910
FXUS66 KPQR 210334 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
ISSUED BY NATIONAL WEATHER SERVICE SEATTLE WA
835 PM PDT TUE MAY 20 2025
UPDATED AVIATION DISCUSSION...
SYNOPSIS
THE RECENT COOL AND WET WEATHER WILL CONTINUE
THROUGH THE END OF THE WEEK AND GIVE WAY TO DRIER WEATHER AND
ABOVE AVERAGE TEMPERATURES AS WE MOVE INTO THE WEEKEND.
SHORT TERM...NOW THROUGH THURSDAY
WATER VAPOR SATELLITE
IMAGERY SHOWS A LOW AMPLITUDE SHORTWAVE TROUGH SLIDING ACROSS
THE PACIFIC NORTHWEST. THIS HAS RESULTED IN SCATTERED, GENERALLY
LIGHT, SHOWERS SPREADING ACROSS WESTERN WASHINGTON AND WESTERN
OREGON TODAY. AS 500MB HEIGHTS BUILD ACROSS THE REGION AND
SURFACE INSTABILITY DECREASES THIS EVENING, EXPECT SHOWERS TO
GRADUALLY DECREASE IN COVERAGE AND INTENSITY. IN AREAS THAT
REMAIN CLEAR LIKE THE UPPER HOOD RIVER VALLEY AND AREAS THAT
GRADUALLY CLEAR THIS EVENING, THERE IS A 50% CHANCE OR MORE FOR
FROST IN OUR COLDEST LOCATIONS LIKE ODELL AND PARKDALE. THE
PROBABILITY FOR TEMPERATURES DROPPING INTO THE MID 30S IS
CONSIDERABLY LOWER (10%-20% CHANCE) FOR AREAS LIKE HILLSBORO,
BATTLE GROUND AND ACROSS MUCH OF THE SOUTHERN WILLAMETTE VALLEY
AND CASCADE FOOTHILL VALLEYS.
BRIEF RIDGING LATE TONIGHT INTO EARLY WEDNESDAY WILL GIVE WAY TO
ANOTHER SHORTWAVE TROUGH SLIDING ACROSS THE REGION LATE
WEDNESDAY INTO EARLY THURSDAY. THIS WILL BRING ANOTHER ROUND OF
LIGHT PRECIPITATION TO THE REGION. ENSEMBLES SUGGEST THE LIGHT
RAIN IS MOST LIKELY TO ARRIVE WEDNESDAY EVENING INTO WEDNESDAY
NIGHT WITH SOME LIGHT PRECIPITATION CHANCES LINGERING INTO
THURSDAY ACROSS MAINLY THE HIGHER TERRAIN. TEMPERATURES LOOK TO
REMAIN NEAR TO SLIGHTLY BELOW AVERAGE FOR THE DATE THROUGH
THURSDAY.
LONG TERM...THURSDAY NIGHT THROUGH TUESDAY
WPC CLUSTERS
SUGGEST THE REGION WILL BE UNDER THE INFLUENCE OF A LINGERING
SHORTWAVE TROUGH THURSDAY NIGHT INTO FRIDAY. HOWEVER, ONLY
20-30% OF GLOBAL ENSEMBLE MEMBERS SUGGEST DEEP ENOUGH TROUGHING
OVER THE REGION TO KEEP SOME LIGHT PRECIPITATION CONTINUING
MAINLY OVER THE NORTHERN HALF OF THE CWA AND THE HIGHER TERRAIN
OF THE COAST RANGE AND CASCADES.
GLOBAL ENSEMBLE MEMBERSHIP IS GENERALLY IN AGREEMENT THAT
SHORTWAVE RIDGING WILL BUILD INTO THE PACIFIC NORTHWEST SATURDAY
INTO SUNDAY LEADING TO THE AREA DRYING OUT FURTHER AND
TEMPERATURES WARMING TO WELL ABOVE AVERAGE BY SUNDAY. WITH THAT
SAID, THERE IS 10-20% OF THE ENSEMBLE GUIDANCE THAT DELAYS
SHORTWAVE RIDGING, WHICH KEEPS SATURDAY COOLER.
UNCERTAINTY IN THE UPPER LEVEL PATTERN GROWS EARLY NEXT WEEK.
THE MAIN UNCERTAINTY REVOLVES AROUND HOW LONG SHORTWAVE RIDGING
PERSISTS OVER THE REGION AND WHEN THE NEXT SHORTWAVE TROUGH
SLIDES INTO THE PACIFIC NORTHWEST. THE CURRENT FORECAST IS VERY
MIDDLE OF THE ROAD, BUT KNOW THERE IS ~25% CHANCE TEMPERATURES
IN THE 80S WILL PERSIST INTO EARLY NEXT WEEK AND THERE IS A ~25%
CHANCE THAT TEMPERATURES DROP INTO THE 60S WITH BENEFICIAL WET
WEATHER RETURNING TO THE PACIFIC NORTHWEST.
AVIATION
WEAK HIGH PRESSURE BEGINS TO BUILD ACROSS THE REGION,
MAINTAINING VFR CONDITIONS THROUGHOUT THE AIRSPACE. INLAND
TERMINALS WILL SEE VFR CONDITIONS PERSIST THROUGH THE TAF PERIOD,
ALONG WITH NORTHERLY TO NORTHWESTERLY WINDS UNDER 8 KT. COASTAL
TERMINALS MAY EXPERIENCE MVFR CIGS BEFORE 06Z WEDNESDAY, BUT
EXPECT VFR FOR THE REST OF THE TAF PERIOD. BETWEEN 20Z WEDNESDAY
AND 03Z THURSDAY, EXPECT GUSTY NORTHWESTERLY WINDS AROUND 10-15
KT WITH GUSTS UP TO 25 KT FOR COASTAL TERMINALS.
PDX AND APPROACHES...PREDOMINANTLY VFR CONDITIONS THROUGH THE TAF
PERIOD WITH WEST TO NORTHWEST WINDS UNDER 8 KT.
~HALL
MARINE
A BENIGN ONSHORE FLOW REGIME WILL MAINTAIN SCATTERED
SHOWERS AND LIGHT TO MODERATE WESTERLY BREEZES OVER THE COASTAL
WATERS THROUGH TONIGHT. SMALL CRAFT ADVISORIES REMAIN IN EFFECT
THROUGH THIS EVENING AS A MID PERIOD PERIOD WESTERLY SWELL KEEPS
SEAS AT OR ABOVE 10 FT. SEAS WILL SUBSIDE OVERNIGHT TO 6 TO 7 FT
BY WEDNESDAY MORNING. EXPECT RELATIVELY CALM CONDITIONS FOR THE
REMAINDER OF THE WEEK AS HIGH PRESSURE YIELDS NORTHERLY WINDS OVER
WATERS FOR WEDNESDAY AND THURSDAY, WITH GUSTS POTENTIALLY UP TO 25
KT LATER WEDNESDAY AFTERNOON. ONSHORE FLOW RETURNS FRIDAY INTO
THE WEEKEND. SEAS REMAIN IN THE 5 TO 7 FT RANGE THROUGH MID WEEK,
SUBSIDING BELOW 5 FT BY FRIDAY. DH/CB
PQR WATCHES/WARNINGS/ADVISORIES
OR...FROST ADVISORY FROM MIDNIGHT TONIGHT TO 8 AM PDT WEDNESDAY FOR
ORZ121.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 2 AM PDT WEDNESDAY FOR PZZ210-251>253-
271>273.
WWW.WEATHER.GOV/PORTLAND
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