307  
FXUS66 KPQR 260447 AAA  
AFDPQR  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE PORTLAND OR  
947 PM PDT MON OCT 25 2021  
   
SYNOPSIS
 
 
ACTIVE WEATHER PATTERN CONTINUES, AS A PARADE OF FRONTS  
REMAIN OFFSHORE. NEXT UP, MORE RAIN LATER TONIGHT INTO TUE. THEN, YET  
ANOTHER FOR LATER WED INTO THU. THEN, LOOKS LIKE A BREAK FOR THE  
COMING WEEKEND, AS MAY SEE DRIER, BUT COOLER WEATHER AS HIGH PRESSURE  
BUILDS INLAND OVER THE PAC NW.  
 

 
   
SHORT TERM... TONIGHT THROUGH THURSDAY
 
UPDATE: RADAR SHOWS  
SHOWERS PERSISTING THIS EVENING ALTHOUGH THEY HAVE BEGUN TO  
EASE. SATELLITE IMAGERY SHOWS MUCH OF THE LOWER CLOUDS THINNING  
AS THE DRY SLOT BEHIND THE ACTIVE WAVE FROM TODAY SHIFTS  
OVERHEAD. NO LONGER A THREAT FOR THUNDERSTORMS, BUT WILL LIKELY  
STILL OBSERVE BREEZY WINDS...ESPECIALLY WITH PASSING SHOWERS.  
-MUESSLE  
 
PREVIOUS DISCUSSION FOLLOWS: LOOKING UPSTREAM OVER THE NORTH  
PACIFIC, NOAA SATELLITE IMAGERY SHOWS A WELL-DEFINED PLUME OF  
MOISTURE AND EMBEDDED SYSTEMS ALONG ROUGHLY LAT 40N WITH THE NEXT  
SYSTEM NOW CROSSING 140W. THIS SYSTEM RIDING STRONG JET, AND  
WILL ARRIVE LATER TONIGHT. AS SUCH, WILL SEE RAIN INCREASING  
ACROSS THE REGION LATER TONIGHT, WITH RAIN INTO TUE AM AS THIS  
FRONT COMES ASHORE. BUT, OVERALL PRESSURE GRADIENTS ARE NOT AS  
IMPRESSIVE AS RECENT SYSTEMS, SO THOUGH MAY BE BREEZY AGAIN  
ALONG THE COAST LATER TONIGHT IN TUE, WILL NOT SEE DAMAGING  
WINDS. AS SUCH, GUSTS 35 TO 45 MPH MORE IN STORE FOR THE COASTAL  
AREAS FOR A TIME TUE AM, WITH STRONGEST BEING ON THE OPEN  
BEACHES AND EXPOSED SOUTH FACING HEADLANDS. FRONT WILL NOT TAKE  
LONG TO PUSH INLAND, WITH TRANSITION TO SHOWERS MID-DAY. SNOW  
LEVELS WILL STAY IN THE 4500 TO 5500 FT RANGE, WITH 3 TO 6  
INCHES LIKELY. WILL NOT ISSUE ANY ADVISORIES. BUT, THOSE HEADED  
TO HIGHER ELEVATIONS SHOULD BE PREPARED FOR SNOWY CONDITIONS  
LATER TONIGHT AND TUE.  
 
AIR MASS REMAINS UNSTABLE FOR TUE NIGHT AND WED, WITH SHOWERS ON TAP.  
EMBEDDED DISTURBANCES IN THE WESTERLY FLOW ALOFT WILL ALLOW FOR  
PERIODS OF ENHANCED SHOWERS AT TIMES.  
 
ANOTHER RATHER WET SYSTEM WILL ARRIVE LATER WED AND WED NIGHT, WITH  
RAIN SPREADING ACROSS THE REGION WED EVENING. AT MOMENT, MODELS HAVE  
BEEN TRENDING HEAVIER PRECIPITATION STAYING OVER WASHINGTON, AND  
NORTHWEST OREGON. WILL TRENDS FORECASTS IN SUCH PATTERN, WITH LOCALLY  
HEAVY RAIN POSSIBLE WED NIGHT INTO THU MORNING FOR AREAS NORTH OF A  
TILLAMOOK TO PORTLAND LINE. FARTHER TO THE SOUTH, MAYBE PROBLEMATIC  
FORECASTING, AS WILL BE LESS POPS. DURING THE DAY ON THU, MODELS IN  
FAIR AGREEMENT THAT THE BAROCLINIC ZONE SHIFTS NORTH OF THE COLUMBIA  
RIVER, POSSIBLY FARTHER NORTHWARD. IF SO, WOULD SEE THE STEADY RAIN  
SHIFT FARTHER NORTHWARD. FOR NOW, WILL KEEP RAIN AND 80 TO 90 POPS  
FOR NORTHERN ZONES, AND DECREASE THE POPS AS MOVE SOUTHWARD ACROSS  
THE AREA TOWARDS LANE COUNTY. CONFIDENCE STILL LOW A BIT, BUT WOULD  
NOT BE SURPRISED IF GOOD PART OF LANE COUNTY STAYS MOSTLY DRY ON THU.  
THIS FRONTAL BOUNDARY OFF TO THE NORTH WILL SAG BACK SOUTHWARD LATER  
THU AND THU NIGHT, WITH RAIN SPREADING BACK ACROSS THE REGION FROM  
NORTHWEST TO SOUTHEAST. -ROCKEY  
 

 
   
LONG TERM...THURSDAY NIGHT THROUGH MONDAY
 
AN UPPER LEVEL TROUGH  
WILL DIP SOUTH THURSDAY NIGHT INTO FRIDAY AS IT MAKES ITS WAY ACROSS  
THE PACIFIC. THE SOUTHWESTERLY FLOW ALOFT WILL KEEP A CONNECTION TO  
THE TROPICS AND PROVIDE ENOUGH SUPPORT TO LOW LEVEL DISTURBANCES  
TO KEEP RAIN IN THE FORECAST THROUGH EARLY FRIDAY MORNING. FORECASTED  
24 HR QPF TOTALS STARTING THURSDAY NIGHT SHOWS THAT THE BULK OF THE  
PRECIPITATION RANGING BETWEEN 1-2 INCHES WILL REMAIN IN THE  
WASHINGTON CASCADES, THE NORTH OREGON COAST AND CASCADE RANGE AS WELL  
AS THE WILLAPA HILLS.  
 
THE UPPER LEVEL TROUGH WILL INTENSIFY AND CONTINUE TO DIP SOUTH  
EVENTUALLY BREAKING AWAY FROM THE MAIN FLOW. DEPENDING ON WHAT MODEL  
YOU LOOK AT THE UPPER LEVEL CUTOFF LOW WILL MOVE ONSHORE SOMEWHERE  
BETWEEN SAN FRANCISCO AND MEDFORD SATURDAY NIGHT. THIS WILL PUT THE  
PACIFIC NW UNDER A WEAK RIDGING PATTERN FRIDAY AFTERNOON WHICH WILL  
ALLOW THE AREA TO POTENTIALLY DRY OUT OVER THE WEEKEND. BECAUSE THERE  
IS SO MUCH UNCERTAINTY WITH THE TRACK OF THE UPPER LEVEL LOW, A  
SLIGHT CHANCE OF POPS REMAIN THROUGH THE WEEKEND.  
 
THE SURFACE LOW WILL TRACK SOUTH AND HIGH PRESSURE WILL BUILD  
OFFSHORE OF WASHINGTON SETTING UP A NORTH, NORTHEASTERLY WIND PATTERN  
OVER THE CWA FRIDAY AFTERNOON. THIS WILL BRING OVERNIGHT  
TEMPERATURES DOWN INTO THE LOW TO MID 40S. OFFSHORE WINDS WILL  
STRENGTHEN AS A LOW PRESSURE TO THE NORTHWEST NEAR THE ALEUTIAN  
ISLANDS SLOWLY PUSHES EAST. THE COOL CONTINENTAL AIRMASS WILL BE  
PULLED WEST BUT LOOKING AT 850MB TEMPS IT LOOKS LIKE THE COLD  
AIRMASS IS DAMMING UP AGAINST THE CASCADES. TIGHT GRADIENTS ACROSS  
THE COLUMBIA RIVER GORGE WILL LIKELY PRODUCE BREEZY CONDITIONS ACROSS  
THE METRO SUNDAY. SNOW LEVELS WILL ALSO DROP ACROSS THE CASCADES TO  
AROUND 4500 FT BUT IT'LL STAY DRY DURING THIS TIME. -BMUHLESTEIN  
 

 
   
AVIATION
 
06Z TAFS: UNSETTLED PATTERN PERSISTS WITH PLENTY OF  
SHOWERS REMAINING OVER THE FORECAST AREA THIS EVENING. THERE WILL  
LIKELY BE SOME DECREASE IN SHOWER COVERAGE UNTIL ROUGHLY 09Z,  
THEN SHOWERS WILL INCREASE AGAIN AS A PACIFIC WARM FRONT  
APPROACHES THE COAST. MOUNTAIN OBSCURATIONS ARE LIKELY TONIGHT  
AND WELL INTO TUESDAY DUE TO THE MOIST AIR MASS. OTHERWISE,  
EXPECT PRIMARILY VFR CONDITIONS OUTSIDE OF SHOWERS BEFORE  
CONDITIONS DETERIORATE TO MVFR IN RAIN FOR MOST TERMINALS BY  
12Z. LOWER CIGS SHOULD BREAK UP A BIT AS TUESDAY PROGRESSES,  
WITH VFR LIKELY TO PREVAIL OUTSIDE OF SCATTERED SHOWERS DURING  
THE AFTERNOON. GUSTY S-SW WINDS WILL CONTINUE TUESDAY WITH GUSTS  
UP TO 25-35 KT INLAND AND GUSTS UP TO 35-40 KT ALONG THE COAST.  
THESE WINDS SHOULD BEGIN TO EASE TOWARD SUNSET TUESDAY.  
 
FOR DETAILED REGIONAL PAC NW AVIATION WEATHER INFORMATION, GO  
ONLINE TO: HTTPS://WEATHER.GOV/ZSE  
 
KPDX AND APPROACHES...VFR CONDITIONS THIS EVENING WITH SPOTTY  
MVFR IN SHOWERS. EXPECT SHOWERS TO INCREASE AGAIN LATER TONIGHT,  
WITH STEADIER RAIN AND MVFR CONDITIONS LIKELY BY 12Z. THIS BAND  
OF RAIN SHOULD MOVE EAST OF THE METRO AREA BY 19Z, YIELDING  
MOSTLY VFR CONDITIONS OUTSIDE OF SCATTERED SHOWERS TUE AFTERNOON.  
S-SW WINDS WILL BE BREEZY AGAIN TUESDAY WITH GUSTS 25-30 KT  
POSSIBLE ACROSS THE METRO AREA BEFORE SLOWLY EASING AFTER ABOUT  
23Z TUE. -WEAGLE  
 

 
   
MARINE
 
 
THE INTENSE SURFACE LOW WHICH HAS BEEN THE CAUSE OF THE  
SIGNIFICANT WEATHER ACROSS THE REGION WILL GRADUALLY WEAKEN AS  
IT TRACKS TOWARDS VANCOUVER ISLAND AND FURTHER INLAND THROUGH  
TONIGHT. SMALL CRAFT ADVISORY WINDS WILL CONTINUE THROUGH THE  
OVERNIGHT HOURS, WHICH WILL BE FOLLOWED BY ANOTHER ROUND OF  
SOUTHERLY GALES EARLY TUESDAY MORNING AS ANOTHER FRONT CROSSES  
THE WATERS. TUESDAY AFTERNOON, SUSTAINED WINDS SHOULD FALL BELOW  
20 KT WITH GUSTS FALLING BELOW 30 KT THROUGH LATE TUESDAY.  
WEDNESDAY AND CONTINUING INTO THROUGH THE END OF THE WEEK, WINDS  
SHOULD REMAIN BELOW SMALL CRAFT ADVISORY CONDITIONS. HOWEVER,  
THURSDAY THERE IS A CHANCE FOR ANOTHER ROUND OF SMALL CRAFT WIND  
GUSTS AS ANOTHER, MUCH WEAKER, LOW PASSES OFFSHORE.  
 
SEAS WILL CONTINUE TO BE TREACHEROUS FOR AT LEAST THE NEXT 72  
HOURS AS A LARGE WESTERLY SWELL MOVES THROUGH THE WATERS. SEAS  
WILL SLOWLY SUBSIDE BELOW 20 FEET BY LATE TONIGHT/EARLY TUESDAY  
MORNING. THERE COULD BE A PERIOD OF 10 TO 12 FT SEAS TUESDAY  
NIGHT/WEDNESDAY MORNING, THESE LOWER SEAS WILL BE SHORT LIVED AS  
A FRESH SWELL IS EXPECTED TO BRING SEAS BACK INTO THE 12 TO 15  
FT RANGE WEDNESDAY AND THURSDAY. SEAS ARE NOT EXPECTED TO DROP  
BELOW 10 FEET UNTIL THE END OF THE WEEK. /42  
 

 
   
PQR WATCHES/WARNINGS/ADVISORIES
 
 
OR...HIGH SURF ADVISORY UNTIL 3 AM PDT TUESDAY FOR ORZ001-002.  
WA...HIGH SURF ADVISORY UNTIL 3 AM PDT TUESDAY FOR WAZ021.  
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT TUESDAY FOR PZZ250-255-270-  
275.  
GALE WARNING FROM 5 AM TO 11 AM PDT TUESDAY FOR PZZ250-255-270-  
275.  
SMALL CRAFT ADVISORY UNTIL 11 PM PDT TUESDAY FOR PZZ210.  
 

 
 

 
 
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