236
FXUS66 KPQR 140433 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
933 PM PDT SAT SEP 13 2025
UPDATED AVIATION AND MARINE DISCUSSIONS.
SYNOPSIS
OUR NEXT FRONTAL SYSTEM RAPIDLY APPROACHES THE
REGION MARKING THE START OF A FAIRLY PROGRESSIVE WEATHER PATTERN
THROUGH NEXT WEEK. AFTER A BAND OF WIDESPREAD RAIN TONIGHT AND
SHOWERS ON SUNDAY, CONDITIONS DRY OUT AND WARM UP AGAIN EARLY
NEXT WEEK. THERE CONTINUES TO A WINDOW FOR OFFSHORE WINDS MONDAY
NIGHT THROUGH TUESDAY. ANOTHER WEAK FRONT RETURNS ONSHORE FLOW
AND PRECIPITATION CHANCES MID-WEEK.
SHORT TERM...NOW THROUGH MONDAY NIGHT
LATE THIS AFTERNOON
SATELLITE IMAGERY DEPICTS OUR INCOMING FRONTAL BOUNDARY
BEGINNING TO MOVE TOWARDS THE COASTLINE HERALDING THE END TO THE
RATHER PLEASANT CONDITIONS WE'VE SEEN TODAY. CONFIDENCE IS HIGH
(80-90%) THE INITIAL RAINFALL BAND MAKES LANDFALL LATE IN THE
EVENING BEFORE MOVING INTO THE WILLAMETTE VALLEY LATE OVERNIGHT.
WIDESPREAD RAIN SHOWERS PERSIST SUNDAY MORNING AS THE AXIS OF
THE SHORTWAVE TROUGH SWINGS THROUGH WESTERN OREGON AND SOUTHWEST
WASHINGTON. WHILE PRECIPITATION ALONG THE IMMEDIATE FRONTAL
BOUNDARY MAY BE MORE STRATIFORM IN NATURE, RAINFALL QUICKLY
TRANSITIONS TO LINGERING SHOWERS BY THE MIDDAY HOURS. IT'S WORTH
NOTING A FEW EMBEDDED THUNDERSTORMS CAN'T BE RULED OUT RIGHT
ALONG THE FRONTAL AS IT MOVING INTO THE COASTAL AREAS
- SOME LIGHTNING HAS ALREADY BE OBSERVED OVER THE EASTERN
PACIFIC THIS AFTERNOON. THE LATEST FORECAST RAINFALL TOTALS FROM
LATE SATURDAY EVENING THROUGH SUNDAY EVENING ARE FORECAST TO BE
IN THE 0.15-0.35" RANGE ACROSS MOST INTERIOR VALLEYS,
0.40-0.80" ALONG THE COAST, AND 0.30-0.60" ACROSS THE COAST
RANGE, WILLAPA HILLS, AND CASCADES WITH THE HIGHEST RELATIVE
AMOUNTS ON THE WESTERN SLOPES OF THESE TERRAIN FEATURES.
FORTUNATELY CONFIDENCE IN THESE TOTALS HAVE INCREASED AS MOST
MODEL GUIDANCE HAS TRENDED INTO AGREEMENT
BY SUNDAY EVENING, THE FRONT FURTHER WEAKENS AND RAPIDLY EXITS
TO THE EAST ALLOWING ANY LINGERING SHOWER ACTIVITY TO TAPER OFF
OVERNIGHT INTO EARLY MONDAY MORNING. SHORTWAVE RIDGING RETURNS
ON MONDAY AS WILL DRIER CONDITIONS AND CLEARING SKIES BY MONDAY
AFTERNOON. EXPECT HIGH TEMPERATURES TO JUMP INTO THE MID 70S
ACROSS THE INLAND VALLEYS WITH MID TO UPPER 60S ALONG THE COAST,
COAST RANGE, AND CASCADES - RIGHT AROUND NORMAL FOR EARLY
SEPTEMBER. -SCHULDT
LONG TERM...TUESDAY THROUGH FRIDAY
THERE CONTINUES TO BE
EXCELLENT AGREEMENT IN THE RETURN OF AND UPPER-LEVEL RIDGE
MONDAY NIGHT INTO TUESDAY. THIS FEATURE WILL BE IN ADDITION TO
A NEAR SURFACE THERMAL TROUGH AMPLIFYING ACROSS WESTERN OREGON
WITH HIGHER PRESSURE EAST OF THE CASCADES, LEADING TO AN
OFFSHORE FLOW WIND PATTERN AND A SHARP SPIKE IN HIGH
TEMPERATURES. AFTERNOON HIGHS ON TUESDAY ARE FORECAST IN THE MID
80S ACROSS MOST INTERIOR VALLEYS WITH UPPER 60S TO MID 70S
ALONG THE COAST. BEYOND THE RISE IN TEMPERATURES, THE THERMAL
TROUGH IS ALSO EXPECTED TO FACILITATE A -4 TO -5 MB PRESSURE
GRADIENT FROM KTTD TO KDLS TUESDAY MORNING YIELDING BREEZY EAST
WINDS THROUGH THE COLUMBIA RIVER GORGE AND OTHER CASCADES GAPS
WITH GUSTS UP TO 25-35 MPH EAST OF TROUTDALE. FOR OUR TYPICALLY
WINDIEST SPOTS LIKE THREE CORNERS ROCK AND CROWN POINT IN THE
GORGE CAN'T RULE OUT A FEW ISOLATED GUSTS CLOSER TO 40 MPH
TUESDAY MORNING BEFORE THE PRESSURE GRADIENT WEAKENS. IF THERE'S
ANY SILVER LINING THE HIGHEST WINDS AND LOWEST RELATIVE HUMIDITY
WON'T OVERLAP. THIS OFFSHORE FLOW PATTERN LOOKS BRIEF AT LEAST,
SINCE THE THERMAL TROUGH BREAKS DOWN TUESDAY NIGHT.
WEDNESDAY ONSHORE FLOW RETURNS AND MOST ENSEMBLE MEMBERS ARE IN
AGREEMENT OF AN UPPER LEVEL TROUGH IN THE NORTHEAST PACIFIC
APPROACHING BRITISH COLUMBIA. A WEAK FRONT ASSOCIATED WITH THIS
SYSTEM WILL SWING THROUGH THE PACIFIC NORTHWEST AND RETURN
CHANCES (20-40%) FOR RAIN SHOWERS, WITH THE HIGHEST CHANCES
ALONG THE COAST AND SOUTHWEST WASHINGTON. FORECAST CONFIDENCE
DECREASES THURSDAY TO FRIDAY AS ENSEMBLE GUIDANCE STRUGGLES WITH
THE EXACT PROGRESSION OF THE UPPER LEVEL PATTERN. MOST
ENSEMBLES STILL MAINTAIN GENERAL TROUGHING OVER THE AREA,
HOWEVER, THERE IS HIGH UNCERTAINTY WITH THE EXACT MAGNITUDE,
TRACK, AND TIMING OF THE TROUGH. -SCHULDT/ALVIZ
AVIATION
COLD FRONT MOVES IN THIS EVENING BRINGING WIDESPREAD
SHOWERS AND SOUTHWESTERLY FLOW. THUNDERSTORMS ARE ALREADY FORMING
OFF OF THE SHORE OF NEWPORT WHICH WILL BE THE HAZARDOUS WEATHER
COMPONENT OF THE FORECAST. THERE IS A 15-20% CHANCE OF
THUNDERSTORMS THROUGHOUT THE AREA FROM I-5 WESTWARD, WITH THE
HIGHEST PROBABILITY, AND CONFIDENCE ALONG THE COAST, AND COAST
RANGE. MVFR CIGS AND PERIODS OF MVFR VIS WILL BE PRESENT
THROUGHOUT THE FORECAST AREA THOUGH WILL SLOWLY LIFT THROUGH THE
AFTERNOON AFTER 17Z SUN AS RAIN EASES. AFTER 00Z MON, WINDS WILL
BECOME NORTH TO NORTHWESTERLY.
KPDX AND APPROACHES...THE COLD FRONT WILL PUSH EASTWARD THROUGH
THE NIGHT WHICH WILL INCREASE CONVECTION THROUGH THE NEXT 12
HOURS. THUNDERSTORMS MAY BE PRESENT IN THE AREA, BUT THE TERMINAL
WILL SIT RIGHT ALONG THE BOUNDARY OF RISK. THERE IS AROUND A 10%
CHANCE OF THUNDERSTORMS, BUT CONFIDENCE IS LOW. GUSTY OUTFLOW
WINDS EXPECTED IN THUNDERSTORMS OR HEAVIER SHOWERS. -MUESSLE
MARINE
A COLD FRONT MOVES OVER THE WATERS TONIGHT AND WILL
MOVE ACROSS ALL WATERS THROUGH SUNDAY MORNING. THUNDERSTORMS HAVE
BEGUN FORMING JUST SOUTH OF PZZ273 AND ARE MOVING NORTHEASTERLY.
SOUTHERLY WINDS HAVE BEGUN TO INCREASE PERIODICALLY WITH GUSTS
UP TO 20 KT BUT ARE NOT WIDESPREAD. THERE MAY BE OCCASIONAL
GUSTS UP TO 25 KT FOR THE FAR OUTER WATERS AROUND 40-60 NM AWAY
FROM THE COAST, BUT NOT EXPECTED TO BE WIDESPREAD ENOUGH TO
WARRANT A SMALL CRAFT ADVISORY. SEAS 6-8 FEET AT 10-13 SECONDS
EXPECTED THROUGH THE WEEKEND AS A NORTHWESTERLY SWELL MOVES INTO
THE WATERS.
HIGH PRESSURE RETURNS OVER THE WATERS LATE SUNDAY WHICH WILL
RESULT IN A NORTHERLY WIND REVERSAL. LATE MONDAY INTO EARLY
TUESDAY, WEAK OFFSHORE FLOW IS EXPECTED TO DEVELOP, BUT THIS WILL
BE SHORT LIVED AS THE NEXT LOW PRESSURE SYSTEM WILL APPROACH THE
REGION TUESDAY/WEDNESDAY. AS THE SYSTEM APPROACHES, WINDS BECOME
WEST TO NORTHWEST AND WILL INCREASE AND COULD RESULT IN GUSTS UP
25 KT. WHILE CONDITIONS DO NOT LOOK FAVORABLE FOR SMALL CRAFT
CONDITIONS, WILL CONTINUE TO MONITOR WE ARE SLOWLY TRANSITIONING
TO A MORE FALL/WINTER-LIKE PATTERN. -42/HEC
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
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