219
FXUS66 KSEW 111557
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
857 AM PDT THU JUN 11 2026
SYNOPSIS
LOW LEVEL ONSHORE FLOW TODAY WITH WEAK SYSTEM MOVING BY WELL TO
THE NORTH TONIGHT. UPPER LEVEL RIDGE BUILDING OFFSHORE TONIGHT
WILL MOVE EAST ENDING UP OVER WESTERN WASHINGTON BEGINNING SATURDAY.
THERMALLY INDUCED SURFACE TROUGH DEVELOPING ALONG THE COAST
SATURDAY NIGHT WITH THE LOW LEVEL FLOW TURNING OFFSHORE. RECORD
HIGHS LIKELY BOTH SUNDAY AND MONDAY. UPPER LEVEL RIDGE WEAKENING
AND LOW LEVEL FLOW TURNING ONSHORE TUESDAY FOR SOME COOLING.
INCREASING ONSHORE FLOW WEDNESDAY BRINGING TEMPERATURES DOWN TO
NEAR NORMAL.
SHORT TERM /TODAY THROUGH SATURDAY/
NO MAJOR UPDATES FOR THE MORNING AFD ISSUANCE. -HPR
SATELLITE IMAGERY SHOWS PATCH OF STRATUS OVER THE NORTHEAST
SLOPES OF THE OLYMPICS OTHERWISE CLEAR SKIES OVER THE AREA THIS
MORNING. TEMPERATURES AT 3 AM/10Z WERE IN THE MID 40S TO MID
50S.
PRETTY NORMAL MID JUNE DAY ACROSS THE AREA TODAY WITH
NORTHWESTERLY FLOW ALOFT AND LIGHT NORTHWESTERLY SURFACE
GRADIENTS. A FEW PLACES ALREADY REPORTING 100 PERCENT HUMIDITY
SO COULD SEE PATCHY FOG FORM THIS MORNING. WHAT DOES FORM WILL
BE SHALLOW AND NOT LAST LONG. HIGH TEMPERATURES WITH PLENTY OF
SUNSHINE IN THE MID 60S COAST AND MID 60S TO MID 70S INLAND.
LITTLE CHANGE IN THE PATTERN TONIGHT AND FRIDAY. WEAK UPPER
LEVEL SYSTEM MOVING BY WELL TO THE NORTH TONIGHT WILL KEEP THE
LIGHT NORTHWESTERLY LOW LEVEL ONSHORE FLOW PATTERN INTACT. WEAK
SYSTEM WILL ALSO DELAY THE RIDGE BUILDING OVER THE AREA INTO
FRIDAY AFTERNOON. LOWS TONIGHT IN THE 40S AND LOWER 50S. HIGHS
FRIDAY JUST A TOUCH WARMER WITH THE RIDGE STARTING TO BUILD, IN
THE MID 60S TO UPPER 70S.
UPPER LEVEL RIDGE OFFSHORE BUILDING FRIDAY NIGHT AND SATURDAY
WITH THE RIDGE AXIS SATURDAY ON A LINE FROM OFF THE COAST
THROUGH VANCOUVER ISLAND INTO THE INTERIOR OF BRITISH COLUMBIA.
NORTHWESTERLY ONSHORE SURFACE GRADIENTS CONTINUING GIVING
LOCATIONS NEAR THE WATER A GOOD SEABREEZE SATURDAY AFTERNOON.
THIS WILL KNOCK A FEW DEGREES OFF THE HIGHS IN LOCATIONS NEAR
THE WATER. AWAY FROM THE WATER TEMPERATURES ALOFT WARMING WITH
THE RIDGE BUILDING WILL START THE WARMING TREND. HIGHS IN THE
MID 70S TO MID 80S.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
GOOD RUN TO RUN CONSISTENCY IN THE MODELS. THERMALLY INDUCED
SURFACE TROUGH DEVELOPING ALONG THE COAST SATURDAY NIGHT TURNING
THE LOW LEVEL FLOW OFFSHORE. THE OFFSHORE FLOW WILL CONTINUE
INTO MONDAY. TEMPERATURES ALOFT WARMING WITH 850 MB TEMPERATURES
PEAKING NEAR PLUS 20C MONDAY. RECORD HIGH TEMPERATURES BOTH
DAYS WITH HIGHS IN THE 80S AND LOWER 90S SUNDAY AND 80S TO MID
90S MONDAY. MODERATE HEATRISK BOTH DAYS WITH A 30-50% CHANCE OF
MAJOR HEATRISK IN THE SOUTHWEST INTERIOR AND LOWER CHEHALIS
VALLEY. LOWS WILL BE MILD, IN THE MID 50S TO LOWER 60S.
FORECAST HIGH FOR SEATTLE MONDAY IS 91 DEGREES. 90 DEGREE PLUS
DAYS ARE NOT UNHEARD OF THIS TIME OF YEAR BUT ARE RARE. ONLY 7
PERCENT ( 19 OUT OF 276 ) OF THE 90 DEGREE PLUS DAYS AT
SEATTLE-TACOMA AIRPORT HAVE OCCURRED IN MAY AND THE FIRST HALF
OF JUNE. LAST YEAR SEATTLE ALSO HAD AN EARLY FIRST 90 DEGREE
PLUS DAY WITH 90 DEGREES ON JUNE 8TH.
UPPER LEVEL RIDGE WEAKENING TUESDAY WITH THE LOW LEVEL FLOW
TURNING ONSHORE DURING THE DAY. MODELS YESTERDAY WERE TRENDING
TOWARDS A WEAKER MARINE PUSH SCENARIO AND THE CURRENT RUNS HAVE
GONE THAT WAY WITH 5-10 DEGREES OF COOLING FOR THE INTERIOR.
MUCH COOLER ON THE COAST WITH HIGHS IN THE 60S. LOWS TUESDAY
MORNING WILL BE THE WARMEST OF THE EXTENDED PERIOD, A FEW
DEGREES EITHER SIDE OF 60.
RIDGE CONTINUING TO WEAKEN TUESDAY NIGHT INTO WEDNESDAY WITH
INCREASING LOW LEVEL ONSHORE FLOW. MARINE LAYER MOVING INTO THE
INTERIOR TUESDAY NIGHT INTO WEDNESDAY COOLING HIGHS BACK DOWN
INTO THE LOWER TO MID 70S. HIGHS ON THE COAST MID 60S. WITH THE
ARRIVAL OF THE REFRESHING MARINE AIR LOWS WEDNESDAY MORNING
IN THE LOWER TO MID 50S. FELTON
AVIATION
VFR WITH CLEAR SKIES EXPECTED TODAY. REMAINING PATCHY FOG IN THE
SOUTH INTERIOR HAS CLEARED. INCREASING NORTHERLY WINDS 5-12 KT
THIS AFTERNOON, WITH THE STRONGEST WINDS ALONG THE COAST AND
STRAIT OF JUAN DE FUCA. TOMORROW MORNING, THE PROBABILITY OF LOW
CEILINGS AND OR/VISIBILITIES IS 40-60% ALONG THE COAST, 60-80%
IN THE MOUNTAINS, AND LESS THAN 10% IN THE INTERIOR/PUGET SOUND
AREAS. THE CEILINGS/VISIBILITIES ALONG THE COAST/MOUNTAINS MAY
BE AS LOW AS IFR/LIFR AT TIMES FRIDAY MORNING, BEFORE CLEARING.
KSEA...VFR CONDITIONS EXPECTED. NORTHEASTERLY WINDS EARLY THIS
MORNING 4-6 KT WILL TRANSITION TO THE NORTHWEST AFTER 16Z AT 5-8
KT. WINDS WILL REVERT BACK TO THE NORTHEAST AFTER 06Z.
29/HPR
MARINE
ANOTHER PUSH OF WESTERLIES IS EXPECTED THIS EVENING ACROSS THE
STRAIT OF JUAN DE FUCA. WITH, MODERATE TO HIGH CONFIDENCE, A SMALL
CRAFT ADVISORY HAS BEEN ISSUED FOR THE CENTRAL AND EASTERN PORTIONS
OF THE STRAIT. BROAD HIGH PRESSURE WILL CONTINUE TO BUILD OVER THE
NE PACIFIC TODAY. ON FRIDAY, HIGH PRESSURE WILL BEGIN BUILDING OVER
AREA WATERS AND WILL REMAIN THE DOMINANT WEATHER FEATURE THROUGH
MONDAY. WITH HIGH PRESSURE SITUATED OVER AREA WATERS, NORTHERLY FLOW
WILL BE ESTABLISHED ACROSS AREA WATERS. HIGH PRESSURE WILL WEAKEN ON
TUESDAY AS THE BROAD AREA OF HIGH PRESSURE RETREATS BACK INTO THE
OPEN WATERS OF THE PACIFIC. LONG TERM GUIDANCE HIGHLIGHTS INCREASED
ONSHORE FLOW ON TUESDAY WITH THE POTENTIAL (50-70% CHANCE) FOR GALES
ACROSS THE STRAIT OF JUAN DE FUCA.
29
FIRE WEATHER
WARM, DRY AND UNSTABLE PATTERN DEVELOPING OVER WESTERN
WASHINGTON SATURDAY WITH THE PATTERN CONTINUING THROUGH MONDAY.
WETTING RAINS EARLIER IN THE WEEK WILL BRIEFLY HELP THE FINE
FUELS FROM REACHING CRITICAL THRESHOLDS THIS WEEKEND INTO
MONDAY FOR RED FLAG CONDITIONS. MINIMUM RELATIVE HUMIDITY (RH)
VALUES WILL DROP AS LOW AS 15 TO 20 PERCENT FOR PORTIONS OF THE
SOUTH PUGET SOUND AND SOUTHWEST INTERIOR SUNDAY AND MONDAY.
THESE DRY HUMIDITY VALUES, COMBINED WITH AN UNSTABLE AIRMASS DUE
TO DAYTIME HEATING AND LIGHT OFFSHORE WINDS WILL LEAD TO
ELEVATED FIRE WEATHER CONCERNS ACROSS THE REGION. FUELS THAT
WILL BE MOST SUSCEPTIBLE TO THE ELEVATED FIRE WEATHER CONCERNS
ARE DRY/SHRUBBY GRASSY AREAS (ESPECIALLY THOSE NEAR ROADS), AS
WELL AS PILES OF DRY FUELS. LOW LEVEL ONSHORE FLOW WILL RETURN
TUESDAY, WITH A GRADUAL COOL DOWN AND IMPROVEMENT IN MINIMUM
RELATIVE HUMIDITY VALUES. FELTON/HPR
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 1 AM PDT
FRIDAY FOR CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY FROM 5 PM THIS AFTERNOON TO 1 AM PDT
FRIDAY FOR EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE
FUCA.
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