558
FXUS66 KSEW 120317
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
817 PM PDT SAT JUL 11 2026
SYNOPSIS
WEAK SYSTEM MOVING BY TO THE NORTH WILL ENHANCE THE
LOW LEVEL ONSHORE FLOW OVERNIGHT. LOW LEVEL FLOW TURNING
NORTHERLY SUNDAY AFTERNOON AND REMAINING NORTHERLY INTO TUESDAY
LEADING TO LESS MORNING CLOUDS AND WARMER DAYS. WEAK UPPER LEVEL
TROUGH MOVING OVER THE AREA WEDNESDAY AFTERNOON THROUGH
THURSDAY. UPPER LEVEL RIDGE BUILDING OVER WESTERN WASHINGTON
BEGINNING FRIDAY.
SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/
SATELLITE IMAGERY
SHOWS PLENTY OF FAIR WEATHER CUMULUS OVER WESTERN WASHINGTON
WITH A WEAK UPPER LEVEL SHORTWAVE JUST OFFSHORE THIS AFTERNOON.
TEMPERATURES A LITTLE BELOW NORMAL, MID 60S TO LOWER 70S OVER
THE INTERIOR AND MID 60S ALONG THE COAST.
WEAK UPPER LEVEL SHORTWAVE MOVING BY TO THE NORTH TONIGHT.
INCREASING LOW LEVEL ONSHORE FLOW WITH AND BEHIND THE SHORTWAVE
WITH THE MARINE LAYER MAKING ITS WAY BACK INLAND EARLY SUNDAY
MORNING. LOWS TONIGHT IN THE UPPER 40S TO MID 50S.
MOSTLY CLOUDY SUNDAY MORNING. LOW LEVEL FLOW TURNING NORTHERLY
SUNDAY AFTERNOON. THIS WILL GET RID OF THE MARINE LAYER OVER THE
INTERIOR RESULTING IN SOME AFTERNOON SUNSHINE. HIGHS IN THE MID
60S TO MID 70S.
LOW LEVEL NORTHERLY FLOW CONTINUING THROUGH MONDAY NIGHT WHICH
WILL KEEP THE MARINE LAYER AT BAY. TEMPERATURES ALOFT WARMING
SLIGHTLY WITH 500 MB HEIGHTS NEAR 580 DMS MONDAY AFTERNOON.
HIGHS WARMING INTO THE 70S AND LOWER 80S. LOWS MONDAY MORNING IN
THE UPPER 40S TO MID 50S. FELTON
LONG TERM /TUESDAY THROUGH SATURDAY/
UPPER LEVEL TROUGH
DIGGING OFFSHORE TUESDAY PUSHING 500 MB HEIGHTS INTO THE LOWER
TO MID 580 DMS OVER WESTERN WASHINGTON. HIGHS WARMING INTO THE
MID 70S TO MID 80S OVER THE INTERIOR AND NEAR 70 ALONG THE
COAST.
UPPER LEVEL TROUGH AXIS REACHING THE COAST WEDNESDAY AFTERNOON
WITH THE TROUGH SLOWLY MOVING OVER THE REMAINDER OF THE AREA
WEDNESDAY NIGHT INTO THURSDAY. SLIGHT CHANCE OF SHOWERS IN THE
MOUNTAINS AS THE TROUGH MOVES OVERHEAD. FOR THE LOWLANDS SLOW
COOLING TREND WITH HIGH WEDNESDAY IN THE LOWER 70S TO LOWER 80S
AND JUST 70S FOR THURSDAY.
UPPER LEVEL TROUGH MOVING EAST THURSDAY NIGHT. UPPER LEVEL RIDGE
BUILDING FRIDAY AND SATURDAY WITH 500 MB HEIGHTS RISING INTO THE
MID 580 DMS. THIS COULD BE THE START OF A SUSTAINED WARM SPELL
OVER THE AREA. HIGHS WARMING INTO THE MID 70S TO MID 80S BY
SATURDAY INLAND WITH HIGHS ON THE COAST REMAINING NEAR 70.
FELTON
AVIATION
WIDESPREAD VFR CONDITIONS OVER W WA THIS EVENING
WITH THE EXCEPTION OF ALONG THE COAST WHERE MARINE STRATUS HAVE
ALREADY STARTED TO PUSH INLAND, TRIGGERING MVFR CONDITIONS
THERE. ANOTHER ROUND OF STRONG LOW-LEVEL ONSHORE FLOW TONIGHT
WILL BRING THESE MARINE STRATUS INTO THE REMAINDER OF WESTERN
WASHINGTON BY EARLY SUNDAY MORNING WITH WIDESPREAD MVFR CIGS
LIKELY BY 12Z. STRATUS WILL BURN OFF, RESUMING VFR BY 18-21Z
SUNDAY. BREEZY WEST TO SOUTHWESTERLY WINDS FOR PUGET SOUND
TERMINALS AND COASTAL TERMINALS THIS EVENING AND EARLY TONIGHT
WITH GUSTS NEAR 20-25 KT. SURFACE WINDS SHOULD SUBSIDE ON SUNDAY
MORNING.
KSEA...VFR CONDITIONS WILL PREVAIL INTO TONIGHT. THE NBM HAS A 20-
25% CHANCE OF CEILINGS BELOW 3,000 FT DEVELOPING OVER THE TERMINAL
AFTER 09Z BUT IF MANIFEST, VFR SHOULD RETURN BY 18Z. SOUTHWEST WINDS
GUSTS UP TO 20-25 KT TONIGHT AFTER 06Z BUT SHOULD SUBSIDE BY 12Z
SUNDAY MORNING.
MARINE
A WEAK SURFACE TROUGH WILL REMAIN OVER THE OFFSHORE
WATERS TONIGHT BEFORE HIGH PRESSURE BROADLY REBUILDS INTO THE
COASTAL AND OFFSHORE WATERS SUNDAY AND MONDAY AND REMAINING INTO
MIDWEEK. THIS WILL PROMOTE A FAIRLY TYPICAL SUMMER PATTERN WITH
VARYING DEGREES OF ONSHORE FLOW PROMOTING A DIURNALLY DRIVEN
INCREASE IN WESTERLIES THROUGH THE STRAIT OF JUAN DE FUCA NEAR
DAILY. NORTHWEST WINDS OVER THE COASTAL WATERS ARE LIKELY TO
INCREASE LATER MONDAY INTO TUESDAY AS THERMALLY INDUCED SURFACE
LOW PRESSURE EXPANDING OVER THE INTERIOR OF WESTERN WASHINGTON
TIGHTENS THE ONSHORE GRADIENT.
FIRE WEATHER
THE LACK OF OFFSHORE FLOW THROUGH THE MIDDLE OF
NEXT WEEK WILL KEEP FIRE WEATHER CONCERNS AT A MINIMUM. WARMING
TEMPERATURES LATE NEXT WEEK WILL BEGIN TO INCREASE THE FIRE
WEATHER RISKS GOING INTO THE WEEKEND. FELTON
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 3 AM PDT SUNDAY FOR CENTRAL U.S.
WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE U.S. WATERS
STRAIT OF JUAN DE FUCA.
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