129
FXUS66 KPQR 181715
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
915 AM 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 NEXT SEVERAL 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.
DISCUSSION...SUNDAY MORNING THROUGH SATURDAY
A STRONG RIDGE
OF HIGH PRESSURE CONTINUES OVER THE WEST COAST WITH A THERMALLY
INDUCED TROUGH REMAINING ALONG THE OR AND WA COAST AT THE
SURFACE. THERE IS HIGH CONFIDENCE FROM ENSEMBLE GUIDANCE THAT
THIS PATTERN WILL CONTINUE THROUGH TUESDAY. THIS PATTERN IS
LEADING TO DRY WEATHER, MOSTLY CLEAR SKIES, AND WARMER THAN
NORMAL DAYTIME TEMPERATURES. ADDITIONALLY, THE SURFACE THERMAL
TROUGH HAS CAUSED A STRONG PRESSURE GRADIENT OVER THE CASCADES.
OBSERVATIONS INDICATE THE GRADIENT FROM KPDX TO KDLS HAS
REMAINED AROUND -8.5 TO -9 MB SINCE LAST EVENING INSTEAD OF
FALLING TO AROUND -6 TO -7 MB AS PREVIOUS GUIDANCE SUGGESTED.
LATEST CAMS NOW INDICATE THE GRADIENT WILL REMAIN ELEVATED
AROUND -7 TO -9 MB THROUGH AT LEAST MONDAY AND POSSIBLY INTO
TUESDAY. NOW THIS GRADIENT IS STILL JUST SLIGHTLY WEAKER THAN
THE PREVIOUS TWO DAYS, SO PEAK GUSTS IN THE FAR EASTERN PORTLAND
METRO ARE MAINLY AROUND 30-40 MPH, GENERALLY AROUND AND EAST OF
TROUTDALE. HOWEVER, AROUND THE MOUTH OF THE WESTERN COLUMBIA
GORGE, WIND GUSTS ARE STILL HOWLING WITH GUSTS OF 45-55 MPH,
LOCALLY UP TO 60-70 MPH AT THE KNOWN WINDY LOCATIONS OF CROWN
POINT AND CORBETT. EXPECTING WIND GUSTS TO GENERALLY REMAIN AT
THESE LEVEL INTO MONDAY NIGHT, THOUGH IF THE PRESSURE GRADIENT
DOES SLACKEN SOME, COULD SEE A BIT OF A DECREASE IN GUSTS.
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 TUESDAY NIGHT, DROPPING
OVERNIGHT LOWS TO NEAR OR BELOW FREEZING ACROSS THE WILLAMETTE
VALLEY AND SOUTHWEST WA LOWLANDS AS WELL AS THE HOOD RIVER
VALLEY. HIGH CONFIDENCE REMAINS THAT THIS WOULD FAVOR
WIDESPREAD FROST DEVELOPMENT AND/OR FREEZING FOG, ESPECIALLY
OVER GRASSES AND METAL SURFACES. FREEZING FOG IS NOT EXPECTED TO
BE WIDESPREAD AS THE COLD TEMPERATURES WILL LIKELY LIMIT FOG
DEVELOPMENT IN MOST AREAS EXCEPT FOR TYPICAL FOG PRONE AREAS.
FREEZING FOG 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 IS INCREASINGLY A CONCERN UNDER THIS
SUBSIDENCE INVERSION AS THE WINDS DECREASE, LEADING TO AIR
QUALITY CONCERNS INTO AT LEAST TUESDAY. AN AIR STAGNATION
ADVISORY IS IN EFFECT FOR MOST OF THE WILLAMETTE VALLEY DUE TO
THIS CONCERN.
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 40-60% CHANCE FOR
THE INTERIOR LOWLANDS AND 60-75% FOR THE COAST AND TERRAIN,
CONTINUING INTO SATURDAY. ONSHORE FLOW APPEARS TO RETURN
THURSDAY AS WELL, BRINGING MORE MILD AIR. HOWEVER, IF EASTERLY
WINDS CONTINUE THROUGH THE COLUMBIA RIVER GORGE, COLD AIR MAY
LINGER LONGER ACROSS THE CENTRAL GORGE AND UPPER HOOD RIVER
VALLEY. THIS WOULD RESULT IN WINTERY PRECIPITATION FOR THESE
AREAS, ESPECIALLY IF THE INCOMING MOISTURE OVERLAPS THE SAME
TIME AS THE FREEZING AIR. SPECIFIC DETAILS WILL BECOME MORE
CLEAR AS WE GET CLOSER TO PRECIPITATION RETURNING. -03/10
AVIATION
PERSISTENT UPPER-LEVEL RIDGING OVER THE REGION WILL
CONTINUE TO YIELD LARGELY VFR CONDITIONS THROUGHOUT THE PERIOD.
POCKETS OF NIGHTLY FOG IN SHELTERED VALLEYS, MOST NOTABLY THE
FAR SOUTHERN WILLAMETTE AND NORTHERN COWLITZ VALLEYS, CONTINUE
TO SLOWLY ERODE THIS MORNING AS INSOLATION AND MIXING INCREASE,
WITH A RETURN TO VFR CONDITIONS EXPECTED BY 21Z SUN. SIMILAR
CONDITIONS ARE POSSIBLE TONIGHT, THOUGH WITH LOWER CONFIDENCE
THAN PREVIOUS DAYS. THROUGH THE COLUMBIA RIVER GORGE, INCLUDING
AT K4S2, MVFR STRATUS IS LIKELY TO PERSIST THROUGH MUCH OF
TODAY. A MODEST OFFSHORE PRESSURE WILL BE MAINTAINED THROUGH THE
PERIOD, SUPPORTING CONTINUED EAST WINDS AT PORTLAND-AREA
TERMINALS AND ALONG THE COAST, WITH LIGHT NORTHERLY FLOW
EXPECTED THROUGH THE WILLAMETTE VALLEY. STRONG GUSTS OF 35-40 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 BENEATH
LARGELY CLEAR SKIES. EAST-SOUTHEAST WINDS WILL RISE TO 10-15 KT
BY 20-21Z SUN, THEN EASE BELOW 10 KT LATE THIS EVENING. -36
MARINE
STRONG RIDGING ALOFT CONTINUES THROUGH THE WEEKEND
FAVORING PERSISTENT EASTERLY OFFSHORE FLOW. 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. THIS OFFSHORE FLOW WILL
PERSIST INTO MIDWEEK. SEAS REMAIN BELOW 10 FT AROUND 10-13
SECONDS THROUGH THE MIDDLE OF THE WEEK. -03
PQR WATCHES/WARNINGS/ADVISORIES
OR...AIR STAGNATION ADVISORY UNTIL 10 AM PST TUESDAY FOR ORZ109-
114>118.
WA...NONE.
PZ...NONE.
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