291
FXUS66 KPQR 081734 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE PORTLAND OR
1034 AM PDT FRI AUG 8 2025
UPDATED THE AVIATION DISCUSSION
SYNOPSIS
A ROBUST RIDGE OF HIGH PRESSURE DEVELOPING OVER THE
EASTERN PACIFIC WILL USHER IN A SHARP WARMING TREND PEAKING
SUNDAY AND MONDAY, FOR WHICH AN EXTREME HEAT WATCH REMAINS IN
EFFECT ACROSS THE LOWER INLAND VALLEYS. CONDITIONS ARE FAVORED
TO RETURN CLOSER TO NORMAL BY THE MIDDLE OF NEXT WEEK, HOWEVER
THERE REMAINS SIGNIFICANT UNCERTAINTY IN THIS TRANSITION.
SHORT TERM...NOW THROUGH SATURDAY NIGHT
AN UPPER-LEVEL LOW
OVER THE NORTHERN ROCKIES CONTINUES TO SLOWLY TRACK EASTWARD
ALONG THE US-CANADA BORDER WHILE A BUILDING UPPER-LEVEL RIDGE
OVER THE NORTHEASTERN PACIFIC HAS BEGUN TO RAISE HEIGHTS ALOFT
LOCALLY. THIS TREND WILL CONTINUE INTO THE WEEKEND, BRINGING
STEADY WARMING ACROSS THE REGION. AMPLE SUNSHINE IS EXPECTED,
ASIDE FROM NIGHTLY MARINE STRATUS AND COASTAL FOG WEST OF THE
COAST RANGE AND WILLAPA HILLS, AND PASSING HIGH CLOUDS ON
SATURDAY AS A WEAK SHORTWAVE TRACKS OVERHEAD. TEMPERATURES WILL
RISE TO NEAR-NORMAL VALUES THIS AFTERNOON IN THE 60S TO 70S
ALONG THE COAST AND LOW TO MID 80S ACROSS INLAND VALLEYS, BEFORE
RISING A FEW DEGREES ABOVE NORMAL ON SATURDAY. NIGHTLY LOWS
SIMILARLY INCREASE FROM WIDESPREAD 50S TONIGHT TO MID 50S TO
LOW 60S ON SATURDAY NIGHT. -PICARD
LONG TERM...SUNDAY THROUGH THURSDAY
HIGH-AMPLITUDE UPPER
RIDGING AND SURFACE HIGH PRESSURE WILL CONTINUE TO BUILD OVER
THE NORTHEASTERN PACIFIC INTO EARLY NEXT WEEK. AS HEIGHTS ALOFT
CONTINUE TO RISE OVERHEAD, 850-HPA TEMPERATURES WILL REACH
AROUND 20C ON SUNDAY WHICH, COMBINED WITH A SLIGHT OFFSHORE
COMPONENT TO LOW-LEVEL WINDS, WILL PUSH SURFACE TEMPERATURES
WELL ABOVE NORMAL TO AFTERNOON HIGHS IN THE 70S ALONG THE COAST
AND MID TO UPPER 90S FOR MOST INLAND VALLEY AREAS. CHANCES FOR
REACHING 95 DEGREES ON SUNDAY ARE 35-50% IN THE LOWER COLUMBIA
AND COWLITZ VALLEYS, 60-80% IN THE PORTLAND/VANCOUVER METRO AND
COLUMBIA GORGE, AND 80-95% IN THE WILLAMETTE VALLEY. CHANCES TO
REACH 100 DEGREES ON SUNDAY ARE 10-25% IN THE LOWER COLUMBIA AND
COWLITZ VALLEYS, 20-40% IN THE PORTLAND/VANCOUVER METRO AND
COLUMBIA GORGE, AND 60-80% IN THE WILLAMETTE VALLEY. SUNDAY
NIGHT, VERY MILD TEMPERATURES WILL CONTINUE ACROSS THE REGION
WITH MODERATE TO HIGH CHANCES, GENERALLY 50-80% INLAND, OF
REMAINING ABOVE 65 DEGREES OVERNIGHT. SOME LOCATIONS IN THE
COLUMBIA GORGE, COAST RANGE, AND WESTERN SLOPES OF THE CASCADES
WILL EVEN HAVE A 20-50% CHANCE OF REMAINING ABOVE 70 DEGREES.
A BIT MORE UNCERTAINTY ENTERS THE FORECAST ON MONDAY. ON THE
SYNOPTIC SCALE, GLOBAL ENSEMBLES SHOW A WEAK SHORTWAVE ERODING
HEIGHTS ALOFT ON THE DOWNSTREAM FLANK OF THE RIDGE, HOWEVER THE
LOCATION AND AMPLITUDE OF THIS FEATURE REMAIN LOWER CONFIDENCE.
A STRONGER SHORTWAVE WOULD INCREASE NORTHWESTERLY ONSHORE FLOW,
WHICH WOULD SEE THE LARGEST EFFECT ALONG THE COAST AND UP THE
COLUMBIA RIVER INTO THE PORTLAND AREA, WHERE TEMPERATURES MAY
COOL SLIGHTLY. FARTHER TO THE SOUTH THROUGH THE WILLAMETTE
VALLEY, EVEN A MORE ROBUST SHORTWAVE WOULD ONLY MINIMALLY AFFECT
THE FORECAST. CONVERSELY, GIVEN THE VERY WARM START EXPECTED
MONDAY MORNING, EVEN A WEAK SHORTWAVE WOULD SEE NET WARMER
SURFACE TEMPERATURES ACROSS THE REGION THAT AFTERNOON DESPITE
SLIGHT COOLING ALOFT. THEREFORE, TEMPERATURES MONDAY WILL MOST
LIKELY BE SIMILAR TO OR SLIGHTLY WARMER THAN SUNDAY, BUT THE
SPREAD IN POTENTIAL OUTCOMES WILL BE HIGHER ACROSS NORTHERN
AREAS GIVEN THE UNCERTAINTY AROUND INCREASED ONSHORE FLOW. THESE
FACTORS RESULT IN 60-75% CHANCES OF EXCEEDING 95 DEGREES IN THE
LOWER COLUMBIA AND COWLITZ VALLEYS, 70-85% CHANCES IN THE
PORTLAND/VANCOUVER METRO AND COLUMBIA GORGE, AND 80-95% IN THE
WILLAMETTE VALLEY. CHANCES OF REACHING 100 DEGREES ARE 25-45% IN
THE LOWER COLUMBIA AND COWLITZ VALLEYS, 30-50% IN THE COLUMBIA
GORGE AND PORTLAND/VANCOUVER METRO, AND 65-85% IN THE WILLAMETTE
VALLEY. CHANCES OF TEMPERATURES REMAINING BELOW 90 DEGREES, OR
THE SCENARIOS WITH THE STRONGEST ONSHORE FLOW, ARE 10-20% IN
THE LOWER COLUMBIA AND COWLITZ VALLEYS (AN INCREASE FROM 5-10%
ON SUNDAY), AND 5-15% IN THE PORTLAND/VANCOUVER METRO (AN
INCREASE FROM 5% OR LESS ON SUNDAY).
REGARDLESS OF A FEW DEGREES OF DIFFERENCES IN POTENTIAL
AFTERNOON HIGHS, THE COMBINATION OF HOT DAYTIME TEMPERATURES
AND LACK OF SUFFICIENT OVERNIGHT COOLING CAN RAISE THE
CUMULATIVE HEAT STRESS AND ELEVATE THE RISK FOR HEAT ILLNESS,
RESULTING IN AREAS OF MAJOR HEATRISK MOST PREVALENT ACROSS
INLAND VALLEYS. AN EXTREME HEAT WATCH THEREFORE REMAINS IN
EFFECT FROM NOON SUNDAY THROUGH 8 PM MONDAY THROUGHOUT THE
PORTLAND/VANCOUVER METRO, COLUMBIA GORGE AND HOOD RIVER VALLEY,
LOWER COLUMBIA AND COWLITZ VALLEYS, AND THE WILLAMETTE VALLEY.
ALL RESIDENTS, BUT ESPECIALLY THOSE WITHOUT ACCESS TO ADEQUATE
COOLING OR HYDRATION, SHOULD MAKE PLANS FOR THIS PERIOD OF
HAZARDOUS HEAT.
ENSEMBLE GUIDANCE CONTINUES TO DIVERGE WITH RESPECT TO THE
BREAKDOWN OF UPPER RIDGING THROUGH THE MIDWEEK PERIOD. IN THE
MEAN, THE RIDGE RETROGRADES WESTWARD AWAY FROM THE REGION WITH
HEIGHTS ALOFT DECREASING LOCALLY, YIELDING A COOLING TREND
THROUGH THE WORKWEEK. SOME MEMBERS FAVOR A MORE PRONOUNCED UPPER
TROUGH DEVELOPING OVER WESTERN CANADA, WHICH WOULD SEE MORE
ROBUST COOLING, RESULTING IN SUBSTANTIAL UNCERTAINTY IN
TEMPERATURES PARTICULARLY ON TUESDAY. FARTHER OUT INTO THE
WORKWEEK, THE SIGNAL FOR STEADY EASING OF TEMPERATURES TOWARD
SEASONAL NORMS BECOMES MORE ROBUST. -PICARD
AVIATION
HIGH PRESSURE WILL RESULT IN CLEAR SKIES AND VFR
CONDITIONS INLAND THROUGH TONIGHT.MARINE STRATUS OFFSHORE WILL
MOVE CLOSER TO THE COAST THIS EVENING WITH MVFR CIGS FLIRTING WITH
THE COASTAL AIRPORTS. NORTH-NORTHEAST WINDS ARE EXPECTED TO KEEP
THE CLOUDS OFFSHORE FOR AREAS SOUTH OF TILLAMOOK TONIGHT. FURTHER
NORTH, NORTHWEST WINDS INCREASE THE CHANCE FOR MVFR CIGS TO IMPACT
THE COASTAL AIRPORTS INCLUDING KAST OVERNIGHT TONIGHT. THE
PROBABILITY FOR MVFR CIGS AT KAST INCREASES FROM 10% THIS EVENING
TO 30% AT 2 AM AND UP TO 60% BY 5 AM. THE MARINE STRATUS WILL
PUSH UP THE COLUMBIA RIVER A BIT EARLY SATURDAY MORNING WITH KKLS
HAVING A 20% CHANCE FOR MVFR CEILINGS BY 7 AM. ANY MARINE STRATUS
THAT FORMS INLAND WILL CLEAR QUICKLY.
PDX AND APPROACHES...PREDOMINATELY VFR WITH MOSTLY SUNNY SKIES
THROUGH THE TAF PERIOD. THERE IS A 10% CHANCE OF BRIEF MVFR
STRATUS AT AND AROUND KPDX AROUND 15Z SATURDAY. NORTHWEST WINDS
5-10 KT EXPECTED THROUGH THIS AFTERNOON. LIGHT WINDS OVERNIGHT. ~TJ
MARINE
HIGH PRESSURE ACROSS THE WATERS WILL MAINTAIN
NORTHERLY WINDS THROUGH EARLY NEXT WEEK. PRESSURE GRADIENTS
ARE FORECAST TO TIGHTEN THIS WEEKEND AS HIGH PRESSURE BUILDS,
INCREASING NORTHERLY WIND SPEEDS SATURDAY EVENING INTO SUNDAY.
THIS WOULD RESULT IN WIND GUSTS TO 25-30 KT, SO A SMALL CRAFT
ADVISORY HAS BEEN ISSUED FROM 1700 SATURDAY TO 0500 SUNDAY FOR
ALL WATERS SOUTH OF CAPE FALCON. WINDS DON'T LOOK AS STRONG
ACROSS THE NORTHERN WATERS, SO HELD OFF FROM ISSUING A SMALL
CRAFT ADVISORY FOR THOSE AREAS FOR NOW. SEAS WILL GENERALLY BE
WIND-DRIVEN AND AROUND 3-5 FT AT 10-11 SEC THROUGH SATURDAY,
THEN GRADUALLY BUILD TO 6-7 FT AT 11-12 SEC HEADING INTO THE
LATTER HALF OF THE WEEKEND. BREEZY NORTHERLY WINDS CONTINUE INTO
MONDAY, SO COULD SEE WAVE HEIGHTS BUILD CLOSER TO 8-10 FT EARLY
NEXT WEEK. GUIDANCE SUGGESTS A 60-80% CHANCE OF WAVE HEIGHTS
EXCEEDING 8 FT BY MONDAY, WITH THE HIGHEST CHANCES OVER THE
OUTER WATERS (BEYOND 10 NM) DUE TO STRONGER WINDS. -ALVIZ
PQR WATCHES/WARNINGS/ADVISORIES
OR...EXTREME HEAT WATCH FROM SUNDAY AFTERNOON THROUGH MONDAY EVENING
FOR ORZ108>118-120>122.
WA...EXTREME HEAT WATCH FROM SUNDAY AFTERNOON THROUGH MONDAY EVENING
FOR WAZ204>207-209-210.
PZ...SMALL CRAFT ADVISORY FROM 5 PM SATURDAY TO 5 AM PDT SUNDAY FOR
PZZ252-253-272-273.
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