495
FXUS66 KPQR 072220
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
320 PM PDT THU AUG 7 2025
SYNOPSIS
GOING FORWARD EXPECT A NOTICEABLE PATTERN SHIFT AS
A ROBUST RIDGE OF HIGH PRESSURE DEVELOPS OVER THE EASTERN
PACIFIC USHERING IN A SHARP WARMING PEAKING SUNDAY AND MONDAY.
AN EXTREME HEAT WATCH REMAINS IN EFFECT ACROSS THE LOWER INLAND
VALLEYS FOR THOSE TWO AFOREMENTIONED DAYS. CONDITIONS RETURN
CLOSER TO NORMAL BY THE MIDDLE OF NEXT WEEK (WEDNESDAY/THURSDAY)
HOWEVER SIGNIFICANT UNCERTAINTY REMAINS REGARDING HOW QUICKLY
THIS TRANSITION OCCURS.
SHORT TERM...NOW THROUGH SATURDAY
THIS AFTERNOON ONSHORE
NORTHWESTERLY FLOW CONTINUES AS AN UPPER-LEVEL LOW VISIBLE VIA
SATELLITE IMAGERY PROGRESSES THROUGH WESTERN WASHINGTON INTO THE
ROCKIES. BUILDING HEIGHTS ALOFT HEADED INTO FRIDAY MORNING WILL
ALLOW FOR AT LEAST SOME PARTIAL CLEARING WHICH COMBINED WITH THE
RECENT PRECIPITATION AND LIGHT WINDS NEARING SUNRISE SHOULD
FACILITATE POCKETS OF PATCHY FOG - MINIMAL IMPACTS. BOTH
DETERMINISTIC AND ENSEMBLE GUIDANCE HAS ALL BOUGHT INTO A MAJOR
PATTERN SHIFT EXPECTED OVER THE WEEKEND THANKS TO STRONG UPPER-
LEVEL RIDGING OVERHEAD WITH THE CENTER OF THE HIGH PRESSURE
HOLDING OFF THE COAST. THIS'LL LEAD TO HIGH TEMPERATURES
JUMPING INTO THE LOW TO MID 80S ACROSS THE LOWER ELEVATIONS AWAY
FROM THE COASTLINE FRIDAY AFTERNOON TO THE UPPER 80S FOR THESE
SAME LOCATIONS SATURDAY AFTERNOON. IT'S WORTH NOTING THE SPREAD
WITHIN THE NBM ENSEMBLE AND OTHER ENSEMBLE SYSTEMS FOR THAT
MATTER ARE FAIRLY TIGHT ADDING CONFIDENCE TO THIS RAMP-UP IN
TEMPERATURES MOVING FORWARD. -SCHULDT
LONG TERM...SATURDAY NIGHT THROUGH THURSDAY
TEMPERATURES
LIKELY CLIMB TO UNSEASONABLY WARM VALUES ACROSS THE REGION LATE
WEEKEND INTO EARLY NEXT WEEK, PEAKING SUNDAY/MONDAY WITH THE
HEAT WILL REACH HAZARDOUS LEVELS WITHIN INLAND VALLEYS.
PARTICULARLY ON SUNDAY, MODELS NOW FAVOR A WEAK OFFSHORE FLOW
COMPONENT FROM THE SURFACE TO 850MB WHICH WILL HELP TO FURTHER
BOOST TEMPERATURES IN ADDITION TO FACILITATING LOWER AFTERNOON
RELATIVE HUMIDITY SUNDAY AFTERNOON- SOMETHING TO WATCH. AFTERNOON
HIGHS WILL VERY LIKELY EXCEED 90 DEGREES ALONG THE WILLAMETTE
VALLEY AND COLUMBIA GORGE, AND IN THE PORTLAND/VANCOUVER METRO:
80-100% CHANCES ON SUNDAY AND 70-100% ON MONDAY, WITH HIGHER
LIKELIHOODS TO THE SOUTH BOTH DAYS. SLIGHTLY LOWER CHANCES
EXTEND INTO THE LOWER COLUMBIA AND COWLITZ VALLEYS, 60-85% ON
SUNDAY AND 40-60% ON MONDAY. SOME LOCALES MAY ALSO RECORD THEIR
FIRST TRIPLE DIGIT TEMPERATURES OF THE YEAR; CHANCES TO EXCEED
100 DEGREES ARE 10-25% ON SUNDAY AND 25-40% ON MONDAY IN THE
PORTLAND/VANCOUVER METRO AND COLUMBIA GORGE, 40-60% ON SUNDAY
AND 60-75% ON MONDAY IN THE WILLAMETTE VALLEY, AND LESS THAN 15%
ON SUNDAY AND 15-30% ON MONDAY IN THE LOWER COLUMBIA AND
COWLITZ VALLEYS. TEMPERATURES WILL ALSO BE VERY MILD ON SUNDAY
NIGHT, GENERALLY IN THE LOW TO MID 60S, THEN A FEW DEGREES
COOLER ON MONDAY NIGHT INTO TUESDAY MORNING.
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 REMAINS IN EFFECT FROM NOON SUNDAY THROUGH 8
PM MONDAY THROUGHOUT THE PORTLAND/VANCOUVER METRO, COLUMBIA
GORGE AND LOWER 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.
THERE STILL APPEARS TO BE A SIGNIFICANT AMOUNT OF UNCERTAINTY
AMONG ENSEMBLE SYSTEMS COME TUESDAY AS MODELS DIVERGE IN THE
PROGRESSION OF THE UPPER-LEVEL PATTERN. ENSEMBLES LIKE THE NBM,
EPS, GEFS, ECMWF AIFS ENS, ETC. ALL SHOW A LARGE RANGE IN
POTENTIAL HIGH TEMPERATURES TUESDAY AFTERNOON HIGHLIGHTING THIS
UNCERTAINTY; HIGHS FROM THE UPPER 70S/LOW 80S (MORE PROGRESSIVE
TROUGH SOLUTION) TO THE UPPER 90S (LESS PROGRESSIVE SOLUTION
WITH LINGERING RIDGING) ARE ALL IN PLAY. IN THE MEAN, THE
PATTERN DEAMPLIFIES AND RETROGRADES THE RIDGE WEST AWAY FROM THE
REGION AS UPPER-LEVEL TROUGHING DEVELOPS OVER THE PACIFIC
NORTHWEST, ALLOWING TEMPERATURES TO EASE COOLER BACK TOWARD MORE
SEASONAL VALUES. THE AMPLITUDE AND TIMING OF POTENTIAL
TROUGHING REMAINS VERY UNCERTAIN, AND SOME MEMBERS INSTEAD
MAINTAIN UPPER-LEVEL RIDGING INTO THE MIDDLE OF THE WEEK, WHICH
COULD PROLONG HEAT IMPACTS (30-35% OF ENSEMBLE SOLUTIONS). AT
THE LAST THE VAST MAJORITY OF GUIDANCE SUPPORTS SOME DEGREE OF
UPPER-LEVEL TROUGHING COUPLED WITH NOTICEABLE ONSHORE FLOW
RETURNING TO THE REGION BY THURSDAY. -SCHULDT/PICARD
AVIATION
SATELLITE IMAGERY SHOWS SCATTERED CLOUDS OVER MUCH OF
THE AREA LEADING TO A MIXTURE OF MVFR AND VFR CIGS. MOST
PREDOMINATELY IT HAS BEEN VFR AND WILL CONTINUE THAT TREND OVER
THE NEXT 24 HOURS OR SO. THE ONLY CONCERN MOVING FORWARD IS
WHETHER MVFR OR EVEN IFR CONDITIONS WILL REFORM OVERNIGHT. AS IT
STANDS, THERE IS AROUND A 60% CHANCE OF MVFR CIGS, AND A 20-30%
CHANCE OF IFR CIGS ALONG THE NORTHERN COASTS, AND AREAS ALONG THE
FOOTHILLS OF THE SOUTH WASHINGTON AND NORTH OREGON CASCADES.
PDX AND APPROACHES...GENERALLY VFR THROUGH 13Z FRIDAY WITH A 30%
CHANCE OF IFR CIGS FORMING THEREAFTER. IF SKIES BECOME COMPLETELY
CLEAR, FOG IS POSSIBLE, ESPECIALLY GIVEN HOW LOW THE DEWPOINT
DEPRESSION IS. NO OTHER CONCERNS. -MUESSLE
MARINE
SEAS WILL STAY AROUND 6 FT AT 10 SECONDS THROUGH AT
LEAST FRIDAY. WINDS WILL REMAIN ELEVATED AROUND 10 TO 15 KT WITH
GUSTS UP TO 20 KT, MOSTLY IN THE SOUTHERN WATERS TODAY INTO FRIDAY
AFTERNOON. FRIDAY NIGHT AND THROUGH THE WEEKEND, A RIDGE WILL
BUILD WITH A NORTHERLY WIND REVERSAL AND CONDITIONS WILL TAKE ON A
TYPICAL SUMMER PATTERN. AS TEMPERATURES WARM CONSIDERABLY THROUGH
THE WEEKEND, EXPECT WINDS TO RAMP UP THROUGHOUT ALL THE WATERS,
WITH COMBINED SEAS BEING DOMINATED BY WIND WAVE. INCREASING
PROBABILITY OF SMALL CRAFT ADVISORY CONDITIONS IN THE SOUTHERN
WATERS SATURDAY AFTERNOON. GUSTS UP TO 25 KT SATURDAY EVENING
THROUGH MONDAY. SEAS WILL BUILD TO NEAR 10 FT ON MONDAY.
-HALL/MUESSLE
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...NONE.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
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X.COM/NWSPORTLAND
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