548
FXUS66 KPQR 082118
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
218 PM PDT THU OCT 8 2026
SYNOPSIS
UNSEASONABLY WARM AND DRY WEATHER WILL GIVE WAY TO
COOLER TEMPERATURES AND CHANCES FOR LIGHT RAIN AS AN UPPER TROUGH
MOVES OVER THE REGION FRIDAY INTO SATURDAY. COOL NIGHTS WILL BRING
CHANCES FOR MORNING FROST IN RURAL VALLEYS AWAY FROM URBAN CORES
THIS WEEKEND INTO EARLY NEXT WEEK. DRY CONDITIONS WITH SEASONABLE
TEMPERATURES ARE EXPECTED SUNDAY AND MONDAY BEFORE ANOTHER ROUND OF
LIGHT RAIN IS POSSIBLE ON TUESDAY.
SHORT TERM...NOW THROUGH SATURDAY NIGHT
SUNNY SKIES UNDER BROAD
UPPER LEVEL RIDGING WILL MAINTAIN WARM AND DRY CONDITIONS THROUGH
THIS EVENING. A BIT OF A PATTERN CHANGE IS FORTHCOMING AS THE
WEATHER TRANSITIONS TOWARD MORE TYPICAL FALL-LIKE CONDITIONS. WATER
VAPOR SATELLITE IMAGERY REVEALS THE UPPER LEVEL TROUGH CURRENTLY
OVER THE GULF OF ALASKA THAT IS EXPECTED TO DROP SOUTH INTO THE
PACIFIC NORTHWEST ON FRIDAY. AS THIS UPPER TROUGH APPROACHES, IT
WILL PUSH A DECAYING COLD FRONT ACROSS THE AREA LATER FRIDAY MORNING
THROUGH THE AFTERNOON. EXPECT CLOUDS COVER TO INCREASE TONIGHT WITH
LIGHT RAIN PUSHING ONTO THE SOUTH WA/NORTH OR COAST EARLY FRIDAY
MORNING. BEST CHANCE FOR RAIN ALONG THE I-5 CORRIDOR WILL BE LATER
FRI MORNING INTO THE AFTERNOON. RAIN ACCUMULATIONS WILL BE FAVORED
ALONG THE NORTH OR AND SOUTH WA 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.
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 CLOSED UPPER LOW WHICH WILL SETTLE SOUTH
OVER CALIFORNIA BY EARLY NEXT WEEK. THIS FEATURE WILL PRODUCE A
SECOND CHANCE OF LIGHT RAIN LATER FRIDAY NIGHT INTO SATURDAY AS
SCATTERED SHOWERS DEVELOP WITHIN THE COOLER AIR ALOFT. MEAN FORECAST
RAINFALL TOTALS DURING THIS PERIOD ARE 0.10-0.25 INCH NORTH OF
LINCOLN CITY AND IN THE CASCADES AND FOOTHILLS NORTH OF US-20, WITH
0.10 INCH OR LESS ELSEWHERE. 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. A
FROST ADVISORY IS IN EFFECT FOR PORTIONS OF THE UPPER HOOD RIVER
VALLEY COUNTY LATE FRIDAY NIGHT INTO SAT MORNING.
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. DH/36
LONG TERM...SUNDAY THROUGH WEDNESDAY NIGHT
ENSEMBLE GUIDANCE IS
IN GOOD AGREEMENT THAT THE ELONGATED UPPER TROUGH DROPS SOUTH OVER
CALIFORNIA ON SUNDAY AND EVENTUALLY SPLITS INTO A CUTOFF UPPER LOW
EARLY NEXT WEEK. WEAK UPPER LEVEL RIDGING OF THE NE PACIFIC WILL
NUDGE BACK OVER THE REGION, LEADING TO DRY AND MORE SEASONABLY WARM
TEMPERATURES INTO THE MID TO UPPER 60S. SUNDAY MORNING WILL FEATURE
A NEAR-REPEAT OF SATURDAY MORNING, IF NOT COOLER UNDER MORE CLEAR
SKIES, WITH WIDESPREAD CHANCES FOR FROST IN SHELTERED VALLEYS AWAY
FROM URBAN AREAS AND CHANCES FOR A FREEZE WITHIN THE UPPER HOOD
RIVER VALLEY. 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 TO MODERATE (35-
55%) CHANCES FOR RAIN ARE ASSESSED DURING THIS PERIOD UNTIL
CONFIDENCE IN THE EVOLUTION OF THIS FEATURE INCREASES. DH/36
AVIATION...THROUGH 18Z FRIDAY
CURRENTLY VFR CONDITIONS
THROUGHOUT THE AIRSPACE, ALTHOUGH KONP COULD STILL EXPERIENCE
MOMENTS OF LIFR STRATUS THIS AFTERNOON AS MARINE STRATUS LINGERS
NEAR THE COASTLINE. LOOKING AHEAD, COASTAL TERMINALS WILL LIKELY
DROP BACK DOWN TO LIFR/IFR CONDITIONS BY 02-04Z FRI, WITH CHANCES
OF LIFR CONDITIONS AROUND 20-50% (HIGHEST AT KONP) AND CHANCES OF
IFR AROUND 30-60%. ADDITIONALLY, KEUG HAS A 15-25% CHANCE OF LIFR
AND 25-35% CHANCE OF IFR CONDITIONS AFTER 06-08Z FRI.
INTO EARLY TOMORROW, A TROUGH DIPS INTO THE REGION, BRINGING RAIN
TO KAST AROUND 12Z FRI AND THEN INTERIOR LOWLAND TERMINALS AROUND
15-20Z FRI AS THE FRONT MOVES SOUTHWARD (KPDX: AROUND 15Z, KEUG:
AROUND 19Z). ADDITIONALLY, THIS TROUGH WILL BRING A 20-40% CHANCE
OF MVFR CIGS.
OTHERWISE, EXPECT NORTH TO NORTHWEST WINDS AROUND 5-10 KT INLAND
AND 10-15 KT WITH GUSTS NEAR 20 KT ALONG THE COAST THIS AFTERNOON.
WINDS WILL THEN EASE TO 5 KT OR LESS BY THIS EVENING. EXPECT
SIMILAR WINDS TOMORROW AFTERNOON, ALTHOUGH POSSIBLY A LITTLE
STRONGER WITH THE PASSING WEATHER SYSTEM.
KPDX AND APPROACHES...VFR WITH HIGH CLOUD COVER THROUGH MOST OF
THE PERIOD. NORTHWEST WINDS AROUND 4 TO 6 KT THIS AFTERNOON, THEN
EASING INTO THE EVENING. AS A TROUGH APPROACHES TOMORROW MORNING,
EXPECT RAIN TO ARRIVE AROUND 16Z FRI AND A 30-40% CHANCE OF MVFR
CIGS. ADDITIONALLY, WINDS WILL LIKELY INCREASE TOMORROW AFTERNOON,
TO AROUND 8 TO 10 KT. ~12
MARINE
HIGH PRESSURE AT THE SURFACE OVER THE NORTHEASTERN
PACIFIC TODAY CONTINUES TO BRING AFTERNOON/EVENING WIND GUSTS OF
20-25 KT. AS A RESULT, SMALL CRAFT ADVISORIES FOR THE WATERS
SOUTH OF CAPE FALCON REMAIN IN EFFECT UNTIL 11 PM TONIGHT.
ANTICIPATE LARGELY WIND-DRIVEN SEAS OF 6-9 FT WITH AN UNDERLYING
WEST-NORTHWEST SWELL DURING THE ADVISORIES. WHILE WEAKENING HIGH
PRESSURE ALOFT WOULD CONTINUE TO SUPPORT AREAS OF FOG IN THE
MORNING HOURS TOMORROW, AN APPROACHING WEATHER SYSTEM THAT WILL
BRING RAIN AND WIND WILL LIKELY INHIBIT FOG FROM BECOMING DENSE.
THIS WEATHER SYSTEM ON FRIDAY AND THROUGH THE WEEKEND, WHICH IS A
TROUGH OVER THE GULF OF ALASKA PUSHING SOUTHWARD, WILL GENERATE A
NORTHWEST SWELL IN ADDITION TO THE ARRIVAL OF A FRONTAL BOUNDARY.
WINDS OUT OF THE NORTHWEST ASSOCIATED WITH THE FRONTAL BOUNDARY
WILL INCREASE TO AROUND 20 TO 25 KT ON FRIDAY, ESPECIALLY NORTH
OF CAPE FALCON, WHILE SEAS PEAK AT 8-12 FT FRIDAY EVENING 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. ~12/36
PQR WATCHES/WARNINGS/ADVISORIES
OR...FROST ADVISORY FROM MIDNIGHT FRIDAY NIGHT TO 9 AM PDT SATURDAY
FOR ORZ121.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 11 AM TO 6 PM PDT FRIDAY FOR PZZ210.
SMALL CRAFT ADVISORY FROM 8 AM TO 2 PM PDT FRIDAY FOR PZZ251.
SMALL CRAFT ADVISORY UNTIL 11 PM PDT THIS EVENING FOR PZZ252-253-
272-273.
SMALL CRAFT ADVISORY FROM 5 AM TO 2 PM PDT FRIDAY FOR PZZ271.
WWW.WEATHER.GOV/PORTLAND
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