054
FXUS66 KSEW 161549
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
849 AM PDT SUN AUG 16 2026
SYNOPSIS
THE THUNDERSTORM THREAT WILL WIDELY DIMINISH TODAY. ANOTHER TROUGH
WILL MOVE ACROSS THE REGION LATE MONDAY INTO TUESDAY. A WARMER
AND DRIER TREND IS THEN EXPECTED MID TO LATE WEEK AS A RIDGE
STARTS TO BUILD INTO THE REGION, HOWEVER SHOWER CHANCES MAY
INCREASE AGAIN BY FRIDAY AND INTO SATURDAY AS A DISTURBANCE
APPROACHES FROM THE WEST.
SHORT TERM /TODAY THROUGH TUESDAY/
BROAD TROUGHING REMAINS OVER THE NE PAC WHILE VAST RIDGING
RESIDES UPSTREAM, NOSING INTO THE PNW TODAY. MARINE STRATUS
AGAIN FILLING UP ACROSS W WA AS MID-HIGH LEVEL CLOUDS TRACK
OVERHEAD SO FAR THIS MORNING. A CHANCE (15-25%) OF THUNDERSTORMS
IS FORECAST FOR THE NORTH CASCADES WITH LESSER PROBABILITIES
ELSEWHERE GIVEN NBM PROB THUNDER. MONDAY'S FORECAST IS QUITE
SIMILAR IN REGARDS TO CONVECTION BUT PROBABILITIES SHOULD REMAIN
CAPPED AT 10-15%, LIKELY DUE TO MORE LARGE-SCALE SUBSIDENCE
PROVIDED BY MORE PRONOUNCED RIDGING OVERHEAD. HIGHS FOR SUNDAY
AND MONDAY IN THE MID 70S TO MID 80S WITH OVERNIGHT LOWS IN THE
LOWER TO UPPER 50S. COASTAL AREA HIGHS ARE FORECAST IN THE 60S.
A RATHER TYPICAL PATTERN OF ONSHORE LOW-LEVEL FLOW MAINTAINING
MORNING CLOUDS, WITH SOME CLEARING IN THE AFTERNOON ON TUESDAY.
A PASSING TROUGH COULD PROVIDE A REINFORCING PUSH OF CLOUDS AND
KNOCK TEMPERATURES DOWN A FEW DEGREES, MAINLY FOR THE SW INTERIOR.
OTHERWISE, BENIGN CONDITIONS ARE IN STORE WITH HIGHS IN THE MID
70S TO LOWER 80S ACROSS THE INTERIOR AND 60S ALONG THE COAST.
OVERNIGHT LOWS ARE FORECAST INTO THE 50S AREA WIDE.
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
AN UPPER-RIDGE LOOKS TO BUILD ACROSS THE REGION DURING THE
SECOND HALF OF THE WEEK. CONTINUED LOW-LEVEL ONSHORE FLOW WILL
HELP TO KEEP TEMPERATURES FROM WARMING TOO AGGRESSIVELY. THE
PATTERN WILL THEN BEGIN TO CHANGE TOWARDS FRIDAY AND SATURDAY AS
ENSEMBLE GUIDANCE SUGGESTS THE NEXT DISTURBANCE MAY GET CLOSE
ENOUGH TO BRING ANOTHER ROUND OF SHOWER AND POTENTIAL
THUNDERSTORM CHANCES. AND WITH THAT, TEMPERATURES COULD COOL
BELOW AVERAGE FOR THE FIRST TIME IN A WHILE.
AVIATION
CEILINGS RANGE PRIMARILY BETWEEN MVFR/IFR FOR TERMINALS UNDER LOW
STRATUS THIS MORNING. STRATUS SHOULD SLOWLY SCATTER IN THE LATE
MORNING HOURS, SCATTERING BETWEEN AROUND 19-21Z. STRATUS WILL LIKELY
REMAIN IN PLACE ALONG THE IMMEDIATE COAST AND SET THE STAGE FOR A
MORE TRADITIONAL MARINE PUSH LATE TONIGHT INTO MONDAY MORNING. LIGHT
SOUTHWEST TO WEST WINDS PREVAIL THIS MORNING, INCREASING IN THE
AFTERNOON TO AROUND 5-10 KT. WINDS THROUGH THE PUGET SOUND WILL
SHIFT NORTHERLY BY AROUND 19-21Z AND THROUGH THE EVENING.
KSEA...MVFR CIGS CONTINUE THIS MORNING. STRATUS SHOULD BEGIN TO LIFT
AND SCATTER TO VFR AFTER 19-20Z WITH DECREASING CLOUDS THROUGH THIS
EVENING. STRATUS IS EXPECTED TO RETURN AGAIN AFTER 12Z-14Z MONDAY
FOR ANOTHER ROUND OF MVFR CIGS. SOUTHWEST WINDS 5-8 KT WILL CONTINUE
THROUGH THIS MORNING, TURNING TO BECOME MORE NORTHWESTERLY AFTER
AROUND 19-21Z AND PERSIST THROUGH THIS EVENING AT 5-7 KT. LIGHT
NORTHEASTERLY WINDS OVERNIGHT. 62/29
MARINE
BROAD HIGH PRESSURE WILL REDEVELOP OVER THE FAR OFFSHORE WATERS
TODAY AND STRENGTHEN GOING INTO NEXT WEEK, MAINTAINING NORTHWESTERLY
WINDS OVER THE COASTAL WATERS. SEAS LOOK TO RISE TO AROUND 4-6 FT
TONIGHT. SEAS THEN LOOK TO BECOME STEEPER MONDAY NIGHT INTO TUESDAY
TO AROUND 6-8 FT AT 7 SECONDS AS WINDS INCREASE OVER THE OUTERMOST
COASTAL WATERS. STEEP SEAS LOOK TO CONTINUE THROUGH THURSDAY.
DIURNALLY DRIVEN WESTERLY WINDS WILL CONTINUE TO OCCUR EACH
AFTERNOON AND EVENING THROUGH THE STRAIT OF JUAN DE FUCA. THE
STRONGEST PUSH LOOKS TO BE TONIGHT, FOR WHICH A SMALL CRAFT ADVISORY
HAS BEEN ISSUED. THE WESTERLY PUSHES WILL GRADUALLY WEAKEN THROUGH
THE WEEK WITH ADDITIONAL HEADLINES UNLIKELY AT THIS TIME. 62/29
FIRE WEATHER
CONVECTION WILL BE LARGELY CONFINED TO NORTHERN CASCADE CREST
WHERE A 15-20% CHANCE OF THUNDERSTORM IS IN THE FORECAST ACCORDING
TO THE NBM. CONTINUED ONSHORE FLOW AND EXCELLENT OVERNIGHT HUMIDITY
RECOVERIES WILL THEN HELP MITIGATE FIRE WEATHER CONDITIONS TO
START THE WEEK. WHILE SOME UNCERTAINTY REMAINS IN THE LONG TERM
PATTERN, ENSEMBLE GUIDANCE HAS INCREASINGLY COME TO CONSENSUS
THAT A WARMING AND DRYING TREND IS LIKELY MID TO LATE WEEK,
BEFORE THE POTENTIAL FOR SHOWER AND THUNDERSTORM CHANCES INCREASES
AGAIN LATE WEEK AS THE NEXT DISTURBANCE APPROACHES FROM THE WEST.
THIS COULD POTENTIALLY REINTRODUCE SOME ELEVATED FIRE WEATHER
CONCERNS TO THE AREA.
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 3 AM PDT
MONDAY FOR CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-
EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
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