586
FXUS66 KPQR 162359
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
306 PM PST THU JAN 16 2025
SYNOPSIS
HIGH PRESSURE OVER THE REGION WILL BRING MAINLY DRY
WEATHER AND COOL TEMPERATURES THROUGH THE MIDDLE OF NEXT WEEK. EXPECT
LOW TEMPERATURES TO DROP DOWN INTO THE 20S AND LOW 30S FOR MOST
VALLEY LOCATIONS BEGINNING THIS WEEKEND AND CONTINUING THROUGH MUCH
OF NEXT WEEK.
DISCUSSION...TONIGHT THROUGH THURSDAY
FOG AND LOW CLOUDS REMAIN
ENTRENCHED ACROSS MUCH OF THE WILLAMETTE VALLEY. AREAS OF DENSE FOG
REMAIN IN THE SOUTHERN WILLAMETTE VALLEY. A WEAK FRONT IS CURRENTLY
PUSHING THROUGH SOUTHWEST WASHINGTON AND NORTHWEST OREGON. AREAS OF
LIGHT DRIZZLE HAVE DEVELOPED AROUND THE PORTLAND/VANCOUVER METRO, BUT
THE PROBABILITY FOR MEASURABLE PRECIPITATION AT ANY GIVEN LOCATION
APPEARS TO BE 10% OR LESS OVER THE NEXT FEW HOURS. OTHERWISE, EXPECT
FOG AND LOW CLOUDS TO REMAIN STUCK ACROSS THE LOWLANDS OF INTERIOR
SOUTHWEST WASHINGTON AND NORTHWEST OREGON INTO FRIDAY MORNING. ANY
CLEARING THIS EVENING BEHIND THE FRONT SHOULD BE SHORT LIVED AS
AREAS FOG BACK IN OVERNIGHT PER HREF.
MODELS AND THEIR ENSEMBLE SYSTEMS ARE IN GOOD AGREEMENT SHORTWAVE
RIDGING WILL AMPLIFY OVER THE EASTERN PACIFIC AND SLOWLY SHIFT
EASTWARD OVER THE PACIFIC NORTHWEST AND BRITISH COLUMBIA THIS WEEKEND
INTO EARLY NEXT WEEK. SHORTWAVE TROUGHS DROPPING DOWN THE BACKSIDE OF
THE RIDGE WILL BRING ARCTIC AIR SOUTHWARD OUT OF CANADA TO AREAS
MAINLY EAST OF THE ROCKIES. NONETHELESS, PRESSURE GRADIENT FORCES
WILL TURN OFFSHORE AND RESULT IN INCREASING NORTH TO NORTHEASTERLY
TO EASTERLY WINDS AS MODESTLY COLDER AND DRIER AIR FILTERS INTO THE
REGION. THIS WILL REDUCE FOG AND LOW CLOUD COVERAGE, END AIR
STAGNATION CONCERNS AND ALLOW AREAS THAT DECOUPLE FROM THE BREEZY
CONDITIONS TO DROP WELL BELOW FREEZING. UNCERTAINTY IN THE LOW
TEMPERATURE FORECAST WILL PRIMARILY REVOLVE AROUND WHETHER OR NOT
LOCATIONS DECOUPLE AND ARE ABLE RADIATIVELY COOL EFFICIENTLY.
SATURDAY, SUNDAY AND MONDAY NIGHTS GENERALLY HAVE SIMILAR
PROBABILITIES FOR COLD TEMPERATURES TO OCCUR. FOR EXAMPLE, THERE IS
CURRENTLY 20% CHANCE OR LESS FOR THE INNER PORTLAND/VANCOUVER METRO
AND AREAS NEAR THE GORGE TO REACH 25F, BUT THE PROBABILITIES
INCREASE TO 50-80% ACROSS LARGE PORTIONS OF THE WILLAMETTE AND LOWER
COLUMBIA RIVER VALLEYS WHERE WINDS ARE MORE LIKELY TO TEMPORARILY
DIMINISH OVERNIGHT THIS WEEKEND INTO EARLY NEXT WEEK.
UNCERTAINTY IN THE FORECAST DOES BEGIN TO GROW LATE TUESDAY INTO
WEDNESDAY AND FURTHER MORE MOVING TOWARDS FRIDAY NEXT WEEK. THERE
ARE A SMALL PERCENTAGE OF MODELS THAT SUGGEST A WEAK STORM SYSTEM
WILL BRUSH THE REGION LATE TUESDAY OR WEDNESDAY. NBM POPS OF 10-20%
ACROSS MOST OF THE REGION SEEM ENTIRELY REASONABLE. THERE IS A SMALL
CHANCE (5% OR LESS) THAT ANY LIGHT PRECIPITATION COULD FALL
INITIALLY AS FLURRIES ACROSS THE LOWLANDS INSTEAD OF LIGHT RAIN
DURING THAT TIME. THERE ARE MORE GLOBAL ENSEMBLE MEMBERS (~20-30%)
THAT SUGGEST ANOTHER STORM SYSTEM WILL IMPACT THE REGION TOWARDS
NEXT FRIDAY. NBM PROBABILITIES FOR PRECIPITATION HEAVILY TILT
TOWARDS RAIN FALLING DURING THIS TIME ACROSS THE VALLEYS OF
NORTHWEST OREGON AND SOUTHWEST WASHINGTON VS. PRECIPITATION FALLING
AS SNOW. NONETHELESS, THE MOST LIKELY SCENARIO STILL APPEARS THAT WE
REMAIN DRY THROUGH NEXT FRIDAY.
AVIATION
DRY, WEST TO NORTHWESTERLY FLOW ALOFT. A WEAK AND
MOSTLY DRY FRONT WILL MOVE ACROSS THE AREA TODAY. CURRENTLY A MIX
OF VFR AND MVFR CIGS AT THE COAST WITH INCREASING ONSHORE FLOW
TODAY. STILL HAVE A SUBSIDENCE INVERSION OVER THE INLAND VALLEYS
WHERE IFR TO LIFR CIGS AND VIS ARE EXPECTED TO PERSIST THIS
AFTERNOON. THEN, CEILINGS EXPECTED TO LIFT TO IFR/MVFR WITH
POSSIBLE IMPROVING CONDITIONS WITH THE FRONTAL PASSAGE. THERE IS
AROUND A 50% CHANCE FOR A BRIEF PERIOD OF VFR CONDITIONS LATER
THIS AFTERNOON INTO EARLY EVENING. SUSPECT CLOUD COVER WILL REMAIN
IN PLACE THROUGH AT LEAST FRIDAY MORNING DUE TO A LACK OF LOW-
LEVEL MIXING AND MINIMAL CHANGE IN THE OVERALL PATTERN.
PDX AND APPROACHES...CIGS JUMPING BETWEEN IFR AND LIFR AS STRATUS
AND REDUCED VIS REMAIN IN PLACE AS OF 22Z, LIKELY PERSISTING
THROUGH AT LEAST 00Z. THEN, CIGS LIKELY LIFT TO MVFR AS A WEAK
FRONT PASSES THROUGH. THERE IS AROUND A 50% CHANCE FOR BRIEF VFR
CONDITIONS BETWEEN 02-08Z FRIDAY. LIFR TO IFR CONDITIONS MAY
RETURN AFTER 12Z FRIDAY (50% CHANCE). WINDS REMAIN GENERALLY LIGHT
AND VARIABLE, THOUGH NORTHWEST WINDS LATER TO AROUND 5 KT WILL BE
POSSIBLE LATER TODAY. /DH
MARINE
HIGH PRESSURE REMAINS OVER THE WATERS THROUGH THE
WEEKEND RESULTING IN PERSISTENT NORTHERLY FLOW. A WEAK FRONT WILL
CONTINUE TO DROP SOUTH ACROSS THE COASTAL WATERS TODAY. NORTH
WINDS BEHIND THE FRONT ARE EXPECTED TO INCREASE WITH GUSTS UP TO
25 KT, MAINLY ACROSS THE OUTER COASTAL WATERS, THROUGH TONIGHT. A
SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR THAT TIME. WINDS EASE
FRIDAY, GENERALLY REMAINING BELOW 20 KT, AND BECOME MORE
NORTHEASTERLY AS A THERMAL TROUGH RETURNS TO THE OREGON COAST AND
PERSISTS THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. SEAS
LIKELY HOVER AROUND 6 TO 9 FT THROUGH FRIDAY. A LONG PERIOD SWELL
IS EXPECTED TO PUSH INTO THE COASTAL WATERS ON SATURDAY WITH A
PERIOD OF AROUND 20 SECONDS, WITH SEAS LIKELY REMAINING AROUND 7
TO 9 FT THROUGH SUNDAY. RELATIVELY QUIET WEATHER CONTINUES INTO
EARLY NEXT WEEK. /DH
PQR WATCHES/WARNINGS/ADVISORIES
OR...DENSE FOG ADVISORY UNTIL 1 PM PST THIS AFTERNOON FOR ORZ109-110-
113>118-124-125.
AIR STAGNATION ADVISORY UNTIL 10 AM PST FRIDAY FOR ORZ114>118.
WA...DENSE FOG ADVISORY UNTIL 1 PM PST THIS AFTERNOON FOR WAZ205.
PZ...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 8 PM PST THIS
EVENING FOR PZZ210.
SMALL CRAFT ADVISORY UNTIL MIDNIGHT PST TONIGHT FOR PZZ251.
SMALL CRAFT ADVISORY UNTIL 4 AM PST FRIDAY FOR PZZ271-272.
SMALL CRAFT ADVISORY UNTIL 4 AM PST FRIDAY FOR PZZ273.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
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