590
FXUS66 KPQR 211133
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
433 AM PDT TUE JUL 21 2026
SYNOPSIS
HOT WEATHER WILL PERSIST THROUGH WEDNESDAY, WITH THE
WARMEST CONDITIONS LIKELY TODAY. CONFIDENCE REMAINS HIGH THAT
INLAND AREAS WILL SEE WELL ABOVE NORMAL TEMPERATURES THIS
AFTERNOON, WHILE CONFIDENCE IS LOWER FOR WEDNESDAY DUE TO THE
POTENTIAL FOR INCREASING CLOUD COVER, DEEPER MOISTURE, AND A FEW
THUNDERSTORMS NEAR THE CASCADES. A COOLING TREND WITH STRONGER
ONSHORE FLOW IS THEN EXPECTED TO BEGIN THURSDAY.
DISCUSSION...NOW THROUGH MONDAY
UPPER RIDGING OVER THE
PACIFIC NORTHWEST CONTINUES, SUPPORTING ANOTHER VERY WARM DAY
ACROSS SOUTHWEST WASHINGTON AND NORTHWEST OREGON. COMPARED TO
YESTERDAY, SKIES SHOULD BE MORE FAVORABLE FOR HEATING TODAY,
THOUGH THERE IS STILL SOME UNCERTAINTY TIED TO THE POSSIBLE
RETURN OF SOUTHERLY FLOW ALOFT, ALONG WITH AREAS OF HIGH CLOUD
COVER AND PERHAPS SOME SMOKE. EVEN WITH THOSE LIMITING FACTORS,
TODAY STILL APPEARS TO BE THE HOTTEST DAYS OF THE WEEK FOR MUCH
OF THE INTERIOR LOWLANDS.
HIGH TEMPERATURES THIS AFTERNOON ARE STILL EXPECTED TO RISE
WELL INTO THE UPPER 90S ACROSS INLAND VALLEYS, WITH THE WARMEST
SPOTS APPROACHING NEAR 100. THERE REMAINS SOME ROOM FOR MINOR
FORECAST ADJUSTMENTS DEPENDING ON HOW MUCH CLOUD COVER AND HAZE
DEVELOP, BUT THE OVERALL SIGNAL FOR SIGNIFICANT HEAT REMAINS
STRONG. OVERNIGHT RELIEF WILL ALSO REMAIN LIMITED, ESPECIALLY IN
THE URBAN CORRIDOR AND OTHER LOWER ELEVATION INTERIOR
LOCATIONS. ALONG THE COAST, CONDITIONS WILL STAY MUCH COOLER,
AND HIGHER TERRAIN WILL ALSO AVOID THE MOST EXTREME HEAT.
FORECAST CONFIDENCE DECREASES WEDNESDAY AS THE SYNOPTIC SETUP
BECOMES LESS STRAIGHTFORWARD. ENSEMBLE GUIDANCE CONTINUES TO
MAINTAIN RIDGING NEARBY, BUT NORTHWEST OREGON AND SOUTHWEST
WASHINGTON APPEAR LIKELY TO REMAIN NEAR THE EDGE OF THAT RIDGE.
AT THE SAME TIME, MOISTURE ASSOCIATED WITH A TROUGH OFF THE
CALIFORNIA COAST MAY BEGIN LIFTING NORTHWARD INTO THE REGION.
THAT INTRODUCES GREATER UNCERTAINTY IN HOW MUCH HEATING OCCURS
WEDNESDAY AFTERNOON. IF CLOUD COVER BECOMES MORE WIDESPREAD,
TEMPERATURES COULD END UP LOWER THAN TUESDAY. ON THE OTHER
HAND, IF ENOUGH SUN BREAKS DEVELOP, INLAND AREAS COULD STILL END
UP QUITE HOT AND POTENTIALLY REACH A DEGREE OR TWO WARMER THAN
TODAY (10-30% CHANCE TO EXCEED 100 DEGREES TODAY, 30-60% CHANCE
ON WEDNESDAY).
THE MONSOONAL MOISTURE ALSO BRINGS AT LEAST SOME THUNDERSTORM
POTENTIAL ON WEDNESDAY, MAINLY OVER THE CASCADES. AT THIS POINT,
THE BETTER CHANCE APPEARS TO BE OVER THE OREGON CASCADES AND
CASCADE FOOTHILLS, WHERE INCREASING INSTABILITY ALOFT COULD
SUPPORT ISOLATED CONVECTION. THUNDERSTORM DEVELOPMENT WILL
DEPEND ON WHETHER SUFFICIENT BREAKS IN THE CLOUDS OCCUR. EVEN
WITH RELATIVELY WEAK FORCING ALOFT, THE ENVIRONMENT MAY BECOME
SUPPORTIVE OF A FEW ELEVATED STORMS, AND ANY STORMS THAT DO
FORM COULD LEAN ON THE DRIER SIDE.
HEAT IMPACTS REMAIN A SIGNIFICANT CONCERN THROUGH WEDNESDAY.
SEVERAL CONSECUTIVE DAYS OF ABOVE NORMAL TEMPERATURES COMBINED
WITH ONLY MODEST NIGHTTIME RECOVERY WILL MAINTAIN AT LEAST
MODERATE HEATRISK ACROSS MUCH OF THE INTERIOR. THE MOST NOTABLE
CONCERN REMAINS ACROSS THE PORTLAND/VANCOUVER METRO, TUALATIN
VALLEY, COLUMBIA RIVER GORGE INCLUDING HOOD RIVER COUNTY,
CENTRAL WILLAMETTE VALLEY, AND THE KELSO/LONGVIEW AREA, WHERE A
HEAT ADVISORY REMAINS IN EFFECT THROUGH WEDNESDAY EVENING.
MAJOR HEATRISK REMAINS POSSIBLE IN THOSE AREAS AS WELL,
ESPECIALLY WHERE THE WARMEST DAYTIME HIGHS COMBINE WITH POOR
OVERNIGHT COOLING. THOSE WITH OUTDOOR PLANS OR WITHOUT EFFECTIVE
COOLING SHOULD BE PREPARED FOR ELEVATED HEAT IMPACTS. SO, DRINK
PLENTY OF FLUIDS, STAY IN A COOL PLACE DURING THE HEAT OF THE
DAY, STAY OUT OF THE SUNSHINE, AND CHECK UP ON RELATIVES AND
NEIGHBORS.
BY THURSDAY, THE RIDGE BEGINS TO WEAKEN AS A BROADER TROUGH
MOVES TOWARD THE PACIFIC NORTHWEST. THIS SHOULD PROMOTE A RETURN
TO MORE NOTICEABLE ONSHORE FLOW AND BEGIN A GRADUAL COOLING
TREND THAT CARRIES INTO LATE WEEK. TEMPERATURES ARE STILL LIKELY
TO REMAIN SOMEWHAT ABOVE SEASONAL NORMALS THURSDAY AND FRIDAY,
BUT NOT TO THE DEGREE SEEN EARLIER IN THE WEEK. LOOKING BEYOND
FRIDAY, FORECAST GUIDANCE CURRENTLY DOES NOT SHOW A STRONG
SIGNAL FOR MEANINGFUL PRECIPITATION, WHILE TEMPERATURES TREND
TOWARD THE LOWER 80S THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. ~12
AVIATION
CURRENT VFR CONDITIONS AND SCT/BKN HIGH CLOUDS
AT INLAND TERMINALS WILL CONTINUE THROUGH THE TAF PERIOD
LIGHT TO CALM WINDS EARLY THIS MORNING WILL BUILD TO AROUND 5-7
KT OUT OF THE NORTH TO NORTHWEST BY 18-23Z TUE, THEN AGAIN LIGHT
TO CALM TUE NIGHT.
ALONG THE COAST, LOW MARINE STRATUS BEGINS TO PUSH IN, CURRENTLY
ONLY PRESENT AT KTMK AND SOUTHWARD. EXPECT CURRENT LIFR/IFR
CONDITIONS AT KONP AND KTMK TO EXPAND NORTHWARD, EVENTUALLY
REACHING KAST BY 12-13Z TUE. LIFR CONDITIONS ARE LESS LIKELY AT
KAST (50-60% CHANCE OF LIFR) COMPARED TO KONP (80-90% CHANCE OF
LIFR). SLOW IMPROVEMENT TO MVFR/VFR IS EXPECTED AFTER 17-19Z
TUE, ALTHOUGH GUIDANCE SUGGESTS LESS FAVORABLE CHANCES AT KONP
(60% CHANCE OF MVFR, 50% CHANCE OF IFR, 20% CHANCE OF LIFR). BY
00-03Z WED, MARINE STRATUS WILL ONCE AGAIN PUSH IN, BRINGING A
50-70% CHANCE OF LIFR/IFR CONDITIONS TO COASTAL TERMINALS. NEARLY
CALM WINDS TONIGHT WILL BUILD OUT OF THE WEST TO NORTHWEST AT
5-10 KT BY 18-21Z TUE.
KPDX AND APPROACHES...VFR CONDITIONS BENEATH SCT/BKN HIGH CLOUDS
AND LIGHT NORTHWEST WINDS ARE EXPECTED. WINDS WILL BUILD
SLIGHTLY TO 5-7 KT BY TUESDAY AFTERNOON. ~12
MARINE
A TYPICAL SUMMERTIME PATTERN WILL CONTINUE THROUGH
THE MIDDLE OF THIS WEEK WITH PERSISTENT NORTH TO NORTHWEST WINDS
OVER THE COASTAL WATERS. WINDS THEN SHIFT SOUTHWEST TO WESTERLY
THURSDAY INTO THE WEEKEND AS WEAK LOW PRESSURE DEVELOPS OVER
THE WATERS. WINDS WILL REMAIN LIGHT LESS THAN 10-15 KTS. SEAS
WILL BE 3-6 FT AT 8-9 SECONDS THROUGH THE WEEKEND. -03
PQR WATCHES/WARNINGS/ADVISORIES
OR...HEAT ADVISORY FROM 10 AM THIS MORNING TO 11 PM PDT WEDNESDAY
FOR ORZ108>115-120>122.
WA...HEAT ADVISORY FROM 10 AM THIS MORNING TO 11 PM PDT WEDNESDAY
FOR WAZ204>207-209-210.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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