349
FXUS66 KPQR 042215
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
300 PM PDT SUN OCT 4 2026
SYNOPSIS
UNSEASONABLY WARM AND DRY CONDITIONS CONTINUE
THROUGH THURSDAY WITH AREAS OF EARLY MORNING VALLEY FOG AND COASTAL
FOG. WEAK ONSHORE FLOW MONDAY AND TUESDAY TRANSITIONS TO WEAK
OFFSHORE FLOW WEDNESDAY AND THURSDAY, BRINGING SLIGHTLY WARMER
TEMPERATURES MID-WEEK. A TROUGH MOVING INTO THE PACIFIC NORTHWEST
WILL BRING COOLER TEMPERATURES AND CHANCES FOR LIGHT RAIN FRIDAY INTO
NEXT WEEKEND.
SHORT TERM...NOW THROUGH WEDNESDAY NIGHT
CONDITIONS WILL REMAIN
UNSEASONABLY WARM AND DRY THROUGH WEDNESDAY WITH RELATIVELY LIGHT
WINDS AND AREAS OF EARLY MORNING VALLEY FOG AND COASTAL FOG. AS OF 3
PM PDT SUNDAY, OBSERVED SURFACE TEMPERATURES WERE ALREADY IN THE
UPPER 70S TO LOWER 80S OVER INLAND VALLEYS. TEMPERATURES ARE STILL
EXPECTED TO PEAK BY 4-5 PM PDT SUNDAY WITH HIGHS PEAKING BETWEEN 80-
83 DEGREES, WHICH IS MORE TYPICAL FOR JULY OR AUGUST RATHER THAN
OCTOBER. AVERAGE HIGHS FOR THE PORTLAND METRO AND WILLAMETTE VALLEY
THIS TIME OF YEAR ARE IN THE UPPER 60S TO AROUND 70 DEGREES, WHICH
MEANS TEMPERATURES CONTINUE TO RUN 10-15 DEGREES ABOVE AVERAGE.
BASED ON CURRENT TEMPERATURES, RECORD HIGHS ARE NOT ANTICIPATED
DESPITE THE ABNORMAL WARMTH IN PLACE.
TEMPERATURES WILL DROP FAIRLY QUICKLY LATE TONIGHT, WITH LOWS RANGING
ANYWHERE FROM THE MID 40S TO MID 50S, COOLEST IN RURAL AREAS AND IN
THE UPPER HOOD RIVER VALLEY AND WARMEST IN URBAN CORES. OBSERVED LOWS
SUNDAY MORNING WERE SEVERAL DEGREES COOLER THAN NBM GUIDANCE, AS IS
OFTEN THE CASE THIS TIME OF YEAR WHEN CLEAR SKIES AND CALM WINDS ARE
IN PLACE DURING THE OVERNIGHT HOURS. THEREFORE, THE NBM WAS NUDGED
DOWNWARD A FEW DEGREES FOR OVERNIGHT LOWS TONIGHT, BUT DO EXPECT LOWS
A DEGREE OR TWO WARMER THAN LAST NIGHT DUE TO SLIGHTLY WARMER EVENING
TEMPERATURES. WITH AN IDEAL SET-UP FOR RADIATIONAL COOLING TONIGHT,
AREAS OF EARLY MORNING VALLEY FOG AND COASTAL FOG WILL DEVELOP AGAIN.
SOME LOCATIONS WILL OBSERVE DENSE FOG, MOST LIKELY ALONG PORTIONS OF
THE CENTRAL OREGON COAST, SOUTHERN WILLAMETTE VALLEY, AND FAR EASTERN
PORTLAND METRO NEAR THE MOUTH OF THE COLUMBIA RIVER GORGE. THESE
AREAS HAVE THE HIGHEST PROBABILITIES FOR SURFACE VISIBILITIES BELOW
1/2 MILE BY SUNRISE ON MONDAY PER THE LATEST REFS GUIDANCE (60-75%
CHANCE). ANYONE IN THESE AREAS PLANNING TO COMMUTE MONDAY MORNING
SHOULD CONSIDER ALLOWING EXTRA TIME FOR THEIR COMMUTE, ESPECIALLY IF
A DENSE FOG ADVISORY IS ISSUED. AFTER AREAS OF MORNING FOG BURN OFF,
EXPECT ANOTHER MOSTLY SUNNY DAY ON MONDAY WITH TEMPERATURES REMAINING
WARM. THAT SAID, HIGHS WILL BE A FEW DEGREES COOLER THAN SUNDAY AS
WEAK ONSHORE FLOW RETURNS AND TEMPERATURES ALOFT COOL A FEW DEGREES.
WITH VERY LITTLE CHANGE TO THE OVERALL WEATHER PATTERN HEADING INTO
TUESDAY AND WEDNESDAY, EXPECT VERY SIMILAR WEATHER CONDITIONS HEADING
INTO THE MIDDLE PART OF THE WEEK WITH CONDITIONS REMAINING DRY AND
UNUSUALLY WARM. -23
LONG TERM...THURSDAY THROUGH SATURDAY NIGHT
REMAINING WARM AND DRY
ON THURSDAY WITH SUNNY SKIES AND LIGHT OFFSHORE FLOW. TEMPERATURES
ARE EXPECTED TO INCREASE A FEW DEGREES COMPARED TO THE MIDDLE OF THE
WEEK, WITH HIGHS RISING BACK INTO THE LOW TO MID 80S OVER INLAND
VALLEYS AND AROUND 70 DEGREES AT THE COAST. THIS COULD VERY WELL BE
THE LAST 80+ DEGREE DAY OF THE YEAR, AS CONDITIONS WILL FINALLY COOL
DOWN CLOSE TO SEASONAL NORMALS FRIDAY INTO NEXT WEEKEND.
HOWEVER, THIS IS NOT A GIVEN BASED ON CLIMATOLOGICAL RECORDS. WHILE
WE ARE ALREADY BEYOND THE CLIMATOLOGICAL AVERAGE FOR THE LAST 80+
DEGREE DAY (WHICH IS SEPTEMBER 28 FOR THE PORTLAND INTERNATIONAL
AIRPORT), THE LATEST 80+ DEGREE DAY EVER RECORDED AT PORTLAND
INTERNATIONAL AIRPORT IS OCTOBER 21. THIS RECORD WAS SET BACK IN
2003. DAILY RECORD HIGHS FOR THURSDAY, OCT. 8, ARE GENERALLY IN THE
83-89 DEGREE RANGE FOR THE PORTLAND METRO AND WILLAMETTE VALLEY. THE
CURRENT FORECAST SUGGESTS MOST LOCATIONS WILL NOT BREAK DAILY RECORD
HIGHS, BUT THIS CANNOT BE COMPLETELY RULED OUT FOR A SITE OR TWO,
ESPECIALLY SALEM AND EUGENE WHERE RECORD HIGHS ARE LOWEST (84 AND 83
DEGREES, RESPECTIVELY).
AS MENTIONED ABOVE, CONDITIONS TREND COOLER FRIDAY INTO NEXT WEEKEND
IN RESPONSE TO AN INCOMING UPPER LEVEL TROUGH. MODEL ENSEMBLE
GUIDANCE VARIES ON THE EXACT AMPLITUDE AND TIMING OF THIS TROUGH AND
WHETHER OR NOT LIGHT RAIN WILL FALL BEGINNING SOMETIME ON FRIDAY OVER
SOUTHWEST WA AND NORTHWEST OR. REGARDLESS OF THE EXACT EVOLUTION OF
THIS TROUGH, CONFIDENCE IS HIGH TEMPERATURES WILL BECOME NOTICEABLY
COOLER BY FRIDAY WITH INLAND HIGHS RANGING SOMEWHERE BETWEEN THE MID
60S AND MID 70S AND SOMEWHERE IN THE 60S ON SATURDAY. IF RAIN DOES
OCCUR, CONFIDENCE IS HIGH AMOUNTS WOULD BE LIGHT AND NON-IMPACTFUL
WITH TOTAL RAIN AMOUNTS UNDER 0.25 INCHES (85-95% CHANCE). LOOKING AT
THE 12Z/OCT. 4 ITERATION OF THE ENS/GEFS/GEPS FOR 6-HR QPF, IT IS
CLEAR THERE ARE SIGNIFICANT MODEL ENSEMBLE DIFFERENCES. THE ENS IS
CONFIDENT AT LEAST SOME LIGHT RAIN WILL FALL ON FRIDAY AND/OR
SATURDAY AS ONLY 10% OF THE ENSEMBLE MEMBERS ARE DRY DURING THAT
TIME. MEANWHILE, NEARLY 75% OF ENSEMBLE MEMBERS FROM THE GEFS ARE
DRY. LASTLY, 30% OF ENSEMBLE MEMBERS FROM THE GEPS ARE DRY. AS A
RESULT OF THESE TIMING AND AMOUNT DIFFERENCES, NBM 6-HR POPS ARE
FAIRLY LOW AND ONLY PEAK BETWEEN 10-30%. THE HIGHEST POPS ARE OVER
THE CASCADES, SOUTH WA/NORTH OR COAST, AND WILLAPA HILLS.
CHANCES FOR MORNING FROST INCREASE NEXT WEEKEND OVER THE UPPER HOOD
RIVER VALLEY AND OUTLYING RURAL AREAS WITHIN THE WILLAMETTE VALLEY,
ESPECIALLY THE SOUTHERN WILLAMETTE VALLEY. THE NBM IS SHOWING A 5-
25% CHANCE FOR MORNING LOWS BELOW 37 DEGREES SATURDAY NIGHT/SUNDAY
MORNING WITHIN THESE AREAS, EXCEPT A 50-75% CHANCE IN THE UPPER HOOD
RIVER VALLEY. ANYONE GROWING OUTDOOR VEGETATION THAT IS SUSCEPTIBLE
TO FROST DAMAGE SHOULD MONITOR THE FORECAST OVER THE NEXT SEVERAL
DAYS. -23
AVIATION...THROUGH 00Z TUESDAY
CURRENTLY WIDESPREAD VFR INLAND
AND ALMOST WIDESPREAD VFR ALONG THE COAST AS KTMK AND KONP
CONTINUES TO CLEAR OUT. HEADING TOWARDS 03-06Z MON, MARINE
STRATUS WILL PUSH BACK INTO THE COAST, BRINGING LIFR FOG TO THE
COASTAL TERMINALS (25-50% CHANCE OF LIFR CONDITIONS).
ADDITIONALLY, CHANCES FOR STRATUS IN THE SOUTHERN WILLAMETTE
VALLEY INCREASE, WITH PROBABILISTIC GUIDANCE SUGGESTING A 15-25%
CHANCE OF LIFR CONDITIONS AT KEUG BETWEEN 09-17Z MON. AS FOR OTHER
INLAND TERMINALS, A 10-15% CHANCE OF LIFR CONDITIONS BETWEEN
12-17Z MON.
NORTH TO NORTHWEST WINDS AT AROUND 5 TO 7 KT THIS AFTERNOON WILL
EASE AROUND 03Z MON. WINDS OF 8-12 KT WITH GUSTS UP TO 20 KT ARE
POSSIBLE THIS AFTERNOON AT KONP.
KPDX AND APPROACHES...VFR CONDITIONS THROUGHOUT THE PERIOD, WITH
A 10-15% CHANCE OF IFR/LIFR CONDITIONS AROUND 12-17Z MON. DIURNAL
NORTHWEST WINDS AROUND 5 TO 7 KT THIS AFTERNOON WILL EASE BY 03Z
MON. ~12
MARINE
HIGH PRESSURE OFFSHORE CONTINUES, MAINTAINING NORTHERLY
WINDS THROUGH THE WEEK. CHANCES FOR PEAK WIND GUSTS OF 20 TO 25 KT
INCREASE MONDAY THROUGH WEDNESDAY, GENERALLY DURING THE AFTERNOON
AND EVENING. EXPECT WIND-DRIVEN SEAS AROUND 4 TO 6 FT THROUGH
EARLY THIS WEEK, WITH A WEST TO NORTHWEST SWELL AT 8 TO 9 SECONDS
INCREASING TO 10 TO 12 SECONDS BY MONDAY.
AS A RESULT OF WINDS INCREASING AND BRINGING GUSTS UP TO 25 KT ON
MONDAY, A SMALL CRAFT ADVISORY HAS BEEN ISSUED FOR THE WATERS
SOUTH OF CAPE FOULWEATHER OR FROM 11 AM TO 11 PM MONDAY.
HIGH PRESSURE ALOFT THIS WEEKEND WILL ALSO SUPPORT AREAS OF
DENSE FOG DEVELOPING NIGHTLY AS CLOUD BASES ARE COMPRESSED
DOWN TO THE SURFACE. WE WILL CONTINUE TO MONITOR CONDITIONS OVER
THE WATERS EACH NIGHT AS FOG MAY LOWER VISIBILITY TO UNDER 1 SM,
RESULTING IN DIFFICULT NAVIGATION.
MORE ACTIVE MARINE CONDITIONS ARE LIKELY IN THE LATTER HALF OF
THE WEEK AS TROUGHING OVER THE GULF OF ALASKA GENERATES A
BUILDING NORTHWEST SWELL AND CHANCES FOR RAIN RETURN TO THE
REGION FRIDAY INTO NEXT WEEKEND. SEAS WILL INCREASE TO AROUND 7
TO 9 FT WEDNESDAY INTO THURSDAY, THEN DECREASE FRIDAY. A LONGER
PERIOD NORTHWESTERLY SWELL MAY ALSO BRING A MODERATE SNEAKER WAVE
THREAT WEDNESDAY THROUGH THURSDAY. ~12/36
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 11 AM TO 11 PM PDT MONDAY FOR PZZ253-
273.
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