313
FXUS66 KPQR 252203
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
303 PM PDT FRI APR 25 2025
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
MORNING MARINE MVFR CLOUDS HAVE MOSTLY DISSIPATED
THROUGHOUT THE AREA, AND WE'RE CURRENTLY SEEING VFR CONDITIONS
THROUGHOUT MOST OF THE AREA. FOR MOST TERMINALS, VFR CONDITIONS
PERSIST UNTIL AROUND 10-12Z SAT, WHEN MVFR CIGS RETURN WITH 40-50%
CONFIDENCE. THE EXCEPTION WILL BE COASTAL TERMINALS (KAST, KONP).
EXPECTING MVFR CLOUD COVER TO BE INTERMITTENT THROUGHOUT THE
DAY, WITH AN 80% CHANCE OF IFR CIGS DEVELOPING AT SOUTHERN
COASTAL TERMINALS AFTER 03Z SAT. IFR CIGS REMAIN THERE
THROUGHOUT FRIDAY NIGHT.
A FEW WEAK SHOWERS BEGIN PUSHING IN TO THE SOUTHERNMOST TERMINALS
(KONP, KEUG) AROUND 21-23Z FRI. GENERALLY WESTERLY WINDS WITH
GUSTS UP TO 10 KTS AT ALL TERMINALS FRIDAY AFTERNOON.
PDX AND APPROACHES...VFR CONDITIONS EXPECTED THROUGHOUT MOST OF
DAYTIME HOURS FRIDAY. MVFR CIGS RETURN WITH 50% CONFIDENCE AFTER
11Z SAT. NORTHWESTERLY GUSTS UP TO 10 KTS POSSIBLE FROM 1Z SAT
ONWARDS, DECREASING AGAIN GOING INTO FRIDAY NIGHT. -JLIU
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.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSPORTLAND
X.COM/NWSPORTLAND
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page