043
FXUS66 KPQR 202320
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
320 PM PST TUE JAN 20 2026
SYNOPSIS
OUR EXTENDED DRY STRETCH LIKELY CONTINUES THE
REMAINDER OF THE WEEK AS HIGH PRESSURE STUBBORNLY HOLDS
OVERHEAD. CLEAR SKIES AND LIGHT WINDS AWAY FROM THE COLUMBIA
RIVER GORGE WILL RESULT IN FROST AND/OR FREEZING FOG FORMATION
FOR A DECENT SWATH OF THE INTERIOR LOWLAND VALLEYS AND COAST
RANGE VALLEYS. NEAR/BELOW FREEZING TEMPERATURES IN COMBINATION
WITH ANY FOG MAY LEAD TO LOCALLY SLICK ROAD CONDITIONS.
GUSTY/BREEZY WINDS PERSIST THROUGH THE COLUMBIA GORGE AS WELL.
CHANCES FOR PRECIPITATION RETURN LATE THIS WEEKEND INTO NEXT
WEEK, BUT DETAILS ON THE EXACT TIMING AND IMPACTS REMAIN RATHER
NEBULOUS AT THIS TIME.
DISCUSSION...NOW THROUGH MONDAY NIGHT
THIS AFTERNOON
SATELLITE IMAGERY SHOWS A FEW HIGH CLOUDS STREAMING ACROSS THE
REGION WITH OTHERWISE MOSTLY CLEAR SKIES SITTING OVERHEAD.
GOING THROUGH WEDNESDAY (REALLY THROUGH THE END OF THE WEEK)
EXPECT LARGELY A PERSISTENCE FORECAST WITH SIMILAR CONDITIONS
DAY TO DAY THANKS TO A ROBUST RIDGE OF HIGH PRESSURE HOLDING
OVERHEAD, ALTHOUGH IT IS BEGINNING TO TEMPORARILY WEAKEN. THE
PRESSURE GRADIENT BETWEEN KPDX TO KDLS HAS BEEN STRONG TODAY
PEAKING AROUND -10 MB WITH PEAK GUSTS OF 60-75MPH RECORDED NEAR
CORBETT, AND GENERALLY 25-45 MPH GUSTS ACROSS THE EASTERN
PORTLAND METRO, STRONGEST OUT TOWARDS TROUTDALE AND GRESHAM. THE
EPS INDICATES AS THE RIDGE WEAKENS INTO THURSDAY SO WILL THIS
GRADIENT BUT IF YOU LIVE IN A SPOT PRONE TO EASTERLY WINDS THEY
LIKELY WON'T LET UP FOR SOME TIME, ONLY SLOWLY DECREASE.
AWAY FROM THE IMMEDIATE INFLUENCE OF THE COLUMBIA RIVER GORGE
THESE CLEAR/MOSTLY CLEAR SKIES AND LIGHT WINDS WILL FACILITATE
RATHER EFFICIENT RADIATIONAL COOLING EACH NIGHT THROUGH THE END
OF THE WEEK, CONTINUING TO DROP OVERNIGHT LOWS BELOW FREEZING
ACROSS THE WILLAMETTE VALLEY, TUALATIN VALLEY, SOUTHWEST
WASHINGTON LOWLANDS, COAST RANGE VALLEYS, AND UPPER HOOD RIVER
VALLEY - FROST IS LIKELY TOO. THIS SET-UP IN COMBINATION WITH
OUR SUBSIDENCE INVERSION ALOFT OFTEN LEADS TO BOUNDARY LAYER
DECOUPLING WHICH CAN PUSH TEMPERATURES EVEN LOWER FOR OUR
CLIMATOLOGICALLY COOLER SPOTS LIKE HILLSBORO, BATTLEGROUND,
EUGENE, ETC. WE WILL LIKELY SEE APPARENT TEMPERATURES DIP BELOW
25F FOR SOME OF THESE AREAS APPROACHING SUNRISE EACH MORNING,
BUT THE CONFIDENCE IN THE DURATION AND AREAL COVERAGE OF THESE
SUB-25F TEMPERATURES ARE NOT HIGH ENOUGH TO ISSUE A COLD WEATHER
ADVISORY. IF TEMPERATURES TREND A TOUCH LOWER, WE MAY NEED TO
EXPLORE ISSUING THIS HEADLINE. FREEZING FOG ALSO DEVELOPS IN
SOME LOCATIONS, PARTICULARLY ACROSS THE SOUTHERN WILLAMETTE
VALLEY AND LOWER ELEVATIONS OF COWLITZ COUNTY WHERE SURFACE
CONDITIONS ARE MORE MOIST AND PROTECTED FROM THE DRY AIR
FILTERING THROUGH THE CASCADE GAPS. ANY FREEZING FOG THAT
DEVELOPS COULD LEAD TO LOCALLY SLICK ROAD CONDITIONS.
ADDITIONALLY, STAGNANT AIR WILL BE A CONTINUED CONCERN UNDER
THE SUBSIDENCE INVERSION, LEADING TO AIR QUALITY CONCERNS
THROUGH THURSDAY INTO FRIDAY. MIXING HEIGHTS WILL REMAIN LOW
AND TRANSPORT WINDS WILL BE WEAK THROUGH THE WEEK. THEREFORE,
THE AIR STAGNATION ADVISORY WAS EXTENDED THROUGH MIDDAY FRIDAY
AFTER WHICH POINT THERE'S MODERATE CONFIDENCE IN IMPROVEMENT.
THE PORTLAND METRO AREA FROM THE WEST HILLS EASTWARD WERE NOT
INCLUDED IN THIS ADVISORY DUE TO STRONGER WINDS FROM THE GORGE
MAINTAINING A MORE MIXED ATMOSPHERE.
HEADED INTO THURSDAY, THE MAJORITY OF GFS, EURO, AND CANADIAN
ENSEMBLE MEMBERS AND THEIR DETERMINISTIC COUNTERPARTS INDICATE
A TROUGH MOVING THROUGH THE CENTRAL PACIFIC THAT WILL PINCH OFF
INTO A CUTOFF LOW AND MOVE TOWARDS CALIFORNIA, UNDERCUTTING THE
RIDGE OF HIGH PRESSURE INSTEAD OF BREAKING IT DOWN COMPLETELY.
THIS EVENTUALLY LEAVES US IN A DRY REX BLOCK PATTERN LATER ON.
THE SUBSIDENCE INVERSION AND VERY TIGHT PRESSURE GRADIENTS OVER
THE CASCADES SHOULD DEGRADE WITH A MODERATING OF OVERNIGHT
TEMPERATURES AND POOR RH RECOVERIES IN THE FOOTHILLS AND HIGHER
TERRAIN. THIS SHIFT IN THE UPPER-LEVEL PATTERN WILL ALSO ALLOW
FOR A WEAK SHORTWAVE TO MOVE SOUTHWARD ALONG THE FLOW OVER THE
PACNW, HOWEVER PRECIPITATION CHANCES LOCALLY ARE NOW RATHER LOW,
ONLY 5-15%, SO THE DRY WEATHER LIKELY PERSIST.
THEN, A SIGNIFICANT NUMBER OF ENSEMBLE MEMBERS SUGGEST A LOW
MOVING THROUGH THE NE PACIFIC WILL FINALLY FLATTEN AND BREAK
DOWN THE RIDGING SOMETIME LATE SUNDAY AND MONDAY, WITH
INCREASING CHANCES OF PRECIPITATION TO AROUND 30-50%. THIS WOULD
BE A PRETTY WEAK SYSTEM BY THE TIME IT MOVES INTO THE PACNW
WITH LIMITED PRECIPITATION ACCUMULATION. HOWEVER, THERE ARE
STILL A COUPLE OF ITEMS TO KEEP EYES ON AS THIS SYSTEM MOVES
INLAND. FIRST, IF THERE IS PRECIPITATION LATE SATURDAY NIGHT
INTO SUNDAY MORNING, A HANDFUL OF ENSEMBLE MEMBERS SUGGEST THAT
OVERNIGHT/EARLY MORNING TEMPERATURES WILL REMAIN COLD ENOUGH TO
RESULT IN WET, NON-IMPACTFUL SNOW OR RAIN/SNOW MIX FALLING DOWN
TO THE VALLEY FLOOR WHEN PRECIPITATION RETURNS. IF THIS OCCURS,
IMPACTS WOULD BE MINIMAL GIVEN AIR TEMPERATURES WILL BE
MARGINALLY FREEZING DUE TO ONSHORE FLOW AND ROADS WOULD BE TOO
WARM TO ACCUMULATE SNOW. SECOND IS PRECIPITATION TYPE IN THE
CENTRAL COLUMBIA RIVER GORGE AND UPPER HOOD RIVER VALLEY AS
PRECIPITATION BEGINS. IF EASTERLY WINDS CONTINUE INTO THE
WEEKEND, THEN COLDER AIR MAY LINGER LONGER FOR THESE AREAS. THIS
COULD RESULT IN WINTERY PRECIPITATION, ESPECIALLY IF THE
INCOMING MOISTURE OVERLAPS AT THE SAME TIME AS THE FREEZING AIR
NEAR THE SURFACE. THESE AREAS CAN REMAIN MUCH COLDER THAN OTHER
INTERIOR VALLEYS LIKE THE WILLAMETTE VALLEY AND SOUTHWEST WA
LOWLANDS, AND MODEL GUIDANCE IS GENERALLY TOO QUICK IN SCOURING
OUT THE COLD AIR. SPECIFIC DETAILS WILL BECOME MORE CLEAR AS WE
GET CLOSER TO PRECIPITATION RETURNING. -99/03
AVIATION
DRY NORTHWESTERLY FLOW ALOFT TODAY AS AN UPPER LEVEL
RIDGE PERSISTS OVER THE REGION. THIS WILL MAINTAIN WIDESPREAD VFR
CONDITIONS FOR MOST TERMINALS THROUGH THE PERIOD. THE MAIN
EXCEPTIONS WILL BE THE DEVELOPMENT OF FOG OR LOW STRATUS OVERNIGHT
INTO THE MORNING HOURS UNDERNEATH THE SURFACE INVERSION. BY 08Z
WEDNESDAY, PROBABILITIES FOR IFR TO LIFR FOG/STRATUS INCREASE TO
AROUND 50% FOR KEUG, AND UP TO 20-30% ELSEWHERE FOR LOCATIONS SUCH
AS KSLE AND KHIO AFTER 14Z WED. IN THE LOWER LEVELS THE OFFSHORE
PRESSURE GRADIENT CONTINUES TO SUPPORT EASTERLY WINDS THROUGH THE
COLUMBIA RIVER GORGE AND ACROSS PORTIONS OF THE EASTERN PORTLAND
METRO. EXPECT GUSTS TO AROUND 35 KT AT KTTD AND UP TO 65 KT AT THE
WESTERN END OF THE GORGE. MODEL GUIDANCE SUGGESTS WINDS EASE
AGAIN SOMEWHAT BY 08Z WEDNESDAY.
KPDX AND APPROACHES...VFR WITH A FEW HIGH CLOUDS IN THE AREA
TODAY. SOUTHEAST WINDS WITH GUSTS UP TO 20 KT EXPECTED THROUGH 08Z
WED. EAST WINDS REMAIN BREEZY FOR EAST APPROACHES WITH GUSTS TO
AROUND 35 KT AT KTTD. /DH
MARINE
HIGH PRESSURE INLAND AND LOWER PRESSURE OVER THE COASTAL
WATERS WILL MAINTAIN OFFSHORE EASTERLY FLOW THROUGH WEDNESDAY.
HIGH PRESSURE BUILDS OFFSHORE BY THURSDAY, RETURNING MORE
NORTHERLY WINDS ACROSS THE WATERS LATER THIS WEEK. WINDS GENERALLY
REMAIN AROUND 10 KT OR LESS, EXCEPT AREAS DOWNWIND OF GAPS IN THE
COASTAL TERRAIN, WHERE GUSTS UP TO 20 KT WILL BE POSSIBLE. WINDS
TURN OFFSHORE AGAIN THIS WEEKEND.
SEAS CURRENTLY AT AROUND 5 TO 6 FT WITH A PERIOD OF 15 SECONDS
SLOWLY SUBSIDE TO AROUND 4 TO 5 FT AT 12-13 SECONDS ON WEDNESDAY.
NOT MUCH CHANGE TO THE SEA STATE AS A PERSISTENT WESTERLY SWELL
EBBS AND FLOWS THROUGH THE WEEK. /DH
PQR WATCHES/WARNINGS/ADVISORIES
OR...AIR STAGNATION ADVISORY UNTIL NOON PST FRIDAY FOR ORZ109-
114>118.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSPORTLAND
X.COM/NWSPORTLAND
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