516
FXUS66 KPQR 010540 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
1040 PM PDT FRI JUL 31 2026
UPDATED AVIATION DISCUSSION.
SYNOPSIS
A PROGRESSIVE WEATHER PATTERN WITH PREVAILING
ONSHORE FLOW CONTINUES THROUGH THE WEEKEND. WEAK COLD FRONT ON
SATURDAY USHERS IN COOLER TEMPERATURES, CHANCES FOR LIGHT RAIN,
AND LOCALLY GUSTY WEST WINDS OVER THE WEEKEND. WIND RELATED
IMPACTS ARE HIGHEST IN THE CENTRAL COLUMBIA GORGE. TRAILING THIS
FRONTAL SYSTEM, A BROAD PATTERN CHANGE FAVORING WARMER AND
DRIER WEATHER IS EXPECTED BY THE MIDDLE OF NEXT WEEK WITH A
PERIOD OF NORTHERLY TO NORTHEASTERLY WINDS AS WELL. ELEVATED
TEMPERATURES ON TUESDAY BEFORE COOLING DOWN THE REMAINDER OF THE
WEEK.
SHORT TERM...NOW THROUGH SUNDAY NIGHT
CLEAR SKIES TODAY LEAD
TO WARMER TEMPERATURES THAN PREVIOUS DAYS. A SLIGHT NORTHEAST
WIND ALONG THE CASCADES BROUGHT IN SOME SMOKE FROM AREA FIRES TO
THE GOVERNMENT CAMP AREA, BUT HAS NOT BEEN WIDESPREAD. WESTERLY
FLOW RETURNS TONIGHT WHICH WILL KEEP ANY SMOKE AT BAY ON
SATURDAY, MAINTAIN COOLER TEMPERATURES, BRING CLOUD COVER, AND
EVEN SOME CHANCES FOR LIGHT RAIN. THIS IS A HIGH PROBABILITY OF
PRECIPITATION BUT LOW ACCUMULATION SCENARIO WITH AROUND AN 80%
CHANCE ALONG THE COAST NORTH OF TILLAMOOK, AND LESS THAN 20%
CHANCE INLAND. AREAS WITHIN WASHINGTON WILL SEE HIGHER
PROBABILITIES AS THE SYSTEM APPEARS TO STAY NORTH OF THE AREA.
ANOTHER COMPONENT TO DISCUSS ON SATURDAY IS THE WIND POTENTIAL.
WHILE IT IS NOT EXPECTED TO BE WIDESPREAD OR SIGNIFICANT, WE
WILL SEE STRONGER WINDS DUE TO A JUXTAPOSITION OF THE FRONT,
HIGH PRESSURE OVER THE ROCKIES, AND THE TEMPERATURE GRADIENT.
THESE WINDS WILL MOSTLY BE OBSERVED THROUGH EAST-WEST ALIGNED
TERRAIN LIKE THE COLUMBIA RIVER GORGE, UPPER HOOD RIVER VALLEY,
AND THE GAPS OF THE COAST RANGE. THE CASCADES TOO WILL SEE THESE
GUSTY WEST WINDS. ON SUNDAY WE WILL SEE RESIDUAL SHORT WAVE
TROUGHS PASS OVER THE REGION WHICH WILL MAINTAIN SIMILAR
CONDITIONS. HOWEVER, NO RAIN IS EXPECTED AND WIND WILL BE MUCH
LESS AND MORE NORTHWESTERLY.-27
LONG TERM...MONDAY THROUGH FRIDAY
WHILE SUNDAY WILL SEE
LITTLE CHANGE, THE SAME CANNOT BE SAID FOR MONDAY AND TUESDAY.
ON MONDAY THERE CONTINUES TO BE GROWING CONFIDENCE IN A LARGE
SCALE RIDGING PATTERN BUILDING OVER THE PACIFIC NORTHWEST. WHILE
THERE CONTINUE TO BE ENSEMBLE MODELS THAT FAVOR A TROUGH OR
ZONAL FLOW, NEARLY ALL OF THE 500 MB CLUSTERS SHOW AT LEAST SOME
FORM OF A RIDGE FORMING. THIS RIDGE WILL LEAD TO WARMING
TEMPERATURES AND LOWER RELATIVE HUMIDITY ON BOTH MONDAY AND
TUESDAY. A FEATURE WE CONTINUE TO DIVE INTO IS THE THERMAL
TROUGH AND WHETHER OR NOT THAT IS GOING TO DEVELOP ON MONDAY.
BASED ON SURFACE ANALYSIS PLOTS, THERE APPEARS TO BE A THERMAL
TROUGH FORMING ALONG THE COAST WHICH MOVES INLAND THROUGH THE
AFTERNOON ON MONDAY. THIS TROUGH WOULD CAUSE NORTHERLY WINDS TO
AMPLIFY IN THE LOWER ELEVATIONS, AND INCREASE EASTERLY WINDS AT
850 MB (AROUND 5000 FT). THESE EASTERLY WINDS WILL BRING IN
DRIER AIR FROM EAST OF THE CASCADES AND THE DOWNSLOPING ACTION
WILL INCREASE DRYING IN THE LOWER ELEVATIONS AND IN THE
WILLAMETTE VALLEY. COMBINE THIS WITH DAYTIME HEATING AND A DEEP
LAYER OF DRY AIR, WE WILL SEE RELATIVE HUMIDITY DROP WITHIN THE
INTERIOR LOWLANDS ON MONDAY. IN ADDITION, THE THERMAL TROUGH
WILL NARROW THE ISOBARS IN THE AREA AND THUS INCREASE THE
PRESSURE DRIVEN NORTHERLY WIND. THEREFORE, COULD SEE GUSTS UP TO
25 MPH WITHIN THE WILLAMETTE VALLEY, CLARK COUNTY LOWLANDS, AND
ALONG THE COAST. IN THE SOUTHERN WILLAMETTE VALLEY AROUND
EUGENE THERE IS A HIGHER PROBABILITY OF SEEING THESE WIND SPEEDS
THAN IN THE NORTH. THIS IS LIKELY DUE TO MORE OF A CHANNELING
COMPONENT AND MORE OF A STARK NORTH-SOUTH PRESSURE GRADIENT.
THESE DRY AND WINDY CONDITIONS MAY LEAD TO INCREASED FIRE
WEATHER CONCERNS.
WHILE THIS IS STILL THE FAVORED PATTERN RIGHT NOW, IT IS NOT THE
ONLY POSSIBILITY. THERE STILL REMAINS THE POTENTIAL FOR ZONAL OR
FLOW AND MORE OF A ZONAL FLOW WHICH WOULD CAUSE HUMIDITY TO
INCREASE ABOVE CRITICAL LEVELS AND WINDS WOULD BE MORE WESTERLY
AND THUS NOT NEARLY AS STRONG. CURRENTLY, THE GFS ENSEMBLES SHOW
A MUCH WEAKER PATTERN ON MONDAY WHICH WOULD FAVOR GUSTS CLOSER
TO 15 MPH WHILE THE ECMWF IS CLOSER TO 25-30 MPH.
THE OTHER IMPACTFUL WEATHER COMPONENT IS THE HEAT THAT WILL
ARRIVE ON TUESDAY. TEMPERATURES CONTINUE TO STAY STEADY WITH
MOST AREAS SEEING AT LEAST A 75-80% CHANCE OF MEETING OF
EXCEEDING 90 DEGREES F. MODERATE HEATRISK REMAINS FOR MUCH OF
THE WILLAMETTE VALLEY AND THE LOWER I-5 CORRIDOR. MID TO LATE
WEEK IT'LL ALL COME DOWN TO THE EXACT PATTERN AMPLIFICATION AND
LONGITUDINAL PLACEMENT OF THE RIDGE OVER THE FAR EASTERN
PACIFIC. IN THE WARMER SOLUTIONS (FAVORED BY GFS AND MORE GEFS
MEMBERS), STRONGER INLAND RIDGING AND THE RESULTING COASTAL
THERMAL TROUGH MAY BE SUFFICIENT TO DRIVE DECENT OFFSHORE FLOW
AND POTENTIAL GUSTY NORTH TO NORTHEAST WINDS ALONG THE COAST AND
WITHIN THE WILLAMETTE VALLEY. THE EPS KEEPS THIS RIDGE
FLATTENED COMPARATIVELY BUT STILL SHOWS A SIGNAL FOR NORTH TO
NORTHEAST WINDS, ALBEIT WEAKER. AT LEAST THE BULK OF
DETERMINISTIC AND ENSEMBLE GUIDANCE DEPICT A RETURN TO W-NW
WINDS BY LATE THURSDAY SIGNALING MODERATING CONDITIONS.
-27/99
AVIATION...THROUGH 06Z SUNDAY
VFR CONDITIONS PERSIST INLAND
WHILE MARINE STRATUS HAS PUSHED INTO THE COAST, PRODUCING MVFR
CIGS AT BOTH KAST AND KONP. MVFR CIGS OR LOWER EXPECTED TO PERSIST
THROUGH 20-22Z ALONG THE COAST. PROBABILITIES HAVE INCREASED FOR
MVFR CIGS DEVELOPING INLAND WITH A 40-70% CHANCE FROM 10-18Z FOR
ALL TERMINALS. BEYOND 18Z, MVFR CIGS REMAIN POSSIBLE BUT BECOME
MORE ISOLATED AS A COLD FRONT MOVES THROUGH. EXPECT WINDS TO
BECOME SOUTH TO SOUTHWESTERLY AT 5 KT OR LESS OVERNIGHT THEN
WESTERLY SATURDAY AFTERNOON BEHIND THE COLD FRONT. WINDS COULD BE
GUSTY IN THE WESTERN COLUMBIA RIVER GORGE UP TO 25 KT.
THE WEAK COLD FRONT MOVING THROUGH IS EXPECTED TO BRING LIGHT
SHOWERS TO THE COASTAL TERMINALS AND POSSIBLY AROUND KPDX AND
APPROACHES SATURDAY MORNING INTO THE EARLY AFTERNOON.
KPDX AND APPROACHES...VFR CONDITIONS WITH LIGHT WINDS. CHANCES FOR
MVFR CIGS INCREASE BETWEEN 10-18Z TO 40-70% SO EXPECTING A PERIOD
OF LOWER CLOUD COVER TO START THE DAY. WINDS LIGHT AND VARIABLE
OVERNIGHT BECOMING WESTERLY SATURDAY AFTERNOON AROUND 10 KT. -19
MARINE
FAIRLY BENIGN CONDITIONS CONTINUE ACROSS THE WATERS
TODAY AS WINDS REMAIN OUT OF THE WEST TO NORTHWEST. ON SATURDAY,
A FRONTAL SYSTEM APPROACHING THE WATERS BRINGS INCREASING
WINDS, MAINLY FOR THE OUTER WATERS AND THE INNER WATERS NORTH OF
CAPE FALCON. THIS FRONT WILL BRING CHANCES FOR LIGHT RAIN
SATURDAY MORNING, LIKELY DISSIPATING DURING THE AFTERNOON HOURS.
WESTERLY FLOW BEHIND THE FROST WILL THEN SHIFT NORTHERLY BY
SUNDAY AS SURFACE HIGH PRESSURE BUILDS OFFSHORE. CHANCES FOR
MAXIMUM WIND GUSTS OF AT LEAST 21 KT ARE AROUND 80-90% FROM
SUNDAY AFTERNOON/EVENING THROUGH AT LEAST TUESDAY EVENING -
HIGHEST PROBABILITIES IN THE OUTER WATERS. ADDITIONALLY, THERE IS
A CHANCE FOR A PERIOD OF MARGINAL GALE FORCE NORTHERLY WINDS LATE
MONDAY AFTERNOON (20-40% CHANCE SOUTH OF CAPE FOULWEATHER, MAINLY
THE INNER COASTAL WATERS). WAVE HEIGHTS THROUGH THIS TIME PERIOD
REMAIN AROUND 5-7 FT AT 7-9 SECONDS, EXCEPT FOR UP TO 8-9 FT IN
THE OUTER WATERS SOUTH OF CAPE FOULWEATHER OR.-12/99
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
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