462
FXUS66 KPQR 260520
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1020 PM PDT TUE AUG 25 2026
UPDATED AVIATION DISCUSSION.
SYNOPSIS
A GRADUAL COOLING TREND IS UNDERWAY ACROSS THE
PACIFIC NORTHWEST AS AN UPPER-LEVEL TROUGH DEVELOPS OFFSHORE.
INTERIOR LOWLAND HIGHS WILL REMAIN IN THE 80S TODAY BEFORE
DROPPING INTO THE 70S LATER THIS WEEK. INCREASING ONSHORE FLOW
WILL BRING A STRONGER PUSH OF MARINE AIR INTO THE INTERIOR
TONIGHT INTO WEDNESDAY. COOLER AND MORE UNSETTLED CONDITIONS ARE
FAVORED INTO THE WEEKEND, WITH PERIODIC FRONTAL PASSAGES
BRINGING LOW PRECIPITATION CHANCES.
DISCUSSION...NOW THROUGH MONDAY
A BROAD TROUGH OVER THE
NORTHEAST PACIFIC IS BEGINNING TO SHIFT EASTWARD TOWARDS THE
PACIFIC NORTHWEST, RESULTING IN A TREND TOWARDS MODEST COOLING
TEMPERATURES. TODAY IS THE ONLY EXCEPTION, WITH HIGH
TEMPERATURES GENERALLY IN THE MID TO UPPER 80S ACROSS THE
INTERIOR LOWLANDS AND 60S ALONG THE COAST. ONSHORE FLOW WILL
BECOME INCREASINGLY ESTABLISHED THIS AFTERNOON AND EVENING, WITH
WINDS TURNING WESTERLY AS A STRONGER MARINE PUSH DEVELOPS
TONIGHT. MARINE AIR SHOULD SPREAD INLAND THROUGH THE OVERNIGHT
HOURS, WHILE ANY LINGERING WILDFIRE SMOKE IS DISPLACED EAST OF
THE CASCADES BY WEDNESDAY. ALONG WITH THIS MARINE PUSH, FOG MAY
PUSH INTO THE COAST AS A RESULT OF FOG FORMATION OVER THE OCEAN,
BRINGING A POTENTIAL REDUCTION OF VISIBILITY, PRIMARILY NEAR
THE COASTLINE.
THE UPPER TROUGH WILL CONTINUE PROGRESSING TOWARD THE PACIFIC
NORTHWEST ON WEDNESDAY, WITH THE AXIS SHIFTING FARTHER NORTHEAST
AND BRINGING ADDITIONAL COOLING. INCREASING ONSHORE INFLUENCE
SHOULD RESULT IN AREAS OF LOW STRATUS ACROSS THE INTERIOR
LOWLANDS WEDNESDAY MORNING, WHICH WILL LIMIT AFTERNOON WARMING.
HIGHS ARE EXPECTED TO REACH THE LOWER 80S INLAND, WITH COOLER
CONDITIONS ALONG THE COAST.
THE BROADER PATTERN REMAINS FAVORABLE FOR CONTINUED TROUGHING
ACROSS THE PACIFIC NORTHWEST THROUGH THE LATTER HALF OF THE
WEEK. SEVERAL SMALLER-SCALE DISTURBANCES ARE EXPECTED TO ROTATE
THROUGH THE TROUGH, REINFORCING THE COOLER REGIME. TEMPERATURES
SHOULD CONTINUE TRENDING DOWNWARD, WITH THE POTENTIAL FOR
ADDITIONAL MARINE PUSHES AND INCREASING CLOUD COVER. PRECIPITATION
CHANCES REMAIN RELATIVELY LIMITED BUT ARE EXPECTED TO INCREASE
SOMEWHAT AS THE PATTERN BECOMES MORE ACTIVE. A WEAK FRONTAL
PASSAGE IS POSSIBLE THURSDAY, FOLLOWED BY ANOTHER WEAK FRONT
SATURDAY, WITH PRECIPITATION CHANCES GENERALLY AROUND 10-20%.
NEITHER SYSTEM APPEARS PARTICULARLY WET AT THIS POINT, THOUGH
TIMING AND STRENGTH WILL BE REFINED AS THE WEEK PROGRESSES.
BY LATE WEEKEND, ENSEMBLE GUIDANCE SUGGESTS THE UPPER-LEVEL
PATTERN BEGINS TO FLATTEN, WHICH COULD ALLOW TEMPERATURES TO
REBOUND TOWARD THE 80S. HOWEVER, ENSEMBLE GUIDANCE ALSO SUGGESTS
A BROAD TROUGH MAY DIG SOUTH INTO THE PNW MONDAY INTO TUESDAY,
BRINGING A POSSIBILITY OF MORE RAIN. CONFIDENCE IS LOWER DURING
THIS PORTION OF THE FORECAST AS THE EVOLUTION OF THE TROUGH AND
EMBEDDED DISTURBANCES REMAINS SOMEWHAT UNCERTAIN. ~12
AVIATION...THROUGH 06Z THURSDAY
INLAND PENETRATION OF LOW
STRATUS WILL AGAIN YIELD LOWERED CIGS ACROSS THE AIRSPACE
THROUGH TONIGHT. ALONG THE COAST, MVFR CIGS ARE ALREADY IN
PLACE THIS EVENING, WITH INCREASING CHANCES FOR IFR CIGS,
ESPECIALLY AFTER 09-12Z WED. THE HIGHEST CONFIDENCE IN IFR CIGS
IS ALONG THE CENTRAL OREGON COAST (KONP), DECREASING TO THE
NORTH. AT TERMINALS ALONG THE I-5 CORRIDOR, CHANCES FOR MVFR
CIGS INCREASE AFTER 09-10Z WED, REACHING 50-70% AT TERMINALS IN
THE LOWER COLUMBIA VALLEY, PORTLAND AREA, AND SOUTHERN
WILLAMETTE VALLEY. CONFIDENCE IS LOWER (30-50% CHANCE OF MVFR
CIGS) IN THE CENTRAL WILLAMETTE VALLEY (KSLE, KUAO, KMMV) WHERE
CLOUD COVERAGE MAY BE LOWER. LOW CLOUDS WILL MIX OUT BY 18-19Z
WED INLAND, YIELDING A RETURN TO VFR CONDITIONS, WHILE MORE
PERSISTENT LOW CLOUDS AT 2-3 KFT MAY SEE MVFR CONDITIONS LINGER
LATER ON THE COAST. LIGHT SOUTH WINDS THIS EVENING AND TONIGHT
WILL BUILD TO 5-10 KT OUT OF THE SOUTHWEST AND VEER MORE
WESTERLY THROUGH MUCH OF THE DAY, BEFORE EASING WEDNESDAY
EVENING. STRENGTHENED ONSHORE FLOW SHOULD KEEP SMOKE FROM FIRES
IN THE CASCADES AND ATTENDANT VIS RESTRICTIONS TO THE EAST OF
AREA TERMINALS.
KPDX AND APPROACHES...VFR CONDITIONS EXPECTED TO PREVAIL THROUGH
10-14Z WED, WHEN LOW CLOUDS REACHING INLAND ALONG THE COLUMBIA
RIVER WILL INCREASE THE CHANCES FOR MVFR CIGS, WHICH REACH
50-70% FROM 14-18Z WED BEFORE CLOUD COVER DECREASES AS LOW
CLOUDS MIX OUT BY THE AFTERNOON. LIGHT NORTHWEST WINDS THIS
EVENING WILL SHIFT OUT OF THE SOUTH OVERNIGHT, THEN BUILD TO
AROUND 5 KT AND VEER OUT OF THE SOUTHWEST TO WEST THROUGH MUCH
OF WEDNESDAY. -36
MARINE
A WEAK MESO-LOW IS MOVING UP THE NORTH OREGON COAST
THIS AFTERNOON BRINGING GUSTY SOUTH-SOUTHWEST WINDS TO THE INNER
WATERS. WILL MAINTAIN THE SMALL CRAFT ADVISORY FOR GUSTS UP TO
25 KT FOR THE INNER WATERS NORTH OF CAPE FALCON AND THE COLUMBIA
RIVER BAR THROUGH 7 PM THIS EVENING. OTHERWISE, HIGH PRESSURE
WILL BUILD NORTH ALONG THE COAST TONIGHT AS LOW PRESSURE WELL
OFFSHORE WEAKENS AS IT MOVES NORTHEAST TOWARD VANCOUVER ISLAND
THROUGH WEDNESDAY NIGHT. SOUTHERLY WINDS EASE OVERNIGHT BEFORE
INCREASING AGAIN ON WEDNESDAY AS A WEAK FRONT APPROACHES THE
OUTER WATERS. ANOTHER WEAK FRONT APPROACHES THE INNER WATERS
THURSDAY MORNING, BRIEFLY INCREASING SOUTHERLIES AGAIN, BUT IN
GENERAL, WINDS ARE EXPECTED TO REMAIN BELOW 20 KT.
HIGH PRESSURE BEGINS TO REBUILD OVER THE WATERS LATER THURSDAY
INTO FRIDAY RETURNING NORTH TO NORTHWEST WINDS ACROSS THE COASTAL
WATERS INTO THE WEEKEND. PREDOMINATELY WIND DRIVEN SEAS ARE
EXPECTED TO REMAIN AROUND 3 TO 6 FT THROUGH THE WEEKEND. SOMEWHAT
MORE ACTIVE PATTERN MAY RETURN EARLY NEXT WEEK. /DH
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
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