578
FXUS66 KPQR 110608
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1108 PM PDT FRI APR 10 2026
UPDATED AVIATION DISCUSSION.
SYNOPSIS
UNSETTLED CONDITIONS CONTINUE THROUGH TODAY AS
BROAD SOUTHERLY FLOW AND BREAKS IN CLOUD COVER SUPPORT SCATTERED
SHOWERS AND THUNDERSTORMS, ESPECIALLY ACROSS THE OREGON
CASCADES AND ADJACENT FOOTHILLS. THUNDERSTORM CHANCES RETURN
SATURDAY AFTERNOON AND EVENING, WITH THE GREATEST COVERAGE OVER
THE CENTRAL OREGON CASCADES AND FOOTHILLS. COOLER CONDITIONS
DEVELOP SUNDAY INTO EARLY NEXT WEEK AS FLOW TURNS MORE WESTERLY
TO NORTHWESTERLY. ANOTHER SYSTEM MAY BRING WIDESPREAD
PRECIPITATION AND CASCADE SNOW BY THE MIDDLE OF NEXT WEEK.
SHORT TERM...NOW THROUGH SUNDAY NIGHT
AS OF MID-AFTERNOON, A
VERTICALLY STACKED LOW REMAINS POSITIONED OFF THE NORTHERN
CALIFORNIA COAST, MAINTAINING MOIST SOUTHERLY TO SOUTHEASTERLY
FLOW ACROSS THE REGION. THIS PATTERN CONTINUES TO SUPPORT
INCREASING INSTABILITY AND A TRANSITION TO MORE CONVECTIVE
CONDITIONS THROUGH THIS AFTERNOON AND EVENING. RECENT
OBSERVATIONS SHOW PARTIAL IN SOME AREAS, ALLOWING FOR SUFFICIENT
SURFACE HEATING TO SUPPORT THUNDERSTORM DEVELOPMENT WHERE CLOUD
COVER HAS THINNED.
EARLIER TODAY, STORM PREDICTION CENTER UPDATED THE DAY 1
CONVECTIVE OUTLOOK TO INCLUDE A MARGINAL RISK FOR SEVERE WEATHER
ACROSS PORTIONS OF THE WILLAMETTE VALLEY SOUTH OF WILSONVILLE,
INCLUDING THE SALEM, CORVALLIS/ALBANY, AND EUGENE/SPRINGFIELD
AREAS. THE CASCADE FOOTHILLS FROM MOLALLA SOUTHWARD, INCLUDING
SWEET HOME, ARE ALSO INCLUDED. WITHIN THIS AREA, THE PRIMARY
HAZARDS WITH ANY STRONG THUNDERSTORMS INCLUDE DAMAGING WINDS AND
LARGE HAIL OF 1 INCH OR GREATER IN DIAMETER. THIS CORRESPONDS
TO ROUGHLY A 5-15% CHANCE OF SEVERE HAZARDS OCCURRING WITHIN 25
MILES OF A POINT. AREAS OUTSIDE OF THE MARGINAL RISK STILL CARRY
A THUNDERSTORM RISK THIS AFTERNOON AND EVENING, THOUGH THE
PROBABILITY OF SEVERE THUNDERSTORMS REMAINS BELOW 5%.
RECENT MODEL SOUNDINGS CONTINUE TO SUGGEST 400-850 J/KG OF
MUCAPE THIS AFTERNOON, WITH EFFECTIVE SHEAR AROUND 20-25 KT.
THESE VALUES ARE SUFFICIENT TO SUPPORT ISOLATED THUNDERSTORMS,
WITH THE POTENTIAL FOR A FEW MULTICELL STRUCTURES, MAINLY SOUTH
OF THE PORTLAND METRO WHERE INSTABILITY IS GREATER. OUTSIDE OF
ANY STRONGER STORMS, THE PRIMARY IMPACTS WILL BE BRIEF HEAVY
RAINFALL, CLOUD-TO-GROUND LIGHTNING, SMALL HAIL, AND LOCALIZED
GUSTY OUTFLOW WINDS.
IN TERMS OF TIMING, CONVECTIVE INITIATION IS EXPECTED TO FOCUS
INITIALLY OVER LANE COUNTY AND THE CENTRAL OREGON CASCADES,
WHERE ACTIVITY WILL DEVELOP THROUGH THE MID TO LATE AFTERNOON.
COVERAGE MAY EXPAND NORTHWARD ALONG THE CASCADES AND INTO
PORTIONS OF THE I-5 CORRIDOR THROUGH THE LATE AFTERNOON INTO
EARLY EVENING. THERE REMAINS SOME UNCERTAINTY REGARDING WESTWARD
EXTENT, WHICH WILL DEPEND ON CLOUD COVER TRENDS, INSTABILITY,
AND THE EXACT ORIENTATION OF FLOW ALOFT. AREAS THAT MAINTAIN
GREATER BREAKS IN CLOUD COVER WILL HAVE A HIGHER LIKELIHOOD OF
SEEING THUNDERSTORMS DRIFT WEST OF THE CASCADES. THUNDERSTORM
PROBABILITIES GENERALLY RANGE FROM 15-40% ACROSS MUCH OF
NORTHWEST OREGON THIS AFTERNOON AND EVENING, WITH THE HIGHEST
CHANCES OVER THE CENTRAL OREGON CASCADES AND FOOTHILLS.
ACTIVITY SHOULD GRADUALLY DIMINISH LATER THIS EVENING WITH THE
LOSS OF DAYTIME HEATING, TRANSITIONING TO SCATTERED SHOWERS
OVERNIGHT.
BY SATURDAY, ENSEMBLE GUIDANCE SUPPORTS CONTINUED CYCLONIC FLOW
AND ANOTHER ROUND OF SCATTERED SHOWERS AND THUNDERSTORMS AS
ANOTHER LOW DEVELOPS TO THE SOUTH. INSTABILITY APPEARS SOMEWHAT
REDUCED COMPARED TO TODAY, WITH MUCAPE GENERALLY IN THE 300-600
J/KG RANGE, THOUGH SUFFICIENT FOR ISOLATED THUNDERSTORMS.
THUNDERSTORM PROBABILITIES RANGE FROM 15-30%, HIGHEST ACROSS THE
CASCADES AND FOOTHILLS.
BY SUNDAY, THE UPPER-LEVEL LOW SHIFTS INLAND, TRANSITIONING THE
REGION TO MORE WESTERLY FLOW AND EFFECTIVELY ENDING MOST
THUNDERSTORM POTENTIAL OUTSIDE OF A SLIGHT CHANCE (AROUND 15%)
OVER THE FAR SOUTHERN PORTION OF THE LANE COUNTY CASCADES.
SHOWERS PERSIST UNDER WRAP-AROUND MOISTURE, WITH POPS OF 60-90%
OVER THE CASCADES AND FOOTHILLS AND 30-60% ELSEWHERE.
TEMPERATURES COOL BACK INTO THE UPPER 50S TO LOW 60S INLAND,
CLOSER TO SEASONAL NORMALS.
LONG TERM...MONDAY THROUGH THURSDAY
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 50-90% CHANCE OF SHOWERS, HIGHEST
ACROSS THE CASCADES. TEMPERATURES REMAIN NEAR TO SLIGHTLY BELOW
NORMAL.
SHOWER ACTIVITY DECREASES MONDAY NIGHT INTO TUESDAY AS A
TRANSIENT RIDGE BRIEFLY BUILDS OVERHEAD. ATTENTION THEN TURNS TO
THE NEXT PACIFIC FRONTAL SYSTEM EXPECTED BETWEEN LATE TUESDAY
AND WEDNESDAY. WHILE TIMING DIFFERENCES REMAIN, CONFIDENCE IS
INCREASING IN A RETURN TO WIDESPREAD PRECIPITATION DURING THIS
PERIOD.
COOLING 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 60-80% CHANCE OF 6+ INCHES OF SNOWFALL AT THE
CASCADE PASSES OVER 48 HOURS (BETWEEN TUESDAY AND THURSDAY
AFTERNOON). AS FOR 12+ INCHES OF SNOWFALL, THERE IS A 40-60%
CHANCE DURING THE AFOREMENTIONED TIME. 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. CURRENT GUIDANCE SUGGESTS A 30-60% CHANCE
OF FROST (LESS THAN 36 F) IN THE UPPER HOOD RIVER VALLEY TUESDAY
NIGHT INTO WEDNESDAY MORNING. AS FOR WEDNESDAY NIGHT INTO
THURSDAY MORNING, GUIDANCE SUGGESTS A 30-70% CHANCE OF
WIDESPREAD FROST ACROSS MOST INLAND LOCATIONS. THURSDAY MORNING
MAY BE MUCH COLDER, WITH A 5-30% CHANCE OF FREEZING TEMPERATURES
ACROSS MOST INLAND LOCATIONS, EXCEPT FOR A 50-80% CHANCE IN THE
UPPER HOOD RIVER VALLEY (CHANCES FROM ODELL TO PARKDALE).
~12
AVIATION
UPPER LEVEL LOW PRESSURE OFF THE NORTHERN CALIFORNIA
AND OREGON COASTS CONTINUES TO BE THE MAIN DRIVER IN THE WEATHER
PATTERN HEADING INTO THE WEEKEND. MOIST, SOUTHERLY FLOW CONTINUES
TO SUPPORT LIGHT RAIN OVER PORTIONS OF NORTHWEST OREGON AND
SOUTHWEST WASHINGTON. THUNDERSTORM CHANCES HAVE SUBSIDED WITH THE
LACK OF INSTABILITY. LIGHT RAIN WILL CONTINUE THROUGH THE
OVERNIGHT AND THROUGH MUCH OF THE DAY SATURDAY AS THE UPPER LEVEL
LOW CONTINUES TO SHIFT NORTHWARD.
VFR CONDITIONS PREVAIL ACROSS MUCH OF THE AREA BUT GUIDANCE
SUGGESTS MVFR CIGS DEVELOPING OVER THE NEXT FEW HOURS AND
PERSISTING THROUGH SATURDAY MORNING.
THERE IS ANOTHER CHANCE FOR THUNDERSTORMS SATURDAY AFTERNOON.
CHANCES ARE HIGHEST IN THE SOUTHERN WILLAMETTE VALLEY AT 25-30%
AROUND KEUG AND 15-20% ELSEWHERE.
KPDX AND APPROACHES...VFR CONDITIONS EXPECTED TO TREND TOWARD MVFR
AS CIGS LOWER TO AROUND 2000 FEET. LIGHT RAIN CONTINUES TONIGHT
AND INTO SATURDAY MORNING. LOW 15-20% CHANCE FOR THUNDERSTORMS
SATURDAY AFTERNOON. -19
MARINE
OVERALL CONDITIONS REMAIN RATHER BENIGN THROUGH THE
WEEKEND AS SEAS REMAIN IN THE 4 TO 7 FOOT RANGE WITH WINDS BELOW
20 KT. THE NEXT SEVERAL DAYS WILL SEE SOUTH/SOUTHWEST WINDS
SLOWLY BECOME MORE NORTH/NORTHWEST BY SATURDAY AND THESE WINDS
ARE EXPECTED TO PERSIST THROUGH AT LEAST MONDAY NIGHT. LOOKING
TOWARDS THE MIDDLE OF NEXT WEEK (TUESDAY/WEDNESDAY) A DECENTLY
ROBUST FRONTAL BOUNDARY WILL LIKELY (40-60% CHANCE) RESULT IN
SMALL CRAFT ADVISORY WIND GUSTS AND SEAS AROUND 7 TO 10 FEET.
IT'S WORTH NOTING THAT THERE IS A 5-10% CHANCE OF THUNDERSTORMS
THIS AFTERNOON AND SATURDAY AFTERNOON ACROSS ALL WATERS FROM
THE SOUTHEAST. ANY THUNDERSTORMS THAT DO DEVELOP COULD PRODUCE
LIGHTNING, HAIL, GUSTY AND ERRATIC WINDS AS WELL AS A LESS THAN
2% CHANCE FOR A FUNNEL CLOUD OR WATERSPOUT. /42-99
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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