959
FXUS66 KPQR 142142
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
242 PM PDT SUN SEP 14 2025
SYNOPSIS
LINGERING SHOWERS BEHIND TODAYS FRONTAL BOUNDARY
WILL BE ON THE DECREASED HEADED INTO THE EVENING HOURS BEFORE
DRY AND CALMER WEATHER RETURNS ON MONDAY. OFFSHORE WINDS
INCREASE MONDAY NIGHT SETTING US UP FOR RATHER WARM DAY ON
TUESDAY. THEN, ANOTHER WEAK FRONT RETURNS ONSHORE FLOW TO THE
REGION MID-WEEK ALTHOUGH ANY CHANCES FOR LIGHT SHOWERS LIKELY
STAY CONFINED TO THE COAST.
SHORT TERM...NOW THROUGH TUESDAY NIGHT
CURRENT RADAR AND
SATELLITE IMAGERY THIS AFTERNOON SHOW LINGERING SHOWER ACTIVITY
MAINLY CONFINED TO THE CASCADES AND COAST RANGE WITH SOME
PARTIAL CLEARING TAKING PLACE ACROSS THE I-5 CORRIDOR. HEADED
THROUGH THE REST OF THE DAY INTO THE EVENING HOURS THIS'LL STAY
THE TREND WITH THE BEST CHANCES FOR RAIN SHOWERS STAY OVER THE
HIGHER TERRAIN FEATURES, MAINLY IN THE CASCADES. ONCE UPPER-
LEVEL HEIGHTS BEGIN TO RISE IN EARNEST TONIGHT, COMPLETELY DRY
CONDITIONS RETURN. GIVEN THE CONTINUATION OF CLEARING, AMPLE
SURFACE MOISTURE FROM RECENT RAINFALL, AND FAIRLY LIGHT WINDS,
PATCHY FOG FORMATION IS LIKELY HEADED INTO THE SUNRISE HOURS
MONDAY, ESPECIALLY IN MORE PROTECTED VALLEY LOCATIONS. LOCALLY
DENSE FOG (<1/4 MILE VISIBILITY) CAN'T BE RULED OUT EITHER.
SHORTWAVE RIDGING CONTINUES ON MONDAY. EXPECT HIGH TEMPERATURES
TO INCREASE TO NEAR-NORMAL VALUES FOR THIS TIME OF YEAR, WITH
MID TO UPPER 70S ACROSS INTERIOR VALLEYS AND MID 60S ALONG THE
COAST. THERE REMAINS EXCELLENT AGREEMENT FOR THE DEVELOPMENT
AND NORTHWARD PROGRESSION OF A SURFACE THERMAL TROUGH ACROSS
OREGON AND SOUTHWEST WASHINGTON LEADING TO AN OFFSHORE FLOW
PATTERN MONDAY EVENING/NIGHT THROUGH 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 AND COAST RANGE. WINDS PEAK EARLY TUESDAY MORNING WHEN
OFFSHORE PRESSURE GRADIENTS PEAK BETWEEN -4 TO -6 MB BETWEEN
KTTD AND KDLS ACCORDING TO DETERMINISTIC GUIDANCE. THIS WILL
YIELD BREEZY EASTERLY WINDS THROUGH THE COLUMBIA RIVER GORGE,
CASCADES GAPS, AND ACROSS THE CASCADE FOOTHILLS RIDGETOPS (AT
LEAST INITIALLY) 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 40-45 MPH
(50-60% CHANCE) EARLY TUESDAY MORNING. EVERYWHERE OUTSIDE OF
THE INFLUENCE OF THE WESTERN COLUMBIA GORGE, TOPS OF THE COAST
RANGE, OR CASCADE GAPS, EASTERLY WIND GUSTS ARE FORECAST AROUND
10-20 MPH OR LESS.
THESE OFFSHORE WINDS GRADUALLY WEAKEN THROUGHOUT THE AFTERNOON
TUESDAY AS PRESSURE GRADIENTS EASE. FORTUNATELY, THE STRONGEST
WINDS WON'T OVERLAP WITH THE LOWEST RELATIVE HUMIDITIES OF THE
DAY, SO THIS HELPS MINIMIZE THE POTENTIAL FOR FIRE WEATHER
HEADLINES. FIRE WEATHER CONDITIONS MONDAY NIGHT AND TUESDAY
CERTAINLY APPEAR BE ELEVATED BUT NOT CRITICAL. THE REGION CAN
ALSO ANTICIPATE A SHARP SPIKE IN HIGH TEMPERATURES TUESDAY
AFTERNOON DUE IN PART TO COMPRESSIONAL HEATING FROM DOWNSLOPING
WINDS. TUESDAY AFTERNOON HIGHS ARE FORECAST IN THE MID TO UPPER
80S ACROSS INTERIOR VALLEYS AND MID 70S ALONG THE COAST.
-SCHULDT/ALVIZ
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. HOWEVER, THE LATEST GUIDANCE HAS BACKED OFF THE
EASTERN EXTENT OF SAID SHOWER ACTIVITY WEDNESDAY KEEPING IT
ALMOST EXCLUSIVELY PINNED TO THE COASTLINE - DRY WEATHER
FAVORED INLAND. DETERMINISTIC AND ENSEMBLE GUIDANCE BEGIN TO
DIVERGE THE LATTER HALF OF THE WEEK AS THEY STRUGGLE 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). -SCHULDT/ALVIZ
AVIATION
A POST FRONTAL AIRMASS WILL SLOWLY SETTLE OVER THE
AIRSPACE TONIGHT AS SHOWERS CONTINUE TO PUSH FURTHER EASTWARD OVER
THE CASCADES. CURRENT VFR CONDITIONS EXPECTED TO PERSIST THROUGH
AT LEAST 00Z MONDAY. HOWEVER, GUIDANCE SHOWS A 20-40% PROBABILITY
OF DEVELOPING MVFR/IFR CONDITIONS FOR INLAND LOCATIONS AND KAST
STARTING AROUND 14Z-16Z MONDAY. THESE LOWERED FLIGHT CONDITIONS,
IF THEY DO DEVELOP SHOULD IMPROVE TO VFR AROUND 17Z-20Z MONDAY.
EXPECT WEST/NORTHWEST WINDS LESS THAN 10 KT.
KPDX AND APPROACHES...VFR CONDITIONS TO PREVAIL THROUGH AROUND 14Z
MONDAY. 20-40% PROBABILITY OF DEVELOPING MVFR/IFR CONDITIONS
STARTING AROUND 14Z MONDAY, WITH ANY LOWERED FLIGHT CONDITIONS
EXPECTED TO IMPROVE AFTER 17Z MONDAY. EXPECT WEST/NORTHWEST WINDS
LESS THAN 10 KT. /42
MARINE
WEST/NORTHWEST WINDS WITH GUSTS UP TO 20 KT. SEAS 6-8
FEET AT 10-13 SECONDS EXPECTED THROUGH THE MIDDLE OF THE WEEK AS
A NORTHWESTERLY SWELL MOVES INTO THE WATERS. HIGH PRESSURE BUILDS
OVER THE WATERS THROUGH MONDAY. NORTHERLY WINDS INCREASE MONDAY
AFTERNOON AND EVENING WITH GUSTS UP TO 20 KTS, MAINLY FOR ZONES
PZZ272, 273, 252, AND 253. THERE COULD BE SOME ISOLATED GUSTS UP
TO 25 KT FOR THOSE ZONES AS WELL THROUGH MONDAY, BUT NOT
WIDESPREAD ENOUGH TO RATE A SMALL CRAFT ADVISORY AT THIS TIME.
WILL MONITOR OBSERVATIONS IN CASE THIS CHANGES.
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/NORTHWEST AND WILL INCREASE WITH GUSTS UP TO 25 KTS.
SEAS WILL ALSO BUILD TOWARDS 7-10 FT FOR THE MIDWEEK AS WELL.
THERE STILL REMAINS SOME UNCERTAINTY AS TO THE EXACT TIMING AND
OVERALL STRENGTH OF THE MIDWEEK SYSTEM SO, WILL HOLD OFF ON
ISSUING ANY SMALL CRAFT ADVISORIES AT THIS TIME. /42
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
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