339
FXUS66 KPQR 182309
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
310 PM PST TUE FEB 18 2025
SYNOPSIS
LIGHT RAIN RETURNS THIS EVENING AS A FRONTAL SYSTEM
PUSHES ACROSS THE REGION THROUGH WEDNESDAY. BREEZY WINDS LIKELY
WEDNESDAY, WITH GUSTS UP TO 50 MPH ALONG THE COAST AND UP TO 40 MPH
INLAND. ANOTHER ROUND OF SNOW EXPECTED FOR THE CASCADES THROUGH WED
NIGHT, WITH 4 TO 8 INCHES OF SNOW EXPECTED AT PASS LEVEL. THEN,
TRENDING DRIER AND SLIGHTLY WARMER THURSDAY INTO FRIDAY. LATER
SATURDAY, POTENTIAL FOR HEAVIER RAIN RETURNS THROUGH EARLY NEXT WEEK
AS A MODERATE ATMOSPHERIC RIVER TAKES AIM AT THE PACIFIC NW.
SHORT TERM...NOW THROUGH WEDNESDAY NIGHT
WATER VAPOR SATELLITE
IMAGERY THIS AFTERNOON SHOWS AN AMPLIFIED UPPER LEVEL PATTERN
SHIFTING EAST ACROSS THE PACIFIC TOWARD PACIFIC NW. WE SEE TO SOME
EXTENT A BAROCLINIC LEAF DEVELOPING DOWNSTREAM OF A PV ANOMALY AT
THE BASE OF THE UPPER LEVEL TROUGH. A WEAK SURFACE LOW WILL LIKELY
DEVELOP TONIGHT AS THE WEATHER SYSTEM APPROACHES THE REGION. THIS
LOW MOVES NORTH TOWARD VANCOUVER ISLAND WHILE A WARM FRONT LIFTS
ACROSS THE AREA, WITH LIGHT RAIN THROUGH THIS EVENING. THE MAIN
UNCERTAINTY COMES WITH THE POTENTIAL OF A SECONDARY, COMPACT SURFACE
LOW DEVELOPING NEAR THE OREGON COAST WEDNESDAY MORNING. THIS WOULD
BRING THE POTENTIAL FOR MORE IMPACTFUL SOUTH TO SOUTHWESTERLY WINDS.
FORTUNATELY, THE LATEST MODEL RUNS HAVE BEEN TRENDING AWAY FROM THIS
SOLUTION. STILL, WILL LIKELY SEE WINDS INCREASING WEDNESDAY MORNING.
THE HREF SHOWS SOUTHERLY WINDS WITH GUSTS UP TO 40-50 MPH ALONG THE
COAST BECOMING WESTERLY BY THE AFTERNOON. AND ALTHOUGH THERE IS
STILL POTENTIAL FOR A LOW TO SPIN UP QUICKLY NEAR THE COAST, THE
PROBABILITY OF EXCEEDING 60 MPH IS QUITE LOW, AROUND 10%. BREEZY
SOUTHERLY WINDS LIKELY THROUGH THE WILLAMETTE VALLEY AS WELL MID-DAY
WEDNESDAY, WITH GUSTS UP TO 30-40 MPH. THOSE IN THE COLUMBIA RIVER
GORGE AND EAST PORTLAND/VANCOUVER METRO WILL ALSO NOTICE THE
EASTERLY WINDS PICK-UP WED MORNING AS THE KTTD-KDLS PRESSURE
GRADIENT INCREASES TO AROUND -7 TO -8 MB.
PRECIPITATION RATES WILL LIKELY INCREASE ON WEDNESDAY AS THE UPPER
TROUGH PUSHES AN OCCLUDING FRONT ACROSS THE REGION. SNOW LEVELS
ABOVE 5000 FT WEDNESDAY MORNING WILL GRADUALLY FALL TO AROUND 3500-
4000 FT BY WEDNESDAY EVENING. THE HIGHER CASCADES ARE EXPECTED TO
PICK UP ANOTHER ROUND OF SNOW, WITH AROUND 4 TO 8 INCHES OF SNOW
LIKELY AT PASS LEVEL, THEREFORE HAVE ISSUED A WINTER WEATHER
ADVISORY FOR THE CASCADES. HEAVIEST SNOWFALL RATES EXPECTED BETWEEN
8 AM AND 4 PM ON WEDNESDAY.
THE UPPER HOOD RIVER VALLEY WILL POTENTIALLY SEE A MIX OF WINTRY
WEATHER TONIGHT INTO EARLY WED MORNING. PROBABILITIES HAVE DECREASED
AS FORECASTED TEMPERATURES MARGINALLY FALL TO BELOW FREEZING. BUT
THERE REMAINS A LOW CHANCE (10-30%) OF AREAS ABOVE 1000 FT TO SEE A
FREEZING RAIN WITH ICE ACCUMULATIONS UP TO A TENTH AN INCH OR SNOW
UP TO A HALF INCH. /DH
LONG TERM...THURSDAY THROUGH TUESDAY
MODELS AND THEIR ENSEMBLES
REMAIN IN GOOD AGREEMENT OF UPPER LEVEL RIDGING BUILDING OVER THE
REGION LATER THIS WEEK. EXPECT A MOSTLY DRY DAY ON THURSDAY. BUT
WITH CLOUDS, TEMPERATURES ONLY WARM INTO THE LOWER 50S. MOST
CLUSTERS KEEP THE AREA DRY ON FRIDAY, ALTHOUGH THERE IS AROUND A 40%
CHANCE THAT A FRONT IS ABLE TO PUSH RAIN BACK INTO SOUTHWEST
WASHINGTON AND FAR NW OREGON BY FRIDAY AFTERNOON. TEMPERATURES ARE
LIKELY TO CONTINUE THE GRADUAL WARMING TREND INTO THE MID TO UPPER
50S INTO THE WEEKEND AND EARLY NEXT WEEK.
LIGHT RAIN SHOWERS LATE FRIDAY INTO SATURDAY TURNS TO HEAVIER RAIN
LATER IN THE WEEKEND AS THE NEXT WEATHER SYSTEM WILL LIKELY BE
ASSOCIATED WITH A MODERATE ATMOSPHERIC RIVER, POTENTIALLY PERSISTING
THROUGH MONDAY. BOTH THE GEFS AND THE EUROPEAN ENSEMBLE SUGGESTS
MEAN PWAT AMOUNTS OF AROUND 1.1-1.2 INCH NOW. UNCERTAINTY REMAINS
WITH WHERE THE BAND OF HEAVIER MOISTURE SETS UP. THE HIGHEST CHANCES
OF IVT VALUES > 500 KG/M/S (OF AROUND 70-90%) HAVE SHIFTED SLIGHTLY
SOUTHWARD, ACCORDING TO THE CW3E IVT LANDFALL TOOL, TO MUCH OF THE
CENTRAL AND NORTHERN OREGON COAST. ALTHOUGH LATEST HEFS FORECASTS
SHOW A 5-15% CHANCE OF LOCAL TRIBUTARY RIVERS REACHING MINOR FLOOD
STAGE, WILL NEED TO MONITOR THE FLASHIER RIVERS AS WE GET CLOSER TO
SUNDAY. /DH
AVIATION
AN APPROACHING FRONTAL SYSTEM WILL SEE CONTINUED
OVERCAST SKIES AND RAIN SPREADING FROM SOUTHWEST TO NORTHEAST,
BRINGING MIXED VFR/MVFR CONDITIONS TO AREA TERMINALS. RAIN HAS
ALREADY BEGUN AT ONP AND IS EXPECTED BY 20-21Z TUE AT AST
MAINTAINING MVFR CIGS AND RESTRICTING VSBYS TO MVFR LEVELS AS WELL.
INLAND TERMINALS WILL SEE RAIN LIFT SOUTH TO NORTH, YIELDING CIGS
TRENDING DOWNWARD TOWARD MVFR OR LOW-VFR AT 2-4 KFT BY 21-24Z TUE,
ALTHOUGH VSBYS MAY REMAIN AT 6SM OR GREATER AT MOST SITES. EAST TO
SOUTHEAST WINDS AT 5-10 KT WILL CONTINUE THROUGH THE WARM FRONTAL
PASSAGE.
BY 03-08Z WED, COVERAGE OF RAIN WILL DECREASE TO INTERMITTENT
SHOWERS, WITH CIGS/VSBYS RETURNING TO VFR LEVELS. AS THE SURFACE
PRESSURE GRADIENT TIGHTENS AHEAD OF THE APPROACHING COLD FRONT,
OFFSHORE WINDS WILL INCREASE TO 8-12 KT, HOWEVER PDX/TTD MAY SEE
SPEEDS OF 15-20 KT DUE TO COLUMBIA GORGE OUTFLOW. PERIODS OF LOW-
LEVEL WIND SHEAR ARE EXPECTED ALONG THE COAST AT AST/ONP AS WINDS AT
2 KFT INCREASE OUT OF THE SOUTH TO SOUTH-SOUTHWEST TO 35-40 KT AFTER
09-10Z WED. SCATTERED TO NUMEROUS SHOWERS RETURN AFTER 12Z WED AS
THE COLD FRONT NEARS FROM THE WEST.
PDX AND APPROACHES...LARGELY LOW-VFR CIGS AT 3-4 KFT EXPECTED
THROUGH THE PERIOD WITH RAIN ARRIVING THIS AFTERNOON. SOME PERIODS
OF MVFR CIGS/VSBYS CANNOT BE RULED OUT DURING STEADY LIGHT RAIN
THROUGH THIS EVENING, WITH AN IMPROVEMENT BACK TO VFR FAVORED AFTER
08Z WED. EAST TO EAST-SOUTHEAST WINDS AT 6-10 KT EXPECTED THROUGH
MUCH OF TODAY, INCREASING TO 10-15 KT OVERNIGHT AFTER 08Z WED.
EASTERLY GUSTS OF 20-25 KT ARE POSSIBLE AFTER 12-15Z WED. -PICARD
MARINE
A FRONTAL SYSTEM WILL PUSH THROUGH THE WATERS THIS
EVENING INTO WEDNESDAY, RETURNING GUSTY SOUTHERLY WINDS AND
BUILDING SEAS. THE GALE WATCH PREVIOUSLY ISSUED ACROSS THE OUTER
WATERS HAS BEEN UPGRADED TO A GALE WARNING BEGINNING 4 PM TUESDAY,
WITH SOUTHERLY WIND GUSTS UP TO 35 KT EXPECTED. MEANWHILE, A
SMALL CRAFT ADVISORY HAS BEEN ISSUED FOR THE INNER WATERS AND
COLUMBIA RIVER BAR BEGINNING 4 PM TUESDAY AS WELL, HOWEVER,
OCCASIONAL GUSTS UP TO 35 KT ARE STILL POSSIBLE (30-50% CHANCE).
GOING INTO EARLY WEDNESDAY MORNING, THE SMALL CRAFT ADVISORY OVER
THE INNER WATERS TRANSITIONS INTO A HAZARDOUS SEAS WARNING AS THIS
SYSTEM BRINGS STEEP AND CHOPPY SEAS. COMBINED SEAS WILL BUILD TO
12-15 FEET BY WEDNESDAY MORNING.
CURRENTLY, THERE ARE NO MARINE HAZARDS ISSUED BEYOND 10 AM
WEDNESDAY. THERE IS STILL SOME UNCERTAINTY WITH HOW THE LOW
PRESSURE SYSTEM WILL PROGRESS BEYOND THIS TIME. ONE MODEL (GFS) IS
DEPICTING AN EXTREME SOLUTION WHERE THE LOW STRENGTHENS FURTHER
AND TREKS DIRECTLY OVER OUR WATERS. THIS COULD RESULT IN A STING
JET WHICH WOULD CONTINUE GALES ACROSS ALL OF THE WATERS AND
POTENTIALLY RESULTS IN STORM FORCE GUSTS UP TO 50 KT (10-20%
CHANCE). IN THIS SCENARIO, THE INNER WATERS COULD GET UPGRADED TO
A GALE WARNING. MEANWHILE, OTHER GUIDANCE SUGGESTS THAT THE LOW
WILL MOVE NORTHWARD AND WEAKEN, RAMPING WINDS DOWN TO SMALL CRAFT
LEVELS (MOST LIKELY SCENARIO). -ALVIZ
PQR WATCHES/WARNINGS/ADVISORIES
OR...WINTER WEATHER ADVISORY FROM 4 AM WEDNESDAY TO 4 AM PST THURSDAY
FOR ORZ126>128.
WA...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 4 AM PST
THURSDAY FOR WAZ211.
PZ...SMALL CRAFT ADVISORY UNTIL 4 PM PST WEDNESDAY FOR PZZ210.
SMALL CRAFT ADVISORY UNTIL 7 AM PST WEDNESDAY FOR PZZ251.
GALE WATCH FROM WEDNESDAY MORNING THROUGH WEDNESDAY AFTERNOON
FOR PZZ251.
SMALL CRAFT ADVISORY UNTIL 4 AM PST WEDNESDAY FOR PZZ252-253.
GALE WARNING FROM 4 AM TO 4 PM PST WEDNESDAY FOR PZZ252-253.
SMALL CRAFT ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR
PZZ271>273.
GALE WARNING UNTIL 4 PM PST WEDNESDAY FOR PZZ271>273.
WWW.WEATHER.GOV/PORTLAND
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