620
FXUS66 KSEW 181016
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
316 AM PDT MON MAY 18 2026
SYNOPSIS
HIGH PRESSURE WILL REMAIN SITUATED OFFSHORE THROUGH
MUCH OF NEXT WEEK, MAINTAINING NEAR-NORMAL TEMPERATURES ACROSS
WESTERN WASHINGTON WITH CLOUDY MORNINGS AND SUNSHINE IN THE
AFTERNOONS. A FEW WEAK SYSTEMS WILL MOVE OVER THE TOP OF THE
RIDGE TOWARDS THE MIDDLE OF NEXT WEEK, BRINGING LITTLE MORE THAN
A FEW PERIODS OF SPRINKLES.
SHORT TERM /TODAY THROUGH WEDNESDAY/
UPPER-TROUGHING CURRENTLY OVER THE GREAT BASIN WHILE AN UPPER-
LEVEL RIDGE IS JUST OFFSHORE THE PNW. HIGH CLOUDS ARE CURRENTLY
STREAMING IN UNDER NORTHWEST FLOW ALOFT. AREAS OF FOG/LOW
STRATUS ARE STILL LIKELY TO DEVELOP THIS MORNING BUT COVERAGE
WILL BE AT A MINIMUM. ANY FOG THAT SHOULD FORM WILL GIVE WAY TO
SUNSHINE TODAY AS THE AFOREMENTIONED RIDGE CENTERS OVERHEAD.
HIGH TEMPERATURES ARE FORECAST IN THE 60S ACROSS THE INTERIOR
WITH 50S ALONG THE COAST. INCREASING ONSHORE FLOW WILL LEAD TO
BREEZY WINDS THROUGH THE STRAIT OF JUAN DE FUCA THIS EVENING
WITH GUSTS UP TO 30 MPH ON WHIDBEY ISLAND BEFORE GRADUALLY
DECREASING LATER TONIGHT. HREF SUGGESTS A 35% CHANCE OF GUSTS
EXCEEDING 35 MPH. OVERNIGHT LOWS WILL FALL INTO THE 40S.
UPPER-RIDGING IS LIKELY TO MAINTAIN THROUGH MIDWEEK AS
CONDITIONS REMAIN RATHER BENIGN. WEAK DISTURBANCES WILL ATTEMPT
TO TRAVERSE ALONG THE PERIPHERY OF THE RIDGE - MAINTAINING
SLIGHT (15% OR LESS) POPS BUT MOSTLY FOR THE MOUNTAINS.
TEMPERATURES ARE TO REMAIN NEAR-SEASONAL THROUGHOUT THIS PERIOD
WITH HIGHS IN THE 60S TO NEAR LOWER 70S AND LOWS IN THE 40S.
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
THE UPPER LEVEL RIDGE OFFSHORE WILL BEGIN TO FLATTEN ON THURSDAY
AS A LOW PRESSURE SYSTEM SLOWLY STRENGTHENS AND LOWERS FROM THE
GULF OF ALASKA. CONDITIONS ARE FAVORED TO REMAIN DRY INTO THE
FIRST HALF OF THE WEEKEND AS ZONAL FLOW SETS UP ALOFT, WITH
CONTINUED MILD TEMPERATURES. ENSEMBLES ARE HONING IN ON A
POTENTIAL PATTERN CHANGE BY THE END OF NEXT WEEKEND, WITH
INCREASING CHANCES FOR WIDESPREAD RAINFALL ARRIVING SUNDAY
EVENING. HOWEVER, THE DETAILS REMAIN UNCERTAIN AT THIS TIME.
41
AVIATION
NORTH/NORTHWESTERLY WINDS WILL PERSIST ALOFT AS AN UPPER LEVEL
RIDGE REMAINS NUDGED OVER THE REGION. ONSHORE FLOW WILL CONTINUE
IN THE LOW LEVELS, ALLOWING FOR ANOTHER ROUND OF STRATUS TO PUSH
INLAND THIS MORNING, MAINLY FOR AREAS ALONG THE COAST, THE SOUTHWEST
INTERIOR, AND THE SOUTH SOUND. A FEW ISOLATED SPOTS OF PATCHY FOG
MAY ALSO DEVELOP ACROSS THE CHEHALIS VALLEY AND KITSAP PENINSULA
EARLY THIS MORNING, THOUGH HIGH CLOUDS STREAMING IN OVERHEAD
SHOULD HELP HINDER ANY WIDESPREAD DEVELOPMENT. CONDITIONS AT THE
AREA TERMINALS REMAIN VFR, THOUGH COULD SEE TERMINALS BRIEFLY DIP
DOWN TO MVFR BETWEEN 12-15Z (MOST LIKELY FOR KHQM, KPWT, AND
KOLM). EXPECT CIGS AT THE REMAINDER OF THE TERMINALS TO REMAIN
VFR THROUGH THE DAY.
WINDS REMAIN LIGHT SOUTHERLY AT 6 KT OR LESS ACROSS THE MAJORITY
OF THE INTERIOR TERMINALS THIS MORNING, OUTSIDE OF KPAE, WHERE
WINDS CONTINUE OUT OF THE NORTH. WINDS ALONG THE COAST ARE LIGHT
NORTHWESTERLY AND KCLM REMAINS WESTERLY BETWEEN 8-12 KT UNDER
INCREASED ONSHORE FLOW. WINDS WILL INCREASE TO 7-10 KT THIS
AFTERNOON AND LOOK TO SWITCH TO THE NORTH ACROSS THE INTERIOR
BETWEEN 00-03Z TONIGHT. A WEAK, SPLITTING FRONTAL SYSTEM WILL
MOVE INTO THE AREA TONIGHT INTO TUESDAY, WITH THE MAIN IMPACT
BEING MORE WIDESPREAD STRATUS BY TUESDAY MORNING.
KSEA...CEILINGS LOOK TO REMAIN VFR THROUGH THE DAY, WITH A FEW
SCATTERED CLOUDS POSSIBLE AT THE TERMINAL BETWEEN 2000-3000 FT
EARLY THIS MORNING. THE LATEST PROBABILITY OF CEILINGS DIPPING
TO MVFR IS 15 PERCENT THIS MORNING. A MUCH GREATER PROBABILITY
(40-45 PERCENT) EXISTS OF CEILINGS DROPPING TO MVFR BY TUESDAY
MORNING. WINDS ARE SOUTHERLY AND WILL INCREASE TO 7-10 KT THIS
AFTERNOON, BEFORE SWITCHING TO THE NORTH BETWEEN 00-03Z.
14
MARINE
HIGH PRESSURE WILL REMAIN SITUATED OVER THE NORTHEASTERN
PACIFIC THROUGH MUCH WEEK, BRINGING A PROLONGED PERIOD OF
NORTH/NORTHWESTERLY WINDS TO THE COASTAL WATERS. A WEAK,
SPLITTING FRONTAL SYSTEM WILL MOVE INTO THE WATERS TONIGHT INTO
TUESDAY AND WILL BRING AN INCREASE OF ONSHORE FLOW ALONG THE
CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA, WITH ANOTHER ROUND
OF SMALL CRAFT WESTERLIES EXPECTED THIS AFTERNOON AND EVENING.
HIGH PRESSURE WILL BUILD BACK INTO THE COASTAL WATERS IN THE
WAKE OF THE FRONT. ONSHORE FLOW WILL PERSIST THROUGHOUT MUCH OF
THE WEEK AND WILL RESULT IN DAILY PUSHES OF WESTERLY WINDS ALONG
THE STRAIT. THE NEXT WEAK FRONTAL SYSTEM LOOKS TO MOVE INTO THE
AREA WATERS THURSDAY INTO FRIDAY, FOLLOWED BY ANOTHER LATE NEXT
WEEKEND.
SEAS WILL GENERALLY HOVER BETWEEN 6-8 FT THROUGH THE FIRST HALF
OF THE WEEK, BEFORE INCREASING TOWARDS 8-10 FT MID TO LATE WEEK.
THE LATEST GEFS PROBABILISTIC GUIDANCE IS HIGHLIGHTING ROUGHLY
A 20-40 PERCENT CHANCE OF SEAS EXCEEDING 9 FT BY NEXT WEEKEND.
14
HYDROLOGY
THE DAILY HYDROLOGY DISCUSSION HAS ENDED UNTIL THE
START OF THE NEXT RAINY SEASON; IT WILL ONLY BE UPDATED DURING
THIS TIME AS NEEDED.
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT EARLY THIS MORNING FOR
CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE
U.S. WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 5 AM PDT
TUESDAY FOR CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-
EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
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