076
FXUS66 KPQR 312221
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
321 PM PDT MON MAR 31 2025
SYNOPSIS
UPPER LEVEL TROUGHING SUPPORTS SEASONABLY COOL AND
SHOWERY CONDITIONS THROUGH WEDNESDAY. UPPER LEVEL RIDGING WILL THEN
BRING AN EXTENDED PERIOD OF DRY WEATHER FROM THURSDAY ONWARD, WITH
TEMPERATURES GRADUALLY WARMING EACH DAY. THE WARMEST TEMPS ARE
EXPECTED THIS WEEKEND WITH WIDESPREAD HIGHS IN THE 70S. ALSO OF NOTE
IS THE POTENTIAL FOR FROST WEDNESDAY NIGHT AND/OR THURSDAY NIGHT.
SHORT TERM...MONDAY NIGHT THROUGH WEDNESDAY NIGHT
THE SHORT TERM
FORECAST IS HIGHLIGHTED BY SEASONABLY COOL AND SHOWERY WEATHER
THROUGH WEDNESDAY, WITH HIGH TEMPS IN THE LOW TO MID 50S ACROSS THE
LOWLANDS EACH DAY. THERE WILL BE A BRIEF BREAK FROM SHOWERY ACTIVITY
MONDAY NIGHT THROUGH TUESDAY MORNING AS A WEAKENING UPPER LEVEL LOW
SHIFTS SOUTHEASTWARD INTO SOUTHWEST OR AND NORTHERN CA, BRINGING
RELATIVELY DRIER NORTHERLY FLOW TO SOUTHWEST WA AND NORTHWEST OR.
SHOWERY ACTIVITY WILL RETURN TUESDAY AFTERNOON WITH DAYTIME HEATING,
HOWEVER MODEL SOUNDINGS SUGGEST THESE RAIN SHOWERS WILL BE QUITE
SHALLOW AND WEAK WITH EQUILIBRIUM LEVELS AROUND 700 MB OR LOWER.
TEMPERATURES AT THIS LEVEL ARE AROUND -10 DEGREES CELSIUS, SUGGESTING
IT WILL BE DIFFICULT FOR MIXED-PHASED CLOUDS CAPABLE OF CHARGE
SEPARATION AND/OR HAIL. NBM PROBABILITIES FOR THUNDER ARE LOW AT
5-10%, WHICH HELPS BACK THIS UP. OVERALL NOT EXPECTING THUNDERSTORMS
OR HAIL ON TUESDAY UNLESS IT IS WITH ONE OR TWO ISOLATED CELLS THAT
MANAGE TO OVERPERFORM AND PRODUCE ONE OR TWO LIGHTNING FLASHES. MUCH
OF THE DAY WILL BE DRY ASIDE FROM LIGHT HIT-OR-MISS RAIN SHOWERS IN
THE AFTERNOON.
OVERNIGHT LOWS TREND COOLER WEDNESDAY NIGHT WITH THE POTENTIAL FOR
PATCHY FROST. HIGH PRESSURE WILL YIELD CALM WINDS AND CLEARING SKIES
OVER THE AREA, RESULTING IN AN IDEAL SETUP FOR RADIATIONAL COOLING.
FORECAST LOWS CURRENTLY RANGE BETWEEN 34-38 DEGREES ACROSS THE
LOWLANDS. FOR FROST FORECASTING, WE TYPICALLY LOOK FOR 2-M SURFACE
TEMPERATURES NEAR 35F OR COLDER ON CLEAR/CALM NIGHTS WITH DRY
NORTHERLY FLOW JUST ABOVE THE SURFACE/ALOFT, AS THIS TENDS TO FAVOR
FROST FORMATION RATHER THAN FOG. GIVEN GOOD MODEL AGREEMENT THIS
PATTERN WILL BE IN PLACE WEDNESDAY NIGHT, HAVE DECIDED TO INTRODUCE A
MENTION OF FROST IN THE FORECAST FOR LOWLAND LOCATIONS EXPECTED TO
SEE LOWS NEAR 35F OR COLDER. NBM PROBABILITIES FOR LOW TEMPS OF 35F
OR COLDER RANGE FROM 40-70% ACROSS THE CENTRAL AND SOUTHERN
WILLAMETTE VALLEY, CASCADE FOOTHILLS AND COWLITZ VALLEY.
PROBABILITIES ARE LESS THAN 5-10% AT THE COAST, AND 5-15% FOR THE
PORTLAND/VANCOUVER METRO AREA (EXCEPT 40-60% FOR HILLSBORO, FOREST
GROVE AND BANKS). IF CONFIDENCE INCREASES FOR WIDESPREAD LOWS BETWEEN
33-35, WILL LIKELY NEED TO ISSUE A FROST ADVISORY FOR SOME ZONES NOW
THAT THE GROWING SEASON IS UPON US. THIS OUTCOME IS MOST LIKELY TO
OCCUR FOR OUTLYING RURAL AREAS. -TK
LONG TERM...THURSDAY THROUGH SUNDAY NIGHT
THE PATTERN WILL START
TO TRANSITION ON THURSDAY AS UPPER LEVEL RIDGING BEGINS TO DEVELOP
OVER WESTERN WASHINGTON/OREGON, AFTER WHAT LOOKS TO BE A POTENTIALLY
FROSTY START TO THE DAY FOR SOME LOCATIONS WITH CHILLY MORNING LOWS
IN THE 30S. THIS WILL BE ESPECIALLY TRUE FOR OUTLYING RURAL AREAS
WHERE PROBABILITIES FOR LOWS OF 35F OR COLDER ARE HIGHEST (40-50%,
EXCEPT 70% FROM CORVALLIS TO JUNCTION CITY). PROBABILITIES FOR THE
PORTLAND/VANCOUVER METRO RANGE FROM 15-35%, 35% IN SALEM AND 50% IN
EUGENE-SPRINGFIELD.
DESPITE CHILLY MORNING TEMPS, EXPECT AFTERNOON HIGHS WELL INTO THE
50S TO NEAR 60 DEGREES ACROSS THE LOWLANDS. DRY NORTHERLY FLOW WILL
SUPPORT BREAKS OF SUNSHINE, MAKING FOR A RATHER MILD AND PLEASANT
SPRING DAY. IF YOU PREFER WARMER TEMPERATURES, YOU'RE IN LUCK COME
FRIDAY THROUGH SUNDAY. THIS IS WHEN MODELS AND THEIR ENSEMBLES SHOW
GOOD AGREEMENT FOR THE AFOREMENTIONED UPPER LEVEL RIDGE TO BECOME
HIGHLY AMPLIFIED OVER THE REGION, RESULTING IN WIDESPREAD HIGH TEMPS
IN THE 70S FOR THE UPCOMING WEEKEND. IN FACT, HIGHS IN THE LOWER 80S
CANNOT BE RULED OUT ON SUNDAY ACCORDING TO THE NBM. THIS IS WHEN
THERE IS A 5-20% CHANCE FOR HIGHS OF 80 DEGREES OR WARMER, WITH THE
HIGHEST PROBABILITIES IN PORTLAND. THIS EXCLUDES THE COAST WHERE
PROBABILITIES ARE NEAR ZERO. CONDITIONS WILL ALSO BE DRY FRIDAY
THROUGH SUNDAY, MAKING FOR IDEAL CONDITIONS FOR OUTDOOR ACTIVITIES.
-TK
AVIATION
LATE THIS AFTERNOON CONDITIONS REMAIN A MIX OF VFR TO
HIGH END MVFR (3-5KFT) WITH ONGOING SCATTERED SHOWER ACTIVITY
ACROSS WESTERN OREGON AND WASHINGTON. CIGS AND TO SOME EXTENT VIS
WILL CONTINUE TO FLUCTUATE WITH ANY PASSING SHOWERS BUT AT LEAST
HIGH RESOLUTION GUIDANCE LIKE THE HREF IS CONFIDENT IN A DECREASE
AND EVENTUAL END IN LINGERING ACTIVITY LATER THIS EVENING BY
04-06Z. THIS IS ALL THANKS TO A WEAK LOW PRESSURE SYSTEM
UNDERCUTTING THE REGION TO THE SOUTH. WHILE THIS WILL HELP
GENERALLY MAINTAIN VFR CONDITIONS OVERNIGHT, DEVELOPING LIGHT
NORTHERLY FLOW IN THE WILLAMETTE VALLEY AND PROXIMITY TO THE
AFOREMENTIONED DISTURBANCE KEEPS A HIGHER LIKELIHOOD FOR MVFR
CIGS AT KEUG/KSLE; AROUND 40-65% BETWEEN 12-18Z TUESDAY. WE'LL
ALSO NEED TO WATCH THE AMOUNTS OF CLEARING AS WELL WHICH COULD
FACILITATE PATCHY FOG FORMATION AT INLAND TERMINALS - A 20-40%
CHANCE. WINDS WHICH HAVE BEEN OCCASIONALLY BREEZY TODAY SHOULD
DECREASE AFTER SUNSET, REMAINING LIGHTER (<5-10 KNOTS) THE REST OF
THE TAF PERIOD.
PDX AND APPROACHES...EXPECT SHOWERS TO PERSIST THROUGH THE FIRST
HALF OF THE EVENING WITH PERIODS OF MVFR CIGS/VIS AND GUSTY WINDS
POSSIBLE THE NEXT FEW HOURS WITHIN THE VICINITY OF HEAVIER
ACTIVITY. DRY AND CALMER CONDITIONS RETURN OVERNIGHT WITH WINDS
STAY LESS THAN 5-8 KNOTS THROUGH TUESDAY. WE WILL HAVE TO WATCH
FOR PATCHY FOG 09-16Z TUESDAY WHICH MAY SIGNIFICANTLY DETERIORATE
CONDITIONS IF IT DEVELOPS (30-40% CHANCE LOCALLY). -SCHULDT
MARINE
CONDITIONS ARE STILL FAIRLY ACTIVE ACROSS THE COASTAL
WATERS THIS AFTERNOON WITH WAVE HEIGHT AROUND 7-10 FT AT 8 SECONDS
WITH WINDS OCCASIONALLY GUSTING TO 25 KNOTS. SMALL CRAFT
CONDITIONS LIKELY PERSIST INTO THE EVENING HOURS BEFORE WINDS
DECREASE. HOWEVER, SEAS WILL GRADUALLY INTO TUESDAY MORNING DUE
TO THE ARRIVAL OF A FRESH SOUTHWESTERLY SWELL WITH SEAS PEAKING
8-13 FEET - HIGHEST SOUTH OF CAPE FOULWEATHER. FORTUNATELY SEAS
THEN DISSIPATE THROUGH THE REST TUESDAY INTO WEDNESDAY BOTTOMING
OUT 4-6 FT LATE WEEK THANKS TO A RIDGE OF HIGH PRESSURE BUILDING
OVERHEAD. EXPECT WINDS TO TURN NORTHERLY THURSDAY INTO FRIDAY AS
WELL. -SCHULDT
BEACH HAZARDS
MINOR COASTAL FLOODING DUE TO TIDAL OVERFLOW
WILL BE POSSIBLE ALONG THE NORTH OREGON COAST AND SOUTH WASHINGTON
COAST LATE TONIGHT INTO TUESDAY MORNING DUE TO A FAIRLY ROBUST
HIGH TIDE IN COMBINATION WITH LINGERING SURGE FROM THIS PAST
WEATHER DISTURBANCE. WITH A TOTAL TIDE OF ~10.5-11.2 FEET IN THIS
REGION, FLOODING UP TO ONE FOOT ABOVE GROUND LEVEL WILL BE
POSSIBLE FOR THE LOWEST LYING COASTAL AREAS LIKE ALONG PORTIONS
OF HIGHWAY 101 NEAR RAYMOND. ANY THREAT FOR TIDAL OVERFLOW END BY
7-8AM TUESDAY MORNING. -SCHULDT
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 10 PM PDT THIS EVENING FOR PZZ210.
SMALL CRAFT ADVISORY FROM 5 AM TO 11 AM PDT TUESDAY FOR PZZ210.
SMALL CRAFT ADVISORY UNTIL 5 AM PDT TUESDAY FOR PZZ251>253-
271>273.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSPORTLAND
X.COM/NWSPORTLAND
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