478
FXUS66 KPQR 312209
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
309 PM PDT FRI JUL 31 2026
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 00Z SUNDAY
CURRENTLY, WIDESPREAD VFR
CONDITIONS WITH CLEAR SKIES AND COASTAL STRATUS HANGING AWAY FROM
THE COAST. INLAND TERMINALS WILL CONTINUE TO SEE VFR CONDITIONS
THROUGH THE TAF PERIOD (WITH JUST A 20-30% CHANCE OF MVFR CIGS
BETWEEN 12-19Z SAT), WHILE COASTAL TERMINALS WILL SEE CONDITIONS
DETERIORATE TOWARDS MVFR/IFR/LIFR BY 02-04Z SAT AS LOW STRATUS
PUSHES INTO THE COAST. GUIDANCE CURRENTLY SHOWS A 70-90% CHANCE
OF MVFR CONDITIONS, 30-50% CHANCE OF IFR, AND 20-30% CHANCE OF
LIFR BETWEEN 02-18Z SAT. BEYOND 18Z SAT, COASTAL TERMINALS MAY
STAY MVFR (30-60% CHANCE OF MVFR CIGS). OTHERWISE, EXPECT WINDS
AROUND 5-10 KT THROUGH THE PERIOD, NORTHWESTERLY THROUGH THE
AFTERNOON, THEN SHIFTING SOUTHWESTERLY BY 03-09Z SAT FOR MOST
TERMINALS. WINDS WILL THEN GRADUALLY SHIFT MORE WESTERLY THROUGH
LATE SATURDAY.
KPDX AND APPROACHES...CLEAR SKIES AND VFR CONDITIONS WILL CONTINUE
THROUGH THE PERIOD, WITH NORTHWEST WINDS GENERALLY 5-10 KTS
SHIFTING TO SOUTHWESTERLY AROUND 12Z SAT. ADDITIONALLY, THERE IS A
20% CHANCE OF MVFR CIGS BETWEEN 12-19Z SAT. -12
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
FIRE
ON MONDAY THERE IS THE POTENTIAL FOR THE AREA TO ENTER
INTO A PATTERN THAT WOULD FAVOR WARM AND DRY CONDITIONS WITH
NORTHERLY WINDS. THERE IS HIGHER CONFIDENCE IN A RIDGE BUILDING
OVER THE REGION WHICH WOULD CREATE A THERMAL TROUGH OVER WESTERN
OREGON. THIS THERMAL TROUGH WOULD PROMOTE STRONGER NORTHERLY
WINDS. WHILE THERE CONTINUES TO BE A WIDE SPREAD IN POTENTIAL
WIND GUST SPEEDS, THERE IS A TREND TOWARDS FWZ685 REACHING GUSTS
OF 20-25 MPH. THESE SPEEDS WOULD BE OBSERVED THROUGH THE
AFTERNOON ON MONDAY. IN ADDITION, THERE WILL BE LOWERING
HUMIDITY WITHIN THE LOWLANDS AND ALONG THE CASCADES. RIGHT NOW
THERE IS AROUND A 30-50% CHANCE (DEPENDING ON WHERE YOU LOOK)
FOR WIND SPEEDS AND RELATIVE HUMIDITY TO REACH WHAT WE WOULD
CONSIDER RED FLAG WARNING CONDITIONS. THE CHALLENGE IS THAT ON
BOTH THE WIND AND THE RH SIDE, CONDITIONS ARE MARGINAL AND COULD
EASILY SHIFT DEPENDING ON HOW THIS PATTERN SHAKES OUT. IF WE SEE
TEMPERATURES SLIGHTLY COOLER THEN THE TROUGH WILL BE WEAKER AND
THUS WINDS WILL BE LESS (CLOSER TO 15-20 MPH). IN CONTRAST, IF
IT AMPLIFIES, THE RH WILL DROP FURTHER AND MAKE IT EASIER TO
MEET CRITERIA. AT THIS TIME WE HAVE NOT ISSUED ANY PRODUCTS, BUT
WILL CONTINUE TO WATCH OVER THE COMING DAYS TO SEE IF THERE
BECOMES MORE CERTAINTY FOR FWZ685. WILL NOTE THAT WHILE
CONDITIONS WILL BE WINDY AND DRY ELSEWHERE, THEY ARE EITHER NOT
MEETING THE LEVELS NEEDED OR FUELS HAVE NOT BEEN DEEMED READY.
-27
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
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