201
FXUS66 KPQR 232125
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
225 PM PDT WED SEP 23 2026
SYNOPSIS
SEASONABLY COOL AND DRY WEATHER CONTINUES INTO
THURSDAY BEFORE A FRONTAL SYSTEM MOVES ONSHORE THURSDAY
AFTERNOON. CONFIDENCE REMAINS HIGH IN A WIDESPREAD SOAKING RAIN
AND BREEZY WINDS ACROSS THE REGION, WITH LOWER CONFIDENCE IN THE
PLACEMENT OF POTENTIAL STRONGEST WINDS ALONG THE COAST. DRY
WEATHER THEN VERY LIKELY RETURNS THIS WEEKEND WITH ADDITIONAL
CHANCES FOR RAIN NEXT WEEK.
SHORT TERM...NOW THROUGH FRIDAY NIGHT
PLEASANT EARLY FALL
WEATHER CONTINUES INTO THURSDAY MORNING AS WEAK SURFACE HIGH
PRESSURE OFFSHORE IS REPLACED BY AN APPROACHING LOW AND ITS
ASSOCIATED FRONTAL BOUNDARIES. SCATTERED HIGH CLOUDS WILL YIELD
A COOL EVENING AS TEMPERATURES LARGELY FALL TO OVERNIGHT LOWS IN
THE 40S. BY EARLY THURSDAY MORNING, MID AND HIGH-LEVEL CLOUDS
WILL INCREASE RAPIDLY, BUT BREEZY SOUTH TO SOUTHWEST WINDS
BEHIND A WEAK WARM FRONT WILL AID IN PUSHING TEMPERATURES NEAR
TO A FEW DEGREES WARMER THAN WEDNESDAY, NAMELY THE LOW TO MID
60S ON THE COAST AND LOW TO MID 70S WITHIN INLAND VALLEYS. RAIN
WILL SPREAD FROM WEST TO EAST AS THE COLD FRONT MOVES ONSHORE,
REACHING THE COAST MOST LIKELY BETWEEN 2-5 PM PDT, AND INLAND TO
THE WILLAMETTE VALLEY AND I-5 CORRIDOR BY 5-8 PM PDT. STEADY
RAIN WILL TRANSITION TO MORE ON-AND-OFF RAIN SHOWERS BEHIND THE
BOUNDARY LATE THURSDAY EVENING THROUGH THURSDAY NIGHT. WINDS
WILL VEER OUT OF THE WEST TO SOUTHWEST BEHIND THE COLD FRONT ON
FRIDAY, WHILE POST-FRONTAL INSTABILITY WILL FAVOR CONVECTIVE
RAIN SHOWERS AND A 15-25% CHANCE OF ISOLATED THUNDERSTORMS
PERSISTING THROUGH THE AFTERNOON. ANY INCREASE IN SUNBREAKS
THROUGH FRIDAY MORNING WILL ACT TO INCREASE INSTABILITY AND
COULD YIELD INCREASED COVERAGE OF THUNDERSTORMS. FOLLOWING THE
LOSS OF SURFACE HEATING FRIDAY EVENING, RAIN SHOWER COVERAGE
WILL QUICKLY DIMINISH AND BREEZY WINDS WILL EASE.
FORECAST RAINFALL AMOUNTS OVER 36 HOURS FROM MIDDAY THURSDAY
THROUGH FRIDAY EVENING ARE EXPECTED TO REMAIN BETWEEN 0.45-0.85
INCHES ALONG THE I-5 CORRIDOR, WITH THE HIGHEST AMOUNTS NORTH OF
THE COLUMBIA RIVER AND THE LOWEST AMOUNTS IN THE SOUTHERN
WILLAMETTE VALLEY. RAINFALL AMOUNTS ARE LIKELY TO BE HIGHER
ALONG THE COAST, IN THE COAST RANGE AND WILLAPA HILLS, AND IN
THE CASCADES, WHERE 0.6-1.2 INCHES ARE EXPECTED. WHILE THESE ARE
"MOST-LIKELY" RAINFALL TOTALS, THE DISTRIBUTION OF RAIN SHOWERS
ON FRIDAY WILL RESULT IN SOME AREAS SEEING HIGHER TOTALS WHILE
OTHER SEE LESS; THOSE AREAS THAT SEE REALIZE THE 15-25% CHANCE
OF THUNDERSTORMS MAY SEE IN EXCESS OF 1.25-1.5 INCHES OF RAIN,
WHILE THOSE THAT MISS OUT MAY INSTEAD ACCUMULATE ONLY 0.25-0.5
INCHES. CONVECTIVE SHOWERS AND THUNDERSTORMS WILL ALSO BE
CAPABLE OF GENERATING GUSTY AND ERRATIC WINDS AS LOW-LEVEL SHEAR
WILL BE SUFFICIENT DESPITE THE LIKELY SHALLOW EXTENT OF ANY
UPDRAFT. PEAK GUSTS FROM ANY STORM OR HEAVY SHOWER OUTFLOW HAVE
A 40-50% CHANCE OF REACHING 40 MPH OR HIGHER IN INLAND AREAS,
AND 35-50% CHANCE OF 45 MPH OR HIGHER IN COASTAL COMMUNITIES.
THE WIND FORECAST ALSO REMAINS SENSITIVE TO THE TRACK OF THE
WEAKENING SURFACE LOW AS IT NEARS THE COAST. SHORT-RANGE
ENSEMBLES CONTINUE TO HIGHLIGHT THE REGION BETWEEN LINCOLN
COUNTY, OR AND GRAY'S HARBOR, WA AS THE AREA WHERE THE LOW MAY
MOVE ONSHORE, WITH THE COMMUNITIES JUST TO THE SOUTH OF THE LOW
CENTER AS MOST LIKELY TO SEE THE STRONGEST WINDS. GIVEN THE
SHEAR ENVIRONMENT, AN ISOLATED COLD CORE FUNNEL ALSO CANNOT BE
RULED OUT THROUGH THE DAY ON FRIDAY, EVEN IN THE ABSENCE OF
LIGHTNING. IN GENERAL, THESE RAINFALL TOTALS AND WIND SPEEDS ARE
UNLIKELY TO PRODUCE IMPACTS, WITH THE LOCAL AREA OF STRONGEST
WINDS MOST LIKELY TO SEE DOWNED TREES OR SCATTERED POWER OUTAGES
AS LEAVES RESULT IN MORE DRAG ON TREES AND BRANCHES THAN IS
TYPICAL FOR A FALL OR WINTER-SEASON STORM. -36
LONG TERM...SATURDAY THROUGH WEDNESDAY
AS THE TROUGH LIFTS
INTO THE CANADIAN PRAIRIE PROVINCES BY SATURDAY MORNING, LOW
AMPLITUDE AND TRANSIENT SHORTWAVE RIDGING WILL SEE A RETURN TO
DRY CONDITIONS IN THE PACIFIC NORTHWEST. SEASONABLY COOL WEATHER
WILL PERSIST INTO THE WORKWEEK, WITH AFTERNOON HIGH TEMPERATURES
ONLY REACHING THE LOW 60S ALONG THE COAST AND MID 60S WITHIN
INTERIOR VALLEYS THROUGH MONDAY. OVERNIGHT LOWS WILL SIMILARLY
REMAIN COOL, LARGELY IN THE 40S SATURDAY NIGHT THROUGH AT LEAST
MONDAY NIGHT, WITH THE COOLEST TEMPERATURES OCCURRING IN THE
UPPER HOOD RIVER VALLEY. CHANCES FOR FROST WITH MORNING LOWS OF
36 DEGREES OR COOLER REMAIN AT 5-10% IN THE ODELL AREA, AND
35-55% NEAR PARKDALE AND DEE.
ADDITIONAL UPPER-LEVEL TROUGHING NEXT WEEK MAY BRING ADDITIONAL
CHANCES FOR RAIN TO THE REGION SOME TIME DURING THE FIRST HALF
OF THE WORKWEEK. UNCERTAINTY IN THE EVOLUTION OF THE LARGE-SCALE
PATTERN REMAINS HIGH AT THIS LEAD TIME, RESULTING IN 10-30%
CHANCES FOR RAIN ACROSS MUCH OF THE REGION DURING THIS TIME. -36
AVIATION...THROUGH 00Z FRIDAY
WEST TO SOUTHWEST FLOW ALOFT
CONTINUES THROUGH THE TAF PERIOD. HIGH BROKEN CLOUDS CONTINUE TO
MOVE ACROSS THE AREA. CURRENT WIDESPREAD VFR CONDITIONS WILL
CONTINUE THROUGH AT LEAST 10Z THU. AROUND 10-12Z THU, CHANCES OF
DETERIORATED CONDITIONS INCREASE, PRIMARILY AT KONP.
PROBABILISTIC GUIDANCE SUGGESTS A 20-30% CHANCE OF LIFR AND
30-40% CHANCE OF IFR CONDITIONS AT KONP, 10-20% CHANCE OF
LIFR/IFR CONDITIONS AT KEUG, AND JUST A 5-15% CHANCE OF MVFR
CIGS AT ALL OTHER TERMINALS. ANY DETERIORATED CONDITIONS SHOULD
LIFT AND CLEAR OUT BY 17-19Z THU, ALTHOUGH THERE IS A 30-40%
CHANCE OF MVFR CONDITIONS HANGING AROUND AT KONP PAST 19Z THU.
OTHERWISE, NORTH TO NORTHWESTERLY WINDS AROUND 5-10 KT TODAY
WILL BECOME LIGHT AND MAY BECOME MORE NORTHEASTERLY BY 06Z THU.
BRIEF GUSTS UP TO 18 KT ARE POSSIBLE LATE THIS AFTERNOON AT
KONP. WINDS LOOKS TO BE LIGHT AND VARIABLE THU AFTERNOON.
KPDX AND APPROACHES...VFR CONDITIONS WITH SCATTERED TO BROKEN
HIGH CLOUDS. NORTHWEST WINDS AROUND 4-7 KT THROUGH THE TAF
PERIOD. ~12
MARINE
NORTHERLY WINDS CONTINUE ACROSS THE WATERS TONIGHT,
THEN BECOME NORTHEASTERLY EARLY THURSDAY MORNING THROUGH EARLY
THURSDAY AFTERNOON AS A LOW PRESSURE SYSTEM APPROACHES. THIS
SYSTEM WILL MOVE OVER THE COASTAL WATERS LATE THURSDAY INTO
FRIDAY, BRINGING RAPIDLY INCREASING WINDS AND SEAS ALONG WITH
WIDESPREAD RAIN. GUIDANCE HAS NOT COME INTO AGREEMENT YET ON THE
EXACT TRACK AND STRENGTH OF THIS LOW PRESSURE SYSTEM, WHICH
MEANS EXACT WIND SPEEDS AND WAVE HEIGHTS ARE UNCERTAIN THURSDAY
NIGHT INTO FRIDAY.
WITH THAT BEING SAID, THERE IS HIGH CONFIDENCE FOR AT LEAST
SMALL CRAFT ADVISORY WIND GUSTS OF 21 KT OR STRONGER WITH THIS
SYSTEM. GIVEN A 30-50% CHANCE OF GALE FORCE WIND GUSTS OF 34 KT
OR STRONGER, A GALE WATCH HAS BEEN ISSUED FROM 8 PM THURSDAY TO
11 AM FRIDAY FOR ALL OF THE WATERS, AND 11 PM THURSDAY TO 11 AM
FRIDAY FOR THE COLUMBIA RIVER BAR. UNCERTAINTY REMAINS MAINLY
DUE TO LOCATION, WHERE A RELATIVELY STRONG LOW PRESSURE SYSTEM
IS EXPECTED TO TRACK SOMEWHERE OVER THE COASTAL WATERS.
ADDITIONALLY, WITH LOW CHANCES OF A NARROW BELT OF HIGH WINDS
DEVELOPING ON THE SOUTH SIDE OF THIS SYSTEM, THERE IS LOW
CONFIDENCE ON WHERE AND HOW STRONG WIND GUSTS COULD MATERIALIZE
OVER THE WATERS. WITH THIS SYSTEM, THE LOW CHANCE OF A NARROW
BELT OF HIGH WINDS IS WELL REPRESENTED BY A 10-20% CHANCE OF MAX
WIND GUSTS OF 48 KT OR STRONGER.
IF THIS LOW TAKES A FAVORABLE TRACK AND STRENGTHENS AS IT
APPROACHES THE COAST, THEN HAZARDOUS SEAS AS HIGH AS 15-17 FT
WOULD BE POSSIBLE (5-10% CHANCE). IF THE LOW COMES IN WEAKER,
PEAK WINDS WOULD LIKELY RANGE SOMEWHERE BETWEEN 25-35 KT AND
SEAS WOULD LIKELY PEAK CLOSER TO 10-13 FT. THE LATTER IS
CURRENTLY THE MOST LIKELY OUTCOME, HOWEVER THE FORECAST SHOULD
BE MONITORED OVER THE COMING DAYS FOR UPDATES. ~12/23
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...GALE WATCH FROM THURSDAY EVENING THROUGH FRIDAY MORNING FOR
PZZ210.
GALE WATCH FROM THURSDAY EVENING THROUGH FRIDAY MORNING FOR
PZZ251>253-271>273.
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