837
FXUS66 KPQR 132214
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
314 PM PDT SAT SEP 13 2025
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/ALVIS
AVIATION
CURRENTLY, WIDESPREAD VFR ACROSS THE AIRSPACE.
HOWEVER, AN INCOMING COLD FRONT AROUND 06Z-08Z SUNDAY, WILL BRING
LIGHT SHOWERS AND MVFR TO LIFR CONDITIONS TO THE COAST. SHOWERS
AND MVFR/IFR CONDITIONS EXPECTED INLAND STARTING AROUND 10Z-12Z
SUNDAY. ALONG WITH THE FRONT, THERE IS AN INCREASE IN THUNDERSTORM
PROBABILITY, FROM 04Z-12Z SUNDAY THERE IS A 10-20% PROBABILITY
FOR THUNDERSTORMS ALONG THE COAST. INLAND LOCATIONS WILL SEE A
10-20% PROBABILITY FOR THUNDERSTORMS FROM 06Z-15Z SUNDAY.
COULD ALSO SEE SOME SOUTH/SOUTHWESTERLY GUSTS ALONG THE COAST UP
TO 20 KT THROUGH 06Z SUNDAY.
KPDX AND APPROACHES...VFR CONDITIONS EXPECTED TO DETERIORATE AS AN
INCOMING COLD FRONT WILL BRING SHOWERS AND MVFR/IFR CONDITIONS AT
OR NEAR THE TERMINAL AROUND 10Z SUNDAY. 30-45% PROBABILITY FOR
IFR CONDITIONS STARTING AROUND 15Z SUNDAY. ALSO, THERE IS A 10-20%
PROBABILITY FOR THUNDERSTORMS FROM 06Z-15Z SUNDAY. /42
MARINE
A COLD FRONT APPROACHES THIS EVENING AND WILL MOVE
ACROSS ALL WATERS THROUGH SUNDAY MORNING. SOUTHERLY WINDS
EXPECTED TO INCREASE THROUGH THE EVENING TOWARDS 10-15 KT WITH
GUSTS UP TO 20 KT THROUGH SUNDAY MORNING WITH OCCASIONAL GUSTS UP
TO 25 KT FOR THE FAR OUTER WATERS AROUND 40-60 NM AWAY FROM THE
COAST. WITH GUSTS ABOVE 21 KTS NOT EXPECTED TO BE WIDESPREAD, NO
SMALL CRAFT ADVISORY IS BEING ISSUED. 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 SUNDAY AFTERNOON WHICH WILL
RESULT IN NORTHERLY WINDS RETURNING. 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.
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