840
FXUS66 KPQR 130539 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
1039 PM PDT MON OCT 12 2026
UPDATED AVIATION DISCUSSION.
SYNOPSIS
DRY WEATHER CONTINUES THROUGH THE WORKWEEK AS HIGH
PRESSURE STRENGTHENS OVER THE PACIFIC NORTHWEST. FROST REMAINS A
CONCERN ACROSS INTERIOR VALLEYS TONIGHT, FOLLOWED BY A WARMING
TREND LATE IN THE WEEK AS RIDGING AMPLIFIES AND EASTERLY FLOW
DEVELOPS. A RETURN TO COOLER, WETTER CONDITIONS IS POSSIBLE OVER
THE WEEKEND AS A TROUGH APPROACHES FROM THE GULF OF ALASKA.
DISCUSSION...NOW THROUGH SUNDAY
HIGH PRESSURE WILL MAINTAIN
GENERALLY QUIET WEATHER ACROSS NORTHWEST OREGON AND SOUTHWEST
WASHINGTON THROUGH MIDWEEK. AN UPPER-LEVEL LOW OVER EASTERN
OREGON AND WASHINGTON CONTINUES TO WEAKEN AND SHIFT SOUTH, WHILE
RIDGING BUILDS INLAND FROM THE NORTHEAST PACIFIC. AFTERNOON
TEMPERATURES WILL GRADUALLY RECOVER FROM THE MID 60S TODAY AND
TUESDAY INTO THE LOWER 70S WEDNESDAY.
THE PRIMARY NEAR-TERM CONCERN IS ANOTHER ROUND OF FROST TONIGHT
AS CLEAR SKIES AND LIGHT WINDS FAVOR EFFICIENT RADIATIONAL
COOLING. INTERIOR VALLEYS AWAY FROM URBAN CENTERS ARE EXPECTED
TO SEE TEMPERATURES FALL INTO THE MID 30S, WITH COLDER SHELTERED
LOCATIONS POTENTIALLY APPROACHING FREEZING. FROST ADVISORIES
HAVE BEEN ISSUED FOR PORTIONS OF NORTHWEST AND WEST CENTRAL
OREGON AND SOUTHWEST WASHINGTON FOR TONIGHT INTO TUESDAY
MORNING. TEMPERATURES WITHIN THE PORTLAND METRO SHOULD REMAIN
SOMEWHAT MILDER DUE TO THE URBAN HEAT ISLAND EFFECT.
ADDITIONALLY, THE UPPER HOOD RIVER VALLEY IS EXPECTED TO SEE
SUB-FREEZING TEMPERATURES AS LOW AS 28 TO 32 DEGREES, THEREFORE
A FREEZE WARNING HAS BEEN ISSUED FROM TONIGHT INTO TUESDAY
MORNING. EXPECT THE COLDEST TEMPERATURES NEAR PARKDALE. FROST
AND FREEZE CONDITIONS COULD KILL CROPS, OTHER SENSITIVE
VEGETATION AND POSSIBLY DAMAGE UNPROTECTED OUTDOOR PLUMBING.
CONSIDER TEMPORARILY COVERING SENSITIVE OUTDOOR PLANTS WITH A
LIGHTWEIGHT COTTON FABRIC (SUCH AS BED SHEETS, THIN BLANKETS),
AS THIS WILL HELP RETAIN HEAT AND PROVIDE FROST PROTECTION FOR
YOUR PLANTS.
DRY CONDITIONS ARE EXPECTED TO PERSIST THROUGH WEDNESDAY FOR
MOST OF THE FORECAST AREA. A WEAK SYSTEM TRACKING ALONG THE
NORTHERN PERIPHERY OF THE RIDGE TOWARD BRITISH COLUMBIA MAY
BRING A LIGHT CHANCE OF LIGHT SHOWERS TO THE SOUTH WASHINGTON
COAST WEDNESDAY MORNING, BUT PRECIPITATION IS NOT EXPECTED
ELSEWHERE. FROST POTENTIAL SHOULD DECREASE AFTER TONIGHT AS
INCREASING CLOUD COVER AND A GRADUAL CHANGE IN THE LOW-LEVEL
WIND PATTERN SUPPORT MILDER OVERNIGHT TEMPERATURES.
THE UPPER-LEVEL RIDGE IS FORECAST TO STRENGTHEN FURTHER THURSDAY
AND FRIDAY, ALLOWING TEMPERATURES TO CLIMB INTO THE MID TO
UPPER 70S ACROSS THE INTERIOR LOWLANDS. THERMAL TROUGHING IS
ALSO EXPECTED TO REDEVELOP, BRINGING A RETURN OF EASTERLY
OFFSHORE FLOW THROUGH THE COLUMBIA RIVER GORGE AND CASCADE GAPS
LATE IN THE WEEK. WHILE THE COLUMBIA RIVER GORGE WILL LIKELY
STAY GUSTY THROUGH EACH DAY, WINDS IN THE CASCADES WILL LIKELY
WEAKEN BY THE AFTERNOON EACH DAY, FOLLOWED BY STRENGTHENING
AGAIN OVERNIGHT. THE STRENGTH OF THIS FLOW WILL NEED TO BE
MONITORED AS THE PATTERN EVOLVES.
HEADING INTO THE WEEKEND, GUIDANCE INCREASINGLY FAVORS AN
UPPER-LEVEL TROUGH MOVING SOUTHEAST FROM THE GULF OF ALASKA AND
DISPLACING THE RIDGE EASTWARD. THIS WOULD BRING COOLER
TEMPERATURES AND A RENEWED CHANCE FOR PRECIPITATION ACROSS THE
REGION, POTENTIALLY EXTENDING INTO EARLY NEXT WEEK.
PROBABILISTIC GUIDANCE SUGGESTS A DECENT AMOUNT OF RAIN OVER THE
WEEKEND, WITH CHANCES OF 0.25 INCHES OVER 48 HOURS AROUND
25-50% ALONG THE COAST, 20-30% WITHIN THE INTERIOR LOWLANDS, AND
15-30% OVER THE CASCADES. AS FOR CHANCES OF 0.01 INCHES, 40-70%
ALONG THE COAST, 40-60% WITHIN THE INTERIOR LOWLANDS, AND
30-60% OVER THE CASCADES. WITH CONSIDERABLE UNCERTAINTY IN THE
TIMING, STRENGTH, AND PLACEMENT OF THE TROUGH, CONFIDENCE IN THE
DETAILS OF THE WEEKEND FORECAST REMAINS LIMITED. ~12
AVIATION...THROUGH 06Z WEDNESDAY
HIGH PRESSURE WILL MAINTAIN
VFR CONDITIONS WITH CLEAR SKIES THROUGH THE TAF PERIOD FOR MOST
LOCATIONS. THERE'S A 20-50% CHANCE OF LOCALIZED AREAS OF STRATUS
WITH MVFR/IFR CONDITIONS FORMING AGAIN AROUND 11-14Z TUE FOR
INLAND VALLEYS AND ALONG THE COAST WITH THE HIGHEST CHANCES IN THE
PORTLAND AREA. HAVE ADDED SOME SCT LOW CLOUDS ALONG WITH BCFG
TO SOME SITES THAT HAVE HAD ISSUES THE LAST COUPLE NIGHT. ANY
STRATUS OR FOG THAT DOES FORM SHOULD DISSIPATE AND IMPROVE TO VFR
BY 16-18Z TUE. HOWEVER, A WEAK FRONT BRUSHING THE PACNW WILL
BRING INCREASED HIGH LEVEL CLOUD COVER FROM THE NW AFTER 10-12Z
TUE. DEPENDING ON THE TIMING OF THESE CLOUDS, THIS COULD IMPACT
STRATUS DEVELOPMENT TUESDAY MORNING. LIGHT WINDS THROUGH THE
PERIOD.
KPDX AND APPROACHES...VFR CONDITIONS EXPECTED THROUGH THE PERIOD.
COULD SEE SOME STRATUS DEVELOP AROUND 13-15Z BUT CONFIDENCE IS LOW
BASED ON THE MODELS NOT HANDLING THIS PATTERN WELL. DECIDED TO ADD
A SCT005 DECK. WINDS REMAIN LIGHT AT LESS THAN 5 KT. -19/03
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, THEN
RETURN NORTHERLY BY THE END OF THE WEEK. SEAS REMAIN AROUND 4-6
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. -10/03
PQR WATCHES/WARNINGS/ADVISORIES
OR...FROST ADVISORY UNTIL 8 AM PDT TUESDAY FOR ORZ102>109-112>119-
123>125.
FREEZE WARNING UNTIL 8 AM PDT TUESDAY FOR ORZ121.
WA...FROST ADVISORY UNTIL 8 AM PDT TUESDAY FOR WAZ202-204>208.
PZ...NONE.
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