943
FXUS66 KPQR 181202
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
402 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
AVIATION
RADAR IMAGERY AND SURFACE OBSERVATIONS AS OF 12Z TUE
DEPICTS DECREASING SHOWER ACTIVITY ACROSS THE AREA WITH IFR/MVFR
CIGS ALONG THE COAST AND MVFR/VFR CIGS ACROSS THE WILLAMETTE
VALLEY. EXPECT THIS TREND TO CONTINUE THROUGH 18Z TUE.
THE NEXT FRONTAL SYSTEM APPROACHES THE REGION TODAY, WITH A WARM
FRONT EXPECTED TO ARRIVE LATE THIS MORNING. THIS WILL RETURN RAIN
ALONG THE COAST BY 18-21Z TUE AND THE VALLEY BY 21Z TUE-00Z WED.
EXPECT CIGS TO TREND TOWARDS MVFR DURING THIS FRONTAL PASSAGE.
OFFSHORE PRESSURE GRADIENTS TIGHTEN TONIGHT, SO EXPECT INCREASING
EASTERLY TO SOUTHEASTERLY WINDS ACROSS ALL TERMINALS. EXPECT
GUSTS UP TO 25 KT ALONG THE COAST AND UP TO 30 KT IN THE EASTERN
PORTLAND METRO AREA. NOTE THAT THERE IS POTENTIAL FOR LOW LEVEL
WIND SHEAR ALONG THE COAST TONIGHT AS THE INCOMING SYSTEM BRING
STRONGER SOUTH-SOUTHWESTERLY WINDS AROUND 2000 FT WHILE RELATIVELY
WEAKER SURFACE WINDS REMAIN EASTERLY.
PDX AND APPROACHES...MIX OF MVFR/VFR CIGS THROUGH 18Z TUE, THEN
TRENDING TOWARD PREDOMINATELY MVFR CIGS IN THE AFTERNOON ONCE THE
INCOMING WARM FRONT ARRIVES AND BRINGS RAIN. EASTERLY WINDS
GENERALLY UNDER 10 KT TODAY, INCREASING TO 10-15 KT WITH GUSTS UP
TO 25 KT AFTER 03Z WED. -ALVIZ
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 FROM 10 AM THIS MORNING TO 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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X.COM/NWSPORTLAND
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