488
FXUS66 KPQR 151730
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1030 AM PDT SAT AUG 15 2026
.UPDATED AVIATION DISCUSSION.
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 MORNING 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 18Z SUNDAY
WIDESPREAD MARINE STRATUS WEST
OF THE CASCADES CONTINUES TO SUPPORT LOW-END MVFR CIGS AT
1.5-2 KFT ACROSS THE AIRSPACE LATE THIS MORNING. MODEST CLEARING
WILL SEE A TREND TO VFR CIGS INLAND BY 19-21Z SAT AND HIGH-END
MVFR CIGS WITH A 40-50% CHANCE OF VFR CIGS AT COASTAL TERMINALS
BY 21-23Z SAT. ISOLATED RAIN SHOWERS HAVE LARGELY DISSIPATED
ASIDE FROM ALONG THE CASCADES, WITH THE CHANCES FOR RAIN OR
THUNDER NOW AT 10% OR LESS WEST OF THE MOUNTAINS. OTHERWISE,
HAZY SKIES MAY CONTINUE TO RESTRICT SLANTWISE VIS WHILE TERMINAL
OBSERVATIONS MAINTAIN 7-10 SM AT THE SURFACE. LIGHT WINDS THIS
MORNING WILL BUILD TO 5-10 KT OUT OF THE NORTHWEST THIS
AFTERNOON, THEN EASE BELOW 5 KT TONIGHT.
KPDX AND APPROACHES...LOW-END MVFR CIGS BELOW 2 KFT ARE EXPECTED
TO TREND TO VFR AS SKIES CLEAR AND CLOUD BASES LIFT, WITH A 50%
CHANCE OF VFR CONDITIONS BY 20Z SAT. WEST TO NORTHWEST WINDS
EXPECTED THROUGHOUT THE PERIOD, INCREASING TO AROUND 5 KT THIS
AFTERNOON, THEN EASING TONIGHT. -36
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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