390
FXUS66 KPQR 190436 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
935 PM PDT SUN MAY 18 2025
..UPDATED AVIATION DISCUSSION
SYNOPSIS
LIGHT SHOWERS CONTINUE THIS AFTERNOON, TRENDING
DRIER IN THE EVENING AND EARLY OVERNIGHT. ANOTHER FRONT MOVES
THROUGH THE REGION LATE TONIGHT INTO MONDAY, BRINGING ANOTHER
ROUND OF WIDESPREAD SHOWERS THROUGH MONDAY MORNING. EXPECT
TEMPERATURES TO REMAIN SLIGHTLY BELOW AVERAGE THROUGH MIDWEEK.
TEMPERATURES ARE TRENDING WARMER TOWARDS THE UPPER 60S TO NEAR
70 FOR THE SECOND HALF OF NEXT WEEK WITH THE POTENTIAL FOR WEAK
ACTIVE WEATHER TO CONTINUE.
DISCUSSION...SUNDAY AFTERNOON THROUGH SATURDAY
SUNDAY
MORNING, AN UPPER LEVEL CLOSED LOW MOVED SOUTH FROM VANCOUVER
ISLAND INTO EASTERN WASHINGTON AS HIGH PRESSURE HAS BUILT OVER
THE EASTERN PACIFIC. A WEAK SHORTWAVE HAS DEVELOPED ALONG THE
FLOW OVER SW WASHINGTON AND NW OREGON, WHICH HAS INCREASED THE
COVERAGE OF SHOWERS A BIT MORE THAN GUIDANCE SUGGESTED EARLY
THIS AFTERNOON IN FAR NORTHERN OREGON AND SW WASHINGTON. SHOWERS
EXPECTED TO FORM INTO CENTRAL OREGON THROUGH THE AFTERNOON AS
THE UPPER CLOSED LOW MOVES SOUTHEAST INTO IDAHO, PULLING THE
SHORTWAVE SOUTHEAST, AS WELL. ADDITIONAL ACCUMULATION WITH THESE
SHOWERS WILL BE LIMITED, GENERALLY LESS THAN 0.1 INCH TOTAL.
SHOWERS WILL TAPER OFF BRIEFLY TONIGHT AS A SHORTWAVE RIDGE
MOVES OVER THE PACNW. TEMPERATURES TODAY WILL BE VERY SIMILAR TO
YESTERDAY, PEAKING IN THE LOW TO MID 60S INLAND AND 50S ALONG
THE COAST.
THE NEXT WEATHER SYSTEM AND ASSOCIATED SURFACE FRONTAL SYSTEM
QUICKLY PUSHES INTO THE REGION MONDAY WITH A BAND OF WIDESPREAD
SHOWERS BEGINNING ALONG THE COAST EARLY MONDAY MORNING AND
SPREADING EAST THROUGH THE MORNING HOURS. THIS IS A FAST MOVING
FRONTAL SYSTEM, WITH GUIDANCE INDICATING THE FRONT WILL MOVE
EAST OF THE CASCADES BY MONDAY AFTERNOON, MEANING THE WIDESPREAD
SHOWERS WILL ALSO MOVE EAST OF THE CASCADES BY LATE AFTERNOON.
UPPER LEVEL FLOW IS EXPECTED TO BECOME MORE ZONAL MONDAY AFTERNOON
AS THE UPPER LOW WEAKENS AND ANOTHER LOW WITH MULTIPLE
WAVES MOVES INTO BRITISH COLUMBIA. THIS WILL ALLOW ISOLATED
SHOWERS TO CONTINUE MONDAY AFTERNOON INTO TUESDAY AND KEEP
TEMPERATURES IN THE 60S INLAND AND 50S ALONG THE COAST BOTH
DAYS. EXPECT ADDITIONAL RAIN AMOUNTS FOR MONDAY AND TUESDAY OF
AROUND 0.1-0.25 INCH FOR THE WILLAMETTE VALLEY AND
PORTLAND/VANCOUVER METRO AREA, 0.25-0.5 INCH FOR THE SW
WASHINGTON LOWLANDS, AND 0.3-0.9 INCH ACROSS THE COAST, COAST
RANGE, AND CASCADES, THE MAJORITY OF WHICH WILL FALL MONDAY
MORNING AND EARLY AFTERNOON.
ON WEDNESDAY, ENSEMBLE GUIDANCE IS COMING INTO BETTER AGREEMENT
THAT WEAK RIDGING WILL FORM OVER THE PACNW, ALLOWING FOR DRY
CONDITIONS AND TEMPERATURES TO RISE A FEW DEGREES TO RIGHT
AROUND 70 DEGREES INLAND AND UPPER 50S TO 60S ALONG THE COAST.
COME WEDNESDAY NIGHT THROUGH THE REST OF THE WEEK, ENSEMBLE
CONSENSUS DEGRADES. CLUSTER ANALYSIS INDICATES A POTENTIAL FOR
A QUICK-MOVING UPPER LOW IN THE LATE WEDNESDAY OR THURSDAY
TIMEFRAME, THOUGH DETERMINISTIC GUIDANCE INDICATES DECENT
DIFFERENCES IN TIMING. HOWEVER, THIS LOW WOULD MOVE INTO THE
REGION FROM THE EASTERN PACIFIC AND THEREFORE WOULD NOT CONTAIN
MUCH COLD AIR, SO DAYTIME TEMPERATURES ON THURSDAY ARE EXPECTED
TO REMAIN SIMILAR TO WEDNESDAY OR WARM A COUPLE OF DEGREES.
ADDITIONALLY, LIMITED PRECIPITATION IS EXPECTED WITH THIS LOW.
CONDITIONS BECOME EVEN MORE UNCERTAIN THURSDAY AND BEYOND. THERE
ARE INDICATIONS OF ANOTHER UPPER TROUGH FORMING SOMEWHERE OVER
THE EASTERN PACIFIC INTO THE US WEST COAST, THOUGH THERE ARE
SIGNIFICANT DIFFERENCES IN TIMING, SIZE, AND LOCATION.
ADDITIONALLY, RIDGING COULD BUILD EITHER AHEAD OF OR BEHIND
THIS TROUGH DEPENDING ON TIMING, WHICH WOULD ALLOW TEMPERATURES
TO WARM OUT OF THE 60S INLAND. THE TEMPERATURE SPREAD LATE IN
THE WEEK IS AROUND 10 DEGREES EACH DAY, RANGING FROM THE MID 60S
TO MID 70S FOR INLAND LOCATIONS. -HEC
AVIATION
VFR CONDITIONS WITH BKN/OVC CIGS AROUND 4 TO 6 KFT
CONTINUE ACROSS THE REGION THROUGH 08-09Z MON. AFTERWARDS, THE NEXT
FRONTAL SYSTEM WILL BRING SHOWERS AND IFR/MVFR CIGS ALONG THE COAST
BY 09-11Z MON AND MVFR CIGS ACROSS THE WILLAMETTE VALLEY BY 12-14Z
MON. IFR CIGS ARE ALSO POSSIBLE INLAND (20-40% CHANCE) BETWEEN 14-
18Z MON. MODERATE RAIN AT TIMES COULD LEAD TO BRIEF DROPS IN VIS TO
IFR/MVFR THRESHOLDS. ONCE THE FRONT EXITS WESTERN OREGON, SHOWERS
WILL DECREASE AND CIGS ARE EXPECTED TO IMPROVE TO VFR FOR INLAND
TERMINALS BY 21-23Z MON. MEANWHILE, MVFR CIGS LINGER ALONG THE COAST
THROUGH 00-03Z TUE.
SOUTHERLY WINDS BEFORE THE FRONTAL PASSAGE GENERALLY REMAIN UNDER 10
KT. MEANWHILE, EASTERN PORTLAND METRO TERMINALS MAINTAIN LIGHT
EASTERLY WINDS. ONCE THE FRONT MOVES THROUGH, EXPECT WINDS ACROSS
THE REGION TO TURN MORE WESTERLY/SOUTHWESTERLY AROUND 10-15 KT WITH
WIND GUSTS TO 20-25 KT.
PDX AND APPROACHES...VFR CONDITIONS THROUGH 11-12Z MON. FRONTAL
PASSAGE WILL RETURN MVFR CIGS BETWEEN 13-20Z MON. CONDITIONS IMPROVE
TO VFR AROUND 20-22Z TUE. EXPECT WINDS TURN MORE WEST- SOUTHWESTERLY
WITH THE FRONTAL PASSAGE AND STRENGTHEN TO 8-13 KT WITH GUSTS UP TO
20 KT. -ALVIZ
MARINE
AS OF 2 PM SUNDAY, LIGHT WESTERLY TO SOUTHWESTERLY
WINDS WITH A MID PERIOD WESTERLY SWELL MAINTAINING SEAS AROUND 6 FT
AT 9 TO 10 SECONDS. WINDS WILL SHIFT SOUTHERLY AS THE NEXT FRONT
ARRIVES TONIGHT, BRINGING THE NEXT ROUND OF SMALL CRAFT ADVISORIES
AS WINDS GUST TO 25 TO 30 KT AND BUILDING SHORT PERIOD WAVES
CONTRIBUTE TO A MORE CHAOTIC SEA STATE IN THE 6 TO 8 FT RANGE
THROUGH LATE MONDAY MORNING. CONDITIONS WILL IMPROVE AS WINDS
DECREASE AND VEER WESTERLY IN THE WAKE OF THE FRONT ON MONDAY
AFTERNOON, BUT A BUILDING SWELL WILL QUICKLY PUSH SEAS TO 10-11 FT
MONDAY NIGHT INTO TUESDAY. SEAS WILL THEN DECREASE TO 5 FT BY
WEDNESDAY. ~HALL/CB
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 2 PM PDT MONDAY FOR PZZ210-251>253-
271>273.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
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X.COM/NWSPORTLAND
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