434
FXUS66 KPQR 181822
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1022 AM PST TUE FEB 18 2025
SYNOPSIS
DRY CONDITIONS AND POTENTIAL PATCHY FOG THIS MORNING. LIGHT
RAIN RETURNS THIS AFTERNOON AS ANOTHER WEATHER SYSTEM PUSHES
ACROSS THE REGION THROUGH WEDNESDAY. BREEZY WINDS ALSO POSSIBLE
WEDNESDAY. THEN, LIKELY TRENDING DRIER AND WARMER LATER THIS
WEEK. LATER SATURDAY, POTENTIAL FOR HEAVIER RAIN THROUGH EARLY
NEXT WEEK AS AN ATMOSPHERIC RIVER TAKES AIM AT THE PACIFIC NW.
SHORT TERM...NOW THROUGH THURSDAY MORNING
BRIEF DRY
CONDITIONS AND PATCHY FOG THIS MORNING, AS A SHORTWAVE UPPER
RIDGE PASSES OVER THE REGION PROMOTING STABLE CONDITIONS.
TODAY, A DIGGING UPPER TROUGH WILL APPROACH THE WEST COAST,
BRINGING A WARM FRONT TO PUSH LIGHT RAIN ONSHORE BY THIS
AFTERNOON AND INTO THE WILLAMETTE VALLEY BY THIS EVENING. THIS
DIGGING TROUGH ALSO BRINGS THE POTENTIAL OF A COMPACT LOW
SPINNING UP (DEEPENING TO AROUND 990 MB) OFFSHORE OF THE OREGON
COAST, BUT MODELS STILL HAVE DISAGREEMENT ON WHERE THE LOW WILL
SPIN UP, IF AT ALL. WHILE THIS LOW DOES NOT LOOK TOO IMPACTFUL,
IT COULD BRING SOME ELEVATED BREEZY WINDS SOMEWHERE ALONG THE
COAST WEDNESDAY AFTERNOON AND EARLY EVENING. CURRENT NBM GUIDANCE
SUGGESTS A 20-40% CHANCE OF WIND GUSTS EXCEEDING 50 MPH (LOWEST
TO HIGHEST PROBS FROM ASTORIA TO NEWPORT). PROBABILITY FOR WIND
GUSTS TO EXCEED 60 MPH ARE MUCH LOWER, LESS THAN 10%. HREF
GUIDANCE SUGGESTS EVEN HIGHER CHANCES FOR 50 MPH, AROUND A
30-60% CHANCE. HOWEVER, ITS CHANCES FOR 60 MPH ARE ALSO LESS
THAN 10%. IF THE 60 MPH SCENARIO IS TO PLAY OUT, THESE WINDS
WOULD LIKELY BE A RESULT OF A WESTERLY STRING JET AS THE LOW
NEARS SHORE.
INLAND, EASTERLY WINDS ARE EXPECTED TO INCREASE WEDNESDAY
MORNING, WITH INCREASES IN WIND AS EARLY AS TONIGHT FOR THE
COLUMBIA RIVER GORGE AND THE EASTERN PORTLAND/VANCOUVER METRO.
IN TERMS OF PRESSURE GRADIENTS FROM THE LATEST NAM/GFS, THE
GRADIENT BETWEEN KTTD-KDLS INCREASES TO AROUND -6 MB LATE
TUESDAY NIGHT, THEN AROUND -6 TO -9 MB BY EARLY WEDNESDAY
MORNING (AROUND 4 AM). GFS DEFINITELY LOOKS TO SUGGEST THESE
HIGHER VALUES, AS THE NAM ONLY SUGGESTS GRADIENTS AS HIGH AS -6
MB. HOW THE LOW PROGRESSES (IN TERMS OF STRENGTH AND MOVEMENT)
WILL BE THE BIGGEST FACTOR ON THE POTENTIAL FOR BREEZY
SOUTHERLY WINDS WITHIN THE WILLAMETTE VALLEY FOR WEDNESDAY
AFTERNOON. AS OF NOW, HREF GUIDANCE SUGGESTS A 70-80% CHANCE FOR
WIND GUSTS TO EXCEED 35 MPH, AND A 20-40% CHANCE TO EXCEED 45
MPH. NBM GUIDANCE GIVES MUCH LOWER PROBABILITIES, WITH A 10-20%
CHANCE TO EXCEED 35 MPH AND LESS THAN 5% TO EXCEED 45 MPH. WITH
45 MPH WIND GUSTS REPRESENTING OUR ADVISORY CRITERIA, WILL NEED
TO WATCH THIS TROUGH/POTENTIAL DEEPENING LOW CLOSELY AND
CONTINUE TO ASSESS LATEST MODEL RUNS.
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 4000 FT BY WEDNESDAY EVENING AND TO 3500 FT OVERNIGHT.
LOOKING AT THE CASCADE PASSES, BOTH NBM AND HREF SUGGEST A
40-60% CHANCE FOR SNOW ACCUMULATION TO EXCEED 6 INCHES AND A
10-20% CHANCE TO EXCEED 12 INCHES WEDNESDAY INTO EARLY THURSDAY
MORNING. WITH MODERATE CHANCES TO RECEIVE ADVISORY LEVEL SNOW
ACCUMULATION WEDNESDAY, WILL KEEP A CLOSE EYE ON LATEST MODEL
GUIDANCE AS WE ASSESS IF THERE WILL BE A NEED FOR AN ADVISORY.
THE UPPER HOOD RIVER VALLEY WILL HAVE SNOW LEVELS AROUND
2500-4000 FT WEDNESDAY MORNING BECOMING 3000-3500 FT OVERNIGHT.
GUIDANCE SUGGESTS A MODERATE CHANCE OF A MIX OF WINTRY WEATHER
WEDNESDAY MORNING, WITH A 10-30% CHANCE TO RECEIVE 1 INCH OR
MORE OF SNOW FOR AREAS ABOVE 1000 FT (NBM WITH LOWER CHANCES AND
HREF WITH HIGHER CHANCES). LASTLY, AREAS ABOVE 1000 FT, SUCH AS
PARKDALE, COULD SEE FREEZING RAIN WITH ICE ACCUMULATIONS UP TO
A TENTH OF AN INCH BETWEEN EARLY AND LATE WEDNESDAY MORNING.
WILL NEED TO WATCH LATEST MODEL GUIDANCE CLOSELY AS THE EXPECTED
FREEZING RAIN MAY WARRANT THE ISSUANCE OF AN ADVISORY. ~HALL
LONG TERM...THURSDAY AFTERNOON THROUGH MONDAY
MODELS AND
THEIR ENSEMBLES ARE IN GOOD AGREEMENT LATER THIS WEEK OF UPPER
LEVEL RIDGING BUILDING OVER THE REGION. MOST CLUSTERS KEEP THE
AREA DRY MUCH OF THURSDAY AND FRIDAY, ALTHOUGH THERE IS AROUND A
20-30% 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.
THE NEXT WEATHER SYSTEM THAT BRINGS MORE RAIN TO THE PACIFIC NW
OVER THE WEEKEND WILL LIKELY BE ASSOCIATED WITH A MODERATE TO
STRONG ATMOSPHERIC RIVER, WITH A TOTAL EXPECTED DURATION AROUND
48 HOURS. THE EUROPEAN ENSEMBLE SUGGESTS AVERAGE PWAT AMOUNTS OF
AROUND 1.0-1.1 INCH, WHILE THE GEFS SHOWS SLIGHTLY LOWER
AVERAGE PWAT AMOUNTS OF AROUND 0.9 INCH. UNCERTAINTY REMAINS
WITH WHERE THE BAND OF HEAVIER MOISTURE SETS UP, ALTHOUGH THE
HIGHEST CHANCES ARE NEAR 45N ACCORDING TO THE CW3E IVT LANDFALL
TOOL. ALTHOUGH LATEST HEFS FORECASTS SHOW A 10% OR LESS CHANCE
OF REACHING MINOR FLOOD STAGE, WILL NEED TO MONITOR THE FLASHIER
RIVERS AS WE GET CLOSER TO SUNDAY, INCLUDING THE GRAYS RIVER.
/DH
LONG TERM...THURSDAY THROUGH MONDAY
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.
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...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 4 AM PST
WEDNESDAY FOR PZZ210-251>253.
HAZARDOUS SEAS WARNING FROM 4 AM TO 10 AM PST WEDNESDAY FOR
PZZ210-251>253.
SMALL CRAFT ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR
PZZ271>273.
GALE WARNING FROM 4 PM THIS AFTERNOON TO 10 AM PST WEDNESDAY
FOR PZZ271>273.
WWW.WEATHER.GOV/PORTLAND
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