233
FXUS66 KPQR 212242
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
242 PM PST FRI FEB 21 2025
SYNOPSIS
A SERIES OF FRONTAL SYSTEMS WILL IMPACT THE PACIFIC
NORTHWEST THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. A WEAK
ONE TONIGHT WILL BE FOLLOWED BY MULTIPLE THIS WEEKEND AND MONDAY
ASSOCIATED WITH MODERATE TO STRONG ATMOSPHERIC RIVERS. THESE
SYSTEMS WILL BE VERY WET AND BRING HEAVY RAINFALL. LOCALIZED
FLOODING, ESPECIALLY ALONG THE COAST, IS POSSIBLE. GUSTY WINDS
ARE ALSO EXPECTED SUNDAY AND MONDAY. ADDITIONAL RAIN IS POSSIBLE
MID TO LATE NEXT WEEK, BUT CONFIDENCE IS LOWER IN DETAILS AT
THIS TIME.
SHORT TERM...FRIDAY AFTERNOON THROUGH MONDAY
SATELLITE
IMAGERY EARLY FRIDAY MORNING SHOWS THE WEAK FRONT APPROACHING
THE WEST COAST AS WELL AS THE STREAM OF MOISTURE OVER THE
CENTRAL EASTERN PACIFIC ASSOCIATED WITH AN ATMOSPHERIC RIVER
THAT WILL IMPACT OREGON AND WASHINGTON THIS WEEKEND. VERY LIGHT
RADAR RETURNS ARE MOVING ONSHORE THIS AFTERNOON AND ARE ONLY
EXPECTED TO PRODUCE LIGHT SHOWERS MAINLY IN SW WASHINGTON AND
THE FAR NORTHERN OREGON COAST THIS AFTERNOON. THE MAIN RAINBAND
WITH THIS FIRST FRONT WILL PUSH THROUGH THE REGION OVERNIGHT,
TURNING TO SCATTERED SHOWERS EARLY TOMORROW MORNING. VERY
SCATTERED SHOWERS WILL CONTINUE THROUGH MOST OF THE AFTERNOON
TOMORROW WITH MANY AREAS IN THE INLAND LOWLANDS SEEING VERY
LITTLE TO NO RAIN. OVERALL, LIMITED RAIN AMOUNTS ARE EXPECTED
THROUGH TOMORROW AFTERNOON, GENERALLY A FEW HUNDREDTHS TO 0.15
INCH IN THE INTERIOR LOWLANDS, OREGON CASCADES, AND CENTRAL
OREGON COAST, AND 0.25-0.5 INCH FOR THE NORTHERN OREGON COAST
AND COAST RANGE AND SW WASHINGTON CASCADES.
THE MAIN EVENT STARTS SATURDAY LATE AFTERNOON/EVENING AS A
MODERATE TO STRONG ATMOSPHERIC RIVER (AR) TAKES AIM AT OREGON
AND WASHINGTON THROUGH SUNDAY NIGHT QUICKLY FOLLOWED BY ANOTHER
MODERATE YET SHORTER LIVED ATMOSPHERIC RIVER ON MONDAY. THERE
WILL BE VERY LITTLE BREAK IN THE RAIN BETWEEN THESE EVENTS, WITH
STEADY RAIN OVER THE WEEKEND DECREASING TO SHOWERS BRIEFLY
MONDAY NIGHT BEFORE STEADY RAIN RETURNS AGAIN MONDAY MORNING. AS
SUCH, WILL DISCUSS RAIN AMOUNTS IN ONE 72 HOUR PERIOD FROM 4 AM
SATURDAY TO 4 AM TUESDAY. SOME HEFTY RAIN AMOUNTS ARE POSSIBLE
OVER THE NORTHERN OREGON COAST RANGE AND SW WASHINGTON/FAR
NORTHERN OREGON CASCADES WITH A 50-70% CHANCE OF 5 INCHES OF
RAIN. LOCALIZED AREAS COULD SEE UP TO 6 INCHES DUE TO OROGRAPHIC
LIFT. COASTAL AREAS AND THE REST OF THE COAST RANGE AND CASCADES
HAVE A 60-90% CHANCE OF REACHING AT LEAST 3-4 INCHES OF RAIN.
INLAND LOWLANDS WILL SEE A 60-80% PROBABILITY OF CLOSER TO 2-3
INCHES OF RAIN. THE HEAVIEST BURSTS OF NEAR CONSTANT MODERATE
TO LOCALLY HEAVY RAIN ARE EXPECTED BASICALLY FROM 4PM SATURDAY
TO 4PM SUNDAY AND AGAIN MONDAY MORNING WITH LIGHTER RAIN IN
BETWEEN. THERE IS A CONCERN WITH LOCALIZED URBAN FLOODING,
ESPECIALLY FOR LOW LYING AREAS AND ROADWAYS, ESPECIALLY LATER
SUNDAY AND MONDAY. ADDITIONALLY, FLOODING CONCERNS OF CERTAIN
COAST RANGE AND COASTAL RIVERS HAS INCREASED TO AROUND 20-50%
CHANCE OF MINOR FLOODING, INCLUDING THE WILSON NEAR TILLAMOOK,
THE GRAYS, THE SILETZ AT SILETZ, AND THE LUCKIAMUTE NEAR SUVER.
PEOPLE NEAR THESE LOCATIONS SHOULD KEEP AN EYE ON THE FORECAST
AND MAKE ANY NECESSARY PREPARATIONS. ADDITIONALLY, THESE ARS
WILL USHER WARM PACIFIC AIR INTO THE REGION, CAUSING SNOW LEVELS
TO RISE WELL ABOVE PASS LEVEL SATURDAY INTO MONDAY. THEREFORE,
LIMITED SNOWFALL IS EXPECTED.
WIND IS THE OTHER MAIN CONCERN WITH THESE ARS. WINDS WILL SHIFT
SOUTHERLY TONIGHT AND INCREASE ALONG THE COAST BEGINNING
SATURDAY AFTERNOON, PEAKING SUNDAY. EXPECTING WIND GUSTS UP TO
30-40 MPH ALONG THE COAST AND GUSTS UP TO 45-55 MPH AT BEACHES
AND HEADLANDS. VALLEY LOWLANDS WILL LIKELY SEE WIND GUSTS UP TO
25-30 MPH, WITH INFREQUENT GUSTS UP TO 35-45 MPH POSSIBLE. WINDS
WILL DECREASE SUNDAY NIGHT BEFORE PICKING UP AGAIN ON MONDAY
AFTERNOON AND EVENING WITH SIMILAR GUSTS TO SUNDAY. AS SOILS
BECOME SATURATED DUE TO CONTINUED RAINFALL, IMPACTS SUCH AS
DOWNED WEAKENED OR DEAD TREES ARE POSSIBLE, ESPECIALLY ON MONDAY
WHEN SOILS WILL BE MOST SATURATED. -HEC
LONG TERM...TUESDAY THROUGH THURSDAY
RELATIVELY ZONAL FLOW
EXPECTED ON TUESDAY, WITH POSSIBILITY OF SHOWERS REMAINING.
THAT SAID, POSSIBILITY OF ELEVATED WINDS REMAINING THROUGHOUT
TUESDAY, THOUGH WITH SIGNIFICANT UNCERTAINTY DUE TO THE
UNCERTAINTY IN TIMING OF THE SYSTEM ON MONDAY. NBM 90TH
PERCENTILE OF WIND GUSTS ON TUESDAY MORNING SHOWS SOUTHWESTERLY
25-30 MPH GUSTS REMAINING THROUGHOUT THE WIDER AREA. HEADING
INTO WEDNESDAY, STRONG ENSEMBLE CLUSTER GUIDANCE REGARDING
RIDGING BUILDING INTO THE REGION, POTENTIALLY LASTING FOR AN
EXTENDED PERIOD OF A FEW DAYS. TRENDING DRIER AND WARMER DURING
THIS PERIOD, THOUGH LIGHT SHOWERS AT TIMES ARE NOT OUT OF THE
QUESTION. /JLIU
AVIATION
RADAR, SATELLITE, AND SURFACE OBSERVATIONS AS OF 22Z
FRI DEPICTS VFR CONDITIONS WITH HIGH-LEVEL CLOUDS (~10 KFT OR
HIGHER) AND LIGHT RAIN OFFSHORE AS A FRONTAL SYSTEM APPROACHES
NORTHWEST OREGON AND SOUTHWEST WASHINGTON. TONIGHT AFTER 06Z SAT,
CIGS ARE FORECAST TO FALL TO MVFR ALONG THE COAST AND LOW-END VFR
(4-6 KFT) IN THE WILLAMETTE VALLEY AS THE FRONT PUSHES INLAND AND
BRINGS RAIN. AFTER 12Z SAT, EXPECT SCATTERED POST-FRONTAL SHOWERS
WITH CIGS STILL TRENDING MVFR ALONG THE COAST AND VFR INLAND
THROUGH SATURDAY AFTERNOON. BETWEEN 11-18Z SAT, THERE WILL BE A
20-40% CHANCE THAT CIGS FALL TO MVFR THRESHOLDS OR LOWER WITHIN
THE WILLAMETTE VALLEY.
WINDS WILL GENERALLY BE SOUTHERLY FOR MOST TERMINALS, WITH GUSTS
25-30 KT ALONG THE COAST, MAINLY TONIGHT AND TOMORROW. MEANWHILE,
KTTD-KDLS OFFSHORE GRADIENTS WILL SUPPORT EASTERLY WINDS
CONTINUING THROUGH THE COLUMBIA RIVER GORGE AND INTO THE EASTERN
PORTLAND METRO, WITH GUSTS 20-25 KT THROUGHOUT THE TAF PERIOD.
PDX AND APPROACHES...EXPECT MID TO HIGH LEVEL CIGS THROUGH 06Z
SAT. CIGS FALL TO LOW-END VFR THRESHOLDS AS A COLD FRONT MOVES
THROUGH TONIGHT AND RETURNS RAIN. 20-40% CHANCE FOR MVFR CIGS OR
LOWER BETWEEN 11-18Z SAT. EASTERLY WINDS GENERALLY UNDER 10 KT
TODAY, INCREASING TO 10-15 KT OVERNIGHT INTO SATURDAY. -ALVIZ
MARINE
A SERIES OF SYSTEMS WILL LEAD TO ACTIVE WEATHER ACROSS
THE WATERS THIS WEEKEND INTO EARLY NEXT WEEK. THE FIRST FRONTAL
SYSTEM WILL PUSH THROUGH TONIGHT INTO EARLY SATURDAY MORNING,
BRINGING BREEZY SOUTHERLY WINDS WITH GUSTS UP TO 30 KT. SEAS WILL
ALSO BUILD AROUND 12 TO 16 FEET AT 15 SECONDS AS A WESTERLY SWELL
MOVES IN. THEREFORE, THE HAZARDOUS SEAS WARNING REMAINS IN EFFECT
THROUGH SATURDAY MORNING FOR ALL WATERS INCLUDING THE COLUMBIA
RIVER BAR.
WE'LL SEE A BRIEF LULL IN MARINE CONDITIONS BETWEEN 4-10 AM
SATURDAY, HOWEVER, IT'S NOT A LONG ENOUGH TIME PERIOD TO DOWNGRADE
THE HAZARDOUS SEAS WARNING BEFORE WINDS AND SEAS RAMP UP AGAIN. A
MORE ROBUST FRONTAL SYSTEM WILL ARRIVE LATE MORNING/EARLY
AFTERNOON SATURDAY, WHICH WILL BRING STRONGER SOUTHERLY WINDS 25
TO 35 KT WITH GUSTS UP TO 40 KT THROUGH EARLY SUNDAY MORNING.
WAVES WILL BECOME MORE WIND-DRIVEN DURING THIS TIME WHILE THE
WESTERLY SWELL SUBSIDES, BUT COMBINED SEAS REMAIN AROUND 13 TO 17
FEET AT 13 SECONDS.
FOLLOWING THIS SYSTEM, ANOTHER BREAK ARRIVES BETWEEN SUNDAY
AFTERNOON AND MID-MORNING MONDAY. GUIDANCE IS TRENDING TOWARD
ANOTHER STRONG SYSTEM THAT WILL BRING GALE FORCE SUSTAINED WINDS
WITH GUSTS UP TO 45 KT STARTING MONDAY AFTERNOON. WILL NOTE THAT
THERE IS A 10-20% CHANCE FOR STORM FORCE GUSTS OF 48 KT OR GREATER
WITH THIS SYSTEM, AND A 30-40% CHANCE THAT COMBINED SEAS REACH 20
FEET OR HIGHER MONDAY EVENING. -ALVIZ
HYDROLOGY
A SERIES OF FRONTAL SYSTEMS WILL BRING HEAVY RAINFALL
TO NORTHWEST OREGON AND SOUTHWEST WASHINGTON THIS WEEKEND AND
POTENTIALLY MONDAY. RAIN WILL BEGIN SATURDAY AFTERNOON, AND
INTENSIFY OVERNIGHT THROUGH SUNDAY. THIS WILL LEAD TO RISES ON
RIVERS AND CREEKS, ESPECIALLY ALONG THE COAST ON FEBRUARY 22ND
THROUGH THE 23RD. MAIN STEM RIVERS MAY BE DELAYED TO RESPOND, AND
FLOODING MAY OCCUR BEYOND THIS TIME FRAME.
THERE IS AROUND A 20-25% CHANCE OF THE WILSON RIVER, THE GRAYS
RIVER, AND OTHER LOCALIZED QUICK RESPONDING COASTAL RIVERS OF
REACHING MINOR FLOOD STAGE ON SUNDAY AND POTENTIALLY MONDAY.
CONFIDENCE IN FLOODING IS LOW AS THE LOCATION OF HEAVIEST
PRECIPITATION WILL GREATLY DEPEND ON WHERE THE WARM FRONT SETS
UP. IN THE CASE THAT THIS SYSTEM OVER PERFORMS, MORE WIDESPREAD
FLOODING IS POSSIBLE.
HEAVY RAINFALL ALONG THE CASCADES IS EXPECTED AND COMBINED WITH
RECENT SNOW ACCUMULATION, THERE IS ELEVATED LANDSLIDE RISK.
HEAVY RAINFALL MAY ALSO LEAD TO PONDING OF WATER, GENERAL
LOWLAND FLOODING, AND LOCALIZED URBAN FLOODING, ESPECIALLY IN
LOW-LYING AREAS OR OTHER POOR-DRAINAGE AREAS. HEAVY RAINFALL
WILL ALSO INCREASE THE POTENTIAL FOR LANDSLIDES IN AREAS OF
STEEP TERRAIN AND DEBRIS FLOWS OVER AREAS THAT HAVE BEEN BURNED
BY WILDFIRES OVER THE PAST FEW YEARS. -HALL/MUESSLE
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...HAZARDOUS SEAS WARNING UNTIL 7 AM PST SATURDAY FOR PZZ210-
251>253-271>273.
GALE WARNING FROM 7 AM SATURDAY TO 7 AM PST SUNDAY FOR PZZ210-
251>253.
GALE WARNING FROM 7 AM SATURDAY TO 4 AM PST SUNDAY FOR
PZZ271>273.
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