868
FXUS66 KSEW 211039
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
339 AM PDT FRI AUG 21 2026
SYNOPSIS
ONE MORE WARM DAY TODAY WITH WESTERN WASHINGTON ON THE BACK SIDE
OF AN UPPER LEVEL RIDGE. UPPER LEVEL LOW APPROACHING FROM THE
SOUTHWEST WILL MOVE INTO THE COASTAL WATERS SATURDAY AND INTO
SOUTHERN BRITISH COLUMBIA EARLY SUNDAY MORNING. THIS SYSTEM WILL
BRING COOLER WEATHER WITH A CHANCE OF SHOWERS AND THUNDERSTORMS
SATURDAY. UPPER LEVEL RIDGE REBUILDING SUNDAY WILL MOVE EAST
MONDAY AND TUESDAY. AN UPPER LEVEL TROUGH WILL ARRIVE WEDNESDAY.
SHORT TERM /TODAY THROUGH SUNDAY/
SATELLITE IMAGERY SHOWS STRATUS CONFINED TO THE COAST AND LOWER
CHEHALIS VALLEY EARLY THIS MORNING. CLEAR SKIES OVER THE
REMAINDER OF THE AREA. TEMPERATURES AT 3 AM/10Z WERE IN THE MID
50S TO MID 60S.
UPPER LEVEL LOW CENTERED OFF THE NORTHERN CALIFORNIA COAST
EARLY THIS MORNING WILL CONTINUE TO MOVE SLOWLY NORTHEAST TODAY.
RESULTING UPPER LEVEL RIDGE OUT AHEAD OF THE LOW GIVING WESTERN
WASHINGTON SOUTHERLY FLOW ALOFT. HIGH CLOUDS EMBEDDED IN THE
FLOW ALOFT MOVING OVER THE AREA LATER TODAY. LIGHT SURFACE
GRADIENTS THIS MORNING WITH THE STRATUS DECK NOT GETTING MUCH
FURTHER EAST. BY MIDDAY THE STRATUS DECK WILL BE JUST OFF THE
COAST. HIGH CLOUDS THIS AFTERNOON COULD KNOCK A COUPLE OF
DEGREES OFF THE HIGHS VERSUS YESTERDAY WITH HIGHS IN THE MID 70S
TO MID 80S INLAND AND MID 60S TO LOWER 70S ALONG THE COAST.
UPPER LEVEL LOW OFF THE NORTHERN OREGON COAST BY 12Z SATURDAY.
UPPER LEVEL DISTURBANCE SPINNING OUT OF THE LOW MOVING INTO THE
SOUTHWEST PORTION OF THE AREA IN THE EARLY MORNING HOURS FOR A
CHANCE OF SHOWERS. LOWS IN THE 50S AND LOWER 60S.
UPPER LEVEL DISTURBANCE MAKING IT'S WAY THROUGH THE REMAINDER OF
WESTERN WASHINGTON SATURDAY MORNING INTO THE EARLY AFTERNOON
HOURS. CHANCE OF SHOWERS AND THUNDERSTORMS WITH THIS FEATURE.
FIRE WEATHER WATCH FOR THE OLYMPICS AND NORTH CASCADES WILL
CONTINUE WITH THIS FORECAST PACKAGE. BY LATE AFTERNOON THE
FEATURE WILL BE FAR ENOUGH TO THE NORTH FOR THE CHANCES OF
CONVECTION TO BE NORTH OF SEATTLE. CLOUDY SKIES WILL KEEP
TEMPERATURES WELL BELOW NORMAL. HIGHS IN THE 60S AND LOWER 70S.
LOW MOVES INLAND INTO SOUTHERN BRITISH COLUMBIA EARLY SUNDAY
MORNING. CHANCE OF SHOWERS AND THUNDERSTORMS CONTINUING NORTH
OF SEATTLE WITH THE THUNDERSTORMS THREAT COMING TO AN END IN
THE OVERNIGHT HOURS. LOW LEVEL ONSHORE FLOW WILL KEEP SKIES
MOSTLY CLOUDY BEHIND THE FEATURE. LOWS IN THE 50S.
CHANCE OF SHOWERS LINGERS NEAR THE CANADIAN BORDER SUNDAY
MORNING AS THE LOW WEAKENS AND MOVES NORTHEAST. LOW LEVEL
ONSHORE FLOW CONTINUING KEEPING CLOUD COVER OVER THE AREA AT
LEAST THROUGH THE MORNING HOURS. HIGHS A LITTLE WARMER THAN
SATURDAY BUT STILL BELOW NORMAL, MID 60S TO MID 70S. FELTON
LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/
UPPER LEVEL RIDGE BUILDING OVER THE AREA SUNDAY NIGHT MOVING
EAST MONDAY. WESTERN WASHINGTON REMAINING ON THE BACKSIDE OF THE
RIDGE TUESDAY. MODELS PLAYING PUSH IT BACK WITH NEXT UPPER LEVEL
TROUGH NOW TIMED INTO THE AREA WEDNESDAY INSTEAD OF TUESDAY ON
PREVIOUS RUNS. LOTS OF VARIABILITY WITH THIS FEATURE. A FEW OF
THE ENSEMBLES HAVING WETTING RAIN OVER THE NORTHERN PORTIONS
WEDNESDAY. A VAST MAJORITY OF THE ENSEMBLE SOLUTIONS GOING FOR
A CHANCE OF SHOWERS SCENARIO. IN THE LOWER LEVELS VARYING
DEGREES OF ONSHORE FLOW. AT THIS POINT TUESDAY LOOKS TO BE THE
WARMEST DAYS WITH HIGHS IN THE 70S AND LOWER 80S FOR THE
INTERIOR. HIGHS MOSTLY IN THE 70S ON THE OTHER DAYS. HIGHS ON
THE COAST IN THE MID TO UPPER 60S.
THERE HAS BEEN NO MEASURABLE RAIN AT SEATTLE-TACOMA AIRPORT THIS
MONTH. JUST A TRACE ON THE 1ST. HAVING A DRY FIRST THREE WEEKS
OF AUGUST IN SEATTLE IS NOT THAT COMMON. THIS YEAR WILL BE THE
9TH TIME IN THE 82 YEAR HISTORY OF WEATHER RECORDS AT SEATTLE-
TACOMA AIRPORT. THE LAST TIME IT HAPPENED WAS 2012. THIS YEAR
WILL ONLY BE THE 3RD TIME IN THE LAST 40 YEARS. FELTON
AVIATION
SOUTHERLY FLOW ALOFT WITH LIGHT FLOW IN THE LOWER LEVELS. VFR
CONDITIONS INTO EARLY SATURDAY MORNING FOR THE INTERIOR. LIFR
ALONG THE COAST THIS MORNING IMPROVING TO VFR THIS AFTERNOON.
LIFR CEILINGS RETURNING TO THE COAST THIS EVENING. IFR CEILINGS
SPREADING INLAND AFTER 06Z TONIGHT GETTING EAST OF PUGET SOUND
AROUND 12Z SATURDAY.
KSEA...INCREASING HIGH CLOUDS THIS AFTERNOON AND EVENING. IFR
CEILINGS DEVELOPING AROUND 12Z SATURDAY MORNING. NORTHERLY
WINDS 6 KNOTS OR LESS BECOMING SOUTHWESTERLY AROUND 03Z. FELTON
MARINE
BROAD HIGH PRESSURE OVER THE WATERS WILL WEAKEN TODAY. A WEAK
SURFACE LOW WILL MOVE INTO THE COASTAL WATERS SATURDAY WITH THE
ASSOCIATED FRONT MOVING THROUGH THE INLAND WATERS SATURDAY
MORNING. THE LOW WILL DISSIPATE SATURDAY NIGHT. HIGH PRESSURE
WILL REBUILD SUNDAY AND REMAIN OVER THE AREA THROUGH TUESDAY.
LOW END SMALL CRAFT ADVISORY WESTERLIES IN THE CENTRAL AND
EASTERN STRAIT OF JUAN DE FUCA TONIGHT. INCREASING SOUTHERLY
WINDS OVER THE INLAND WATERS SATURDAY MORNING CURRENTLY FORECAST
TO PEAK AROUND 20 KNOTS.
SEAS REMAINING IN THE 3 TO 5 FOOT RANGE. FELTON
FIRE WEATHER
DRY AND WARM CONDITIONS CONTINUING TODAY. UPPER LEVEL LOW
OFFSHORE MOVING NORTHEAST ENDING UP OFF THE WASHINGTON COAST
EARLY SATURDAY MORNING. CONVECTION DEVELOPING WITH THIS FEATURE
EARLY SATURDAY MORNING OVER THE SOUTHWEST PORTION OF THE AREA.
CONVECTION SPREADING OVER THE ENTIRE AREA BY MID TO LATE
SATURDAY MORNING. PROBABILITIES FOR CONVECTION ARE HIGHEST OVER
THE OLYMPICS AND NORTH CASCADES, PEAKING BETWEEN 20 TO 30
PERCENT. DUE TO THE POTENTIAL OF SCATTERED THUNDERSTORMS FOR
THESE AREAS AND THE VERY DRY CONDITIONS AT THE SURFACE, A FIRE
WEATHER WATCH WILL CONTINUE FOR ZONES 652, 658, AND 661.
CONVECTION MAY EXIST ELSEWHERE HOWEVER UNCERTAINTY EXISTS IN THE
COVERAGE. LIGHTNING MAY LEAD TO NEW FIRE STARTS, AS WELL AS
RESULT IN GUSTY AND ERRATIC WINDS.
LOW LEVEL ONSHORE FLOW INCREASES SATURDAY NIGHT INTO SUNDAY WITH
VARYING DEGREES OF ONSHORE FLOW THROUGH THE MIDDLE OF NEXT WEEK.
GOOD RELATIVE HUMIDITY RECOVERIES EACH NIGHT WILL KEEP FIRE
WEATHER CONCERNS AT A MINIMUM. CHANCE OF SHOWERS IN THE MIDDLE
OF THE WEEK WITH AN UPPER LEVEL TROUGH MOVING INTO THE AREA.
FELTON/JD
SEW WATCHES/WARNINGS/ADVISORIES
WA...FIRE WEATHER WATCH FROM LATE TONIGHT THROUGH SATURDAY EVENING
FOR WEST SLOPES OF THE NORTH CASCADES GENERALLY ABOVE
1500 FEET.
FIRE WEATHER WATCH FROM LATE TONIGHT THROUGH SATURDAY EVENING
FOR EAST PORTION OF THE OLYMPIC MOUNTAINS-WEST PORTION OF
THE OLYMPIC MOUNTAINS.
PZ...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM PDT
SATURDAY FOR CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-
EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
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