511
FXUS66 KSEW 181609
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
909 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. STRATUS HAS BEEN
CONFINED TO WEST CENTRAL WASHINGTON BETWEEN THE KITSAP PENINSULA
AND INTO THE SOUTH SOUND WITH THE EDGES BEGINNING TO ERODE AWAY.
THIS WILL GIVE WAY TO MAINLY JUST HIGH CLOUDS AND SOME FAIR
WEATHER CUMULUS ACROSS THE AREA THIS AFTERNOON. 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, WHICH ALLOWED FOR SOME LOCALIZED STRATUS TO
PUSH INLAND THIS MORNING, MAINLY FOR AREAS ALONG THE COAST, THE
SOUTHWEST INTERIOR, AND THE SOUTH SOUND WHERE THESE TERMINALS
ARE SEEING MVFR/IFR CONDITIONS LIKELY THROUGH 18Z (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...MVFR CEILINGS THIS MORNING WITH BROKEN CLOUDS AT THE
TERMINAL AROUND 1500 TO 2000 FT. CEILINGS WILL REBOUND TO VFR
LIKELY AFTER 17Z AND WILL REMAIN VFR THROUGHOUT THE DAY. 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/MAZURKIEWICZ
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 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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