163
FXUS66 KPQR 260440
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
940 PM PDT FRI APR 25 2025
UPDATED AVIATION DISCUSSION
SYNOPSIS
UPPER LEVEL LOW OVER NORTHERN CALIFORNIA WILL SHIFT
EAST THROUGH THE EVENING INTO SATURDAY. THE POSITION IS
INCREASING SOUTHEASTERLY FLOW USHERING IN MOISTURE ALOFT.
GENERAL ONSHORE FLOW WILL CONTINUE THROUGH MID WEEK DESPITE A
RIDGE OF HIGH PRESSURE FORMING MONDAY. ANOTHER SHORT WAVE MOVES
IN ON TUESDAY WITH ANOTHER CHANCE FOR PRECIPITATION.
SHORT TERM...NOW THROUGH MONDAY NIGHT
CLOUDS ARE BEGINNING
TO DISSIPATE IN THE NORTHERN PORTIONS OF THE FORECAST AREA WHILE
THE SOUTHERN POTIONS REMAIN UNDER DENSE CLOUD COVER. THESE
CLOUDS HAVE BEEN AN INHIBITING FACTOR TO SIGNIFICANT DAYTIME
HEATING LIKE WE SAW YESTERDAY. HOWEVER, WHERE SKIES HAVE
CLEARED, SEEING ABOUT A DEGREE AN HOUR OF WARMING. TO THE SOUTH,
A LOW ALOFT IS SPINNING OVER NORTHERN CALIFORNIA. THIS LOW
CONTINUES TO BE THE MAIN WEATHER MAKER TODAY AS IT ENCOURAGES
SOUTHEASTERLY FLOW AND WRAP AROUND MOISTURE. WHILE RADAR HAS
SHOWED SHOWERS THROUGHOUT THE AREA, ACCUMULATION HAS BEEN
MINIMAL. THIS IS MAINLY DUE TO THE SIGNIFICANT AMOUNT OF DRY AIR
RIGHT AT THE SURFACE AND ABOVE 5000 FT. THE PRECIPITATION HAS
HAD THE OPPORTUNITY TO EVAPORATE BEFORE REACHING THE GROUND
(THIS IS CALLED VIRGA).
OVERNIGHT THE LOW WILL SHIFT EAST SLOWLY WHICH WILL ENHANCE THE
PRECIPITATION POTENTIAL MORE. BASED ON HIGH RESOLUTION MODELS,
THERE IS GOOD CONSENSUS IN PRECIPITATION FALLING ALONG EASTERN
LANE AND LINN COUNTIES THROUGH SATURDAY MORNING. ACCUMULATION
EXPECTED TO BE HIGHEST ALONG THE LEE SIDE OF THE CASCADES.
BECAUSE CONDITIONS WILL BE SHOWERY, EXACT ACCUMULATION IS
DIFFICULT TO NARROW DOWN. UNDER STRONGER SHOWERS WHERE THE
ATMOSPHERE IS MOIST ENOUGH, PRECIPITATION WILL BE HIGHER. IN
CONTRAST, THERE ARE MANY AREAS THAT WILL SEE LITTLE TO NO
ACCUMULATION. IN ADDITION TO THE PRECIPITATION, THE EAST-WEST
PRESSURE GRADIENT WILL REACH AROUND 10 MB. EXPECT GUSTY
WESTERLY WINDS THROUGH THE GORGE, ESPECIALLY IN THE UPPER HOOD
RIVER VALLEY.
ONSHORE FLOW PERSISTS THROUGH THE WEEK WHICH WILL KEEP
TEMPERATURES MODERATED.-MUESSLE
LONG TERM...TUESDAY THROUGH FRIDAY
THE WEAK RIDGE WILL BREAK
DOWN ON TUESDAY AS A ERODING SHORTWAVE TROUGH ADVECTS INLAND
FROM THE NORTHEAST PACIFIC. THIS SHORTWAVE WILL PRODUCE MORE
WIDESPREAD SHOWERS OVER SOUTHWEST WASHINGTON AND NORTHWEST
OREGON. THIS IS A FAIRLY FAST MOVING SYSTEM. HUMIDITY BETWEEN
850-250 MB WILL DRY SIGNIFICANTLY WHICH CAN BE OBSERVED IN
SOUNDINGS FROM THE AREA. THIS WILL LEAD TO LOWER HUMIDITY ALONG
THE MOUNTAINS AND CLEAR SKIES. ON WEDNESDAY, THE RIDGE WILL
INTENSIFY AND A THERMAL TROUGH WILL FORM ALONG THE COAST. WINDS
ALOFT (ABOVE 850 MB) WILL TRANSITION TO THE NORTHEAST BRINGING
IN WARMER AIR FROM EAST OF THE CASCADES. IN THE AFTERNOON THE
TROUGH WILL SHIFT EAST OF THE CASCADES, THEN BACK TO THE WEST
SIDE IN THE EVENING.
THE WILLAMETTE VALLEY TEMPERATURE FORECAST HAS FAIRLY GOOD
AGREEMENT IN THE LONG TERM. THE WARMEST OF THE NEXT WEEK WILL
BE THURSDAY (WHEN THE RIDGE IS AT IT'S PEAK). THE NBM SHOWS A
HIGH TEMPERATURE RANGE IN EUGENE OF 76-80 DEGREES F. ALONG THE
COAST, THAT RANGE IS IN THE UPPER 60S. WILL MENTION THOUGH THAT
THE POTENTIAL DOWNSLOPING EFFECTS OFF OF THE COAST RANGE COULD
CAUSE TEMPERATURES TO BE HIGHER AROUND TILLAMOOK. IN FACT, IN
HOOD RIVER, THE FORECAST IS SHOWING THE 25TH-75TH PERCENTILE OF
TEMPERATURES AT 80-82 DEGREES F WHICH IS INCREDIBLY NARROW.
-MUESSLE
AVIATION
VFR FLYING CONDITIONS CONTINUE ACROSS MUCH OF THE
REGION AS COVERAGE OF HIGH CLOUDS HAS INCREASED FROM THE EAST. A
LARGE UPPER-LEVEL LOW CONTINUES TO SPIN OVER INLAND CALIFORNIA,
ALTHOUGH RAIN SHOWERS WILL LIKELY REMAIN SOUTH OF THE REGION. THE
HIGHEST CHANCES, 20-40%, FOR RAIN WILL BE OVER THE CENTRAL OREGON
CASCADES, WITH LESS THAN A 15% CHANCE OF RAIN REACHING EUG, AND
LESS THAN 10% ELSEWHERE. THEREFORE, NO IMPACTS FROM LIGHT RAIN
SHOWERS ARE EXPECTED AT AREA TERMINALS. LOW-LEVEL CLOUD COVER WILL
OTHERWISE INCREASE ACROSS THE REGION, WITH MVFR CIGS FAVORED AT
ALL TERMINALS OVERNIGHT. AT INLAND SITES, CONFIDENCE IN MVFR CIGS
IS HIGHEST TO THE SOUTH, WITH A 60-80% CHANCE FOR CONTINUED MVFR
CIGS AT EUG THROUGH 18-20Z SAT. BOTH THE DURATION AND LIKELIHOOD
OF MVFR CIGS LESSEN TO THE NORTH, WITH THE SHORTEST DURATION IN
THE PORTLAND AREA BETWEEN 11-18Z SAT. WINDS OF 3-8 KT OUT OF THE
SOUTH TO SOUTHWEST THIS EVENING WILL TURN OUT OF THE NORTHWEST
AFTER 16-20Z SAT AT ALL WILLAMETTE VALLEY TERMINALS.
ALONG THE COAST, PERSISTENT MVFR CIGS ARE LIKELY FOR MUCH OF THE
PERIOD, AND AS INLAND, THERE IS HIGHER CONFIDENCE TO THE SOUTH.
AT ONP, MVFR CIGS ARE VERY LIKELY THROUGHOUT THE PERIOD, AND THERE
IS 40-60% CONFIDENCE IN CONTINUED IFR CIGS THROUGH 18-20Z SAT. TO
THE NORTH AT AST, IFR CIGS ARE EXPECTED OVERNIGHT, MOST LIKELY
FROM 09-14Z SAT, WITH MVFR CIGS OTHERWISE FAVORED THROUGH 20-22Z
SAT. A BRIEF IMPROVEMENT IN FLYING CONDITIONS AFTER 18-22Z SAT
WILL GIVE WAY TO RENEWED MVFR/IFR CONDITIONS AFTER 02-03Z SUN.
NORTHWEST WINDS AT 5-10 KT WILL CONTINUE THROUGH TONIGHT, BEFORE
INCREASING TO 10-15 KT WITH GUSTS TO 20 KT AFTER 18-22Z SAT.
PDX AND APPROACHES...VFR CONDITIONS EXPECTED TO CONTINUE INTO
TONIGHT BENEATH INCREASINGLY CLOUDY SKIES. THERE REMAINS A 40-60%
CHANCE OF MVFR CIGS AT 2-3 KFT AFTER 11-12Z SAT, CONTINUING
THROUGH MID-MORNING. VFR CONDITIONS WILL AGAIN BE FAVORED AFTER 18Z
SAT AS LOW CLOUDS DISSIPATE. NO VIS RESTRICTIONS ARE ANTICIPATED
THROUGHOUT THE PERIOD. WINDS AROUND 5 KT OUT OF THE SOUTHWEST
OVERNIGHT WILL TURN OUT OF THE WEST TO NORTHWEST, INCREASING TO
5-10 KT AFTER 16-18Z SAT. -PICARD
MARINE
WINDS GRADUALLY SHIFTING NORTHWEST THROUGH THIS
AFTERNOON, WITH WIND SPEEDS INCREASING BY TONIGHT. GUSTS MAY
APPROACH 25 KT BY LATE THIS AFTERNOON, PARTICULARLY IN THE OUTER
ZONES. THIS UPTICK IN WINDS IS COINCIDING WITH A BUILDING
WESTERLY SWELL, PUSHING COMBINED SEAS TOWARD 10 TO 11 FEET BY
SATURDAY. AS A RESULT, SMALL CRAFT ADVISORIES WILL BE IN EFFECT
FOR ALL WATERS BY THIS AFTERNOON, WITH CONDITIONS LIKELY
PERSISTING THROUGH AT LEAST SATURDAY. BY LATE SATURDAY NIGHT AND
INTO SUNDAY, BOTH WINDS AND SEASONS WILL BEGIN TO EASE AS HIGH
PRESSURE WEAKENS SLIGHTLY AND MOVES INLAND. THE START OF NEXT
WEEK LOOKS TO BE RATHER QUIET, WITH SEAS AROUND 5 TO 7 FEET AND
WIND GUSTS UNDER 20 KT. -HALL/JLIU
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 2 AM SATURDAY TO 2 AM PDT SUNDAY FOR
PZZ251>253.
SMALL CRAFT ADVISORY UNTIL 2 AM PDT SUNDAY FOR PZZ271>273.
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