572
FXUS66 KPQR 092221
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
321 PM PDT SAT AUG 9 2025
SYNOPSIS
EXPECT ABNORMALLY HOT CONDITIONS SUNDAY THROUGH
TUESDAY THANKS TO A STRONG HIGH PRESSURE BUILDING OVER THE
EASTERN PACIFIC - HIGHEST TEMPERATURES ON SUNDAY/MONDAY.
EXTREME HEAT WARNINGS AND HEAT ADVISORIES ARE NOW IN EFFECT
THROUGH TUESDAY. FORTUNATELY, CONDITIONS RETURN CLOSER TO
NORMAL ON WEDNESDAY WITH A COOLING TREND INTO THE END OF THE
WORK WEEK.
SHORT TERM...NOW THROUGH MONDAY NIGHT
NOT MUCH HAS CHANGED IN
REGARDS TO THE FORECAST THIS WEEKEND AS HOT TEMPERATURES ARE
SLATED TO BEGIN ON SUNDAY LASTING INTO EARLY NEXT WEEK. A RIDGE
OF HIGH PRESSURE CONTINUES TO STRENGTHEN OFFSHORE TONIGHT
ALLOWING 850 MB TEMPS SOAR INTO THE 21-23 C RANGE FOR SUNDAY AND
MONDAY WHICH IS WELL ABOVE THE 90TH PERCENTILE OF EARLY AUGUST
KSLE SOUNDING CLIMATOLOGY. THIS CORRESPONDS TO PEAK TEMPERATURES
SUNDAY/MONDAY SPIKING WELL INTO THE 90S TO NEAR 100 IN THE
INTERIOR VALLEYS, WITH CHANCES FOR THE FIRST TRIPLE DIGIT
READINGS OF THE SEASON RANGING FROM 15-25% IN THE COWLITZ VALLEY
TO 30-50% ACROSS THE PORTLAND/VANCOUVER METRO (HIGHEST ON
MONDAY), TO ABOUT 70-90% IN THE CENTRAL/SOUTH WILLAMETTE
VALLEY (ALSO HIGHEST ON CHANCES ON MONDAY). THIS, ALONG WITH
OVERNIGHT LOWS RUNNING IN THE UPPER 60S TO PERHAPS 70 DEGREES IN
SOME URBAN AREAS, WILL DRIVE NWS HEATRISK INTO THE MAJOR
CATEGORY ACROSS A WIDE SWATH OF THE AREA. WE'LL ALSO HAVE TO
KEEP AN EYE ON A SHORTWAVE/MID-LEVEL LOW FEATURE EMBEDDED IN
THE EASTERN PERIPHERY OF THE RIDGE THAT COULD PROVIDE A MINOR
BOOST IN ONSHORE FLOW ON MONDAY. THIS IS REFLECTED IN A
SLIGHTLY LARGER RANGE OF TEMPERATURE OUTCOMES IN THE NBM,
ALTHOUGH MOST OF THE GUIDANCE CONTINUES TO SUGGEST ANY SENSIBLE
WEATHER IMPACTS ASSOCIATED WITH THIS FEATURE WOULD BE MINIMAL.
THAT SAID, A SLIGHTLY STRONGER SHORTWAVE FEATURE COULD BE THE
DIFFERENCE BETWEEN HIGHS IN THE MID TO UPPER 90S VS THE LOW
TRIPLE DIGITS FROM THE PORTLAND/VANCOUVER METRO TO PARTS OF
SOUTHWEST WASHINGTON, PRODUCING A SMALL BUT NON TRIVIAL
DIFFERENCE IN TERMS OF HEATRISK IMPACTS IN SOME LOCATIONS ON
MONDAY. WHILE THERE HAVE BEEN NO CHANGES TO THE PLACEMENT OF
EXISTING HEAT HEADLINES WITH THIS FORECAST PACKAGE, THE LENGTH
WAS EXTENDED INTO TUESDAY EVENING. -SCHULDT/CB
LONG TERM...TUESDAY THROUGH FRIDAY
TUESDAY REPRESENTS THE
START OF THE TRANSITION OUT OF THIS COMING STRETCH OF HOT
WEATHER AS THE RIDGE BEGINS TO RETROGRADE WESTWARD INTO THE
PACIFIC, OPENING THE DOOR TO A WELCOME COOLING TREND ACROSS THE
PACIFIC NORTHWEST. HOWEVER, IT NOW APPEARS THE STRONGEST PUSH OF
ONSHORE FLOW HOLDS OFF UNTIL TUESDAY EVENING AS DETERMINISTIC
AND ENSEMBLE GUIDANCE HAVE SLIGHTLY DELAYED THE ARRIVAL OF AN
INCOMING UPPER LEVEL TROUGH. AT LEAST, TEMPERATURE GUIDANCE
STILL IS LOWER THAN SUNDAY AND MONDAY BUT HIGHS RESIDE MOSTLY
IN THE MID-90S ACROSS IN THE INTERIOR VALLEYS ON TUESDAY
AFTERNOON, WITH A LINGERING 20-30% CHANCE TO REACH 100 DEGREES
IN THE PORTLAND METRO AND CLOSER TO A 50-60% CHANCE IN EUGENE.
CONFIDENCE IS HIGH THE WESTERN OREGON AND SOUTHWEST WASHINGTON
AREA SHOULD TRANSITION FULLY BACK INTO A COOLER ONSHORE FLOW
REGIME BY WEDNESDAY, WITH TEMPS CLOSER TO OR EVEN SLIGHTLY
BELOW SEASONAL NORMS IN THE UPPER 70S TO LOW 80S THROUGH THE
END OF THE WEEK. THERE IS NO PRECIPITATION IN THE FORECAST FOR
THE NEXT SEVEN DAYS, WITH THE EXCEPTION OF A SLIGHT CHANCE ALONG
THE SOUTH WASHINGTON COAST LATE IN THE WEEK AS ONSHORE FLOW
RETURNS. -SCHULDT/CB
AVIATION
VFR CONDITIONS WILL DOMINATE ACROSS THE REGION WITH
MOSTLY NORTH-NORTHWEST WINDS.INCREASED SUBSIDENCE FROM BUILDING
HIGH PRESSURE WILL RESULT IN A SHALLOWER MARINE LAYER TONIGHT AND
SUNDAY WHICH WILL CONFINE THE MARINE CLOUDS TO THE IMMEDIATE
COAST. THERE IS A 20-40% CHANCE OF IFR CEILINGS TO IMPACT THE
COASTAL TERMINALS 11-17Z. NORTH WIND GUSTS OF 15-20 KT CAN BE EXPECTED
IN THE WILLAMETTE VALLEY AND 25-30 KT ALONG THE COAST SUNDAY
AFTERNOON.
PDX AND APPROACHES...VFR FOR THE NEXT 24 HOURS. NORTHWESTERLY
WINDS UNDER 10 KT THROUGH 21-23Z SAT, THEN INCREASING TO 10-15 KT
WITH GUSTS UP TO 20 KT IN THE EVENING. -TJ
MARINE
HIGH PRESSURE ACROSS THE WATERS WILL MAINTAIN NORTHERLY
WINDS ACROSS THE WATERS THROUGH AT LEAST THURSDAY NEXT WEEK.
PRESSURE GRADIENTS WILL TIGHTEN THIS WEEKEND AS HIGH PRESSURE
BUILDS OVER THE NE PACIFIC, LEADING TO INCREASED WINDS. THE WINDS
WILL BE STRONGEST IN THE AFTERNOON AND EVENINGS AND WILL BE
HAZARDOUS TO SMALL CRAFTS FROM THIS AFTERNOON THROUGH AT LEAST
MONDAY. THE WIND GUSTS WILL RELAX IN THE MORNINGS, ESPECIALLY
CLOSER TO SHORE. SEAS WILL BE MOSTLY WIND-DRIVEN AND AROUND 3-5
FT AT 10-11 SEC TODAY. A FRESH NW SWELL BUILDS SEAS TO 6 TO 7 FT
AT 10-11 SEC SUNDAY, AND 9 TO 10 FT ON MONDAY. HAVE EXTENDED THE
SMALL CRAFT ADVISORY THROUGH MONDAY EVENING TO ACCOUNT FOR THE
STEEP SEAS. THERE IS A 60-80% CHANCE OF WAVE HEIGHTS EXCEEDING 8
FT BY MONDAY, WITH THE HIGHEST CHANCES OVER THE OUTER WATERS.
MARINE ZONE 251 (CAPE SHOALWATER TO CAPE FALCON OUT TO 10 NM)
IS NOT CURRENTLY IN THE SMALL CRAFT ADVISORY DUE TO SLIGHTLY
WEAKER SURFACE PRESSURE GRADIENTS TO THE NORTH. THIS MARINE ZONE
IS STILL SUSCEPTIBLE TO STEEP SEAS ON MONDAY DUE TO STRONGER
WINDS TO THE NORTHWEST, AND WILL MONITOR THE SWELL FORECAST FOR
THIS AREA OVER THE NEXT 12-24 HOURS TO SEE IF THE SEAS WILL BE
CONSIDERED HAZARDOUS TO SMALL CRAFT. -TJ
FIRE WEATHER
ON SUNDAY WE CONTINUE TO WATCH FOR THE
POTENTIAL OF ENHANCED FIRE WEATHER CONCERNS AS THE ORIENTATION
OF A THERMAL TROUGH ALONG THE WEST SLOPES OF THE CASCADES
YIELDS BREEZY NORTH WINDS IN THE WILLAMETTE VALLEY. CURRENTLY WE
DO NOT ANTICIPATE WIDESPREAD CRITICAL FIRE WEATHER CONDITIONS
BEING MET, BUT THE COMBINATION OF MINIMUM RH VALUES IN THE LOW 20S
AND NORTH WINDS GUSTING TO 15-20 MPH DOES RAISE THE POSSIBILITY
THAT CONDITIONS WILL FLIRT WITH RED FLAG CRITERIA IN THE
CENTRAL AND SOUTH WILLAMETTE VALLEY FOR A TIME ON SUNDAY
AFTERNOON. LIGHTER WINDS WILL HELP TO LIMIT FIRE WEATHER
CONCERNS ON MONDAY. -SCHULDT/CB
PQR WATCHES/WARNINGS/ADVISORIES
OR...HEAT ADVISORY FROM NOON SUNDAY TO 10 PM PDT TUESDAY FOR ORZ104-
105-108.
EXTREME HEAT WARNING FROM NOON SUNDAY TO 10 PM PDT TUESDAY FOR
ORZ109>125.
WA...HEAT ADVISORY FROM NOON SUNDAY TO 10 PM PDT TUESDAY FOR WAZ202-
204-208.
EXTREME HEAT WARNING FROM NOON SUNDAY TO 10 PM PDT TUESDAY FOR
WAZ205>207-209-210.
PZ...SMALL CRAFT ADVISORY UNTIL 5 PM PDT MONDAY FOR PZZ252-253-272-
273.
SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 5 PM PDT MONDAY
FOR PZZ271.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSPORTLAND
X.COM/NWSPORTLAND
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