293
FXUS66 KPQR 151043
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
343 AM PDT SAT AUG 15 2026
SYNOPSIS
WARM AND DRY CONDITIONS EXPECTED THROUGH NEXT WEEK
WITH PERSISTENT ONSHORE FLOW. THERE IS A 10-15% CHANCE FOR
ISOLATED, HIGH-BASED THUNDERSTORMS ACROSS INTERIOR VALLEYS AND
THE CASCADES THROUGH THIS MORNING. CHANCES FOR THUNDERSTORMS
DECREASE ACROSS INTERIOR VALLEYS IN THE AFTERNOON, WHILE THE
CASCADES MAINTAIN A 15-25% CHANCE FOR THUNDERSTORMS. THE HIGHEST
CHANCES ARE EXPECTED ALONG THE CREST. ANY PASSING THUNDERSTORMS
MAY RESULT IN LIGHTNING, HEAVY RAIN, AND ERRATIC WINDS. MORNING
CLOUDS EXPECTED TO DISSIPATE THIS AFTERNOON.
DISCUSSION...TODAY THROUGH FRIDAY
RADAR IMAGERY AS OF EARLY
SATURDAY AFTERNOON DEPICTS ISOLATED SHOWERS ACROSS THE CASCADES
DUE TO AN UNSTABLE LAYER IN THE MID-LEVELS OF THE ATMOSPHERE.
THIS INSTABILITY REMAINS ABOVE AN INVERSION PRESENT AROUND
3000-5000 FT. MESOANALYSIS SUGGESTS MUCAPE VALUES ARE CURRENTLY
100-250 J/KG ACROSS INTERIOR VALLEYS AND THE CASCADES, WHICH IS
SUPPORTING CONVECTION. VORTICITY FROM AN UPPER LEVEL TROUGH AS
WELL AS MONSOONAL MOISTURE FROM THE SOUTH IS TAPPING INTO THIS
INSTABILITY. AS A RESULT, THERE IS A 10-15% CHANCE FOR ISOLATED,
HIGH-BASED THUNDERSTORMS THROUGH THIS MORNING ACROSS INTERIOR
VALLEYS AND THE CASCADES. LATER THIS AFTERNOON, THE THUNDERSTORM
THREAT DIMINISHES FOR INTERIOR VALLEYS AS CONDITIONS DRY UP.
HOWEVER, THERE STILL REMAINS A 15-25% CHANCE FOR ISOLATED
THUNDERSTORMS ACROSS THE CASCADES THROUGH THE EVENING WITH THE
HIGHEST CHANCES ALONG THE CREST. ANY PASSING THUNDERSTORMS MAY
RESULT IN LIGHTNING, BRIEF HEAVY RAIN, AND ERRATIC WINDS.
BELOW THE AFOREMENTIONED INVERSION AROUND 3000-5000 FT, A MOIST
LOW LEVEL ATMOSPHERE IS RETURNING A SOLID MARINE LAYER ALONG THE
COAST WITH STRATUS SPREADING INTO THE I-5 CORRIDOR. SIMILAR TO
THE PREVIOUS DAYS, EXPECT THESE CLOUDS TO LAST THROUGH THE
MORNING AND BREAK OUT BY THE EARLY AFTERNOON AS DAYTIME HEATING
PROGRESSES AND MIXES THE ATMOSPHERE. KEEP IN MIND THAT EVEN
THOUGH THERE IS AN INVERSION, HIGH-BASED THUNDERSTORMS CAN STILL
DEVELOP ABOVE THE INVERSION AND IMPACT LOCATIONS, WHICH IS WHAT
WE SAW YESTERDAY MORNING WITH SOME POP-UP THUNDERSTORMS THAT
PROGRESSED FROM THE HILLSBORO, OR AREA TO COWLITZ/SKAMANIA
COUNTIES.
OTHERWISE, EXPECT MOSTLY DRY AND SEASONABLE TEMPERATURES TODAY
AND THROUGH NEXT WEEK FOR THE MAJORITY OF LOCATIONS. GUIDANCE
SUGGESTS HIGH CONFIDENCE FOR NEAR NORMAL TEMPERATURES FOR MID-
AUGUST THROUGH AT LEAST EARLY NEXT WEEK, WITH AFTERNOON HIGHS IN
THE LOW TO MID 80S ACROSS INTERIOR VALLEYS. CLUSTER ANALYSIS OF
500 MB HEIGHTS CONTINUES TO SHOW BROAD UPPER LEVEL TROUGHING
REMAINING WELL-OFFSHORE AND AN UPPER LEVEL RIDGE AXIS OVER THE
ROCKIES TILTING INTO THE PACIFIC NORTHWEST. ENSEMBLES ARE
BEGINNING TO AGREE THAT THIS GENERAL PATTERN CONTINUES THROUGH
MID TO LATE NEXT WEEK, HOWEVER, THERE IS SOME UNCERTAINTY WITH
THE EXACT MAGNITUDE OF RIDGING OVER THE ROCKIES AND PLACEMENT OF
THE OFFSHORE TROUGH. THEREFORE, THERE IS STILL A WIDER SPREAD
OF POTENTIAL HIGH TEMPERATURES LATE NEXT WEEK ACROSS INTERIOR
VALLEYS, RANGING FROM THE MID 70S TO UPPER 80S. IN ANY SCENARIO,
NO PRECIPITATION IS FORECAST AS WE MAINTAIN A DRY SUMMERTIME
AIRMASS. -10
AVIATION...THROUGH 06Z SUNDAY
SOUTH TO SOUTHWEST FLOW ALOFT
CONTINUES AS AN UPPER LEVEL TROUGH MOVES OVER THE REGION. MVFR
CONDITIONS ARE BEING OBSERVED ALONG THE COAST WITH A 60-90%
CHANCE OF IFR/LIFR CONDITIONS TO FORM AT ANY HOUR THROUGH AT
LEAST 16Z SATURDAY, BECOMING MVFR ONCE AGAIN THROUGH THE
MAJORITY OF THE REST OF THE TAF PERIOD AFTER. FOR INLAND
LOCATIONS, MVFR CONDITIONS DUE TO MARINE STRATUS ARE EXPECTED TO
RETURN AROUND 10Z-12Z SATURDAY, IMPROVING TO VFR BY 18Z-21Z.
LIGHT AND VARIABLE WINDS ACROSS THE AIRSPACE WILL BECOME WEST TO
NORTHWEST AND INCREASE TO 6-8 KTS AFTER 18-21Z SATURDAY.
STARTING AROUND 09Z SATURDAY AND THROUGH AT LEAST 15Z SATURDAY,
MODELS ARE SHOWING AROUND A 10-15% CHANCE FOR ELEVATED
THUNDERSTORMS DEVELOPING ANYWHERE WITHIN THE WILLAMETTE
VALLEY, COAST RANGE, AND CASCADES. ANY THUNDERSTORMS THAT
DEVELOP COULD RESULT IN FREQUENT LIGHTNING, HEAVY RAIN, AND
GUSTY AND ERRATIC WINDS.
KPDX AND APPROACHES...VFR CONDITIONS WILL GIVE WAY TO MVFR
CONDITIONS AROUND 12Z-15Z SATURDAY, IMPROVING TO VFR BY 18Z-21Z.
THERE'S A 10-15% CHANCE OF ISOLATED THUNDERSTORMS BETWEEN 09Z-18Z
SATURDAY. NORTHWESTERLY WINDS AROUND 3-7 KT, STRONGEST IN THE
LATE AFTERNOON AND EARLY EVENING. -03/42
MARINE
NO SIGNIFICANT CHANGES IN THE OVERALL PATTERN AS HIGH
PRESSURE OFFSHORE WILL CONTINUE TO SUPPORT NORTH/NORTHWESTERLY
WINDS WITH GUSTS LESS THAN 21 KTS. SEAS ALSO EXPECTED TO REMAIN
AROUND 3-6 FT. THESE BENIGN CONDITIONS ARE EXPECTED ACROSS ALL
WATERS THROUGH AT LEAST THE START OF NEXT NEXT WEEK. -10/42
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
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