189  
FXUS66 KPQR 020540 AAA  
AFDPQR  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE PORTLAND OR  
940 PM PST THU DEC 1 2022  
 
UPDATED AVIATION AND WWA SUMMARY...  
   
SYNOPSIS
 
A COOL SEASONABLE SERIES OF SYSTEMS WILL CONTINUE  
TO PUSH INLAND OVER THE NEXT SEVERAL DAYS. EACH OF THESE  
DISTURBANCES WILL BRING PRECIPITATION WITH A MIX OF  
PRECIPITATION. OVERALL, CONFIDENCE IS FAIRLY LOW IN THE SENSIBLE  
WEATHER IN MID-RANGE FORECAST DUE TO VARIABLE AND SENSITIVE  
THRESHOLDS FOR WINTER WEATHER. TRENDING TOWARDS A DRIER SOLUTION  
FOR NEXT WEEK.  
 

 
   
SHORT TERM /THROUGH SUNDAY NIGHT/
 
THE FIRST DAY OF  
METEOROLOGICAL WINTER HAS BROUGHT QUITE THE GRAB BAG OF WEATHER  
TYPES RANGING FROM SNOW, TO RAIN, TO THUNDER STORMS. RADAR AND  
SATELLITE IMAGERY SHOW THAT THE LOW PRESSURE SYSTEM WHICH  
BROUGHT THE HEAVY RAIN AND SNOW YESTERDAY HAS SHIFTED INLAND TO  
NORTHEAST OF THE CASCADES. THIS LOW SPUN NEARLY STATIONARY OVER  
THE NORTH OREGON AND SOUTH WASHINGTON COAST THROUGH AROUND 20Z  
THURSDAY WHICH PROPAGATED SEVERAL ROUNDS OF SHOWERS OVER THE  
NORTHERN PORTIONS OF THE FORECAST AREA. EVEN WITH TEMPERATURES  
SITTING ABOVE FREEZING, WITH THESE PASSING SHOWERS, WET BULB  
TEMPERATURES DROPPED WHICH ALLOWED FOR COOLING OF THE  
ATMOSPHERE. ALL OF WHICH IS ENOUGH TO CAUSE PRECIPITATION TO  
FALL AS SNOW - ALBEIT FAIRLY WET IN NATURE. OBSERVED ISOLATED  
DUSTINGS OF SNOW THROUGHOUT MOST GEOGRAPHIC REGIONS, BUT DUE TO  
THE SHOWERY NATURE WAS NOT WIDESPREAD OVER HEAVY. AREAS ABOVE  
500 FT ALONG THE COAST RANGE, AND IN COLUMBIA, COWLITZ, AND  
PACIFIC COUNTY ALL RECEIVED ACCUMULATING SNOW. WEB CAMERAS STILL  
SHOW SOME ACCUMULATED SNOW ALONG THE SIDES OF ROADS. THE  
CASCADES AND FOOTHILLS SAW SNOWFALL DWINDLE THIS AFTERNOON WITH  
UP TO 4 INCHES OF ADDITIONAL SNOWFALL ACCUMULATED. LATER THIS  
AFTERNOON, MODELS ARE SUGGESTING THE PROPAGATION OF ANOTHER  
SHORTWAVE TROUGH WHICH MAY AMPLIFY SHOWERS AND INCREASE THE  
INTENSITY AND FREQUENCY OF SHOWERS. FROM A NUMERICAL MODEL  
PERSPECTIVE, HI-RESOLUTION MODELS HAVE HAD A GOOD HANDLE ON THE  
LOCATION AND ACCUMULATIONS OF PRECIPITATION BUT THE NAM HAS  
VERIFIED THE BEST WITH THIS PASSING LOW. HAVE DECIDED TO TREND  
TOWARDS A NAM BASED SOLUTION IN THE SHORT TERM FOR QPF. THERE IS  
A CHANCE THAT A FEW MORE INCHES OF SNOW ARE POSSIBLE ALONG THE  
CASCADES ABOVE 1000 FT SO HAVE DECIDED TO MAINTAIN THE WINTER  
STORM WARNING UNTIL 06Z FRIDAY AS TO FINISH UP THIS SYSTEM.  
 
ON FRIDAY, CONDITIONS ARE A BIT MORE VARIABLE AND THERE IS STILL  
QUITE A BIT OF UNCERTAINTY WHICH STEMS FROM THE SHIFTING OF A  
BROAD LOW PRESSURE SYSTEM DROPPING DOWN FROM THE GULF OF ALASKA  
AND A TRANSIENT WEAK HIGH. BECAUSE OF THIS, PRECIPITATION WILL  
BE LESS WIDESPREAD AND POPS HAVE DECREASED THROUGHOUT MUCH OF  
THE FORECAST AREA ASIDE FROM THE COASTLINE. WITH THIS SHIFT,  
TEMPERATURES ARE NOT EXPECTED TO DIP AS LOW AS THEY WERE  
PREVIOUSLY FORECAST TO BE AND THUS, SNOW LEVELS HAVE RISEN  
SLIGHTLY. MODELED WET BULB 0C HEIGHTS ARE VARIABLE BETWEEN  
MODELS WITH SNOW LEVELS RANGING FROM 600-800 FT SOUTH OF SALEM,  
WHILE THE ECMWF AND CANADIAN ARE HIGHER THAN 1000 FT FRIDAY  
MORNING, RISING TO GREATER THAN 2000 FT IN THE AFTERNOON.  
DECIDED TO SPLIT THE DIFFERENCE DURING THIS BRIEF BREAK BETWEEN  
SYSTEMS. GIVEN THOSE SNOW LEVELS, MOST AREAS WILL SEE ANY  
PRECIPITATION FALLING AS RAIN, WHILE THE MOUNTAINS AND SOME  
AREAS OF THE COAST RANGE CAN EXPECT VERY LIGHT SNOW.  
 
THE LOW PREVIOUSLY MENTIONED WILL BE THE MAIN SENSIBLE WEATHER  
MAKER THROUGH THE WEEKEND. THIS LOW HAS SHIFTED TO BE MORE  
OFFSHORE THAN PREVIOUSLY FORECAST WHICH WILL KEEP MUCH OF THE  
PRECIPITATION CONCENTRATED TO THE COAST WITH ISOLATED SCATTERED  
SHOWERS POSSIBLE INLAND. THE 90TH PERCENTILE FOR PRECIPITATION  
IS AROUND 0.25 THROUGH THE WILLAMETTE VALLEY SLIGHTLY LOWER FOR  
THE CASCADES. THIS REPRESENTS THE "WORST CASE SCENARIO" FOR  
SATURDAY. THIS IS A TYPICAL RAINFALL FOR THIS TIME OF YEAR SO  
THERE AREN'T ANY CONCERNS. THE ONE AREA WE WILL CONTINUE TO  
WATCH IS ON SATURDAY MORNING AS SNOW LEVELS REDUCE AND AN EAST  
WIND KICKS IN. THE FORECAST PRESSURE GRADIENT FROM KTTD TO KDLS  
(A GOOD PROXY FOR EASTERLY WINDS THROUGH THE GORGE AND PASSES)  
RANGES FROM AROUND -4 TO -10 MB WITH THE -10 BEING THE MOST  
INTENSE GRADIENT AND THUS WINDIEST SOLUTION. THIS SUGGESTS THAT  
WE COULD SEE ANOTHER ROUND OF INCREASED EASTERLY WINDS. THE GFS  
IS TRENDING ON THE HIGH SIDE FOR WIND SPEEDS AND THE OVERALL  
PATTERN IS BEGINNING TO TAKE ON MORE OF A DOWNSLOPING PATTERN  
VS A GAP WIND. THUS, IF THERE ARE ANY STRONGER WINDS ALOFT,  
THOSE COULD MIX DOWN TO THE SURFACE. NBM 90TH PERCENTILE WIND  
SPEEDS THROUGH THE COLUMBIA RIVER GORGE AROUND THREE CORNER ROCK  
ARE AROUND 70 MPH, THE 50TH PERCENTILE AROUND 50 MPH, AND THE  
10TH PERCENTILE AROUND 35 MPH. THIS IS SLIGHTLY STRONGER THAN  
THE WEEK OF EASTERLY WINDS THAT WERE EXPERIENCED A FEW WEEKS  
AGO, BUT ARE ONLY EXPECTED FOR TWO DAYS. BUT, WHILE WINDS ARE  
NOT EXCEEDINGLY STRONG, THE IMPACT OF USHERING IN COLD AIR MAY  
BE. WITH THE COLD AIR FILTERING INTO THE WILLAMETTE VALLEY FROM  
BOTH THE GORGE AND THE CASCADE VALLEYS, WE MAY SEE A POOL OF  
COLD AIR AT THE SURFACE.  
 
THIS LOW APPEARS TO START PROGRESSING INLAND LATE SATURDAY INTO  
SUNDAY MOVING FROM SOUTHERN OREGON NORTHWARD. IF THIS  
PRECIPITATION OCCURS DURING THE COLDER PART OF THE NIGHT THERE  
IS A CHANCE THAT IT COULD INTERSECT WITH THE COLD AIR AT THE  
SURFACE AND THUS, SLIGHT CHANCES FOR FREEZING RAIN. AS IT  
STANDS, THERE IS AROUND A 10-20% CHANCE FOR FREEZING RAIN  
AMOUNTING TO A LIGHT GLAZE, BUT THIS EQUALLY MEANS THAT THERE IS  
AN 80-90% CHANCE THAT IT WILL NOT HAPPEN. WE WILL CONTINUE TO  
MONITOR AS IT WILL GREATLY DEPEND ON THE TIMING OF THE  
PRECIPITATION TO WHETHER OR NOT TEMPERATURES REACH FREEZING  
AFTER A DEEP ENOUGH MELTING LAYER.-MUESSLE  
   
LONG TERM /MONDAY THROUGH WEDNESDAY/
 
THE OVERALL WEATHER  
PATTERN EARLY NEXT WEEK WILL BEGIN WITH A TALL RIDGE EXTENDING  
FROM THE PACIFIC NEAR HAWAII ALL THE WAY UP INTO THE ARCTIC  
OCEAN. THIS RIDGE WILL BE SANDWICHED BETWEEN TWO LONGWAVE  
TROUGHS...ONE MOVING OFF OF SIBERIA AND THE OTHER OVER HUDSON  
BAY. ONE SHORTWAVE TROUGH SPINNING OFF OF THE HUDSON BAY LOW IS  
THE LOW THAT HAD BROUGHT WEATHER TO THE FORECAST AREA FOR FRIDAY  
INTO THE WEEKEND, AND WILL HAVE SLID SOUTH OVER NORTHERN  
CALIFORNIA BY MONDAY. NORTHWESTERLY FLOW OVER THE AREA WILL KEEP  
IN COOLER THAN AVERAGE TEMPERATURES, AS WELL AS A SLIGHT CHANCE  
FOR SHOWERS WITH ANY REMAINING MOISTURE. ENERGY SPINNING AROUND  
THE TWO UPPER LOWS WILL SLOWLY PROPEL THEM TOWARD EACH OTHER  
WHICH WILL START PINCHING THE RIDGE AND EVENTUALLY PUSH IT  
SOUTH. DETERMINISTIC MODELS AND THEIR ENSEMBLES ARE IN GREAT  
AGREEMENT ON THIS SET UP, AS EVIDENCED BY WPC'S 500 MB CLUSTERS  
BEING ALMOST MIRROR IMAGES, SO HAVE A HIGH CONFIDENCE IN THIS  
PATTERN. AS THE UPPER LOW OVER NORTHERN CALIFORNIA SLIDES SOUTH,  
RIDGING WILL BE ABLE TO MOVE INLAND A BIT FOR TUESDAY AND  
WEDNESDAY. THIS WILL ALLOW FOR A WARMING TREND OF TEMPERATURES,  
BUT WILL STAY BELOW AVERAGE FOR THIS TIME OF YEAR. NBM KEEPS IN  
A 15 TO 30 PERCENT CHANCE OF SHOWERS FOR THIS TIME FRAME,  
BELIEVE THIS IS OVERDONE A BIT, SO LOWERED THEM TO 10 TO 20  
PERCENT.  
 
ON WEDNESDAY, AN ALL MODELS SHOW AN UPPER TROUGH DROPPING DOWN FROM  
THE GULF OF ALASKA. THIS WILL SPREAD THE NEXT BETTER CHANCE FOR  
PRECIPITATION INTO THE PACIFIC NORTHWEST. WILL KEEP THE 20 TO 50  
PERCENT POPS FROM THE NBM TO SHOW THIS INCREASE. -KRIEDERMAN  
 

 
   
AVIATION
 
06Z TAFS: SHOWER ACTIVITY DIMINISHING IN COVERAGE  
ACROSS THE AREA THIS EVENING AS HIGH PRESSURE TEMPORARILY BUILDS  
ALOFT BETWEEN SYSTEMS. MAINLY SEEING VFR CONDITIONS WITH SOME  
INTERMITTENT BOUTS OF MVFR CEILINGS AS OF 05Z. HREF PROBABILITY  
GUIDANCE STILL DEPICTING A 50-70 PERCENT CHANCE FOR MVFR CIGS TO  
DEVELOP OVERNIGHT FROM ABOUT KSLE NORTH THROUGH THE PORTLAND  
METRO, WITH CIGS TRENDING DOWNWARD BETWEEN 08-12Z. SHOULD SEE  
MOSTLY VFR ACROSS THE AREA BY DAYBREAK FRI, WITH INCREASING  
OFFSHORE FLOW YIELDING EAST WINDS THROUGH THE GORGE IMPACTING  
KTTD AND OTHER PORTLAND AREA TERMINALS AFTER 21Z FRI. A STRONG  
FRONT WILL STALL OFFSHORE LATE IN THE PERIOD, POSSIBLY MOVING  
CLOSE ENOUGH TO NORTHERN COASTAL AREAS TO BRING RAIN BACK TO KAST  
AFTER 00Z SAT.  
 
FOR DETAILED PAC NW AVIATION WEATHER INFORMATION, GO ONLINE TO:  
HTTP://WEATHER.GOV/ZSE  
 
KPDX AND APPROACHES...SHOWERS CONTINUE TO DIMINISH OVERNIGHT, WITH  
MODEL GUIDANCE DEPICTING AN APPROXIMATELY 70 PERCENT CHANCE FOR  
MVFR CIGS FROM FL020-030 AFTER 08Z. CIGS SHOULD IMPROVE BACK TO  
VFR BY DAYBREAK FRI. INCREASING OFFSHORE FLOW WILL INDUCE EASTERLY  
WINDS OUT OF THE COLUMBIA RIVER GORGE FRI AFTERNOON, POSSIBLY  
INCREASING WINDS AT THE TERMINAL TO 10-15 KT AFTER 21Z FRI. /CB  
 

 
   
MARINE
 
BUOY OBSERVATIONS FROM 3 PM PST THURSDAY SHOWED MUCH  
WEAKER WINDS AROUND 5 TO 15 KT. SEAS WERE ALSO ON THE DECREASE  
WITH SIGNIFICANT WAVE HEIGHTS AROUND 9 TO 11 FT WITH A DOMINANT  
WAVE PERIOD AROUND 11 TO 13 SECONDS, LOWEST OVER THE NORTHERN  
WATERS. EXPECT SUB-SMALL CRAFT CRITERIA WINDS AND SEAS ACROSS THE  
NORTHERN WATERS TONIGHT WHILE THE CENTRAL AND SOUTHERN WATERS  
REMAIN RIGHT AROUND 10 FT.  
 
CONDITIONS WILL DETERIORATE QUICKLY ON FRIDAY AS A LARGE LOW  
PRESSURE SYSTEM OVER THE FAR NORTHEAST PACIFIC PUSHES A STRONG  
FRONTAL OVER THE COASTAL WATERS. IT APPEARS THIS FRONT WILL STALL  
OUT, RESULTING IN A FAIRLY PROLONGED PERIOD OF HIGH-END GALE FORCE  
SOUTHERLY WIND GUSTS OF 40-45 KT LATE FRIDAY MORNING THROUGH  
FRIDAY EVENING. THE CHANCE FOR STORM FORCE WIND GUSTS IN EXCESS OF  
48 KT HAS DECREASED EVEN MORE, AND THE NBM V4.0 IS NOW SUGGESTING  
THERE IS ONLY A 1% CHANCE AT BUOY 029 AND BUOY 50. MODEL ENSEMBLE  
GUIDANCE FROM THE GEFS/EPS BACKS THIS UP WELL. IN OTHER WORDS,  
STORM FORCE WIND GUSTS APPEAR HIGHLY UNLIKELY TO OCCUR AT THIS  
POINT. IN ADDITION, A SLIGHT OFFSHORE COMPONENT TO WINDS IS  
EXPECTED OVER THE INNER WATERS, WHICH IS NOT A FAVORABLE SETUP  
FOR A COASTAL JET. THEREFORE, STORM FORCE WIND GUSTS ARE ALSO  
HIGHLY UNLIKELY TO OCCUR OVER THE INNER WATERS. WILL MAINTAIN THE  
CURRENT GALE WARNING IN EFFECT. NEVERTHELESS, WIND WAVES WILL  
LIKELY APPROACH 18-20 FT AND RESULT IN STEEP AND HAZARDOUS SEAS.  
 
WIND GUSTS SHOULD DECREASE A BIT FRIDAY NIGHT AS THE PRESSURE  
GRADIENT WEAKENS OVER THE WATERS, BUT SHOULD STILL BE GUSTING TO  
35 KT OVER THE OUTER WATERS AND TO 25-30 KT OVER THE INNER WATERS.  
LOW-LEVEL OFFSHORE FLOW WILL QUICKLY STRENGTHEN SATURDAY INTO  
SUNDAY, RESULTING IN A TRANSITION TO EASTERLY WINDS OVER THE  
WATERS. THIS WILL BRING DECREASING SEAS AND MUCH LOWER WIND  
SPEEDS, ALTHOUGH WINDS WILL BE LOCALLY ENHANCED DOWNWIND OF GAPS  
IN THE COASTAL TERRAIN. -TK  
 

 
   
PQR WATCHES/WARNINGS/ADVISORIES
 
 
OR...NONE.  
WA...NONE.  
PZ...SMALL CRAFT ADVISORY FROM 9 PM FRIDAY TO 1 PM PST SATURDAY FOR  
COLUMBIA RIVER BAR.  
 
SMALL CRAFT ADVISORY FROM 4 AM TO 10 AM PST FRIDAY FOR COASTAL  
WATERS FROM CAPE SHOALWATER WA TO CAPE FALCON OR OUT 10 NM.  
 
GALE WARNING FROM 10 AM FRIDAY TO 4 AM PST SATURDAY FOR COASTAL  
WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 10 NM.  
 
SMALL CRAFT ADVISORY UNTIL 10 AM PST FRIDAY FOR COASTAL WATERS  
FROM CAPE FOULWEATHER OR TO FLORENCE OR OUT 10 NM.  
 
SMALL CRAFT ADVISORY FROM 4 AM TO 8 AM PST FRIDAY FOR WATERS  
FROM CAPE SHOALWATER WA TO CAPE FALCON OR FROM 10 TO 60 NM.  
 
GALE WARNING FROM 8 AM FRIDAY TO 10 AM PST SATURDAY FOR COASTAL  
WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR FROM 10 TO 60  
NM.  
 
SMALL CRAFT ADVISORY UNTIL 8 AM PST FRIDAY FOR COASTAL WATERS  
FROM CAPE FOULWEATHER OR TO FLORENCE OR FROM 10 TO 60 NM.  
 

 
 

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