595
FXUS66 KPQR 081120
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
420 AM PDT THU OCT 8 2026
UPDATED AVIATION DISCUSSION.
SYNOPSIS
UNSEASONABLY WARM AND DRY WEATHER WITH WEAK
OFFSHORE FLOW WILL PERSIST THROUGH THURSDAY, BEFORE A TROUGH
BRINGS A RETURN TO COOLER TEMPERATURES WITH CHANCES FOR LIGHT
RAIN FRIDAY INTO SATURDAY. COOL NIGHTS WILL BRING CHANCES FOR
MORNING FROST IN RURAL VALLEYS AWAY FROM URBAN CORES THIS
WEEKEND INTO EARLY NEXT WEEK.
SHORT TERM...NOW THROUGH SATURDAY NIGHT
RIDGING ALOFT WILL
BEGIN TO WEAKEN TODAY AHEAD OF AN UPPER- LEVEL TROUGH MOVING
INTO THE REGION FROM THE GULF OF ALASKA FRIDAY INTO THE WEEKEND.
TODAY WILL SEE CONDITIONS SIMILAR TO RECENT DAYS, NAMELY
POCKETS OF MORNING FOG ALONG THE COAST AND WITHIN SHELTERED
VALLEYS GIVING WAY TO A MOSTLY SUNNY AFTERNOON. THE OFFSHORE-
ORIENTED PRESSURE GRADIENT ACROSS THE CASCADES HAS ALREADY BEGUN
TO WEAKEN, WITH ONSHORE FLOW EXPECTED TO STRENGTHEN BEGINNING
TONIGHT. AHEAD OF THIS PATTERN SHIFT, ANOTHER UNSEASONABLY WARM
DAY IS EXPECTED INLAND WITH HIGH TEMPERATURES SOME 10-15 DEGREES
ABOVE NORMAL IN THE UPPER 70S TO MID 80S, WHILE COASTAL AREAS
MAINTAIN SEASONABLE CONDITIONS. DESPITE THE ABNORMAL WARMTH
INLAND, DAILY RECORD HIGH TEMPERATURES APPEAR TO BE OUT OF
REACH, WITH LESS THAN A 5% CHANCE OF TYING EXISTING RECORDS AT
CLIMATE SITES ACROSS THE REGION.
CLOUD COVER WILL BEGIN TO INCREASE LATE THIS EVENING AHEAD OF AN
AN APPROACHING UPPER-LEVEL TROUGH WHICH WILL MOVE OVERHEAD
FRIDAY INTO SATURDAY. A LEADING UPPER SHORTWAVE AND ITS
ASSOCIATED WEAK SURFACE COLD FRONT WILL MOVE INTO THE REGION ON
FRIDAY. RAIN LIKELY BEGINS FRIDAY MORNING ALONG THE COAST BEFORE
REACHING INLAND TO THE I-5 CORRIDOR BY THE AFTERNOON TO EARLY
EVENING. RAIN ACCUMULATIONS WILL BE FAVORED ALONG THE NORTH
OREGON AND SOUTH WASHINGTON COASTS AS WELL AS THE CASCADES AND
THEIR WESTERN SLOPES, WHILE AREAS ALONG THE CENTRAL OREGON COAST
AND WITHIN THE WILLAMETTE VALLEY ARE MORE LIKELY TO STAY DRIER.
MEAN FORECAST RAINFALL TOTALS DURING THIS PERIOD ARE 0.1-0.25
INCHES NORTH OF LINCOLN CITY AND IN THE CASCADES AND FOOTHILLS
NORTH OF US-20, WITH 0.1 INCHES OR LESS ELSEWHERE. AS THE TROUGH
MOVES INLAND, A SECOND SHORTWAVE IMPULSE MOVING SOUTH ON ITS
WESTERN FLANK ON SATURDAY WILL SEE THE TROUGH ELONGATE AND
EVENTUALLY PINCH OFF INTO A CLOSE UPPER LOW WHICH WILL SETTLE
SOUTH OVER CALIFORNIA BY EARLY NEXT WEEK. THIS FEATURE WILL
PRODUCE A SECOND CHANCE FOR LIGHT RAIN FROM FRIDAY NIGHT INTO
SATURDAY MORNING, WITH MORE WIDESPREAD POTENTIAL FOR UP TO 0.1
INCHES OF ADDITIONAL RAIN. ALL TOLD, THE CHANCES FOR 0.25 INCHES
OF RAIN IN 48 HOURS REACH 40-60% IN THE WETTEST AREAS FROM
TILLAMOOK COUNTY NORTH ON THE COAST AND NORTH OF OR-22 IN THE
CASCADES AND FOOTHILLS. ELSEWHERE, THOSE CHANCES ARE 15-25% IN
THE LOWER COLUMBIA AND COWLITZ VALLEYS, AND 5-15% WITHIN THE
WILLAMETTE VALLEY AND ALONG THE COAST SOUTH OF PACIFIC CITY.
AS THE INITIAL FRONT MOVES INLAND FRIDAY THROUGH FRIDAY NIGHT,
PEAK GUSTS OUT OF THE WEST IN THE CASCADES, CENTRAL COLUMBIA
GORGE, AND HOOD RIVER VALLEY COULD REACH 35-45 MPH. BEHIND THE
BOUNDARY AS THE CORE OF COOLER AIR ALOFT MOVES OVERHEAD,
TEMPERATURES WILL QUICKLY FALL BACK TOWARD SEASONAL NORMS IN THE
UPPER 50S AND 60S FRIDAY AND SATURDAY. OVERNIGHT LOWS WILL
SIMILARLY TREND COOLER, ESPECIALLY SATURDAY NIGHT. ON FRIDAY
NIGHT, THERE IS HIGH CONFIDENCE THAT HIGHER ELEVATION PORTIONS
OF THE UPPER HOOD RIVER VALLEY NEAR DEE AND PARKDALE WILL SEE
TEMPERATURES IN THE MID 30S AND AN ELEVATED POTENTIAL FOR FROST.
BY SATURDAY NIGHT, THE CHANCES FOR A TRUE FREEZE IN THE UPPER
HOOD RIVER VALLEY REACH 35-65% IN THOSE SAME AREAS. THERE ARE
ADDITIONALLY GREATER THAN 50% CHANCES FOR TEMPERATURES IN THE
MID 30S AND FROST ON SATURDAY NIGHT IN THE CASCADE FOOTHILLS AND
NORTH OREGON COAST RANGE VALLEYS, AND 25-50% CHANCES IN THE
SOUTHERN WILLAMETTE VALLEY AND HIGHER ELEVATION PORTIONS OF
CLARK AND COWLITZ COUNTY LOWLANDS IN SOUTHWESTERN WASHINGTON.
FROST ADVISORIES AND/OR FREEZE WATCHES MAY THEREFORE BE
NEEDED, AND THOSE WITH AGRICULTURAL INTERESTS SHOULD CONTINUE
TO MONITOR THE FORECAST. -36
LONG TERM...SUNDAY THROUGH WEDNESDAY
SUNDAY INTO EARLY NEXT
WEEK, THE AFOREMENTIONED UPPER LOW SEPARATES FROM THE MEAN MID-
LATITUDE FLOW AND DRIFTS SOUTH OVER CALIFORNIA. LOCALLY,
TRANSIENT UPPER-LEVEL RIDGING WILL REPLACE THE DEPARTING TROUGH,
LEADING TO A DRYING AND MODEST WARMING TREND. SUNDAY MORNING
WILL FEATURE A NEAR-REPEAT OF SATURDAY MORNING WITH WIDESPREAD
CHANCES FOR FROST IN SHELTERED VALLEYS AWAY FROM URBAN AREAS AND
CHANCES FOR A FREEZE WITHIN THE UPPER HOOD RIVER VALLEY. HIGH
TEMPERATURES THEN TREND A FEW DEGREES WARMER INTO THE MID TO
UPPER 60S ACROSS THE REGION BY MONDAY AFTERNOON. THERE IS
INCREASING CONSENSUS AMONG LONG-RANGE ENSEMBLE MEMBERS IN
ADDITIONAL UPPER-LEVEL TROUGHING MOVING INTO THE REGION TUESDAY
INTO WEDNESDAY. AT THIS POINT, LOW CHANCES FOR RAIN ARE ASSESSED
DURING THIS PERIOD UNTIL CONFIDENCE IN THE EVOLUTION OF THIS
FEATURE INCREASES. -36
AVIATION...THROUGH 12Z FRIDAY
LARGELY VFR FLYING CONDITIONS
CONTUSE EARLY THIS MORNING EXCEPT FOR IFR/LIFR CIGS/VIS WITH FOG
OR LOW STRATUS CURRENTLY CONCENTRATED ALONG THE COAST AND IN THE
SOUTHERN WILLAMETTE VALLEY. EFFICIENT RADIATIVE COOLING MAY
ALLOW FOR ADDITIONAL FOG TO DEVELOP IN SHELTERED VALLEYS,
INCLUDING LOW TO MODERATE CHANCES, 10-30%, FOR IFR/LIFR CIGS/VIS
AT ALL OTHER TERMINALS, HIGHEST IN THE CASCADE FOOTHILLS (KTTD)
AND ALONG THE LOWER COLUMBIA/COWLITZ VALLEYS (KKLS, KSPB). ANY
VIS/CIGS RESTRICTIONS WILL TEND TO MIX OUT BY 17-19Z THU INLAND
AND 18-20Z THU ALONG THE COAST AS DAYTIME HEATING AND DIURNAL
WINDS INCREASE. VFR CONDITIONS ARE THEN FAVORED BENEATH
INCREASING HIGH CLOUDS THROUGH MUCH OF THE PERIOD. NORTH TO
NORTHWEST WINDS WILL RISE TO 10-15 KT WITH GUSTS NEAR 20 KT
ALONG THE COAST, AND TO 5-10 KT INLAND, BEFORE EASING BELOW 5 KT
AGAIN THIS EVENING.
KPDX AND APPROACHES...CONTINUED VFR CONDITIONS FAVORED WITH LOW
CHANCES, 20%, FOR IFR/LIFR VIS/CIGS IF FOG OR LOW STRATUS FORMS
NEAR DAWN, MOST LIKELY BY 14-15Z THU. ANY LOW CLOUD OR FOG WILL
MIX OUT BY 17-18Z THU, WITH HIGH CONFIDENCE IN VFR CONDITIONS
THEREAFTER BENEATH INCREASING HIGH CLOUD COVER. DIURNAL
NORTHWEST WINDS WILL RISE TO AROUND 5 KT THIS AFTERNOON, THEN
EASE THIS EVENING. -36
MARINE
HIGH PRESSURE AT THE SURFACE WILL CONTINUE TO LINGER
OVER THE NORTHEASTERN PACIFIC THROUGH TODAY FACILITATING PEAK
AFTERNOON/EVENING WIND GUSTS OF 20-25 KT. AS A RESULT, SMALL
CRAFT ADVISORIES REMAIN IN EFFECT FROM 2 PM THIS AFTERNOON UNTIL
11 PM THIS EVENING FOR THE WATERS SOUTH OF CAPE FALCON. DURING
THIS TIME PERIOD, ANTICIPATE LARGELY WIND-DRIVEN SEAS OF 6-9 FT
WITH AN UNDERLYING WEST-NORTHWEST SWELL. WEAKENING HIGH PRESSURE
ALOFT WILL CONTINUE TO SUPPORT AREAS OF DENSE FOG IN THE MORNING
HOURS AS CLOUD BASES ARE COMPRESSED DOWN TO THE SURFACE TODAY.
MORE ACTIVE MARINE CONDITIONS ARE EXPECTED FROM FRIDAY INTO THE
WEEKEND AS TROUGHING OVER THE GULF OF ALASKA PUSHING SOUTHWARD
GENERATES A REINFORCING NORTHWEST SWELL IN ADDITION TO THE
ARRIVAL OF A FRONTAL BOUNDARY. WINDS OUT OF THE NORTHWEST
ASSOCIATED WITH A COLD FRONT WILL INCREASE TO AROUND 20 KT ON
FRIDAY, ESPECIALLY NORTH OF CAPE FALCON, WHILE SEAS PEAK AT 8-12
FT FRIDAY NIGHT INTO SATURDAY. BY SUNDAY, WINDS EASE AND VEER
OUT OF THE NORTH TO NORTH-NORTHEAST WHILE SEAS FALL BACK TO 5-7
FT THROUGH EARLY NEXT WEEK. -36
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 11 PM PDT
THIS EVENING FOR PZZ252-253-272-273.
SMALL CRAFT ADVISORY UNTIL 8 AM PDT THIS MORNING FOR
PZZ271>273.
WWW.WEATHER.GOV/PORTLAND
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