965
FXUS66 KPQR 191021
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
221 AM PST MON JAN 19 2026
SYNOPSIS
DRY WEATHER PREVAILS AS HIGH PRESSURE CONTINUES
THROUGH AT LEAST THE MIDDLE OF THE WEEK WITH BREEZY EASTERLY
WINDS THROUGH THE COLUMBIA RIVER GORGE AND EASTERN
PORTLAND/VANCOUVER METRO. AS LONG AS HIGH PRESSURE PREVAILS,
CLEAR SKIES AND LIGHT WINDS WILL RESULT IN FROST AND/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 LATE WEEK.
DISCUSSION...MONDAY MORNING THROUGH SUNDAY
THE FORECAST FOR
MONDAY INTO TUESDAY WILL BE A RINSE AND REPEAT OF CONDITIONS
OBSERVED OVER THE WEEKEND. A STRONG RIDGE OF HIGH PRESSURE
REMAINS SITUATED OVER THE WEST COAST THROUGH AT LEAST TUESDAY,
WITH INCREASING CONFIDENCE THROUGH WEDNESDAY, LEADING TO DRY
WEATHER AND MOSTLY CLEAR SKIES ACROSS NW OREGON AND SW
WASHINGTON. THE ONLY EXCEPTION IS THE CENTRAL COLUMBIA RIVER
GORGE AND HOOD RIVER VALLEY WHERE STRATUS HAS REMAINED SOCKED IN
FOR DAYS, AS WELL AS THE SOUTHERN WILLAMETTE VALLEY AROUND AND
SOUTH OF EUGENE WHERE LOW STRATUS AND FOG DEVELOP IN THE LATE
NIGHT THROUGH EARLY MORNING HOURS.
BREEZY EASTERLY WINDS CONTINUE THROUGH THE COLUMBIA RIVER GORGE,
SURROUNDING TERRAIN, AND EASTERN PORTLAND METRO THROUGH MONDAY
DUE TO INCREASED PRESSURE GRADIENTS OVER THE CASCADES UNDER THE
CURRENT PATTERN. THE PRESSURE GRADIENT FROM KPDX TO KDLS HAS
INCREASED FROM -8 TO -9 MB TO -9 TO -10 MB LATE SUNDAY NIGHT
INTO EARLY MONDAY MORNING, LEADING TO AN INCREASE IN WIND GUSTS
COMPARED TO SUNDAY. ULTIMATELY, THE PRESSURE GRADIENT IS
EXPECTED TO FLUCTUATE THROUGH MONDAY BETWEEN -8 TO -10 MB
LEADING TO PEAK WIND GUSTS OF 25-35 MPH THROUGH THE PORTLAND
METRO AREA, 35-45 MPH ACROSS THE EASTERN PORTLAND METRO AREA
AROUND AND EAST OF GRESHAM, AND 50-70 MPH AT THE KNOWN WINDY
LOCATIONS EAST OF TROUTDALE, INCLUDING CROWN POINT AND CORBETT.
GRADIENTS ARE EXPECTED TO BEGIN DECREASING MONDAY NIGHT TO
AROUND -6 TO -8 MB, REMAINING IN THIS RANGE THROUGH AT LEAST
TUESDAY AND NOW LIKELY INTO WEDNESDAY. PEAK WIND GUSTS WOULD
DECREASE BUT STILL REMAIN ELEVATED, ESPECIALLY IN THE LATE
AFTERNOON THROUGH OVERNIGHT HOURS.
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 WEDNESDAY NIGHT,
DROPPING OVERNIGHT LOWS TO NEAR OR BELOW FREEZING ACROSS THE
WILLAMETTE VALLEY, SOUTHWEST WASHINGTON 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 AT LEAST 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.
THE PAST COUPLE OF GFS, EURO, AND CANADIAN ENSEMBLE RUNS HAVE
BEGUN INDICATING HIGH PRESSURE COULD REMAIN IN PLACE OVER THE
EASTERN PACIFIC AND PACIFIC NW ON WEDNESDAY INTO THURSDAY AND
POSSIBLY INTO THE WEEKEND. THIS IS BECAUSE THE MAJORITY OF
ENSEMBLE MEMBERS 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 HAS CAUSED A SIGNIFICANT
DECREASE IN PRECIPITATION CHANCES RETURNING LATE THIS WEEK,
THOUGH IT DOESN'T COMPLETELY ELIMINATE THIS POSSIBILITY. THERE
IS NOW A 15-25% CHANCE OF PRECIPITATION LATE THURSDAY THROUGH
FRIDAY, MAINLY FOR THE COAST AND TERRAIN. FOR THE WEEKEND,
ENSEMBLE 500 MB CLUSTER ANALYSIS INDICATE ABOUT A 25% CHANCE OF
A SHORTWAVE PUSHING SOUTHWEST THROUGH THE GREAT BASIN AND INTO
THE PACNW AND A 20% CHANCE OF A WEAK WEATHER SYSTEM MOVING IN
FROM THE PACIFIC AND BREAKING DOWN THE RIDGE. BOTH SOLUTIONS
PRODUCE AN INCREASED CHANCE FOR PRECIPITATION SATURDAY INTO
SUNDAY. HOWEVER, THAT STILL LEAVES ~55% OF ENSEMBLE SOLUTIONS
CONTINUING RIDGING THROUGH THE WEEKEND WITH MOSTLY DRY WEATHER.
AT ANY RATE, RIDGING THAT CONTINUES WEDNESDAY AND BEYOND WOULD
BE WEAKER THAN EARLIER IN THE WEEK, WHICH COULD LEAD TO A
MODERATING OF DAYTIME TEMPERATURES AND A POTENTIAL BREAKDOWN OF
THE STRONG SUBSIDENCE INVERSION. ADDITIONALLY, ABOUT 15% 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.
ONE LOCATION WE WOULD KEEP A CLOSER EYE ON WHEN PRECIPITATION
RETURNS 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 COULD RESULT IN WINTERY
PRECIPITATION, ESPECIALLY IF THE INCOMING MOISTURE OVERLAPS AT
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. -03/10
AVIATION
A PERSISTENT UPPER LEVEL RIDGE OVER THE REGION WILL
CONTINUE TO YIELD WIDESPREAD VFR CONDITIONS FOR MOST TERMINALS
THROUGH THE PERIOD. LOW STRATUS/FOG HAS DEVELOPED IN PORTIONS OF
THE SOUTHERN WILLAMETTE VALLEY AND THE LOWER COWLITZ. AS HAS
OCCURRED THE PAST FEW DAYS, KEUG WILL SEE VIS FLUCTUATING BETWEEN
ALL FLIGHT LEVELS THROUGH 16-18Z MON BEFORE BECOMING PREDOMINATELY
VFR. EXPECT TO SEE SIMILAR CONDITIONS AGAIN AFTER 07-09Z TUE.
OFFSHORE PRESSURE GRADIENT REMAINS IN PLACE, PRODUCING STRONG
GUSTS OF 30-35 KT AT KTTD, WITH GUSTS UP TO 45-60 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. -19/03
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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