008
FXUS66 KPQR 032226
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
326 PM PDT THU SEP 3 2026
SYNOPSIS
AN UNSETTLED AIRMASS REMAINS OVERHEAD INTO THE
WEEKEND WITH LINGERING SHOWERS GRADUALLY DIMINISHING DAY TO DAY.
THEN CONDITIONS TREND DRIER BY THE EARLY TO MIDDLE PORTION OF
NEXT WEEK AS TEMPERATURES SLOWLY CLAW THEIR WAY BACK NEAR NORMAL
FOR EARLY SEPTEMBER. HOWEVER, UNCERTAINTY IN THE LARGE SCALE
PATTERN GROWS NOTICEABLY AROUND THE MIDDLE PORTION OF NEXT WEEK.
DISCUSSION...TODAY THROUGH THURSDAY
A VERTICALLY STACKED
UPPER-LEVEL LOW CONTINUES TO CHURN OFF THE OREGON COAST THIS
AFTERNOON WITH INSTABILITY REACHING JUST DEEP ENOUGH INTO THE
ATMOSPHERE TO SUPPORT OCCASIONAL LIGHTNING STRIKES IN SOME OF
THE STRONGER CONVECTIVE CELLS. GIVEN THE PLACEMENT OF THE LOW
PRESSURE AND POCKETS LOCALIZED LOW LEVEL SHEAR PARTIALLY INDUCED
BY OUR TERRAIN FEATURES, ONE OR TWO SHOWERS/T-STORMS HAVE
EXHIBITED ROTATION WITH AT LEAST ONE FUNNEL CLOUD REPORTED BY A
WEATHER SPOTTER NEAR MIDDAY TODAY. THE THREAT FOR THUNDERSTORMS
AND VERY ISOLATED COLD-CORE FUNNEL CLOUDS WILL PERSIST INTO THE
EVENING HOURS BEFORE THE LOSS THE DAYTIME HEATING WEAKENS
REMAINING CONVECTION. SHOWER CHANCES LIKELY CONTINUE OVERNIGHT.
COME FRIDAY THE CORE OF THIS LOW PRESSURE FEATURE WILL FINALLY
BEGIN TO SHIFT INTO WESTERN OREGON ALTHOUGH NOT TOO MUCH WILL
CHANGE IN REGARD TO OUR OVERALL CONDITIONS. THAT SAID, MODELS
LIKE THE HREF INDICATE THE COVERAGE OF SHOWERS MAY BE A TOUCH
LOWER THAN TODAY (THURSDAY), AND MORE LIKELY IN THE SOUTHERN
WILLAMETTE VALLEY IN ADDITION TO FAVORING TERRAIN FEATURES LIKE
THE COAST RANGE, AND CASCADES. EXPLORING DETERMINISTIC MODEL
SOUNDINGS FROM THE GFS, NAM, ETC. SHOW JUST ENOUGH CAPE
EXTENDING INTO THE MIX-PHASED REGION OF THE ATMOSPHERE FOR A
LIGHTNING STRIKE OR TWO TO BE PRODUCED IN STRONGER CELLS,
HOWEVER, A GLARING LACK OF VERTICAL SHEAR MEANS ANY STORMS WHICH
DO DEVELOP WILL BE SHORT-LIVED AND PULSE-LIKE. INFREQUENT
LIGHTNING, HEAVY RAIN, AND GUSTY OUTFLOW WINDS ARE THE PRIMARY
IMPACTS. ANY ACTIVITY THEN QUICKLY DECREASES AFTER SUNSET INTO
FRIDAY NIGHT.
OVER THE WEEKEND, THE MAJORITY OF DETERMINISTIC AND ENSEMBLE
MEMBERS CONTINUE TO SHOW THE BROAD UPPER-LEVEL LOW PRESSURE
HOLDING FIRM OVER THE PACIFIC NORTHWEST WITH LINGERING SHOWER
CHANCES MOST LIKELY DURING THE DAYTIME HOURS AND OVER TERRAIN
FEATURES AS DIURNAL HEATING LIKELY PLAYS A MAJOR ROLE IN SHOWER
GENERATION. CONFIDENCE IS HIGH THAT TEMPERATURES REMAIN BELOW
NORMAL FOR THIS TIME OF YEAR BY ROUGHLY 3-12 DEGREES (COOLEST
IN THE CASCADES). IT MIGHT BE WORTH PACKING A JACKET/COAT IF
YOU PLAN ON VENTURING INTO THE MOUNTAINS THIS WEEKEND. EARLY
NEXT WEEK, THE MAJORITY OF ENSEMBLE MEMBERS FINALLY SHOW THE
UPPER LOW BEGINNING TO ACCELERATE EASTWARD FAVORING THE RETURN
OF DRY CONDITIONS AND A GRADUAL WARMING TREND. BUT FROM THIS
POINT FORWARD ENSEMBLES BEGIN TO DEVIATE FROM ONE ANOTHER WHEN
TRYING TO RESOLVE THE UPPER-LEVEL PATTERN, PARTICULARLY IN
REGARDS TO A RIDGE OF HIGH PRESSURE TRYING TO DEVELOP OVER THE
ROCKIES INTO SOUTHEAST OREGON WHILE A TROUGH AMPLIFIES OVER THE
EASTERN PACIFIC. CURRENTLY AROUND 60% OF ENSEMBLES FAVOR A
WARMER/DRIER SOLUTION WITH HIGHS ABOVE NORMAL (MID 80S) BY
WEDNESDAY/THURSDAY WHILE THE REMAINING 40% POINT TO A SOMEWHAT
COOLER SOLUTION (LOW TO MID 70S). WE'LL SEE HOW MODELS TREND
DURING THIS MID-WEEK PERIOD OVER THE NEXT SEVERAL DAYS AS
ENSEMBLE AGREEMENT HOPEFULLY INCREASES. -99
AVIATION...THROUGH 18Z FRIDAY
MOIST, SOUTHWEST FLOW ALOFT WILL
PERSIST TODAY AS A LOW PRESSURE SYSTEM MOVES TOWARD THE OREGON
COAST. THIS SYSTEM WILL MAINTAIN WIDESPREAD RAIN SHOWERS ACROSS
THE AREA WITH AROUND A 15-30% CHANCE OF THUNDERSTORMS THROUGH THIS
AFTERNOON, HIGHEST CHANCES ALONG THE COAST. PREDOMINATELY VFR
CONDITIONS ARE EXPECTED TO PREVAIL, EXCEPT WITH THE HEAVIER
SHOWERS WHICH ARE LIKELY TO PRODUCE BRIEF PERIODS OF MVFR TO IFR
REDUCTIONS IN VISIBILITY AND CIGS. RAIN IS EXPECTED TO GRADUALLY
TAPER OFF FROM NORTH TO SOUTH THROUGH THIS EVENING. PROBABILITIES
FOR WIDESPREAD MVFR OR WORSE REMAINS RELATIVELY LOW AT AROUND 20%
OR LESS, EXCEPT AT KONP WHERE PROBS ARE CLOSER TO AROUND 30-40%.
GENERALLY EXPECTED SOUTH TO SOUTHEASTERLY WINDS WITH BRIEF GUSTS
POSSIBLE UP TO 20 KT. ANY THUNDERSTORMS THAT DO DEVELOP WILL HAVE
THE POTENTIAL TO PRODUCE LIGHTNING AND GUSTY/ERRATIC WINDS.
KPDX AND APPROACHES...PREDOMINATELY VFR EXPECTED WITH BRIEF AND
INTERMITTENT MVFR CONDITIONS POSSIBLE WITH HEAVIER SHOWERS.
GENERALLY LESS THAN A 20% CHANCE FOR MVFR AT ANY GIVEN HOUR
THROUGH THE PERIOD. THERE IS ALSO AROUND A 10-20% CHANCE FOR
THUNDERSTORMS THROUGH THIS AFTERNOON. SOUTH TO SOUTHEAST WINDS
AROUND 10 KT WITH GUSTS UP TO 20 KT EXPECTED TO EASE AFTER 02Z
FRIDAY. /DH
MARINE
A LOW PRESSURE SYSTEM CENTERED APPROXIMATELY 100 NM WEST
OF THE NORTH OREGON COAST WILL GRADUALLY WEAKEN AS IT MOVES TOWARD
THE SOUTHERN OR COAST THROUGH FRIDAY. BREEZY SOUTHERLY WINDS
CONTINUE THROUGH THIS EVENING WITH GUSTS UP TO 30 KT POSSIBLE THIS
AFTERNOON. BUOY OBSERVATIONS THIS AFTERNOON SHOW SEAS AT AROUND
10 FT AT 11 SECONDS. EXPECT SMALL CRAFT ADVISORY CONDITIONS TO
PERSIST ACROSS THE COASTAL WATERS THROUGH 11 PM THIS EVENING.
WINDS OVER THE COASTAL WATERS ARE THEN EXPECTED TO EASE TURNING
MORE EASTERLY OVERNIGHT INTO FRIDAY. ALSO, A 15-30% CHANCE FOR
THUNDERSTORMS EXISTS ACROSS THE WATERS, WHICH COULD PRODUCE
LIGHTNING AND GUSTY/ERRATIC WINDS.
LIGHT OFFSHORE FLOW BECOMES NORTHERLY LATER SATURDAY AND SUNDAY AS
WEAK HIGH PRESSURE REBUILDS OVER THE WATERS. SEAS ARE EXPECTED TO
FALL BELOW 10 FT BY EARLY FRIDAY MORNING, AND CONTINUE TO SUBSIDE
TO AROUND 4 TO 5 FT BY SATURDAY. CONDITIONS LOOK TO REMAIN RATHER
BENIGN INTO EARLY NEXT WEEK. /DH
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 11 PM PDT THIS EVENING FOR PZZ210-
251>253-271>273.
WWW.WEATHER.GOV/PORTLAND
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