212
FXUS66 KPQR 190530 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
930 PM PST SUN JAN 18 2026
UPDATED AVIATION DISCUSSION.
SYNOPSIS
DRY WEATHER PREVAILS AS HIGH PRESSURE CONTINUES
THROUGH THE MIDDLE OF THE WEEK. BREEZY EASTERLY WINDS CONTINUE
THROUGH THE COLUMBIA RIVER GORGE AND EASTERN PORTLAND/VANCOUVER
METRO THROUGH EARLY THIS WEEK. FOR THE FEW NIGHTS, CLEAR SKIES
AND LIGHT WINDS WILL RESULT IN FROST OR FREEZING FOG FORMATION
ACROSS MOST INTERIOR LOWLAND VALLEYS. NEAR/BELOW FREEZING
TEMPERATURES IN COMBINATION WITH ANY FOG MAY LEAD TO LOCALLY
SLICK ROAD CONDITIONS. LOWER CONFIDENCE FOR FOG/FROST FOR
LOCATIONS THAT REMAIN WINDY AND OR HAVE PERSISTENT STRATUS.
CHANCES FOR PRECIPITATION RETURN THURSDAY NIGHT.
DISCUSSION...NOW THROUGH SATURDAY NIGHT
SUNNY SKIES PREVAIL
ACROSS THE MAJORITY OF NORTHWEST OREGON AND SOUTHWEST WASHINGTON
AS STRONG HIGH PRESSURE REMAINS OVERHEAD. AN EXCEPTION IS THE
CENTRAL COLUMBIA RIVER GORGE AND UPPER HOOD RIVER VALLEY, WHERE
LOW STRATUS IS BEING HELD IN PLACE DUE TO THE LOW LEVEL
SUBSIDENCE INVERSION. HIGH CONFIDENCE THAT THIS PATTERN
CONTINUES THROUGH AT LEAST TUESDAY, MAINTAINING DRY WEATHER AND
CHILLY NIGHTS.
BREEZY EASTERLY WINDS CONTINUE THROUGH THE COLUMBIA RIVER GORGE,
SURROUNDING TERRAIN, AND EASTERN PORTLAND METRO THROUGH MONDAY.
OBSERVATIONS AS OF EARLY SUNDAY AFTERNOON SHOW WIND GUSTS OF 25
TO 40 MPH ACROSS THE EASTERN PORTLAND METRO WITH LOCALLY HIGHER
GUSTS OF 40-50+ MPH FOR EXPOSED RIDGETOPS LIKE CROWN POINT.
KTTD-KDLS PRESSURE GRADIENTS ARE AROUND -8 TO -9 MB, AND MOST
GUIDANCE SUGGESTS THAT THESE GRADIENTS WILL HOLD THROUGH MONDAY
AFTERNOON AND MAINTAIN SIMILAR WIND GUSTS. BY MONDAY NIGHT INTO
EARLY TUESDAY MORNING, PRESSURE GRADIENTS EASE TO AROUND -4 TO
-6 MB AND WINDS GRADUALLY WEAKEN.
CLEAR SKIES AND LIGHT WINDS AWAY FROM THE WINDS FROM THE
COLUMBIA RIVER GORGE WILL LEAD TO EFFICIENT RADIATIONAL
COOLING ACROSS THE AREA EACH NIGHT THROUGH AT LEAST TUESDAY
NIGHT, DROPPING OVERNIGHT LOWS TO NEAR OR BELOW FREEZING ACROSS
THE WILLAMETTE VALLEY, SOUTHWEST WA LOWLANDS, AND UPPER HOOD
RIVER VALLEY. HIGH CONFIDENCE REMAINS THAT THIS WOULD FAVOR
WIDESPREAD FROST DEVELOPMENT, ESPECIALLY OVER GRASSES AND METAL
SURFACES. FREEZING FOG MAY ALSO DEVELOP IN SOME LOCATIONS,
PARTICULARLY ACROSS THE SOUTHERN WILLAMETTE VALLEY WHERE SURFACE
CONDITIONS ARE MORE MOIST. ANY FREEZING FOG THAT DEVELOPS COULD
LEAD TO LOCALLY SLICK ROAD CONDITIONS. MEANWHILE, HIGHER
ELEVATIONS ABOVE 1500-2000 FT BUT BELOW 5000 FT WILL REMAIN MUCH
WARMER THAN THE LOWLAND VALLEYS DUE TO A STRONG SUBSIDENCE
INVERSION.
ADDITIONALLY, STAGNANT AIR WILL BE A CONTINUED CONCERN UNDER
THIS SUBSIDENCE INVERSION AS THE WINDS DECREASE, LEADING TO AIR
QUALITY CONCERNS THROUGH MID-WEEK. MIXING HEIGHTS WILL REMAIN
LOW AND TRANSPORT WINDS WILL BE WEAK. THEREFORE, AN AIR
STAGNATION ADVISORY REMAINS IN EFFECT FOR MOST OF THE WILLAMETTE
VALLEY DUE TO THIS CONCERN AND HAS BEEN EXTENDED THROUGH 4 PM
WEDNESDAY. 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.
ENSEMBLE GUIDANCE INDICATES THE STRONG HIGH PRESSURE WILL BEGIN
TO SLOWLY BREAK DOWN WEDNESDAY INTO THURSDAY. CONDITIONS ARE
EXPECTED TO REMAIN DRY ON WEDNESDAY WITH THE SUBSIDENCE
INVERSION LIKELY TO BEGIN TO BREAK DOWN AND TEMPERATURES WILL
BEGIN A RETURN TO NEAR NORMAL FOR JANUARY. THERE'S AROUND A
20-40% CHANCE OF PRECIPITATION RETURNING SOMETIME THURSDAY,
MAINLY OVER THE COAST AND TERRAIN. PRECIPITATION CHANCES
INCREASE LATE THURSDAY NIGHT INTO FRIDAY TO 30-50% CHANCE FOR
THE INTERIOR LOWLANDS AND 40-60% FOR THE COAST AND TERRAIN,
CONTINUING INTO SATURDAY. ONSHORE FLOW APPEARS TO RETURN
THURSDAY AS WELL, BRINGING MORE MILD AIR. HOWEVER, ABOUT 15% OF
ENSEMBLE MEMBERS SUGGEST THAT TEMPERATURES WILL REMAIN COLD
ENOUGH TO RESULT IN WET, NON-IMPACTFUL SNOW OR RAIN/SNOW MIX
FALLING DOWN TO THE VALLEY FLOOR. THIS WOULD MAINLY BE FRIDAY
NIGHT AND SATURDAY NIGHT WHEN TEMPERATURES ARE FORECAST THE
COLDEST. 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.
ONE LOCATION WE WOULD KEEP A CLOSER EYE OUT ON WOULD BE THE
CENTRAL COLUMBIA RIVER GORGE AND UPPER HOOD RIVER VALLEY - IF
EASTERLY WINDS CONTINUE, THEN COLDER AIR MAY LINGER LONGER FOR
THESE AREAS. THIS WOULD RESULT IN WINTERY PRECIPITATION,
ESPECIALLY IF THE INCOMING MOISTURE OVERLAPS THE SAME TIME AS
THE FREEZING AIR. THESE AREAS CAN REMAIN MUCH COLDER THAN OTHER
INTERIOR VALLEYS LIKE THE WILLAMETTE VALLEY AND SOUTHWEST WA
LOWLANDS. SPECIFIC DETAILS WILL BECOME MORE CLEAR AS WE GET
CLOSER TO PRECIPITATION RETURNING. -10/03
AVIATION
A PERSISTENT UPPER LEVEL RIDGE OVER THE REGION WILL
CONTINUE TO YIELD WIDESPREAD VFR CONDITIONS FOR MOST TERMINALS
THROUGH THE PERIOD. GUIDANCE IS VARIED ON WHETHER FOG/LOW STRATUS
DEVELOPS AGAIN THROUGH PORTIONS OF THE SOUTHERN WILLAMETTE VALLEY
AND THE LOWER COWLITZ WITH LOWER CONFIDENCE THAN THE PREVIOUS FEW
NIGHTS. GIVEN SIMILAR CONDITIONS TO LAST NIGHT, KEUG WILL HAVE
THE BEST SHOT AT SEEING SUB-VFR CONDITIONS. HAVE ADDED A PERIOD OF
MVFR VIS FOR THE TERMINAL TONIGHT BUT CAN'T RULE OUT LOWER VIS
REDUCTIONS COMPLETELY BASED ON GUIDANCE. OFFSHORE PRESSURE
GRADIENT REMAINS IN PLACE, PRODUCING STRONG GUSTS OF 30-35 KT
CONTINUE AT KTTD, WITH GUSTS UP TO 45-55 KT EAST OF KTTD AT THE
WESTERN END OF THE COLUMBIA RIVER GORGE.
KPDX AND APPROACHES...VFR FLYING CONDITIONS EXPECTED THROUGH THE
PERIOD. EAST TO SOUTHEAST WINDS AROUND 10 KTS EXPECTED. -19
MARINE
STRONG RIDGING ALOFT CONTINUES FAVORING PERSISTENT
EASTERLY OFFSHORE FLOW THROUGH MIDWEEK. WHILE WINDS ARE LARGELY
AT 10 KT OR LESS, AREAS DOWNWIND OF GAPS IN THE COASTAL TERRAIN
MAY SEE STRONGER FLOW WITH GUSTS UP TO 15 KT, MAINLY WEST OF THE
MOUTH OF THE COLUMBIA RIVER. SEAS REMAIN BELOW 10 FT AT 10-13
SECONDS THROUGH THE MIDDLE OF THE WEEK. -03/36
PQR WATCHES/WARNINGS/ADVISORIES
OR...AIR STAGNATION ADVISORY UNTIL 4 PM PST WEDNESDAY 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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