666
FXUS66 KPQR 120333 AAA
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
833 PM PDT SAT APR 11 2026
UPDATED AVIATION DISCUSSION
SYNOPSIS
UNSETTLED CONDITIONS CONTINUE THROUGH TODAY WITH
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS DEVELOPING THIS
AFTERNOON AND EVENING, ESPECIALLY ACROSS THE CASCADES AND
ADJACENT FOOTHILLS. CONDITIONS TURN COOLER SUNDAY INTO EARLY
NEXT WEEK AS FLOW BECOMES MORE WEST TO NORTHWESTERLY, THOUGH
SHOWERS PERSIST. CONFIDENCE CONTINUES TO INCREASE IN A STRONGER
SYSTEM ARRIVING MIDWEEK, BRINGING WIDESPREAD PRECIPITATION AND A
SHIFT TOWARD CASCADE SNOW IMPACTS AND COOLER OVERNIGHT
TEMPERATURES.
SHORT TERM...NOW THROUGH SUNDAY NIGHT
AS OF MID-AFTERNOON,
A FEW SCATTERED SHOWERS CONTINUE ACROSS NORTHWEST OREGON AND
SOUTHWEST WASHINGTON AS A SHORTWAVE LIFTS NORTH THROUGH
WASHINGTON. COVERAGE HAS BECOME MORE INTERMITTENT COMPARED TO
THIS MORNING, PARTICULARLY ACROSS PORTIONS OF THE WILLAMETTE
VALLEY INTO SOUTHWEST WASHINGTON, THOUGH ADDITIONAL DEVELOPMENT
IS EXPECTED THROUGH THE AFTERNOON.
ATTENTION REMAINS ON THUNDERSTORM POTENTIAL THIS AFTERNOON AND
EVENING. THE BROADER PATTERN REMAINS FAVORABLE, WITH A CLOSED
LOW OFFSHORE MAINTAINING MOIST SOUTHERLY FLOW AND PRECIPITABLE
WATER VALUES AROUND 0.7 TO 0.9 INCHES. THIS SETUP CONTINUES TO
SUPPORT AT LEAST ISOLATED THUNDERSTORM DEVELOPMENT, PARTICULARLY
OVER ELEVATED TERRAIN. INSTABILITY APPEARS SOMEWHAT REDUCED
COMPARED TO YESTERDAY, WITH GUIDANCE SUGGESTING PEAK MUCAPE
VALUES IN THE 300 TO 600 J/KG RANGE THIS AFTERNOON. EFFECTIVE
SHEAR REMAINS MODEST AROUND 20 TO 25 KT. WHILE THIS WILL LIKELY
SUPPORT CONVECTION, LIMITED ORGANIZATION IS EXPECTED. THE
PRIMARY UNCERTAINTY CONTINUES TO BE THE DEGREE OF CLOUD COVER
AND RESULTING SURFACE HEATING. AREAS THAT HAVE SEEN MORE BREAKS
IN THE CLOUD COVER WILL BE MORE FAVORABLE FOR THUNDERSTORM
DEVELOPMENT, WHILE MORE PERSISTENT CLOUDINESS MAY LIMIT
INSTABILITY AND KEEP ACTIVITY PRIMARILY AS SHOWERS. THUNDERSTORM
CHANCES THIS AFTERNOON AND EVENING GENERALLY RANGE FROM 15-35%
ALONG THE I-5 CORRIDOR AND IN ELEVATED TERRAIN, WITH THE HIGHEST
PROBABILITIES OVER THE CASCADES, COAST RANGE, AND ADJACENT
FOOTHILLS WHERE OROGRAPHIC LIFT WILL AID INITIATION. STORMS THAT
DEVELOP WILL BE CAPABLE OF PRODUCING LIGHTNING, SMALL HAIL,
BRIEF HEAVY RAINFALL, AND LOCALIZED GUSTY OR ERRATIC WINDS. AS
OF 2 PM THIS AFTERNOON, THUNDERSTORMS HAVE BEGUN TO DEVELOP IN
SOUTHWEST OREGON, OFTEN WEAKENING AS A FEW OF THEM DRIFT
NORTHEASTWARD TOWARDS THE LANE COUNTY CASCADES AND ADJACENT
FOOTHILLS.
ON SUNDAY, THE UPPER-LEVEL LOW SHIFTS INLAND, TRANSITIONING TO
MORE WESTERLY FLOW AND EFFECTIVELY ENDING MOST THUNDERSTORM
POTENTIAL OUTSIDE OF A SLIGHT CHANCE (AROUND 10-15%) OVER THE
OREGON CASCADES CREST. SHOWERS WILL PERSIST UNDER WRAP-AROUND
MOISTURE, WITH PRECIPITATION PROBABILITIES OF 60-95% OVER MOST OF
NORTHWEST OREGON AND ELEVATED AREAS OF SOUTHWEST WASHINGTON.
NORTH OF TILLAMOOK INTO THE WASHINGTON COAST IS THE MAIN
EXCEPTION, WITH JUST A 30-50% CHANCE OF PRECIPITATION.
TEMPERATURES COOL INTO THE 50S TO LOW 60S INLAND, CLOSER TO
SEASONAL NORMALS (WARMEST TO THE NORTH).
LONG TERM...MONDAY THROUGH FRIDAY
ENSEMBLE GUIDANCE
INDICATES A TRANSITION TO BROAD WEST-NORTHWEST TO NORTHWEST
FLOW ALOFT EARLY NEXT WEEK. A WEAK EMBEDDED SHORTWAVE IS
EXPECTED TO MOVE THROUGH MONDAY, MAINTAINING A 60-90% CHANCE OF
SHOWERS, HIGHEST ACROSS THE CASCADES AND FOOTHILLS, WITH 24 HOUR
RAINFALL TOTALS RANGING FROM 0.1 TO 0.3 INCHES IN THE LOWLANDS
AND 0.3 TO 0.7 INCHES IN THE CASCADES AND FOOTHILLS.
TEMPERATURES REMAIN NEAR TO SLIGHTLY BELOW SEASONAL AVERAGES.
SHOWER ACTIVITY DECREASES MONDAY NIGHT INTO TUESDAY AS A
TRANSIENT RIDGE BRIEFLY BUILDS OVERHEAD. ATTENTION THEN TURNS TO
A STRONGER PACIFIC FRONTAL SYSTEM EXPECTED BETWEEN LATE TUESDAY
AND EARLY WEDNESDAY. CONFIDENCE CONTINUES TO INCREASE THAT THIS
SYSTEM WILL BRING WIDESPREAD PRECIPITATION ACROSS THE REGION.
24 HOUR RAINFALL TOTALS STILL REMAIN UNCERTAIN FROM TUESDAY TO
WEDNESDAY EVENING, WITH TOTALS AROUND 0.2 TO 1.0 INCHES IN THE
LOWLANDS AND 0.5 TO 2.5 INCHES IN THE MOUNTAINS.
COOL TEMPERATURES ASSOCIATED WITH THIS SYSTEM WILL LOWER SNOW
LEVELS TO NEAR OR BELOW CASCADE PASS ELEVATIONS, RAISING THE
POTENTIAL FOR TRAVEL IMPACTS. CURRENT PROBABILISTIC GUIDANCE
INDICATES A 85-95% CHANCE OF 6+ INCHES OF SNOWFALL AT THE
CASCADE PASSES BETWEEN TUESDAY AND THURSDAY EVENING (48 HOURS),
WITH A 40-70% CHANCE OF 12 INCHES OR MORE. IF THESE TRENDS
CONTINUE, WINTER WEATHER HIGHLIGHTS MAY BECOME NECESSARY FOR
PORTIONS OF THE CASCADES. IN ADDITION, COOLER AND POTENTIALLY
CLEARER CONDITIONS BEHIND THE SYSTEM MAY INTRODUCE RENEWED FROST
CONCERNS ACROSS PORTIONS OF THE INTERIOR VALLEYS BY MID TO LATE
WEEK. THE FIRST OPPORTUNITY APPEARS WEDNESDAY NIGHT INTO
THURSDAY, WITH A 30-70% CHANCE OF FROST ACROSS MUCH OF THE
INTERIOR LOWLANDS (LOWEST AROUND THE PORTLAND-VANCOUVER METRO) AND
A 50-90% CHANCE OF FREEZING TEMPERATURES IN THE UPPER HOOD
RIVER VALLEY (CHANCES FROM ODELL TO PARKDALE). SIMILAR
CONDITIONS MAY DEVELOP AGAIN THURSDAY NIGHT INTO FRIDAY MORNING,
BUT WITH SLIGHTLY LOWER CHANCES.
~12
AVIATION
SOUTH TO SOUTHEAST FLOW ALOFT AS A LOW PRESSURE SYSTEM
OFF THE NORTHERN CALIFORNIA COAST MOVES ONSHORE TONIGHT.
PREDOMINATELY VFR CONDITIONS EXPECTED THIS EVENING, WITH PERIODS
OF MVFR CONDITIONS OCCURRING WITH MODERATE RAINFALL ASSOCIATED
WITH A BAND OF SHOWERS LIFTING NORTH ACROSS NW OREGON. CHANCES FOR
THUNDERSTORMS HAVE DECREASED TO BELOW 10% FOR THE REMAINDER OF THE
EVENING. RAINFALL IS ALSO EXPECTED TO DECREASE THIS EVENING WITH
MOSTLY DRY CONDITIONS BETWEEN 06-12Z SUNDAY. CHANCES FOR
WIDESPREAD MVFR BEGIN TO INCREASE AROUND 09-12Z SUNDAY AS STRATUS
DEVELOPS AND CIGS LOWER. LOWER FLIGHT CONDITIONS OF IFR TO MVFR
ARE LIKELY TO PERSIST THROUGH SUNDAY MORNING. ANOTHER ROUND OF
SHOWERS IS EXPECTED TO SPREAD ACROSS THE AREA ON SUNDAY.
KPDX AND APPROACHES...VFR CONDITIONS EXPECTED TO CONTINUE THROUGH
AT LEAST 10Z SUNDAY. LIGHT RAIN SHOWERS POSSIBLE THROUGH 06Z THIS
EVENING WITH BRIEF PERIOD OF MVFR. CHANCES FOR MVFR CIGS INCREASE
TO AROUND 40% AFTER 12Z SUNDAY, FOLLOWED BY ANOTHER ROUND OF
WIDESPREAD SHOWERS THROUGH SUN AFTERNOON. VARIABLE WINDS BECOME
MAINLY NORTHWEST THROUGH SUNDAY MORNING. /DH
MARINE
RATHER BENIGN CONDITIONS EXPECTED THROUGH THE WEEKEND
AS FAR AS THE SEA STATE AND WINDS ARE CONCERNED, WITH SIGNIFICANT
WAVE HEIGHTS HOLDING IN THE 4 TO 7 FOOT RANGE WITH WINDS GUSTS
BELOW 20 KNOTS ACROSS THE INNER AND OUTER WATERS. SOUTH/SOUTHWEST
WINDS SLOWLY BECOME MORE NORTH/NORTHWEST THIS EVENING WITH
NORTHERLY WINDS PERSISTING THROUGH AT LEAST MONDAY NIGHT. THE NEXT
PERIOD OF CONCERN IS WITH A DECENTLY ROBUST FRONTAL BOUNDARY
TUESDAY INTO WEDNESDAY WHICH WILL LIKELY (75-85% CHANCE) RESULT
IN SMALL CRAFT ADVISORY WIND GUSTS OVER 21 KTS AND SEAS BUILDING
TO AROUND 7 TO 10 FEET. WAVE HEIGHTS AND WINDS THEN SLOWLY
DECREASE INTO THE END OF THE WEEK. -03/99
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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