912
FXUS66 KPQR 121823
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1123 AM PDT WED AUG 12 2026
UPDATED AVIATION DISCUSSION.
SYNOPSIS
WARM AND DRY CONDITIONS EXPECTED THROUGH THE
WEEKEND WITH PERSISTENT ONSHORE FLOW. A STRONGER ONSHORE PUSH
WILL BRING INCREASING CLOUDS AND COOLER TEMPERATURES TODAY.
MOSTLY DRY THROUGH THE WEEKEND, WITH A CHANCE OF THUNDERSTORMS
OR SHOWERS OVER THE CASCADE CREST SATURDAY AFTERNOON. THERE ARE
LOW CHANCES FOR MORE WIDESPREAD RAIN RETURNING EARLY NEXT WEEK,
BUT SIGNIFICANT RAIN DOES NOT APPEAR LIKELY.
DISCUSSION...TODAY THROUGH TUESDAY
WATER VAPOR SATELLITE IMAGERY
SHOWS AN UPPER LEVEL TROUGH DROPPING OUT OF BRITISH COLUMBIA INTO
THE PACIFIC NW. THIS TROUGH WILL ALLOW FOR MARINE STRATUS TO SPREAD
INLAND ACROSS MUCH OF SW WASHINGTON AND NW OREGON WITH CLOUDS
LINGERING INTO THE MORNING AND EARLY AFTERNOON. SLIGHTLY COOLER
CONDITIONS ARE EXPECTED TODAY WITH HIGHS RANGING FROM THE MID-70S TO
LOWER 80S, WHILE THE COAST LIKELY REMAINS IN THE 60S. WOULD NOT BE
SURPRISED FOR SOME DRIZZLE AT THE COAST THIS MORNING AS THE MARINE
LAYER DEEPENS. MOST OF THE MOISTURE ASSOCIATED WITH THE
AFOREMENTIONED TROUGH IS EXPECTED TO REMAIN ACROSS PORTIONS OF THE
NORTHERN HALF OF WASHINGTON, KEEPING US DRY.
THERE IS AGREEMENT AMONG THE MODELS AND THEIR ENSEMBLES FOR
LATER IN THE WEEK WITH THE UPPER LEVEL PATTERN TRENDING TOWARD BROAD
UPPER LEVEL TROUGHING AND A CONTINUATION OF ONSHORE FLOW. ONE NUANCE
IN THE MID-LEVELS ON THURSDAY WILL BE SOME LIGHT EASTERLY WINDS IN
THE 850-700 MB LEVELS OF THE ATMOSPHERE, INCLUDING NEAR THE
GRASSHOPPER FIRE. THIS COULD CAUSE SOME WILDFIRE SMOKE TO DRIFT
ACROSS PORTIONS OF THE AREA, MAINLY CAUSING HAZY SKIES BY THU
AFTERNOON. THE POTENTIAL RANGE OF AFTERNOON HIGH TEMPERATURES FROM
THE NBM FOR THURSDAY THROUGH FRIDAY HAS GENERALLY CONSOLIDATED INTO
THE LOWER TO MID-80S, FAVORING NEAR TO SLIGHTLY ABOVE AVERAGE
CONDITIONS FOR MID-AUGUST.
SOME UNCERTAINTY INTO THE WEEKEND, BUT ENSEMBLES ARE SUGGESTING WEAK
UPPER LEVEL RIDGING MAY NUDGE BACK INTO THE PACIFIC NW AS LOW
PRESSURE DEEPENS THE UPPER TROUGH OFFSHORE. THE LATEST CLUSTER
ANALYSIS SHOWS MORE CONSISTENCY BETWEEN THE MODELS OF LOW PRESSURE
DROPPING SOUTH OFF THE CENTRAL CA COAST. THIS COULD RESULT IN A
SLIGHT WARMING TREND, THOUGH MODELS SUGGEST THERE IS ONLY A 10-20%
CHANCE OF EXCEEDING 90 DEGREES ACROSS THE WILLAMETTE VALLEY ON
SUNDAY AND MONDAY. SHORTWAVE TROUGHS WITHIN THE MORE SOUTHWESTERLY
FLOW ALOFT ALONG WITH SOME INCREASING MONSOONAL MOISTURE WILL ALSO
BRING SLIGHT CHANCES (10-20%) FOR THUNDERSTORMS ALONG THE CASCADE
CRESTS OF OREGON FOR SATURDAY AFTERNOON, WITH THE HIGHEST CHANCES
ACROSS THE LANE COUNTY CASCADES.
THE QUESTION THEN TURNS TO THE POSSIBILITY OF RAIN EARLY NEXT
WEEK, BUT CHANCES FOR MEASURABLE PRECIPITATION REMAINS LOW (15-30%)
ACROSS THE AREA NEXT MONDAY AND TUESDAY. CLUSTER ANALYSIS OF 500 MB
HEIGHTS SHOWS A WIDE RANGE OF THE MAGNITUDES AND PLACEMENTS OF THE
UPPER LEVEL TROUGH OFFSHORE, WHILE ONLY 10-15% OF ENSEMBLES SHOW THE
POTENTIAL FOR ANY SUBSTANTIAL RAINFALL (24 HOUR TOTALS OF > 0.25")
ACROSS THE AREA. DH/10
AVIATION...THROUGH 18Z THU
WESTERLY FLOW ALOFT CONTINUES AS AN
UPPER LEVEL TROUGH MOVES OVER THE REGION. MARINE STRATUS MADE A
PUSH INLAND THIS MORNING, BUTTING UP AGAINST THE CASCADE
FOOTHILLS. MVFR CONDITIONS CONTINUE AT INLAND TERMINALS AND SHOULD
IMPROVE TO VFR BY 19-21Z WED. MVFR TO IFR CONDITIONS ARE BEING
OBSERVED ALONG THE COAST. LOWERED FLIGHT CONDITIONS ARE EXPECTED
TO PERSIST THROUGH THE TAF PERIOD ALONG THE COAST WITH AROUND A
50% CHANCE OF BRIEF IMPROVEMENT TO VFR/HIGH MVFR IN THE AFTERNOON
HOURS BETWEEN 20Z WED THROUGH 00Z THU. THEN THERE'S A 60-80%
CHANCE THAT IFR/LIFR CONDITIONS RETURN ALONG THE COAST BETWEEN
02-06Z THU. THE MARINE PUSH WILL BE LESS STRONG TONIGHT INTO
THURSDAY MORNING, SO CHANCES OF MARINE STRATUS PUSHING INLAND
DURING THIS TIME IS LOWER WITH A 25-40% CHANCE OF MVFR CEILINGS
AT ANY HOUR BETWEEN 10-16Z THU. ANY LOWERED CEILINGS THAT DO FORM
SHOULD IMPROVE BY 18-21Z THU. NORTH TO NORTHWEST WINDS ARE
EXPECTED TO INCREASE TO AROUND 8-10 KT THIS AFTERNOON, DECREASING
BY 04-08Z THU.
KPDX AND APPROACHES...EXPECT MVFR CIGS TO PERSIST THROUGH 19-21Z
WED, IMPROVING TO VFR AFTER. LINGERING AFTERNOON CLOUDS ARE
EXPECTED TO GRADUALLY LIFT AND SCATTER OUT, WITH PREDOMINATELY VFR
CONDITIONS LIKELY THROUGH THE REST OF THE TAF PERIOD. HOWEVER,
THERE IS A 25-40% CHANCE OF MVFR CIGS DEVELOPING AGAIN BETWEEN
10-14Z THU. IF THESE FORMED, EXPECT IMPROVE TO VFR CONDITIONS
AGAIN BY 18-20Z THU. NORTHWEST WINDS AROUND 5 KT ARE EXPECTED TO
INCREASE TO 8-10 KT AFTER 23Z WED, DECREASING AFTER 06-08Z THU.
-03
MARINE
NO SIGNIFICANT CHANGES AS HIGH PRESSURE OFFSHORE WILL
CONTINUE TO SUPPORT NORTHERLY WINDS AND FAIRLY BENIGN CONDITIONS
ACROSS THE COASTAL WATERS THROUGH THE WEEK AND INTO THE WEEKEND.
WINDS FROM THE NORTH TO NORTHWEST WITH GUSTS LESS THAN 21 KTS WILL
CONTINUE THROUGH AT LEAST THE END OF THE WEEK. WIND DRIVEN SEAS
ARE EXPECTED TO REMAIN AROUND 3 TO 6 FT THROUGH THE WEEK. /DH
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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