128
FXUS66 KPQR 031646 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
845 AM PST SAT DEC 3 2022
MORNING UPDATE, FOR AVIATION WEATHER
SYNOPSIS
BROAD LOW PRESSURE WILL PERSIST OFF THE S OR/N CA COAST
THROUGH THE WEEKEND, FINALLY DRIFTING ONSHORE MONDAY. HIGH PRESSURE
AND ITS ASSOCIATED COLD POOL ARE BECOMING ESTABLISHED OVER THE
COLUMBIA BASIN. THIS WILL RESULT IN PERSISTENT COLD EAST WIND THROUGH
THE COLUMBIA GORGE, WHICH IS ALREADY BECOMING FAIRLY STRONG CASCADE
LOCKS WESTWARD. THE COLD WIND WILL PERSIST AS A DISTURBANCE SPREADS
PRECIPITATION NORTHWARD FROM CA TONIGHT AND SUNDAY, POSSIBLY
SUPPLYING ENOUGH COLD AIR FOR LIGHT SNOW OR ICE AT TIMES TONIGHT
THROUGH MONDAY, ESPECIALLY IN THE GORGE. RELATIVELY DRIER WEATHER IS
EXPECTED TUESDAY AND WEDNESDAY, THEN THE NEXT FRONTAL SYSTEM WILL
BRING MOSTLY RAIN TO THE LOWLANDS LATER IN THE WEEK, THOUGH THE GORGE
MAY RETAIN ENOUGH COLD AIR FOR ANOTHER ROUND OF SNOW OR ICE.
SHORT TERM...TODAY THROUGH MONDAY
A VERY CHALLENGING WINTER
WEATHER PATTERN WILL PERSIST ACROSS SW WASHINGTON AND NW OREGON
THROUGH AT LEAST MONDAY MORNING AND POTENTIALLY THROUGH THE END OF
THE UPCOMING WEEK. THE MENTION OF WINTER WEATHER HERE DOES NOT
NECESSARILY GUARANTEE LOW ELEVATION SNOW OR ICE, BUT MOST OF THE
FORECAST AREA HAS A CHANCE. THE ONE AREA THAT APPEARS TO BE MOSTLY
SAFE FROM FREEZING/FROZEN PRECIPITATION THE NEXT FEW DAYS IS THE
OREGON COAST NORTHWARD TO ABOUT CANNON BEACH, AS DOWNSLOPING EASTERLY
FLOW IS ALREADY LEADING TO NIGHT TIME TEMPERATURES IN THE MID TO
UPPER 40S - NOT IDEAL FOR WINTRY PRECIPITATION. MEANWHILE, COLD AIR
WILL REMAIN MOST PERSISTENT IN THE COLUMBIA GORGE, DUE TO THEIR
PROXIMITY TO A STRENGTHENING COLD POOL OVER THE COLUMBIA BASIN AND
PERSISTENT EASTERLY FLOW TO PROVIDE A FRESH SUPPLY OF COLD AIR FROM
THE EAST SIDE OF THE CASCADES. WITH HIGHER-RES MODELS STILL SHOWING
EASTERLY KTTD-KDLS MSLP GRADIENTS ON THE ORDER OF 7 TO 9 MB, THE WIND
WILL BE STRONG FOR THE GORGE WEST OF CASCADE LOCKS, AND MAY PROVIDE
GUSTS AS HIGH AS 35-45 MPH FOR EASTERN AND SOUTHWESTERN PORTIONS OF
THE PDX METRO. WE ARE ALREADY SEEING GUSTS 45-55 MPH AT CORBETT HIGH
SCHOOL AND AS HIGH AS 66 MPH AT CROWN POINT - THESE WILL LIKELY BE
RATCHETED UPWARDS AS GRADIENTS CONTINUE TO TIGHTEN AND THE EASTSIDE
COLD POOL BECOMES SHALLOWER. PEAK GUSTS ON THE ORDER OF 65 MPH ARE A
GOOD BET FOR CORBETT AND 80+ MPH FOR CROWN POINT. AT THIS POINT IT
DOES NOT APPEAR 40-45 MPH GUSTS WILL BE WIDESPREAD ENOUGH TO WARRANT
A WIND ADVISORY FOR THE PORTLAND METRO. THESE WINDS WILL LIKELY
CONTINUE THROUGH SUNDAY MORNING, BUT SHOULD BEGIN TO DIMINISH
THEREAFTER AS BOTH THE EASTSIDE HIGH AND WESTSIDE LOW PRESSURE
SYSTEMS WEAKEN, ALLOWING PRESSURE GRADIENTS TO SLACKEN.
OVERALL, NOT MUCH HAS CHANGED IN THE FORECAST OVER THE PAST 24 HOURS.
LATEST SATELLITE IMAGERY SHOWS THAT THE ANTICIPATED GULF OF ALASKA
UPPER LOW HAS ARRIVED BUT REMAINS A BIT OFFSHORE AS EXPECTED. THE
UPPER LOW HAS A BROAD CIRCULATION CENTERED ROUGHLY NEAR 43N/132W AS
OF 3 AM THIS MORNING. MODELS CONTINUE TO PARK THIS UPPER LOW OFF THE
S OR/N CA COAST FOR MUCH OF THIS WEEKEND, EVENTUALLY HAVING IT DRIFT
ONSHORE AND WEAKEN OVER NORTHERN CALIFORNIA MONDAY. THIS IS A
PRECARIOUS SPOT FOR THE UPPER LOW TO STALL, AS IT WILL LIKELY ROTATE
MOISTURE AND SHORTWAVE ENERGY NORTHWARD FROM CALIFORNIA WHILE ALSO
PULLING COLD AND DRY AIR WESTWARD THROUGH THE COLUMBIA GORGE. THIS
MAY - OR MAY NOT - RESULT IN SNOW OR FREEZING RAIN ACROSS THE
INTERIOR LOWLANDS OF SW WASHINGTON AND NW OREGON STARTING TONIGHT AND
CONTINUING THROUGH EARLY MONDAY. THE AIR MASS WILL BE VERY MARGINAL
FOR LOWLAND SNOW, AND SURFACE TEMPERATURES WILL LIKELY RISE ABOVE
FREEZING EACH DAY FOR THE LOWLANDS OUTSIDE OF THE COLUMBIA GORGE, SO
MANY AREAS MAY JUST SEE PERIODS OF COLD RAIN AND TEMPS IN THE MID TO
UPPER 30S. ANOTHER COMPLICATING FACTOR IS THAT THE DRY OFFSHORE FLOW
WILL LIKELY CAUSE SOME PRECIPITATION TO EVAPORATE BEFORE REACHING THE
GROUND, ESPECIALLY NORTH OF SALEM.
VIRTUALLY ALL GUIDANCE SHOWS MEASURABLE PRECIPITATION REACHING AS FAR
NORTH AS EUGENE BY SUNDAY MORNING, AND AS FAR NORTH AS SOUTHERN
WASHINGTON BY SUNDAY EVENING. SO MODELS DO SEEM TO SHOW HIGH
CONFIDENCE THAT THE AIR MASS WILL EVENTUALLY SATURATE SUNDAY, EVEN AS
FAR NORTH AS THE PORTLAND AND VANCOUVER METRO AREA. MODEL SOUNDINGS
VARY IN TERMS OF PRECIPITATION TYPE, AND A LOT WILL PROBABLY DEPEND
ON TWO THINGS: 1) HOW MUCH CLEARING OCCURS TODAY INTO THIS EVENING -
SOME CLEARING IS LIKELY NECESSARY FOR OUR LOWLANDS TO FALL BELOW
FREEZING BY THE TIME CLOUDS INCREASE AGAIN FROM THE SOUTH, AND 2) THE
TIMING OF PRECIPITATION - IF MUCH OF SUNDAY REMAINS DRY AND
ESPECIALLY IF THERE IS SUNSHINE, TEMPS WILL HAVE A VERY HARD TIME
SUPPORTING ACCUMULATING SNOW OR ICE AS LIGHT PRECIP DEVELOPS.
THE 00Z AND 06Z GFS MODEL CYCLES REMAIN STUBBORN IN GENERATING A
PERSISTENT BAND OF PRECIPITATION RIGHT OVER THE PORTLAND METRO AREA
SUNDAY MORNING, PERSISTING THROUGH SUNDAY AND SUNDAY NIGHT BEFORE
FINALLY PETERING OUT MONDAY MORNING. THIS IDEA DOES HAVE SOME SUPPORT
FROM THE 00Z ECMWF AND GEM DETERMINISTIC RUNS, THOUGH QPF IS MUCH
LIGHTER AND LIKELY MORE REASONABLE. SO IT DOES APPEAR THERE WILL BE A
BAND OF PRECIP SUPPORTED BY DEFORMATION AND LOW-LEVEL FRONTOGENESIS
ENHANCED BY THE COLD GORGE OUTFLOW MEETING THE MILDER AIR FROM THE
SOUTH. AT THIS POINT, IT APPEARS THE BEST FORECAST IS RAIN AFTER A
BRIEF PERIOD OF FREEZING RAIN IN SOME OF OUR SOUTHERN VALLEYS SUNDAY
MORNING, TRANSITIONING TO SNOW AS PRECIP SPREADS NORTH OF SALEM.
THERE WILL PROBABLY BE A LOT OF VIRGA OVER THE PORTLAND METRO SUNDAY
AS THE DRY GORGE OUTFLOW EVAPORATES PRECIP INITIALLY. THEN THE BIG
QUESTION WILL BE HOW MUCH MOISTURE REMAINS ONCE THE LOW LEVELS
SATURATE, AND WHETHER OR NOT IT IS SO LATE IN THE DAY SUNDAY THAT BY
THE TIME PRECIP ARRIVES, THE PORTLAND METRO ENDS UP WITH 40 DEGREE
RAIN. SO THERE ARE A LOT OF MOVING PARTS WITH THIS FORECAST, BUT THE
ODDS OF A HIGH IMPACT EVENT SUNDAY INTO MONDAY APPEAR LOW, BUT
NONZERO. FOR WHAT IT'S WORTH, NBM PROBABILITIES HAVE CREPT SLIGHTLY
UPWARD FOR AN INCH OR MORE OF SNOW, WITH NBM V4.1 PROBABILITIES OF AN
INCH OR MORE SITTING AT 25-35 PERCENT SALEM NORTHWARD. THERE ARE A
FEW ENSEMBLE MEMBERS OUT THERE SHOWING SOMETHING SIMILAR TO THE
00Z/06Z GFS, WHICH IS LIKELY WHY THE NBM ALSO SHOWS ABOUT A 10
PERCENT CHANCE OF 4 OR MORE INCHES OF SNOW IN THE PORTLAND/VANCOUVER
METRO NORTHWARD TO THE COWLITZ/LEWIS COUNTY LINE. CHANCES ARE HIGHER
IN THE COLUMBIA GORGE AND HOOD RIVER VALLEY. BY MIDDAY MONDAY,
EASTERLY FLOW SHOULD HAVE WEAKENED ACROSS THE GORGE AND TEMPERATURES
SHOULD CLIMB ABOVE FREEZING FOR JUST ABOUT ALL OF OUR LOWLANDS,
ALLOWING ANY LINGERING PRECIP TO FALL AS RAIN SHOWERS FOR THE
LOWLANDS MONDAY AFTERNOON, EVEN IN THE COLDER MODEL SCENARIOS.
WEAGLE
LONG TERM /MONDAY THROUGH FRIDAY/
THE UPPER LOW WHICH HAD
BROUGHT THE WINTERY MIX PRECIPITATION OVER THE WEEKEND, WILL
CONTINUE MOVING SOUTH MONDAY NIGHT. FOLLOWING BEHIND IT, A TALL
RIDGE EXTENDING UP INTO THE ARCTIC OCEAN WILL BE BEING PRESSED
SOUTHEAST FROM TWO MERGING LOWS NORTH OF 60N. CLEARING SKIES
MONDAY NIGHT WILL BE SHORT LIVED AS A LITTLE RIPPLE IN THE
NORTHWEST FLOW WILL SPREAD CLOUDS OVER, AT LEAST OVER THE
NORTHERN HALF OF THE FORECAST AREA, AND BRING A SLIGHT CHANCE OF
LIGHT SHOWER GOING INTO TUESDAY. TEMPERATURES WILL STAY BELOW
AVERAGE FOR EARLY DECEMBER DUE TO THE NORTHWESTERLY FLOW AS WELL
AS CLOUD COVER TUESDAY.
MOVING ON TO WEDNESDAY, LONGER RANGE DETERMINISTIC MODELS AND THEIR
ENSEMBLE MEANS ALL SHOW AN UPPER TROUGH DROPPING DOWN FROM THE GULF
OF ALASKA, WITH THE GEFS BEING THE SLOWEST AND DEEPEST SOLUTION.
THIS WILL SPREAD THE NEXT BETTER CHANCE FOR PRECIPITATION INTO THE
PACIFIC NORTHWEST WEDNESDAY INTO THURSDAY. WILL KEEP THE 20 TO 50
PERCENT POPS FROM THE NBM TO SHOW THIS INCREASE. DETERMINISTIC MODELS
AND THEIR ENSEMBLES ARE IN GOOD AGREEMENT THROUGH WEDNESDAY, WITH
WPC'S 500 MB CLUSTERS BEING ALMOST MIRROR IMAGES OVER THE WESTERN US,
SO HAVE A HIGH CONFIDENCE IN THIS PATTERN. ON THURSDAY, THE DEPTH OF
THE TROUGH IS WHERE THE ENSEMBLES ARE SEPARATING, SHOWING HIGHER
VARIABILITY IN THEIR SOLUTIONS. HOWEVER, 72 PERCENT OF THE MEMBERS
ARE SHOWING A TROUGH DROPPING INTO THE WEST COAST, SO WILL PUT MORE
CONFIDENCE IN THIS PATTERN. THE REAL QUESTION COMES ABOUT ON WHEN
THE PRECIPITATION MOVES INTO THE COAST AND HOW LONG IT WILL STAY IS
LOWER, AS EVIDENCED BY MORE VARIABILITY IN THE WPC CLUSTERS. LIKE THE
40-60 PERCENT POPS FOR THURSDAY INTO FRIDAY ON THE NBM, WILL KEEP
THIS FOR THE LONG TERM.
-KRIEDERMAN
AVIATION
18Z TAFS: NO BIG CHANGES, WITH VFR. HIGH PRESSURE
REMAINS ANCHORED EAST OF THE CASCADES TODAY INTO SUNDAY. THIS WILL
MAINTAIN MODERATE OFFSHORE FLOW, WITH GUSTY EASTERLY WINDS OVER THE
RIDGES AND THROUGH THE WESTERN COLUMBIA GORGE, AFFECTING MOSTLY KPDX
AND KTTD. LOW PRESSURE OFFSHORE WILL SLOWLY DROP SOUTH TODAY, THEN
INTO NORTHERN CALIF SUNDAY. AS SUCH, WILL SEE INCREASING HIGH CLOUDS
ACROSS REGION TODAY INTO TONIGHT, WITH MID DECK CLOUDS SPREADING
FROM SOUTH OREGON INTO LANE COUNTY TONIGHT. IN ADDITION, EXPECT
TYPICAL EAST SIDE IFR/MVFR WINTER STRATUS TO FORM AND JAM INTO THE
GORGE/HOOD RIVER VALLEY LATER TODAY AND MAINLY TONIGHT THROUGH SUN.
MOISTURE SHOULD REMAIN SOUTH OF THE REGION THROUGH TONIGHT, BUT
COULD SEE SPOTTY LIGHT RAIN OR SNOW OVER LANE COUNTY SUN AM.
FOR DETAILED PAC NW AVIATION WEATHER INFORMATION, GO ONLINE TO:
HTTP://WEATHER.GOV/ZSE
KPDX AND APPROACHES...VFR, WITH INCREASING HIGH CLOUDS THIS
AFTERNOON AND TONIGHT. MAINLY, BREEZY WITH EAST WINDS 15 TO 20 KT,
AND GUSTS 25 TO 30 KT TODAY INTO EARLY SUN. BIT STRONGER GUSTS TO
THE EAST, WITH GUSTS TO 40 KT AT KTTD AND EVEN A TAD STRONGER FOR
MOST EAST WIND-PRONE AREAS AT THE WEST END OF GORGE. /ROCKEY
MARINE
14Z SATELLITE IMAGERY REVEALED AN UPPER LEVEL LOW
PRESSURE AREA CENTERED NEAR 44N 133W AND DRIFTING SOUTH. A FRONTAL
BOUNDARY COULD BE SEEN EXTENDING FROM THE SOUTH WASHINGTON COAST TO
NEAR 40N 130W. THE INITIAL TIME STEPS FROM THE 06Z NAM AND 06Z GFS
VALID 12Z WERE GENERALLY 5-10 KT TOO STRONG, USING THE MODEL
BOUNDARY LAYER WIND SPEEDS AS A PROXY FOR GUSTS. OFFSHORE FLOW
BECOMES MORE PRONOUNCED SATURDAY AFTERNOON AND IS EXPECTED TO
CONTINUE THROUGH EARLY SUNDAY. EASTERLY GUSTS TO 25 KT WILL BE
MAINLY OVER THE NORTHERN ZONES, ESPECIALLY DOWNWIND FROM COASTAL
TERRAIN GAPS.
WIND SPEEDS DIMINISH TO 15 KT OR LESS SUNDAY AFTERNOON AND THEN TO
10 KT OR LESS SUNDAY EVENING THROUGH EARLY NEXT WEEK. LONG RANGE
MODEL GUIDANCE SUGGESTS A RETURN TO A MORE ACTIVE PATTERN LATE
NEXT WEEK. THE NATIONAL BLEND OF MODELS (NBM) V4.0 SHOWS A
GREATER THAN 90 PERCENT CHANCE FOR SMALL CRAFT ADVISORY LEVEL
GUSTS NEXT WEEKEND.
COMBINED SEAS WERE AS HIGH AS 21 FT AT 46089 EARLY SATURDAY
MORNING. LOWER HEIGHTS WERE NOTED WITHIN THE INNER WATERS, PER
BUOY 46243. THE HIGHEST WAVES WILL REMAIN OVER THE OUTER WATERS
THROUGH SATURDAY AFTERNOON, DUE TO THE SUBSTANTIALLY LARGER WIND
WAVE COMPONENT. WILL NEED TO CARRY A SHORT PERIOD OF HAZARDOUS
SEAS AFTER THE GALES END. THE OFFSHORE FLOW WILL ALLOW A QUICK
REDUCTION IN WAVE HEIGHTS. SEAS ARE EXPECTED TO FALL BELOW 10 FT
EARLY SATURDAY EVENING AND THEN DOWN TO AROUND 5 FT EARLY SUNDAY
MORNING. WEISHAAR
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 1 PM PST THIS AFTERNOON FOR COASTAL
WATERS FROM CAPE FOULWEATHER TO FLORENCE OR OUT 10 NM-
COLUMBIA RIVER BAR.
SMALL CRAFT ADVISORY UNTIL 7 PM PST THIS EVENING FOR COASTAL
WATERS FROM CAPE SHOALWATER WA TO CAPE FALCON OR OUT 10 NM.
SMALL CRAFT ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR COASTAL
WATERS FROM CAPE FALCON TO CAPE FOULWEATHER OR OUT 10 NM.
HAZARDOUS SEAS WARNING UNTIL 1 PM PST THIS AFTERNOON FOR
COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR FROM 10
TO 60 NM.
SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 4 AM PST
SUNDAY FOR WATERS FROM CAPE SHOALWATER WA TO CAPE FALCON OR
FROM 10 TO 60 NM.
SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 7 PM PST THIS
EVENING 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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