215
FXUS66 KPQR 061734
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1034 AM PDT WED AUG 6 2025
UPDATED AVIATION DISCUSSION.
SYNOPSIS
UPPER-LEVEL TROUGHING AND A WELCOME AUGUST RAIN
THIS MORNING WILL GIVE WAY TO BUILDING HIGH PRESSURE AND A
WARMING AND DRYING TREND THROUGH EARLY NEXT WEEK. CONTINUED
BELOW-NORMAL TEMPERATURES THROUGH THE WORKWEEK WILL STEADILY
RISE TO HAZARDOUS LEVELS BY SUNDAY AND MONDAY.
SHORT TERM...NOW THROUGH FRIDAY NIGHT
A WEAK SURFACE LOW
CONTINUES TO FILL AS IT MOVES BENEATH AN UPPER-LEVEL LOW NORTH
OF VANCOUVER ISLAND. A PAIR OF SURFACE FRONTS EXTENDING TO THE
SOUTH OF THE LOW HAS BROUGHT OVERCAST SKIES AND LIGHT RAIN TO
THE REGION EARLY THIS MORNING, AS FAR EAST AS THE I-5 CORRIDOR
AS OF 2 AM PDT, AND WILL CONTINUE TO SPREAD EASTWARD THROUGH
DAYBREAK. RAIN WILL TRANSITION TO A MORE SHOWERY DISTRIBUTION
THROUGH THIS MORNING PER LATEST CAM GUIDANCE, WITH DECREASING
SHOWER COVERAGE THROUGH TONIGHT AND ONLY ISOLATED LINGERING
SHOWERS IN AREAS OF HIGHER TERRAIN BY THURSDAY MORNING. WHILE
INSTABILITY WILL BE HIGHER TO THE NORTH CLOSER TO THE UPPER LOW,
A FEW RUMBLES OF THUNDER CANNOT BE RULED OUT THIS AFTERNOON AND
EVENING, WITH A 10-20% CHANCE OVER THE SOUTHERN WASHINGTON AND
FAR NORTHERN OREGON CASCADES.
THE MAIN STORY WITH THIS ONGOING SYSTEM WILL BE POTENTIALLY
SIGNIFICANT MID-SUMMER RAINFALL AMOUNTS. THE ARRIVING AIRMASS
IS ABNORMALLY MOIST, WITH FORECAST PRECIPITABLE WATER OF NEARLY
1.5" ACROSS MUCH OF THE REGION EARLY THIS MORNING; IF THIS
FORECAST IS VERIFIED BY THE 12Z KSLE UPPER AIR LAUNCH, IT WOULD
REPRESENT A RECORD HIGH VALUE FOR THE DATE PER SPC SOUNDING
CLIMATOLOGY. THE RELATIVELY WEAK FORCING ASSOCIATED WITH THE
FIZZLING OCCLUDED LOW AND FRONTS MEANS ACTUAL RAIN AMOUNTS WILL
BE WELL BELOW THESE PW VALUES, BUT TRUE WETTING RAINS OF 0.25"
OR MORE REMAIN FAVORED ACROSS NORTHERN PORTIONS OF THE FORECAST
AREA. THE HIGHEST TOTALS EXCEEDING 0.5" ARE EXPECTED IN THE
HIGHER TERRAIN OF THE WILLAPA HILLS, NORTHERN OREGON COAST
RANGE, SOUTHERN WASHINGTON CASCADES, AND THE MT. HOOD VICINITY,
WHILE OTHER AREAS ALONG THE COAST, IN THE CASCADES AND FOOTHILLS
NORTH OF SANTIAM PASS, AND AT LOWER ELEVATIONS NORTH OF SALEM
WILL SEE 0.1-0.5". INTERIOR PORTIONS OF LANE COUNTY REMAIN THE
LEAST LIKELY TO SEE HIGHER ACCUMULATIONS OF RAINFALL, WITH MOST
LIKELY TOTALS OF 0.05" OR LESS.
DRY WEATHER RETURNS THURSDAY NIGHT THROUGH FRIDAY, AS RISING
HEIGHTS ALOFT AND BUILDING SURFACE HIGH PRESSURE OVER THE
NORTHEAST PACIFIC BEGIN TO FAVOR A WARMING TREND. AFTER A NUMBER
OF DAYS WITH BELOW-NORMAL TEMPERATURES, AFTERNOON HIGHS WILL
AGAIN APPROACH SEASONAL VALUES IN THE 80S ACROSS INLAND VALLEYS
AND 60S TO 70S ALONG THE COAST BY FRIDAY. -PICARD
LONG TERM...SATURDAY THROUGH TUESDAY
THE MAJOR PATTERN SHIFT
WILL CONTINUE THIS WEEKEND INTO NEXT WEEK AS HIGH-AMPLITUDE
UPPER-LEVEL RIDGING BUILDS OVER THE PACIFIC, AND THE WARMING
TREND CONTINUES AT THE SURFACE. TEMPERATURES WILL CONTINUE TO
RISE ABOVE NORMAL THROUGH THE PERIOD, APPROACHING HAZARDOUS
VALUES BY SUNDAY AND MONDAY, BEFORE THE PATTERN BEGINS TO
DEAMPLIFY AND SHIFT WESTWARD AWAY FROM THE REGION ON TUESDAY.
AFTERNOON HIGHS ARE LIKELY (75-95% CHANCE) TO EXCEED 90 DEGREES
ACROSS INTERIOR VALLEYS BOTH SUNDAY AND MONDAY. CONFIDENCE
REMAINS HIGH THAT TEMPERATURES WILL PEAK ON MONDAY, WHEN SOME
LOCATIONS MAY SEE THEIR FIRST TRIPLE-DIGIT TEMPERATURE OF THE
YEAR, WITH 35-75% CHANCES OF REACHING 100 DEGREES ALONG THE
WILLAMETTE VALLEY. DEWPOINTS IN THE LOW TO MID 60S WILL
ADDITIONALLY MAKE CONDITIONS FEEL NOTICEABLY HUMID EACH
AFTERNOON, WHILE OVERNIGHT TEMPERATURES MAY FAIL TO FALL BELOW
60-65 DEGREES BOTH SUNDAY AND MONDAY NIGHTS, MOST LIKELY ACROSS
THE NORTHERN AND CENTRAL WILLAMETTE VALLEY, THE LOWER COLUMBIA
AND COWLITZ VALLEYS, THE PORTLAND/VANCOUVER METRO, AND ALONG
THE COLUMBIA GORGE. THIS LACK OF SUFFICIENT OVERNIGHT COOLING
CAN RAISE THE CUMULATIVE HEAT STRESS AND ELEVATE THE RISK FOR
HEAT ILLNESS, RESULTING IN AREAS OF MAJOR HEATRISK. RESIDENTS
OF THE AFOREMENTIONED AREAS SHOULD THEREFORE BEGIN TO PLAN FOR
THIS PERIOD OF HAZARDOUS HEAT. -PICARD
AVIATION
COLD FRONTAL SYSTEM CONTINUES TO PUSH EASTWARD TODAY
BRINGING WIDESPREAD RAIN AND MVFR STRATUS. THERE HAS BEEN SOME
"BOUNCINESS" IN THE CIGS DUE TO THE SHOWERY NATURE OF THE
RAINFALL. OVERALL, VIS HASN'T BEEN IMPACTED IN THE SAME WAY ASIDE
FROM THE COAST NEAR KAST WHICH HAS SEEN AS LOW AS IFR VIS MOVE IN.
HOWEVER, AS THE BACKSIDE OF THE FRONT SHIFTS INLAND, WILL SEE
IMPROVEMENT THROUGHOUT THE AREA. THE SOUTHERN PORTIONS OF THE AREA
(SOUTH OF KUAO) HAVE REMAINED DRIER AND VFR THROUGH MUCH OF THIS
SYSTEM AND THUS, ARE LESS LIKELY TO SEE STRATUS REFORM OVERNIGHT.
MODELS ARE SUGGESTING THAT THE STRATUS WILL THICKEN OVERNIGHT,
THOUGH NOT NECESSARILY BECOME MVFR EVERYWHERE. IT WILL FLIRT RIGHT
ON THE 2500-3500 FT AGL LEVEL TOWARDS THE END OF THE FORECAST. ONE
AREA TO WATCH THOUGH WILL BE IN THE SOUTHERN WILLAMETTE VALLEY.
BECAUSE SKIES WILL BE MORE BROKEN AND POTENTIALLY SEE PARTIAL
CLEARING OVERNIGHT, CANNOT RULE OUT THE PRESENCE OF FOG. THIS IS
ESPECIALLY THE CASE DUE TO A WEAK NORTHERLY WIND. HOWEVER, SPEEDS
REMAIN ELEVATED ENOUGH THAT IT WILL STRUGGLE TO FORM. BUT, IF
WINDS SETTLE AND SKIES CLEAR, CANNOT RULE IT OUT.
PDX AND APPROACHES...MVFR THROUGH MUCH OF THE FORECAST WITH THE
PASSAGE OF THE FRONT. ADDITIONAL RAIN EXPECTED IN SHOWERS. WITH
SHOWERS, EXPECT MIXING AT THE SURFACE. AFTER 10Z THU, WINDS
BETWEEN 1500-3000 FT WILL BECOME NORTHWESTERLY WHILE SURFACE WINDS
WILL BE LIGHT. NOT NECESSARILY CONCERNED ABOUT LLWS AT THIS TIME
DUE TO A LACK OF SPEED SHEAR. -MUESSLE
MARINE
A FRONTAL SYSTEM CONTINUES TO MOVE THROUGH THE WATERS,
BRINGING INCREASED SOUTHERLY WINDS. BUOY OBSERVATIONS CURRENTLY
SHOW WIND GUSTS UP TO 15 TO 20 KT. EXPECT 10 TO 15 KT WINDS WITH
AREAS OF GUSTS TO 20 KT TO CONTINUE THROUGH THE LATE MORNING,
ESPECIALLY CLOSER TO SHORE. CANNOT RULE OUT AN ISOLATED GUSTS TO
25 KT OR TWO, BUT NOT EXPECTED TO BE WIDESPREAD OR FREQUENT.
SEAS WILL BE GENERALLY UNAFFECTED WITH THIS SYSTEM AND REMAIN
NORTHWESTERLY AT 4-6 FT. THESE CONDITIONS WILL PERSIST THROUGH
TODAY. WEDNESDAY NIGHT INTO THURSDAY MORNING, WINDS WILL WEAKEN
AND SHIFT BACK TO NORTHWESTERLY. BY THURSDAY NIGHT, WINDS WILL
INCREASE ONCE AGAIN AND BRING GUSTS UP TO 20 KT FOR THE SOUTHERN
AND CENTRAL WATERS THROUGH FRIDAY AND INTO THE WEEKEND.
-HALL/MUESSLE
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
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