710
FXUS66 KPQR 121155 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
454 AM PDT MON OCT 12 2026
..UPDATED AVIATION DISCUSSION
SYNOPSIS
HIGH PRESSURE WILL MAINTAIN DRY WEATHER THROUGHOUT
THE WEEK. CLEAR SKIES AND COOL NIGHTS INCREASE CHANCES FOR
FROST ACROSS INTERIOR VALLEYS THIS MORNING AND TONIGHT.
TEMPERATURES TREND WARMER LATE THIS WEEK AS AN UPPER-LEVEL
RIDGE AMPLIFIES OVER THE REGION. CHANCES FOR PRECIPITATION
RETURN TOWARDS THE END OF THE WEEKEND.
SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT
DRY WEATHER
PREVAILS ACROSS THE REGION AS UPPER-LEVEL LOW PRESSURE OVER
EASTERN OR/WA CONTINUES TO WEAKEN AND SHIFT SOUTHWARD WHILE
RIDGING BUILDS OVER WESTERN OR/WA, ALLOWING FOR NORTHERLY FLOW.
MOSTLY CLEAR SKIES AND CALM WINDS IS RESULTING IN EFFICIENT
RADIATIONAL COOLING, WITH TEMPERATURES ALREADY FALLING INTO THE
UPPER 30S TO LOW 40S AS OF EARLY MONDAY MORNING. OVER THE NEXT
SEVERAL HOURS, WILL CONTINUE TO SEE TEMPERATURES DROP INTO THE
LOW TO MID 30S, FAVORING WIDESPREAD FROST DEVELOPMENT. FROST
ADVISORIES REMAIN IN EFFECT THROUGH 8 AM THIS MORNING ACROSS
MOST INTERIOR VALLEYS AND THE COAST RANGE LOWLANDS, WHILE A
FREEZE WARNING IS IN EFFECT FOR THE UPPER HOOD RIVER VALLEY FOR
TEMPERATURES BELOW FREEZING (28-32F). AN EXCEPTION WOULD BE THE
URBAN CORE OF THE PORTLAND METRO AREA, WHERE URBAN HEAT ISLAND
EFFECTS WILL KEEP TEMPERATURES A FEW DEGREES WARMER THAN
OUTLYING AREAS. ANYONE GROWING OUTDOOR PLANTS THAT ARE
SUSCEPTIBLE TO FROST DAMAGE SHOULD CONTINUE TO COVER PLANTS OR
LEAVE PLANTS INDOORS IF POSSIBLE.
DRY WEATHER PREVAILS TODAY THROUGH WEDNESDAY AS UPPER-LEVEL
RIDGING CONTINUES TO AMPLIFY OFFSHORE AND EXTEND OVER WESTERN
OR/WA. TEMPERATURES REMAIN SEASONABLE ACROSS INTERIOR VALLEYS,
WITH AFTERNOON HIGHS PEAKING IN THE MID 60S TODAY AND TUESDAY,
AND LOW 70S ON WEDNESDAY. CLEAR SKIES AND CALM WINDS TONIGHT
WILL RESULT IN RENEWED POTENTIAL FOR FROST DEVELOPMENT AS
TUESDAY MORNING LOWS DROP INTO THE MID 30S AGAIN FOR INTERIOR
LOCATIONS AWAY FROM URBAN CORES. UPPER-LEVEL RIDGING FLATTENS
SLIGHTLY TUESDAY TO WEDNESDAY AS A SYSTEM RIDES THE NORTHERN
PERIPHERY OF THE RIDGE AND HEADS INTO BRITISH COLUMBIA. GIVEN
THAT THIS SYSTEM WILL TRACK FURTHER NORTH, PRECIPITATION IS NOT
EXPECTED FOR THE MAJORITY OF OUR AREA EXCEPT FOR A 15-20% CHANCE
FOR LIGHT SHOWERS ALONG THE SOUTH WASHINGTON COAST WEDNESDAY
MORNING. FROST DEVELOPMENT LOOKS LESS LIKELY AFTER TONIGHT, AS
INCREASED CLOUD COVER TUESDAY NIGHT AND INCREASED OFFSHORE FLOW
WEDNESDAY NIGHT KEEP OVERNIGHT TEMPERATURES SLIGHTLY WARMER.
-10
LONG TERM...THURSDAY THROUGH SUNDAY
THE MAJORITY OF ENSEMBLE
MEMBERS ARE IN AGREEMENT THAT UPPER-LEVEL RIDGING WILL AMPLIFY
FURTHER OTHER THE WESTERN U.S. ON THURSDAY AND FRIDAY. THIS WILL
RESULT IN TEMPERATURES REBOUNDING TO THE LOW TO MID 70S ACROSS
INTERIOR VALLEYS AT THE END OF THE WEEK. GUIDANCE ALSO SUGGESTS
THAT THERMAL TROUGHING WILL ALSO RE-DEVELOP, RETURNING OFFSHORE
EASTERLY FLOW ACROSS THE CASCADES AND COLUMBIA RIVER GORGE LATE
THIS WEEK. HEADING INTO THE WEEKEND, THE UPPER RIDGE GETS PUSHED
FURTHER EAST BY UPPER-LEVEL TROUGHING COMING DOWN FROM THE GULF
OF ALASKA. THERE REMAINS UNCERTAINTY WITH THE TIMING, POSITION,
AND MAGNITUDE OF THE TROUGHING AT THIS POINT, BUT WHAT WE CAN
SAY WITH HIGHER CONFIDENCE IS THAT THIS PATTERN WOULD RETURN
COOLER TEMPERATURES AND CHANCES FOR PRECIPITATION FOR THE
WEEKEND AND INTO EARLY NEXT WEEK. -10
AVIATION...THROUGH 12Z TUESDAY
FROM 12-15Z MON, CLEAR SKIES
AND CALM WINDS WILL SUPPORT TEMPERATURES FALLING TOWARDS 33-36
DEGREES F ACROSS MUCH OF THE AREA OUTSIDE OF THE PORTLAND METRO AND
AS LOW AS 28-32 DEGREES F IN THE UPPER HOOD RIVER VALLEY. LOCATIONS
THAT ARE ABLE TO COOL DOWN TO THESE TEMPERATURES MAY SEE FROST
DEVELOPMENT ON METAL SURFACES. CHANCES FOR LIFR FOG OR STRATUS
ACROSS THE WILLAMETTE VALLEY ARE ONLY 5-10% AT ANY GIVEN HOUR
THROUGH 16-17Z MON. CHANCES ARE SLIGHTLY HIGHER (15-25%) AT KAST,
WHERE OBSERVATIONS AS OF EARLY MONDAY MORNING HAVE SHOWN SOME VIS
REDUCTIONS TO 2-4 SM. ANY FOG OR LOW STRATUS WOULD DISSIPATE BY 17-
18Z MON AS DAYTIME HEATING PROGRESSES. HIGH PRESSURE WILL MAINTAIN
VFR CONDITIONS WITH CLEAR SKIES THROUGH THE TAF PERIOD.
NORTHWESTERLY WINDS THIS AFTERNOON AROUND 5-7 KT OR LESS.
KPDX AND APPROACHES...VFR THROUGH THE TAF PERIOD. NORTHWESTERLY
WINDS UNDER 5 KT. -10
MARINE
BENIGN MARINE CONDITIONS EXPECTED THIS WEEK. A SMALL
CRAFT ADVISORY IS IN EFFECT FOR THE MAIN CHANNEL OF THE COLUMBIA
RIVER BAR FROM 4-9 PM THIS EVENING FOR A STRONG EBB CURRENT
BRINGING SEAS TO 6-7 FT. OTHERWISE, HIGH PRESSURE WILL MAINTAIN
LIGHT NORTHERLY WINDS ACROSS THE WATERS THROUGH TONIGHT. TUESDAY
TO WEDNESDAY, WINDS TURN MORE SOUTHERLY FROM A WEAK FRONT, BUT
RETURN NORTHERLY BY THE END OF THE WEEK. SEAS REMAIN AROUND 4-7 FT
THIS WEEK WITH PERIODS OF 13-16 SECONDS THROUGH WEDNESDAY AND
10-13 SECONDS LATE THIS WEEK INTO THE WEEKEND. A LONG-PERIOD
WEST/NORTHWESTERLY SWELL WILL RESULT IN A MODERATE THREAT FOR
SNEAKER WAVES THIS WEEK. CAUTION SHOULD BE USED WHEN IN OR NEAR
THE WATER. -10
PQR WATCHES/WARNINGS/ADVISORIES
OR...FROST ADVISORY UNTIL 8 AM PDT THIS MORNING FOR ORZ104-107-109-
112>119-123>125.
FREEZE WARNING UNTIL 8 AM PDT THIS MORNING FOR ORZ121.
WA...FROST ADVISORY UNTIL 8 AM PDT THIS MORNING FOR WAZ202-204>208.
PZ...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 9 PM PDT THIS
EVENING FOR PZZ210.
WWW.WEATHER.GOV/PORTLAND
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