271
FXUS66 KPQR 152142
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
242 PM PDT MON SEP 15 2025
SYNOPSIS
DRY AND CALMER CONDITIONS PERSIST THROUGH THE
EVENING. OFFSHORE FLOW WILL STRENGTHEN TONIGHT INTO TUESDAY,
PRODUCING WARM TEMPERATURES AND BREEZY TO LOCALLY STRONG
EASTERLY WINDS THROUGH THE COLUMBIA RIVER GORGE AND CASCADE
GAPS. ONSHORE FLOW RETURNS FOR THE MIDDLE OF THE WEEK AS A WEAK
FRONT BRUSHES THE COAST WITH ONLY LIMITED PRECIPITATION
POTENTIAL. A BROADER TROUGHING PATTERN FROM THE NORTHEAST
PACIFIC LOOKS TO BRING THE BEST PROBABILITY FOR INCREASING RAIN
CHANCES INTO THE WEEKEND.
SHORT TERM...NOW THROUGH TUESDAY NIGHT
A SHORTWAVE RIDGE
WILL BRING DRY CONDITIONS WITH NEAR-SEASONAL DAYTIME HIGHS IN
THE MID TO UPPER 70S INLAND AND MID 60S AT THE COAST TODAY. BY
THIS EVENING, A THERMALLY INDUCED SURFACE TROUGH STRENGTHENS,
WHICH WILL TIGHTEN THE PRESSURE GRADIENT WITH MODELS SHOWING A -4
TO -6 MB KPDX-KDLS DIFFERENCE. TYPICALLY THIS PRESSURE GRADIENT
DIFFERENCE WOULD RESULT IN 30-40 MPH GUSTS WITHIN THE COLUMBIA
RIVER GORGE. WINDS LOOK TO PEAK FROM 4AM-10AM TUESDAY. THERE IS
A 25-40% PROBABILITY FOR GUSTS UP TO 50 MPH. WINDS WILL
GRADUALLY EASE TUESDAY EVENING AS GRADIENTS RELAX, WITH GUSTS
GENERALLY DROPPING BELOW 20 MPH AROUND 12AM-02AM WEDNESDAY.
TEMPERATURES WARM TUESDAY, WITH DAYTIME HIGHS FOR INLAND
LOCATIONS IN THE UPPER 80S TO LOW 90S. WHILE WE ARE EXPECTING
DRY AND BREEZY CONDITIONS ON TUESDAY. IT SHOULD BE NOTED THAT
THE BREEZIEST CONDITIONS ARE EXPECTED FROM 4AM-10AM, THE WINDS
ARE NOT EXPECTED TO COINCIDE WITH THE MINIMUM HUMIDITY FOR THE
DAY, WHICH HAPPENS AROUND 2PM-4PM. IN ADDITION TO THE WIND AND
RH, FUELS MUST ALSO BE TAKEN INTO ACCOUNT AND GIVEN THAT THE
MAJORITY OF THE CWA HAS RECEIVED A FAIR AMOUNT OF PRECIPITATION
OVER THE PAST 48 HOURS IT HAS REDUCED THE AVAILABILITY OF
ENERGY WITHIN THE FUELS.
LONG TERM...WEDNESDAY THROUGH SUNDAY
AS WE MOVE INTO THE
MIDDLE OF THE WEEK, A PATTERN CHANGE WILL BRING A RETURN TO ONSHORE
FLOW AS A VERY ELONGATED FRONT WHICH JUST BRUSHES THE COAST.
THE BULK OF THE PRECIPITATION IS EXPECTED TO REMAIN OFFSHORE
WITH ONLY A 5-15% PROBABILITY OF LIGHT SHOWERS ALONG THE COAST.
AS THURSDAY APPROACHES MODELS SHOW A RATHER CONFUSING, UPPER
AIR PATTERN. MOST ARE SHOWING A RATHER NARROW UPPER LEVEL RIDGE,
WHICH DOES SUPPORT THE DRY PATTERN SEEN WITHIN 70-80% OF
MEMBERS FAVOR DRIER WEATHER THROUGH FRIDAY. BY SATURDAY, A MORE
ROBUST UPPER LEVEL TROUGH FROM THE NORTHEAST PACIFIC STARTS TO
DROP INTO THE REGION AND LOOKS PROVIDE AN OPPORTUNITY FOR
PRECIPITATION. NOW, WHILE THE PRECIPITATION CHANCES AT THIS TIME
ARE MORE FOCUSED TOWARDS FAR NORTHERN OR AND WA STATE AS A
WHOLE, THIS COULD CHANGE DEPENDING ON THE LOCATION OF THE UPPER
LEVEL TROUGH. WHILE THIS TROUGH COULD DIP FURTHER SOUTH INTO OUR
CWA, MOST MODELS MAINTAIN ZONAL FLOW OVER THE REGION THROUGH
THE WEEKEND AND INTO THE START OF THE UPCOMING WEEK. EITHER
SOLUTION THOUGH, WILL MAINTAIN SEASONAL TEMPERATURES IN THE 60S
ALONG THE COAST AND 70S FOR INLAND LOCATIONS. /42
AVIATION
EXPECT CLEAR SKIES AND WIDESPREAD VFR FLIGHT
CONDITIONS ACROSS THE REGION THROUGH TUESDAY AFTERNOON AS HIGH
PRESSURE BUILDS INTO THE AREA. LOW-LEVEL OFFSHORE FLOW WILL
DEVELOP TONIGHT, BRINGING GUSTY EASTERLY WINDS UP TO 25 KT AT KPDX
AND KTTD. WINDS FROM KUAO TO KSLE AND KEUG WILL BE OUT OF THE
NORTH TO NORTHEAST, WITH GUSTS UP TO 15-20 KT, EXCEPT UP TO 25 KT
AT KEUG. OFFSHORE WINDS WILL GRADUALLY WEAKEN TUESDAY AFTERNOON
AND EVENING.
KPDX AND APPROACHES...VFR CONDITIONS ARE EXPECTED TO CONTINUE
THROUGH 00Z WEDNESDAY. GUSTY EASTERLY WINDS DEVELOP TONIGHT AND
CONTINUE THROUGH TOMORROW, STRONGEST BETWEEN 12-21Z WHEN GUSTS UP
TO 25 KT ARE LIKELY. NOTE THERE IS SOME UNCERTAINTY REGARDING THE
EXACT START TIME WINDS WILL BECOME EASTERLY, WHICH COULD HAPPEN AS
EARLY AS 10Z TUESDAY OR AS LATE AS 17Z TUESDAY. -TK
MARINE
BUOY OBSERVATIONS FROM EARLY MONDAY AFTERNOON SHOWED
INCREASING NORTHERLY WINDS OVER THE COASTAL WATERS, STRONGEST OVER
THE SOUTHERN WATERS WHERE GUSTS ARE APPROACHING 20 KT. EXPECT
WINDS TO INCREASE SLIGHTLY MORE LATE THIS AFTERNOON INTO THE
EVENING HOURS WITH GUSTS AS HIGH AS 25 KT OVER THE CENTRAL AND
SOUTHERN WATERS. WHILE MARGINAL, HAVE DECIDED TO ISSUE A SMALL
CRAFT ADVISORY FOR THE COASTAL WATERS SOUTH OF CAPE FALCON TO
COVER THE BREEZY NORTH WINDS. THIS ADVISORY EXPIRES TONIGHT AS
WINDS BECOME MORE EASTERLY. EAST WINDS CONTINUE TOMORROW,
STRONGEST OVER THE INNER WATERS DOWNWIND OF GAPS IN THE COASTAL
TERRAIN. THESE AREAS MAY SEE LOCALIZED WIND GUSTS UP TO 25 KT.
WINDS WILL BECOME SOUTHERLY TOMORROW AFTERNOON AT AROUND 10 KT OR
LESS. THIS CHANGE IN WIND DIRECTION IS IN RESPONSE TO A SURFACE
FRONT THAT WILL BE APPROACHING THE COASTAL WATERS TUESDAY NIGHT
INTO WEDNESDAY MORNING. IT NOW APPEARS THIS FRONT WILL DECAY OVER
THE WATERS BY LATE WEDNESDAY MORNING, BRINGING LITTLE TO NO
IMPACTS.
WINDS WILL INCREASE OUT OF THE NORTH WEDNESDAY EVENING INTO
THURSDAY WITH WIDESPREAD SMALL CRAFT ADVISORY LEVEL WIND GUSTS UP
TO 25 KT LIKELY (90% CHANCE). GUSTS UP TO 30 KT CANNOT BE RULED
OUT OVER THE SOUTHERN WATERS (50-70% CHANCE). -TK
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 10 PM PDT THIS EVENING FOR PZZ252-253.
SMALL CRAFT ADVISORY UNTIL 2 AM PDT TUESDAY FOR PZZ272-273.
WWW.WEATHER.GOV/PORTLAND
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