGNIFICANTLY OVER THE  
PAC NW ON TUE. THIS SHOULD MEAN MAINLY DRY CONDITIONS TUE, WITH MUCH  
WARMER TEMPS. HIGHS OVER THE INTERIOR LOWLANDS WILL LIKELY REACH INTO  
THE MID TO UPPER 60S. THERE IS A SLIGHT CHANCE THAT A WEAK WARM FRONT  
WILL BRUSH THE FAR NORTHERN COASTAL ZONES WITH SOME LIGHT RAIN LATER  
TUE. PYLE  
   
LONG TERM...TUESDAY NIGHT THROUGH SATURDAY
 
NO CHANGES. PREVIOUS  
DISCUSSION FOLLOWS. THE FAIRLY STRONG UPPER LEVEL RIDGE IS EXPECTED  
TO REMAIN OVER THE REGION THROUGH WED. THE MODEL 850MB TEMPS WARM  
CONSIDERABLY WED, SUGGESTING HIGH TEMPS WELL INTO THE 70S ARE LIKELY  
FOR THE INTERIOR LOWLANDS. THE RIDGE AXIS SHIFTS FURTHER EAST INTO  
THE INTERIOR NW THU, WHICH ALLOWS A FAIRLY DEEP TROUGH TO APPROACH  
THE COAST LATER THU AND FRI. THE FCST MODELS BRING INCREASING PRECIP  
CHANCES THU AFTERNOON, WILL THE POTENTIAL FOR SOME THUNDERSTORM  
ACTIVITY. HIGHS ON THU EXPECTED TO REMAIN SEVERAL DEGREES ABOVE  
NORMAL. PRECIP CHANCES CONTINUE FRI AND SAT AS THE TROUGH SHIFTS  
DIRECTLY OVER THE REGION, WITH TEMPS COOLING OFF CONSIDERABLY. PYLE  
 

 
   
AVIATION
 
LOTS OF UNCERTAINTY WITH THE IMMEDIATE FORECASTS AS  
CURRENT OBSERVATIONS ARE NOT ESPECIALLY MATCHING WELL WITH THE  
FORECASTS NOR UPSTREAM OBSERVATIONS. KAST CIGS HAVE NOW LIFTED TO  
VFR ALTHOUGH KUIL AND KHQM BOTH DROPPED TO IFR UNDER SIMILAR  
RADAR SIGNATURES BACK CLOSER TO 00Z. CIGS ARE LOWERING ABOUT ON  
SCHEDULE AT THE INLAND TERMINALS. WILL LIKELY TAKE A MORE  
PESSIMISTIC APPROACH FOR THE COAST THAN CURRENTLY REALITY WOULD  
SUGGEST AS IT APPEARS THE INCOMING COLD FRONT IS SHEARING  
APART. STILL FEEL IFR CIGS AND POSSIBLY VSBYS ARE SIGNIFICANTLY  
POSSIBLE FOR THE COASTAL TAF TERMINALS AND LESS LIKELY VIA A  
COIN FLIP AT WORST INLAND. CONDITIONS IMPROVE BY 18Z OR BETTER  
SUNDAY.  
 
KPDX AND APPROACHES...THE INCOMING FRONT WILL LIKELY BRING A  
PERIOD OF RAIN AND LOWERING CIGS OVERNIGHT WITH MVFR RESTRICTIONS  
LIKELY TO DEVELOP DURING 06-12Z. OTHERWISE, SCT TO BKN CLOUDS AT  
040-050 AGL COULD IMPACT VISUAL APPROACHES THROUGH EARLY EVENING  
SUNDAY. /JBONK  
 

 
   
MARINE
 
A FRONT DROPPING SOUTHEASTWARD WILL CONTINUE TO BRING  
SMALL CRAFT ADVISORY LEVEL WIND GUSTS OF 25 TO 30 KT TO THE  
NORTHERN WATERS THIS EVENING. ADDITIONALLY, BUOY OBS ARE  
INDICATING SQUARE SEAS WILL ACCOMPANY THE WINDS AND LINGER WELL  
INTO SUNDAY MORNING. FOR HOW LONG, HOWEVER, REMAINS A BIG UNKNOWN  
SO HAVE ISSUED A SCA FOR SEAS THROUGH 18Z AS A FIRST GUESS. RECENT  
HI-RES MODEL RUNS AND THEIR PARENT MODELS HAVE BACKED OFF THE  
WIND THREAT FOR THE CENTRAL WATERS. DROPPED THE SCA FOR WINDS  
THERE. MIGHT GET A VERY BRIEF PERIOD OF WIND GUSTS 20-23 KT, BUT  
UNLIKELY TO CREATE PROBLEMS IN THEIR BREVITY.  
 
HIGH PRESSURE WILL THEN SHIFT BACK OVER THE WATERS SUNDAY AND  
MONDAY AND BRING MORE QUIET WEATHER. AFTER A WEAK FRONT SKIRTS  
THE WATERS LATE MONDAY OR EARLY TUESDAY, A SUMMER-LIKE NORTHERLY  
WIND PATTERN SHOULD DEVELOP FOR A COUPLE DAYS TOWARDS THE MIDDLE  
OF NEXT WEEK. A WESTERLY SWELL APPROACHING 10 FT MAY IMPACT THE  
WATERS LATE IN THE WEEK, BUT CONFIDENCE IN THIS SCENARIO IS LOW.  
JBONK/NEUMAN  
 

 
   
PQR WATCHES/WARNINGS/ADVISORIES
 
 
OR...NONE.  
WA...NONE.  
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 AM PDT SUNDAY FOR  
COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR  
OUT 60 NM.  
 
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 PM PDT SUNDAY  
FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD  
OR OUT 60 NM.  
 

 
 

 
 
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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