446
FXUS66 KSEW 081522
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
822 AM PDT SAT AUG 8 2026
SYNOPSIS
GRADUAL COOLING OVER THE WEEKEND TO NEAR-NORMAL TEMPERATURES AS
ONSHORE FLOW PERSISTS. THE BACKSIDE OF AN UPPER LEVEL RIDGE WILL
REMAIN OVER WESTERN WASHINGTON TODAY BEFORE UPPER LEVEL FLOW BECOMES
ZONAL ON SUNDAY. THIS WILL CONTINUE THROUGH AT LEAST THE FIRST PART
OF THE WEEK. UNCERTAINTY IN THE FORECAST INCREASES TOWARDS THE
SECOND PART OF NEXT WEEK.
SHORT TERM /TODAY THROUGH MONDAY/
A SHALLOW MARINE LAYER MADE SIMILAR PROGRESS INLAND THIS MORNING TO
THAT OF YESTERDAY. WITH A LITTLE MORE OF A MARINE INFLUENCE AND HIGH
CLOUD COVERAGE THIS MORNING, MUCH OF THE INTERIOR SHOULD BE ABLE TO
SHAVE 3 TO 5 DEGREES OFF THE HIGH TEMPERATURE OVER YESTERDAY. THE
FORECAST LOOKS ON TRACK OVERALL. PREVIOUS DISCUSSION FOLLOWS. 27
LATEST SATELLITE IMAGERY SHOWS A SIMILAR PICTURE TO 24 HOURS AGO
WITH MARINE STRATUS MOVING IN OVER THE SOUTHERN HALF OF THE W WA
COASTLINE, GETTING AS FAR INLAND AS SHELTON WHILE THE REMAINDER OF
THE CWA SEES ONLY HIGH CLOUDS. EVEN TEMPERATURES THIS EARLY MORNING
ARE NOT SEEING THAT MUCH VARIATION FROM YESTERDAY AT THIS TIME, WITH
ONLY 1 TO 2 DEGREES OF COOLING...IF ANY.
THAT WILL BE THE DEFINING FEATURE OF THE WEEKEND AND START TO NEXT
WEEK: GRADUALLY COOLING TEMPERATURES. MOST LOCATIONS WILL ONLY SEE
ABOUT 2 TO 3 DEGREES OF COOLING COMPARED TO HIGHS YESTERDAY. THE
INTERIOR LOWLANDS ARE EXPECTED TO STILL RANGE FROM THE UPPER 70S TO
LOWER 80S WHILE MID 60S TO AROUND 70 IS EXPECTED ALONG THE COAST AND
IN WATER ADJACENT AREAS. SUNDAY CONTINUES THIS TREND, ABOUT ANOTHER
2 TO 3 DEGREES COOLER, PUTTING DAYTIME HIGHS FOR THE INTERIOR IN THE
MID 70S TO AROUND 80, MID TO UPPER 60S ALONG THE COAST AND STRAIT.
GETTING INTO MONDAY, THIS TREND LEVELS OFF, WITH DAYTIME HIGHS IN
THE SAME RANGES AS SUNDAY.
PERSISTENT ONSHORE FLOW WILL ALSO CONTINUE TO ALLEVIATE SMOKE
CONCERNS OVER W WA AS ANY SMOKE ALOFT WILL BE PUSHED BACK EAST VIA
ZONAL FLOW ALOFT WHILE SURFACE SMOKE WILL BE LIMITED TO THE CASCADES
AND LOCATIONS NEAR WILDFIRES. ANY SMOKE PRESENT THERE WILL MAINLY BE
OF CONCERN OVERNIGHT AND INTO THE MORNING HOURS EACH DAY. BY THE
TIME AFTERNOON WESTERLIES KICK IN, THAT WILL BE ENOUGH TO GIVE
VENTILATION A BOOST, IMPROVING AIR QUALITY.
18
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/
ZONAL FLOW IS FAVORED TO CONTINUE THROUGH AT LEAST INTO MID-WEEK
WITH DAYTIME HIGHS REMAINING STATIC, STAYING NEAR SEASONAL NORMALS.
LONG-RANGE MODELS REMAIN IN ONE OF TWO CAMPS FOR WEDNESDAY AND
BEYOND: EITHER GENERAL TROUGHINESS WITH A CLOSED LOW OVER THE
EASTERN PACIFIC, CYCLING MOISTURE INTO W WA OR A STRONG RIDGE OF
HIGH PRESSURE, KEEPING THE AREA DRY. THE FIRST SCENARIO WOULD LIKELY
KEEP TEMPS WHERE THEY ARE AS WELL AS BRINGING THE PROSPECT OF MUCH
NEEDED RAIN AND NOT-SO-NEEDED THUNDERSTORMS TO THE CWA WHILE THE
LATTER WOULD BRING ANOTHER WARM-UP TO THE AREA, BOOSTING TEMPS BACK
UP INTO THE MID 80S TO NEAR 90. OPERATIONAL NBM LARGELY LEANING
TOWARD THIS LATTER SCENARIO, BUT AGAIN, WITH ABSOLUTELY ZERO
CONSENSUS, IT IS DIFFICULT TO HAVE ANY DEGREE OF CONFIDENCE IN THIS
SOLUTION. THUS, HIGHLY ADVERTISING A 'WAIT-AND-SEE' APPROACH.
18
AVIATION
ZONAL FLOW ALOFT WILL TAKE SHAPE ACROSS WESTERN WASHINGTON TODAY AS
AN UPPER LEVEL RIDGE FLATTENS OVER THE REGION. LOW-LEVEL ONSHORE
FLOW HAS BROUGHT MARINE STRATUS INTO PORTIONS OF THE INTERIOR EARLY
THIS MORNING, WITH SATELLITE IMAGERY SHOWING STRATUS ALREADY MAKING
IT INTO KSHN. STRATUS WILL CONTINUE TO PUSH INLAND INTO THE INTERIOR
OVER THE NEXT FEW HOURS, THOUGH EXPECT STRATUS TO MAINLY RESULT IN
SOME SCATTERED CLOUDS FOR THE MAJORITY OF THE INTERIOR TERMINALS
EAST OF THE SOUND. EXPECT STRATUS TO RETREAT BACK TO THE COAST
AROUND 17Z, BRINGING MOSTLY VFR CONDITIONS TO THE INTERIOR TERMINALS
THROUGH THE REMAINDER OF THE DAY. ANOTHER ROUND OF STRATUS IS
EXPECTED TO PUSH INLAND LATE TONIGHT INTO SUNDAY AND MAY BRING SOME
MVFR TO IFR CONDITIONS TO THE INLAND TERMINALS FOR A FEW HOURS.
KSEA...VFR CONDITIONS CONTINUE EARLY THIS MORNING, WITH WINDS OUT OF
THE SW AT 5 KT OR LESS. LATEST PROBABILISTIC GUIDANCE HAS STARTED TO
BACK OFF ON A STRATUS DECK MAKING IT INTO THE TERMINAL AND ONLY
INDICATES A 10 PERCENT CHANCE OF IFR CONDITIONS DEVELOPING AT THE
TERMINAL THIS MORNING AND A 15 PERCENT CHANCE OF MVFR CONDITIONS
DEVELOPING. ANY STRATUS THAT DOES MAKE IT INTO THE TERMINAL LOOKS TO
BE MORE LIKELY SCT TO FEW IN NATURE. SW WINDS WILL PICK UP TO 4-8 KT
AND SHIFT TO THE NW AFTER 00Z.
14
MARINE
BROAD SURFACE HIGH PRESSURE WILL REMAIN CENTERED OVER THE OFFSHORE
WATERS WITH LOWER PRESSURE EAST OF THE CASCADES INTO NEXT WEEK. THIS
WILL MAINTAIN ONSHORE FLOW OVER THE NEXT SEVERAL DAYS AND BRING
DIURNALLY DRIVEN SMALL CRAFT ADVISORY STRENGTH WESTERLIES TO THE
CENTRAL AND EAST STRAIT OF JUAN DE FUCA DAILY. THE PUSH TONIGHT WILL
BE A BIT STRONGER THAN THIS MORNING, WITH LATEST HREF GUIDANCE
HINTING AT ABOUT A 35-45 PERCENT CHANCE OF GUSTS BRIEFLY REACHING
GALES THIS EVENING.
A SERIES OF WEAK SYSTEMS PASSING TO THE NORTH OF THE AREA NEXT WEEK
WILL STRENGTHEN ONSHORE FLOW AT TIMES FOR ADDITIONAL RISKS OF GALES
ALONG THE CENTRAL AND EASTERN STRAIT.
SEAS ACROSS THE COASTAL WATERS WILL PRIMARILY PERSIST AT 4-6 FT INTO
EARLY NEXT WEEK AND MAY BECOME STEEP AT TIMES THIS WEEKEND UNDER
LOCALLY DRIVEN WINDS. SEAS WILL THEN SUBSIDE TO 2-4 FT BY TUESDAY,
BEFORE INCREASING BACK TO 4-6 FT BY MIDWEEK.
FIRE WEATHER
ONSHORE FLOW WILL KEEP MARINE AIR OVER WESTERN WASHINGTON AT LEAST
FOR THE SHORT TERM PERIOD. VERY ISOLATED AREAS OF 20-25% MIN RHS ARE
POSSIBLE IN THE CASCADE VALLEYS ON SATURDAY BUT WIDESPREAD CONCERNS
ARE NOT EXPECTED - ALLEVIATING THE THREAT FOR ELEVATED FIRE WEATHER
CONCERNS. MORE BENIGN FIRE WEATHER CONDITIONS WILL EMERGE ON SUNDAY
AND LEAD INTO INTO THE MIDDLE NEXT WEEK. COOLER TEMPERATURES AND
INCREASED MOISTURE WITH MUCH BETTER HUMIDITY RECOVERIES ARE EXPECTED
ACROSS THE REGION.
41/18
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 5 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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