803
FXUS66 KPQR 191138 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
438 AM PDT WED AUG 19 2026
..UPDATED AVIATION DISCUSSION
SYNOPSIS
WARM AND DRY CONDITIONS THROUGH THURSDAY. LOW
PRESSURE WILL RETURN COOLER TEMPERATURES AND CHANCES FOR
SHOWERS FRIDAY INTO SATURDAY, WITH A 5-10% CHANCE FOR
THUNDERSTORMS. WINDS OUT OF THE NORTH/NORTHWEST THROUGH
THURSDAY, SHIFTING TO THE WEST/SOUTHWEST ON FRIDAY. SEASONABLE
WEATHER CONTINUES SUNDAY INTO EARLY NEXT WEEK.
DISCUSSION...TODAY THROUGH TUESDAY
DRY AND WARM WEATHER
CONTINUES TODAY AND TOMORROW AS AN UPPER-LEVEL RIDGE AMPLIFIES
OVER THE ROCKIES AND GREAT BASIN. EXPECT HIGH TEMPERATURES NEAR
OR SLIGHTLY ABOVE AVERAGE FOR THIS TIME OF YEAR, WITH MID 80S
THIS AFTERNOON ACROSS INLAND VALLEYS AND 60S ALONG THE COAST.
HIGHS FOR INLAND VALLEYS INCREASE SLIGHTLY INTO THE UPPER 80S AS
THE UPPER RIDGE REACHES ITS PEAK STRENGTH. ONSHORE FLOW
CONTINUES AS BROAD UPPER-LEVEL TROUGHING SITS OVER THE NORTHEAST
PACIFIC WITH LIGHT WINDS FROM THE NORTH/NORTHWEST.
ON FRIDAY, THE AFOREMENTIONED TROUGH OVER THE NORTHEAST PACIFIC
WILL PROGRESS TOWARD THE PACIFIC NORTHWEST, BRINGING SLIGHTLY
COOLER TEMPERATURES, INCREASED CLOUD COVER, AND A 20-30% CHANCE
FOR SHOWERS IN THE AFTERNOON AND EVENING. WILL NOTE THAT THIS
UPPER-LEVEL PATTERN ON FRIDAY LOOKS LIKE A TYPICAL SET-UP FOR
THUNDERSTORM CHANCES, AT LEAST OVER THE CASCADES. SOUTHERLY FLOW
ALOFT WILL BRING INCREASED MOISTURE AND INSTABILITY INTO THE
MID-LEVELS OF THE ATMOSPHERE (5-10 KFT). VORTICITY FROM THE
UPPER-LEVEL TROUGH WILL ALSO PROVIDE THE NECESSARY FORCING FOR
CONVECTION. CURRENTLY, NBM GUIDANCE SHOWS LOW CHANCES (5-10%)
FOR THUNDERSTORMS ON FRIDAY, HOWEVER, IN THE PAST WE'VE SEEN
MODELS STRUGGLE WITH CAPTURING THE POTENTIAL FOR HIGH-BASED
THUNDERSTORMS. THERE IS ALSO UNCERTAINTY AMONG
DETERMINISTIC/ENSEMBLE GUIDANCE WITH HOW MUCH INSTABILITY
(SBCAPE/MUCAPE) THERE WILL BE, HOWEVER, WE WILL CONTINUE TO
EVALUATE THE THUNDERSTORM THREAT TODAY. THOSE WITH OUTDOOR PLANS
ON FRIDAY SHOULD MONITOR THE FORECAST CLOSELY THESE NEXT COUPLE
DAYS.
BY SATURDAY, ENSEMBLE GUIDANCE SHOWS THE UPPER-LEVEL TROUGH
MOVING INTO THE PACIFIC NORTHWEST WITH CHANCES FOR SHOWERS
CONTINUING THROUGH THE MORNING. AS THE ASSOCIATED SURFACE FRONT
MOVES THROUGH, WILL SEE WINDS SHIFT AND COME OUT OF THE
WEST/SOUTHWEST. THE STRONGEST WINDS ARE EXPECTED THROUGH THE
CENTRAL COLUMBIA RIVER GORGE AND HOOD RIVER VALLEY WHERE WINDS
COULD GUST TO 25-35 MPH. THERE IS ALSO A 30-60% CHANCE FOR AT
LEAST ISOLATED GUSTS EXCEEDING 40 MPH FOR THESE AREAS,
ESPECIALLY FOR HIGHER TERRAIN AND EXPOSED RIDGETOPS.
LATE THIS WEEKEND INTO EARLY NEXT WEEK, THE TROUGH WEAKENS AND
MOST ENSEMBLE MEMBERS SUGGEST A RETURN OF ZONAL FLOW BEFORE
ANOTHER UPPER-LEVEL TROUGH DROPS DOWN FROM THE GULF OF ALASKA
AND APPROACHES BRITISH COLUMBIA. AT THIS POINT, THERE STILL
REMAINS HIGH UNCERTAINTY WITH THE EXACT MAGNITUDE AND PLACEMENT
OF THE TROUGH NEXT WEEK. HOWEVER, THIS WOULD SUGGEST THAT
ONSHORE FLOW CONTINUES ACROSS THE REGION RESULTING IN SEASONABLE
TEMPERATURES FOR LATE AUGUST. -10
AVIATION...THROUGH 12Z THURSDAY
SATELLITE IMAGERY AND TERMINAL
OBSERVATIONS AS OF EARLY WEDNESDAY MORNING DEPICTS MARINE STRATUS
ALONG THE COAST BRINGING IFR CONDITIONS TO KAST. KONP HAS BEEN VFR,
HOWEVER, EXPECT THE STRATUS TO FILL IN AND RETURN IFR/MVFR CIGS THIS
MORNING. SOME STRATUS HAS MADE ITS WAY UP THE LOWER COLUMBIA RIVER
VALLEY AND DOWN TOWARD THE EASTERN PORTLAND METRO AREA, SO EXPECT
LOW-END MVFR CIGS (1-2 KFT) AT KPDX AND KTTD AFTER 12-13Z WED. LOW
CONFIDENCE FOR STRATUS TO MAKE IT INTO THE CENTRAL AND SOUTHERN
WILLAMETTE VALLEY THIS MORNING AS GUIDANCE SHOWS A 15-25% CHANCE AT
ANY GIVEN HOUR BETWEEN 13-17Z WED FOR MVFR CIGS. AFTER 17-18Z WED,
DAYTIME HEATING WILL DISSIPATE STRATUS AND RETURN VFR CONDITIONS.
VFR PREVAILS ACROSS THE VALLEY THROUGH THE TAF PERIOD. ALONG THE
COAST, GUIDANCE SUGGESTS BRIEF IMPROVEMENT TO VFR BETWEEN 21Z WED-
01Z THU BEFORE IFR/MVFR STRATUS RETURNS IN THE EVENING. LIGHT
WEST/NORTHWEST WINDS AROUND 5-10 KT ALONG THE COAST AND 4-7 KT
ACROSS THE VALLEY.
KPDX AND APPROACHES...LOW-END MVFR CIGS (1-2 KFT) THROUGH 17-18Z
WED. AFTERWARDS, VFR CONDITIONS PREVAIL THROUGH THE TAF PERIOD.
NORTHWEST WINDS 4-6 KT TODAY. -10
MARINE
HIGH PRESSURE WILL CONTINUE TO SUPPORT NORTHERLY WINDS
ACROSS THE WATERS THROUGH THURSDAY WITH GUSTS REMAINING BELOW 20
KT. FRIDAY TO SATURDAY, WEAK LOW PRESSURE MOVING OVER THE
NORTHEAST PACIFIC WILL SHIFT WINDS OUT OF THE SOUTH TO SOUTHWEST
ACROSS THE WATERS. AS THE SURFACE FRONT MOVES THROUGH SATURDAY
MORNING, THERE WILL BE A 40-50% CHANCE FOR MAXIMUM WIND GUSTS
UP TO 25 KT FOR THE INNER WATERS NORTH OF CAPE FALCON, INCLUDING
THE COLUMBIA RIVER BAR. FOR THE REST OF THE WATERS, CHANCES ARE
AROUND 5-10%.
HIGH PRESSURE AND NORTHERLY WINDS RETURN BY SUNDAY WITH A 50-60%
CHANCE FOR NORTHERLY WIND GUSTS EXCEEDING 21 KTS IN THE AFTERNOON
AND EVENING HOURS SOUTH OF CAPE FOULWEATHER. SEAS OF 4-6 FT
PERSIST THROUGH THE PERIOD. PERIODS AROUND 12 SEC TODAY MAY RESULT
IN A MODERATE RISK FOR SNEAKER WAVES ALONG THE COAST. CAUTION
SHOULD BE USED WHEN IN OR NEAR THE WATER. -10
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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