574
FXUS66 KPQR 140930
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
230 AM PDT SUN SEP 14 2025
SYNOPSIS
A COLD FRONT PUSHING THROUGH THE AREA WILL BRING
WIDESPREAD RAIN SHOWERS AND A 15-25% CHANCE FOR THUNDERSTORMS
ACROSS NORTHWEST OREGON AND SOUTHWEST WASHINGTON THIS MORNING.
THE FRONT WEAKENS AND EXITS BY THIS AFTERNOON, BRINGING CLOUD
BREAKS AND MOSTLY DRY CONDITIONS AS SHOWERS TAPER OFF. DRY AND
WARM CONDITIONS CONTINUE EARLY THIS WEEK WITH OFFSHORE WINDS
MONDAY NIGHT TO TUESDAY. ANOTHER WEAK FRONT RETURNS ONSHORE FLOW
AND PRECIPITATION CHANCES MID-WEEK.
SHORT TERM...NOW THROUGH TUESDAY NIGHT
SATELLITE IMAGERY AS
OF EARLY SUNDAY MORNING DEPICTS RAIN SPREADING ACROSS NORTHWEST
OREGON AND SOUTHWEST WASHINGTON AS OUR NEXT COLD FRONT ARRIVES.
THIS FRONT WILL GRADUALLY PROGRESS INLAND THIS MORNING,
BRINGING WIDESPREAD RAIN AND A 15-25% CHANCE FOR THUNDERSTORMS.
SEVERAL LIGHTNING STRIKES FROM THUNDERSTORMS HAVE ALREADY BEEN
OBSERVED ALONG THE CENTRAL OREGON COAST AND OFFSHORE WATERS.
FREQUENT RAIN, HEAVY RAIN, AND ERRATIC WINDS ARE POSSIBLE WITH
ANY THUNDERSTORMS. WHEN THUNDER ROARS, GO INDOORS! BEHIND THE
FRONT, RAINFALL WILL QUICKLY TRANSITION TO LINGERING SHOWERS.
OVERALL, THERE HAVE BEEN MINIMAL CHANGES TO FORECAST RAINFALL
AMOUNTS FROM THIS SYSTEM: 0.20-0.40" FOR MOST INTERIOR VALLEYS
(EXCEPT LESS THAN 0.10" IN THE UPPER HOOD RIVER VALLEY),
0.50-0.80" ALONG THE COAST, AND 0.30-0.60" ACROSS THE COAST
RANGE, WILLAPA HILLS, AND CASCADES. THE HIGHEST AMOUNTS ARE
EXPECTED ON THE WESTERN SLOPES OF THESE MOUNTAINS DUE TO
ENHANCED OROGRAPHIC LIFT. LOCATIONS WITH PASSING THUNDERSTORMS
MAY ALSO RECEIVE HIGHER RAINFALL TOTALS. EXPECT THIS QUICK-
MOVING FRONT TO FURTHER WEAKEN AND EXIT OUR AREA THIS AFTERNOON,
WITH CONDITIONS DRYING UP AS SHOWERS TAPER OFF. CLOUDS WILL
ALSO BEGIN TO BREAK UP, SO WE MAY SEE SOME SUNSHINE BY THE LATE
AFTERNOON AND EARLY EVENING. TEMPERATURES WILL BE COOLER TODAY,
WITH AFTERNOON HIGHS FORECAST IN THE UPPER 60S TO LOW 70S ACROSS
INTERIOR VALLEYS AND LOW 60S ALONG THE COAST.
SHORTWAVE RIDGING RETURNS ON MONDAY, BRINGING WITH DRY, SUNNY,
AND WARMER CONDITIONS. EXPECT HIGH TEMPERATURES TO INCREASE TO
NEAR-NORMAL VALUES FOR THIS TIME OF YEAR, WITH MID TO UPPER 70S
ACROSS INTERIOR VALLEYS AND UPPER 60S ALONG THE COAST.
HIGH PRESSURE CONTINUES ON TUESDAY, WITH THE UPPER RIDGE AXIS
CENTERING OVER EASTERN OREGON/WASHINGTON. THERE ALSO CONTINUES
TO BE EXCELLENT AGREEMENT FOR THE DEVELOPMENT OF A SURFACE
THERMAL TROUGH, LEADING TO AN OFFSHORE FLOW PATTERN MONDAY NIGHT
TO TUESDAY. THE AXIS OF THIS THERMAL TROUGH APPEARS TO BE
CENTERED ALONG THE COAST OR JUST SLIGHTLY OFFSHORE, FAVORING
EASTERLY WINDS MAKING IT ALL THE WAY TO THE COAST. THE BREEZIEST
WINDS ARE EXPECTED MONDAY NIGHT TO TUESDAY MORNING, WHEN
OFFSHORE PRESSURE GRADIENTS WILL BE BETWEEN -3 TO -5 MB BETWEEN
KTTD AND KDLS. THIS WILL YIELD BREEZY EASTERLY WINDS THROUGH THE
COLUMBIA RIVER GORGE AND CASCADES GAPS, WITH GUSTS UP TO 25-35
MPH. FOR OUR TYPICALLY WINDIEST SPOTS LIKE THREE CORNER ROCK
AND CROWN POINT IN THE GORGE, CAN'T RULE OUT A FEW ISOLATED
GUSTS CLOSER TO 40 MPH (50-60% CHANCE) TUESDAY MORNING.
EVERYWHERE ELSE, EASTERLY WIND GUSTS ARE FORECAST AROUND 10-15
MPH OR LESS.
THESE OFFSHORE WINDS WILL GRADUALLY WEAKEN THROUGHOUT THE
DAY ON TUESDAY AS PRESSURE GRADIENTS EASE. FORTUNATELY, THE
STRONGEST WINDS WON'T BE OVERLAPPING WITH THE LOWEST RELATIVE
HUMIDITIES OF THE DAY, SO THIS HELPS MINIMIZE THE POTENTIAL FOR
FIRE WEATHER HEADLINES. LAST, THIS OFFSHORE FLOW PATTERN WILL
ALSO LEAD TO A SPIKE IN HIGH TEMPERATURES DUE TO COMPRESSIONAL
HEATING OF AIR FROM DOWNSLOPING WINDS. TUESDAY AFTERNOON HIGHS
ARE FORECAST IN THE UPPER 80S ACROSS INTERIOR VALLEYS AND MID
70S ALONG THE COAST. -ALVIZ/SCHULDT
LONG TERM...WEDNESDAY THROUGH SATURDAY
ONSHORE FLOW RETURNS
ON WEDNESDAY WITH MOST ENSEMBLE MEMBERS 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
SATURDAY 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
UNCERTAINTY WITH THE EXACT MAGNITUDE, TRACK, AND TIMING OF THE
TROUGH. ABOUT 60% OF ENSEMBLE MEMBERS SHOW CONDITIONS DRYING
OUT ON THURSDAY, WHILE 40% MAINTAIN POTENTIAL SHOWERS FROM THE
TROUGH (MAINLY FROM THE GEPS). -ALVIZ
AVIATION
A COLD FRONT WILL THROUGH THE AREA SUNDAY MORNING,
MOVING EAST OF THE CASCADES BY 18-20Z SUNDAY. WIDESPREAD RAIN,
HEAVY AT TIMES, IS EXPECTED ALONG AND AHEAD OF THE FRONTAL
PASSAGE, DISSIPATING ALONG THE COAST AFTER 14-16Z AND FOR INLAND
LOCATIONS WEST OF THE CASCADES AFTER 17-19Z. THERE'S A 15-25%
CHANCE OF THUNDERSTORMS AS WELL, MAINLY FOR LOCATIONS WEST OF
INTERSTATE 5. FREQUENT LIGHTNING, HEAVY RAIN, AND ERRATIC WINDS
POSSIBLE WITH ANY THUNDERSTORM. VFR CONDITIONS AHEAD OF THE FRONT
WITH CONDITIONS EXPECTED TO FALL TO MVFR BEHIND THE FRONT FOR
INLAND AREAS AND MVFR/IFR FOR COASTAL AREAS. BRIEF PERIODS OF
IFR/LIFR CONDITIONS POSSIBLE IN HEAVIER SHOWERS OR THUNDERSTORMS.
ALL LOWERED CONDITIONS EXPECTED TO LIFT TO VFR BY 18-20Z SUNDAY
THEN REMAIN VFR THROUGH THE REST OF THE TAF PERIOD. MAINLY
SOUTHERLY WINDS AHEAD OF THE FRONT UP TO 8-10 KTS WITH OCCASIONAL
GUSTS UP TO 20 KTS ALONG THE COAST. WINDS THEN SHIFT NORTHWEST
ALONG THE COAST AFTER 12-14Z AND WESTERLY TO NORTHWESTERLY INLAND
AFTER 16-18Z.
KPDX AND APPROACHES...MVFR CONDITIONS EXPECTED BY 10-11Z SUNDAY
AS A FRONTAL SYSTEM BRINGS WIDESPREAD SHOWERS. SHOWERS SHOULD END
BY 16-18Z WITH CONDITIONS IMPROVING TO VFR BY 18-20Z, REMAINING
VFR THROUGH THE REST OF THE TAF PERIOD. SOUTH WINDS SHIFT
WEST TO NORTHWEST UP TO 8-10 KTS AFTER 14Z, DECREASING AFTER
00-03Z MONDAY. -HEC
MARINE
A COLD FRONT MOVING THROUGH THE WATERS WILL PUSH
INLAND BY 5-7 AM PDT SUNDAY. HEAVY SHOWERS AND ISOLATED
THUNDERSTORMS ARE POSSIBLE ALONG AND AHEAD OF THE FRONT THROUGH
THIS TIME. SOUTHERLY WINDS WITH GUSTS UP TO 20 KT CONTINUE WITH
THE FRONTAL PASSAGE WITH OCCASIONAL, ISOLATED GUSTS UP TO 25
KTS. WINDS WILL SHIFT QUICKLY TO THE NORTHWEST BEHIND THE
FRONTAL PASSAGE AND BEGIN DECREASING. 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 TODAY INTO MONDAY.
NORTHERLY WINDS INCREASE MONDAY AFTERNOON AND EVENING WITH GUSTS
UP TO 20 KTS, MAINLY FOR ZONES PZZ272, 273, 252, AND 253.
THERE'S A 20-35% CHANCE OF HOURLY WIND GUSTS UP TO 25 KTS, BUT
AT THIS TIME NOT EXPECTING THESE GUSTS TO BE WIDESPREAD ENOUGH
FOR A SMALL CRAFT ADVISORY.
WEAK OFFSHORE FLOW WILL DEVELOP BRIEFLY LATE MONDAY NIGHT INTO
TUESDAY MORNING. HOWEVER, THIS WILL BE SHORT LIVED AS ANOTHER
LOW PRESSURE SYSTEM AND ASSOCIATED SURFACE FRONT APPROACHES
THE WATERS TUESDAY INTO WEDNESDAY. AS THE SYSTEM APPROACHES,
WINDS BECOME WEST TO NORTHWEST AND WILL INCREASE WITH GUSTS UP
TO 20 KTS. ONCE AGAIN THERE COULD BE OCCASIONAL GUSTS UP 25 KT,
THOUGH CONFIDENCE IS LOW IN THE STRENGTH AND TIMING OF STRONGEST
WINDS WITH THE FRONTAL PASSAGE. WILL CONTINUE TO MONITOR IF
SMALL CRAFT ADVISORY CONDITIONS WILL DEVELOP. -HEC
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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