187
FXUS66 KPQR 070929
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
229 AM PDT TUE OCT 7 2025
SYNOPSIS
CONDITIONS WILL REMAIN DRY WITH CLEAR SKIES AND
WARM AFTERNOON TEMPERATURES THROUGH TUESDAY. OFFSHORE FLOW WITH
BREEZY WINDS CONTINUE THROUGH TUESDAY MORNING. FROST IS LIKELY
IN THE UPPER HOOD RIVER VALLEY FROM ODELL TO PARKDALE AGAIN
BETWEEN 1-9 AM PDT TUESDAY. A LOW PRESSURE SYSTEM WILL BRING
COOLER TEMPERATURES WEDNESDAY ONWARD WITH PRECIPITATION CHANCES
BEGINNING THURSDAY. UNCERTAINTY REMAINS REGARDING WHEN RAIN
SHOWERS WILL RETURN TO THE AREA, THOUGH MOST GUIDANCE HOLDS OFF
ON PRECIPITATION UNTIL LATE FRIDAY OR SATURDAY.
DISCUSSION...TUESDAY THROUGH MONDAY
OBSERVATIONS EARLY
TUESDAY MORNING SHOW TEMPERATURES ARE COOLING QUICKLY IN THE
UPPER HOOD RIVER VALLEY UNDER HIGH PRESSURE. EXPECTING LOW
TEMPERATURES THIS MORNING IN THE LOW TO MID 30S AGAIN, LEADING
TO A FROST ADVISORY THROUGH 9 AM PDT. ADDITIONALLY, CURRENT
OBSERVATIONS INDICATE EASTERLY WIND GUSTS REMAIN ELEVATED OVER
SOME CASCADE AND COAST RANGE PEAKS AND THROUGH THE WESTERN
COLUMBIA RIVER GORGE, THOUGH PEAK WINDS ARE BEGINNING TO
DECREASE AS PRESSURE GRADIENTS WILL DECREASE THROUGH THE MORNING
HOURS. EXPECT WIND GUSTS UP TO 25-35 MPH OVER THESE AREAS
BEGINNING TO SLOWLY DECREASE AFTER 6 AM PDT, BECOMING MOSTLY
CALM AND BEGINNING TO SHIFT ONSHORE BY MIDDAY, EXCEPT FOR
SLIGHTLY ELEVATED GUSTS THROUGH THE GORGE INTO THE EARLY
AFTERNOON HOURS.
THE CALMER WINDS AND THE WIND SHIFT ARE DUE TO A LOW PRESSURE
SYSTEM DEEPENING IN THE FAR EASTERN PACIFIC AS WELL AS A WEAK
COLD FRONT APPROACHING THE REGION, MOVING THROUGH TONIGHT. MUCH
COOLER DAYTIME TEMPERATURES ARE EXPECTED WEDNESDAY. TEMPERATURES
TODAY ARE FORECAST TO PEAK IN THE UPPER 70S TO LOW 80S FOR
INLAND VALLEYS, AND THEY WILL DROP AROUND 10-15 DEGREES INTO THE
LOW TO MID 60S WEDNESDAY BEHIND THE COLD FRONT.
ENSEMBLES INDICATE THE LOW PRESSURE SYSTEM WILL CONTINUE
DEEPENING OFFSHORE WEDNESDAY INTO THURSDAY. MOST GFS, EURO, AND
CANADIAN ENSEMBLE MEMBERS KEEP THE LOW FAR ENOUGH OFF OF THE
COAST TO KEEP THE AREA DRY THROUGH THURSDAY, THOUGH ABOUT 15-30%
OF THE MEMBERS INDICATE THE LOW COULD BE CLOSE ENOUGH TO THE
PACNW FOR SOME LIGHT RAIN CHANCES BEGINNING LATE WEDNESDAY, UP
TO 45% OVER THE CASCADES. ENSEMBLES THEN INDICATE THE LOW MOVES
INLAND FRIDAY INTO SATURDAY, BRINGING WIDESPREAD PRECIPITATION
TO THE AREA. SOME UNCERTAINTY CONTINUES IN THE TIMING OF
PRECIPITATION BEGINNING FRIDAY, THOUGH CONFIDENCE IS HIGH
(70-90% CHANCE) IN RAIN LATE FRIDAY THROUGH SATURDAY. SHOWERS
WILL LIKELY CONTINUE INTO SUNDAY AS ENSEMBLE GUIDANCE COMES INTO
BETTER AGREEMENT OF TROUGHING CONTINUING OVER THE REGION.
THERE'S A 70-85% CHANCE OF 0.5 INCH OF RAIN FOR INLAND VALLEYS
AND A 85-95% CHANCE FOR THE COAST, COAST RANGE, AND CASCADES
FROM 5 AM FRIDAY THROUGH 5 AM MONDAY. ADDITIONALLY, THERE'S A
60-80% CHANCE OF 1 INCH OF RAIN FOR THE COAST, COAST RANGE, AND
CASCADES AND A 25-45% CHANCE FOR INLAND VALLEYS FOR THE SAME
TIMEFRAME. ENSEMBLE GUIDANCE SUGGESTS BROAD TROUGHING REMAINS
OVER THE WESTERN US ON MONDAY, THOUGH THERE'S MUCH MORE
UNCERTAINTY IN THE EXACT LOCATION OF THE TROUGH. SHOWER CHANCES
DECREASE TO AROUND 20-40%.
TEMPERATURES WILL REMAIN ON THE COOL SIDE THROUGH MONDAY, AND
LOW TEMPERATURES WILL DECREASE SLIGHTLY EACH NIGHT. BY THE
WEEKEND, OVERNIGHT TEMPERATURES IN THE HIGH CASCADES ARE
EXPECTED TO BE IN THE MID TO LOW 30S, WHICH COULD LEAD TO SOME
SNOWFALL FOR ELEVATIONS ABOVE 4500-5500 FEET. AT THE PASSES,
LATEST GUIDANCE ONLY SHOWS LIGHT AMOUNTS THROUGHOUT THE WEEKEND,
SO LIMITED IMPACTS ARE EXPECTED AT THIS TIME. ADDITIONAL FROST
ADVISORIES COULD BE NEEDED FOR THE UPPER HOOD RIVER VALLEY, AS
WELL. -03
AVIATION
HIGH PRESSURE PERSISTS, MAINTAINING OFFSHORE FLOW AT
THE SURFACE AND CLEAR SKIES WITH VFR CONDITIONS THROUGH THE
DAYTIME HOURS. WINDS WILL BE EASTERLY ALONG THE COAST AND NORTH
THROUGH THE WILLAMETTE VALLEY, GENERALLY LESS THAN 10 KTS, EXCEPT
FOR KTTD WHICH WILL BE INFLUENCED BY EASTERLY WINDS FROM THE GORGE
WITH GUSTS UP TO 20-25 KTS THROUGH 18Z TUE.
THE HIGH PRESSURE BREAKS DOWN DURING THE DAY TUE, CAUSING A RETURN
OF ONSHORE FLOW. WINDS SHIFT WEST TO NORTHWEST ALONG THE COAST
AFTER 18Z TUE, IN THE WILLAMETTE VALLEY AFTER 21-23Z TUE, AND AT
KTTD AFTER 01-03Z WED. ADDITIONALLY, THE RETURN OF MARINE STRATUS
AND MVFR CONDITIONS RETURNS TO COASTAL TERMINALS AFTER 00-03Z WED.
KPDX AND APPROACHES...VFR AND CLEAR SKIES WITH WINDS GENERALLY
VARIABLE LESS THAN 6 KTS THROUGH THE TAF PERIOD. -03
MARINE
HIGH PRESSURE OFFSHORE COMBINED WITH A THERMAL TROUGH OF
LOW PRESSURE ALONG THE COAST WILL MAINTAIN NORTHEASTERLY WINDS
ACROSS THE WATERS THROUGH THIS MORNING. LOW PRESSURE SHIFTS
INLAND LATER TODAY AS A WEAK COLD FRONT APPROACHES THE WATERS
FROM THE NORTH, CAUSING WINDS BECOME MORE NORTH TO NORTHWESTERLY
BY THE AFTERNOON. WINDS ARE EXPECTED IN INCREASE THIS AFTERNOON
THROUGH TONIGHT, WITH MORE WIDESPREAD GUSTS TO 25 KT. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FROM LATE THIS MORNING THROUGH 5
AM PDT WEDNESDAY. SEAS AROUND 3 TO 5 FT ARE EXPECTED TO PERSIST
THROUGH TODAY, BEFORE BUILDING TO AROUND 7 TO 9 FT TONIGHT.
AN AREA OF WEAK LOW PRESSURE APPROACHES THE COASTAL WATERS ON
WEDNESDAY WHILE WINDS ARE EXPECTED TO WEAKEN, FOLLOWED BY
OFFSHORE FLOW ON THURSDAY AS THE SURFACE LOW CONTINUES TO DROP
SOUTH. SEAS ARE LIKELY TO LINGER AROUND 6 TO 7 FT THROUGH THE END
OF THE WEEK.
PQR WATCHES/WARNINGS/ADVISORIES
OR...FROST ADVISORY UNTIL 9 AM PDT THIS MORNING FOR ORZ121.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 2 AM PDT
WEDNESDAY FOR PZZ210.
SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 5 AM PDT
WEDNESDAY FOR PZZ251>253.
SMALL CRAFT ADVISORY FROM NOON TODAY TO 5 AM PDT WEDNESDAY FOR
PZZ271>273.
WWW.WEATHER.GOV/PORTLAND
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