493
FXUS66 KPQR 122154
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
254 PM PDT SAT SEP 12 2026
SYNOPSIS
EXPECT COOLER AND UNSETTLED CONDITIONS THROUGH THE
WEEKEND AS AN UPPER-LEVEL LOW PRESSURE SYSTEM PROGRESSES
OVERHEAD. CONDITIONS THEN TURN PROGRESSIVELY WARMER AND DRIER
EARLY NEXT WEEK AS HIGH PRESSURE BUILDS OFFSHORE. INCREASING
EASTERLY FLOW BY WEDNESDAY AND THURSDAY COULD BRING LOCALLY
BREEZY/GUSTY WINDS TO THE GORGE, CASCADES AND NEARBY FOOTHILLS,
WHILE ALSO AIDING THE WARMER AND DRIER WEATHER.
DISCUSSION...NOW THROUGH FRIDAY
THIS AFTERNOON AN UPPER-
LEVEL LOW PRESSURE SYSTEM CONTINUES TO MOVE TOWARDS THE
COASTLINE WITH RAIN AND SHOWERS EXPECTED TO FURTHER DEVELOP
HEADED INTO THE EVENING HOURS. THIS PRECIPITATION LIKELY
PERSISTS AT TIMES OVERNIGHT INTO SUNDAY MORNING AS THE UPPER LOW
GRADUALLY SHIFTS EASTWARD. FROM THIS AFTERNOON THROUGH SUNDAY
EVENING MOST LOCATIONS FROM THE COAST INTO THE WILLAMETTE VALLEY
SHOULD SEE AROUND 0.10-0.30 INCH OF RAINFALL; MEASURABLE
AMOUNTS BUT NOT MUCH MORE. HOWEVER, THERE'S DECENT CONFIDENCE
NOTICEABLY HIGHER AMOUNTS FALL ACROSS THE SOUTHWEST WASHINGTON
FOOTHILLS/CASCADES INTO THE NORTH OREGON CASCADES WHERE CLOSER
TO 0.50-1.25 INCH OF RAIN IS ANTICIPATED. THIS IS DUE TO A
DEFORMATION BAND DEVELOPING ON THE NORTHERN PERIPHERY OF THE
UPPER-LEVEL LOW HELPING TO CONSOLIDATE SHOWERS LEADING TO
LOCALLY MODERATE SUSTAINED RAINFALL. THERE STILL REMAINS A
SLIGHT BIT OF UNCERTAINTY AMONG HIGH-RESOLUTION MODELS AS TO
EXACTLY HOW FAR SOUTH THIS AREA OF STEADIER PRECIPITATION COULD
WANDER. A SLIGHT SOUTHWARD NUDGE WOULD INCREASE RAINFALL TOTALS
ACROSS THE PORTLAND METRO, PARTICULARLY SUNDAY MORNING. AS THE
UPPER LOW MOVES WELL EAST OF THE CASCADES BY SUNDAY AFTERNOON,
SHOWERS SHOULD BECOME MORE SCATTERED AND INCREASINGLY FOCUSED
OVER HIGHER TERRAIN FEATURES. THE INLAND VALLEYS AND IMMEDIATE
COAST LIKELY TREND MOSTLY DRY BY THE MID TO LATE AFTERNOON
HOURS, WHILE THE CASCADES CONTINUE TO SEE LINGERING SHOWERS INTO
THE EVENING.
IT'S WORTH QUICKLY HIGHLIGHTING A ~15% CHANCE OF THUNDERSTORMS
WAS MAINTAINED IN THE FORECAST FOR THIS EVENING AS COLD AIR
MOVING IN ALOFT MAY PROVIDE JUST ENOUGH INSTABILITY FOR A STRAY
SHORT-LIVED T-STORM. COLD-CORE FUNNEL CLOUDS ARE ALSO POSSIBLE
WITH THE STRONGER SHOWERS THROUGH SUNDAY. THESE ARE TYPICALLY
SHORT-LIVED AND LARGELY REMAIN ABOVE THE GROUND.
COME MONDAY AND TUESDAY THE LOW PRESSURE SYSTEM EJECTS FURTHER
EASTWARD WITH LARGE SCALE TROUGHING AND NORTHWESTERLY FLOW HOLDING
IN PLACE ACROSS THE PACIFIC NORTHWEST THANKS TO A SECONDARY
WEAK SHORTWAVE FEATURE SLIDING DOWN THE BC COASTLINE LATE
MONDAY. TEMPERATURES WILL WARM DAY TO DAY COMPARED TO THIS
WEEKEND, ALTHOUGH ONLY A COUPLE DEGREES EACH AFTERNOON. EXPECT
HIGHS IN THE LOW TO MID 70S BY TUESDAY AFTERNOON - MID 60S ALONG
THE COAST.
THEN A MORE NOTICEABLE WARM-UP BEGINS WEDNESDAY INTO THURSDAY
AS A RIDGE OF HIGH PRESSURE WHICH HAD BEEN FORMING OVER THE
EASTERN PACIFIC BEGINS TO SHIFT EASTWARD INTO THE REGION. THE
BULK OF DETERMINISTIC MODELS AND ENSEMBLE SYSTEMS HAVE NOW
CONVERGED ON THIS SOLUTION. HIGH TEMPERATURES TO SOAR WELL INTO
THE 80S ACROSS THE INTERIOR LOWLANDS AS A RESULT OF THIS MORE
SUMMER- LIKE PATTERN. FOR THURSDAY AFTERNOON SPECIFICALLY, THE
LATEST NBM SHOWS A 15-35% CHANCE FOR HIGHS TO EXCEED 90S DEGREES
ACROSS THE CENTRAL/NORTHERN WILLAMETTE VALLEY, 0-10% ELSEWHERE.
EASTERLY FLOW IS ALSO BECOMING MORE LIKELY MIDWEEK. THE
STRONGEST WINDS CURRENTLY APPEAR ON WEDNESDAY INTO THURSDAY
MORNING, WITH GUSTS OF 25-35 MPH AND ISOLATED GUSTS NEAR 40 MPH
POSSIBLE IN MORE WIND-PRONE AREAS OF THE COLUMBIA RIVER GORGE,
CASCADES AND ADJACENT FOOTHILLS. THE TOPS OF THE COAST RANGE
COULD ALSO BECOME BREEZY, ALTHOUGH CONFIDENCE HERE IS LOWER.
CURRENTLY, THERE IS AROUND A 10-15% CHANCE GUSTS COULD EXCEED 45
MPH IN THE MOST EXPOSED LOCATIONS NEAR/WITHIN THE COLUMBIA
RIVER GORGE. THE COMBINATION OF WARMER TEMPERATURES, LOWER
HUMIDITY AND INCREASING EAST WINDS WEDNESDAY AND THURSDAY MAY
PROVIDE A WINDOW OF ELEVATED FIRE-WEATHER CONCERNS. -99/12
AVIATION...THROUGH 00Z MONDAY
VFR CONDITIONS PREVAIL ACROSS THE
AIRSPACE AHEAD OF AN APPROACHING WEAK AREA OF LOW PRESSURE.
SCATTERED TO NUMEROUS RAIN SHOWERS MOVING ONSHORE THE COAST WILL
CONTINUE TO SPREAD INLAND INTO THIS EVENT, ARRIVING AT WILLAMETTE
VALLEY TERMINALS BY 01Z SUN. 15-20% CHANCES OF AN ISOLATED
THUNDERSTORM WILL ALSO PERSIST THROUGH 06Z SUN ACROSS THE REGION.
WHILE CONFIDENCE IS LOW IN THE OCCURRENCE OF TERMINAL IMPACTS AT
ANY PARTICULAR TIME, SHOWERS AND STORMS WILL BE CAPABLE OF
PRODUCING GUSTY, ERRATIC WINDS AND LOCALLY HEAVY RAIN WHICH COULD
BRIEFLY RESTRICT VIS. THE LIKELIHOOD OF MVFR CIGS GENERALLY
INCREASES THROUGH THE EVENING AS RAIN SHOWERS ASSIST IN MOISTENING
THE LOWER ATMOSPHERE. MVFR CHANCES REACH 20-40% AT INLAND
TERMINALS FROM 06-15Z SUN AND 40-60% FROM 15-21Z SUN, WHILE
ALONG THE COAST THEY CONTINUE AT 30-60% INTO TONIGHT, RISING TO
60-80% BY 15Z SUN. AS SHOWERS END FROM WEST TO EAST AFTER 15-18Z
SUN, CONDITIONS MAY BEGIN TO IMPROVE LATE IN THE PERIOD.
SOUTH TO SOUTHWEST WINDS OF 8-12 KT WITH GUSTS UP TO 20 KT AT
COASTAL TERMINALS AND 5-10 KT INLAND WILL EASE TO AROUND 5 KT OUT
OF THE SOUTH TONIGHT, THEN RISE TO 5-10 KT OUT OF THE SOUTHWEST BY
SUNDAY AFTERNOON.
KPDX AND APPROACHES...VFR CONDITIONS FAVORED THROUGH AT LEAST
06-12Z SUN. RAIN SHOWERS WILL SPREAD INLAND THROUGH THE COMING
HOURS AS AN AREA OF LOW PRESSURE NEAR THE COAST, WITH A 15-20%
CHANCE FOR AN ISOLATED THUNDERSTORM THROUGH 06Z SUN. WHILE IMPACTS
ARE UNLIKELY, GUSTY AND ERRATIC WINDS OR HEAVY DOWNPOURS BRIEFLY
RESTRICTING TERMINAL VIS CANNOT BE RULED OUT. CHANCES FOR MVFR
CIGS OTHERWISE GENERALLY INCREASE AS SHOWERS CONTINUE FROM 20-30%
THIS EVENING AND INTO TONIGHT TO 35-50% BY 12-15Z SUN. CONDITIONS
MAY IMPROVE LATE IN THE PERIOD AS SHOWER COVERAGE DWINDLES. SOUTH
TO SOUTHWEST WINDS 4-8 KT CONTINUE THROUGH THE PERIOD. -36
MARINE
A WEAK SURFACE LOW CENTERED OFF THE CENTRAL OREGON COAST
AS OF EARLY SATURDAY AFTERNOON WILL TRAVERSE THE WATERS THIS
AFTERNOON BEFORE MOVING INLAND OVER THE NORTH OREGON COAST BY
EARLY SUNDAY MORNING. AHEAD OF THIS SYSTEM, SOUTHERLY WINDS OF
8-15 KT WILL CONTINUE, WITH THE STRONGEST WINDS AND GUSTS TO 20
KT LIMITED TO AREAS WITHIN 20 NM SOUTH OF CAPE FOULWEATHER.
NUMEROUS RAIN SHOWERS ARE ALSO EXPECTED DURING THIS TIME, AS WELL
AS 15-20% CHANCES OF ISOLATED THUNDERSTORMS CAPABLE OF PRODUCING
GUSTY AND ERRATIC WINDS AND LOCALLY HEAVY DOWNPOURS THROUGH THIS
EVENING. ONSHORE FLOW AT 5-10 KT OUT OF THE WEST TO SOUTHWEST
CONTINUES ON SUNDAY WHILE RAIN SHOWER COVERAGE DECREASES THROUGH
THE DAY. A PERSISTENT NORTHWESTERLY SWELL AT 8-9 SECONDS WILL
MAINTAIN OVERALL SEAS AROUND 5 FT THROUGH THE WEEKEND.
SURFACE HIGH PRESSURE REBUILDS OVER THE WATERS THROUGH THE FIRST
HALF OF NEXT WEEK, WITH NORTHERLY FLOW RETURNING LATE MONDAY.
STRENGTHENING NORTHERLIES THROUGH MIDWEEK WILL SEE 50% OR GREATER
CHANCES OF WINDS 20 KT OR HIGHER ON WEDNESDAY, ESPECIALLY BEYOND
10 NM SOUTH OF CAPE FALCON. SEAS AROUND 5 FT WITH A DOMINANT
NORTHWESTERLY SWELL AT 8-9 SECONDS OTHERWISE CONTINUE. -36
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
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