257
FXUS66 KSEW 291611
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
911 AM PDT SAT AUG 29 2026
UPDATE
KATX/KLGX ANALYSIS SHOWS ONGOING SHOWERS ACROSS WESTERN
WASHINGTON SO FAR THIS MORNING. THE BULK OF THE ACTION IS OVER
THE INTERIOR WITH A FEW STRAGGLERS ALONG THE COAST. HI-RES
MODEL REFLECTIVITY HAS THE ACTIVITY GRADUALLY DIMINISHING INTO
THE AFTERNOON AS AN UPPER-LOW EXITS AND TO BE LATER ON REPLACED
BY AN INCOMING RIDGE. HIGHS TODAY BELOW AVERAGE AS TEMPS TOP
OUT IN THE 60S TO LOWER 70S. THE PREVIOUS DISCUSSION REMAINS
BELOW ALONG WITH AN UPDATED AVIATION SECTION:
SYNOPSIS
SMALL UPPER LEVEL LOW MOVING THROUGH THE NORTHERN PORTION OF THE
AREA TODAY. TEMPORARY UPPER LEVEL RIDGE BUILDING TONIGHT MOVING
EAST MONDAY. STRONG FOR EARLY SEPTEMBER UPPER LEVEL LOW MOVING
DOWN THE BRITISH COLUMBIA COAST TUESDAY. ASSOCIATED WARM FRONT
BRUSHING THE AREA TUESDAY NIGHT. TRAILING COLD FRONT ARRIVING
WEDNESDAY BRINGING RAIN AND LOCALLY GUSTY WINDS. UPPER LEVEL LOW
REMAINING IN THE VICINITY THURSDAY AND FRIDAY KEEPING CONDITIONS COOL
AND UNSETTLED.
SHORT TERM /TODAY THROUGH MONDAY/
SATELLITE IMAGERY SHOWS SMALL UPPER LEVEL LOW OVER SOUTHWEST
BRITISH COLUMBIA. DOPPLER RADAR HAS SHOWERS SPINNING AROUND THE
LOW ALONG THE COAST AND OVER THE NORTHERN PORTION OF THE AREA.
TEMPERATURES AT 3 AM/10Z WERE IN THE MID 50S TO LOWER 60S.
UPPER LEVEL LOW MOVING SOUTHEAST TODAY ENDING UP IN EASTERN
WASHINGTON BY LATE AFTERNOON. SHOWERS OVER THE ENTIRE AREA
EARLY THIS MORNING AS THE LOW MOVES OVERHEAD. SHOWER CHANCES
DECREASING ALONG THE COAST LATER THIS MORNING WITH SHOWER
CHANCES CONFINED TO PUGET SOUND EASTWARD BY THIS AFTERNOON. THE
EXCEPTION TO THIS WILL BE OVER THE NORTHERN PORTION OF THE HOOD
CANAL EASTWARD AS A CONVERGENCE ZONE FORMS LATER THIS MORNING.
QUICK SHOT OF COOLER AIR ALOFT ASSOCIATED WITH THE LOW WILL
DESTABILIZE THE AIR MASS ENOUGH FOR A SLIGHT CHANCE OF
THUNDERSTORMS EAST OF PUGET SOUND LATER THIS MORNING INTO THE
AFTERNOON HOURS. HIGHS IN THE 60S AND LOWER 70S. SEATTLE HAS A
CHANCE TO BREAK THE CONSECUTIVE DAY STREAK OF HIGHS 70 DEGREES
PLUS TODAY.
UPPER LEVEL RIDGE BUILDING OVER WESTERN WASHINGTON TONIGHT WILL
BRING AN END TO THE SHOWER ACTIVITY PRETTY QUICKLY THIS EVENING.
WITH THE LONGER NIGHTS PATCHY FOG FORMING IN THE FOG PRONE
PLACES LIKE THE SOUTHWEST INTERIOR AND CASCADE RIVER VALLEYS
BEFORE THE STRATUS DEVELOPS IN THE EARLY MORNING HOURS.
TEMPERATURES ALOFT STILL COOL IN THE WAKE OF THE LOW. COLDEST
MORNING IN A COUPLE MONTHS SUNDAY WITH LOWS IN THE MID 40S TO
LOWER 50S.
CLOUDY START TO THE DAY SUNDAY. THE UPPER LEVEL RIDGE WILL BE
WEAK AND NOT PROVIDE MUCH IN THE WAY OF SUBSIDENCE. LOW LEVEL
ONSHORE FLOW WEAKENING AS THE DAY WEARS ON WILL HELP ERODE THE
MARINE LAYER BUT A SYSTEM MOVING INTO BRITISH COLUMBIA WILL
SPREAD MIDDLE AND HIGH LEVEL CLOUDS OVER THE AREA ESPECIALLY
IN THE AFTERNOON. END RESULT IS A MOSTLY CLOUDY DAY EVEN WITH
THE RIDGING. HIGHS AGAIN ONLY IN THE 60S AND LOWER 70S.
UPPER LEVEL TROUGH DIGGING OFFSHORE SUNDAY NIGHT INTO MONDAY.
FLOW ALOFT BECOMING SOUTHWESTERLY PUSHING WARMER AIR ALOFT INTO
THE AREA. SHALLOW MARINE LAYER LATE SUNDAY NIGHT INTO MONDAY
MORNING. STRATUS WILL HAVE A HARD TIME GETTING EAST OF PUGET
SOUND MONDAY MORNING. HIGH CLOUDS EMBEDDED IN THE FLOW ALOFT
MOVING THROUGH AT TIMES. HIGHS WARMING INTO THE MID 60S TO MID
70S. ANOTHER COOL MORNING, LOWS IN THE MID 40S TO MID 50S.
FELTON
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/
UPPER LEVEL TROUGH REMAINING OFFSHORE MONDAY NIGHT AS A STRONG
FOR SEPTEMBER SYSTEM STARTS TO MAKE ITS WAY DOWN THE BRITISH
COLUMBIA COAST. UNDER MOSTLY CLOUDY SKIES LOWS IN THE 50S.
UPPER LEVEL TROUGH MESHING WITH THE WARM FRONT ASSOCIATED WITH
THE INCOMING SYSTEM MOVING INTO THE AREA TUESDAY FOR A CHANCE OF
RAIN. HIGHS IN THE MID 60S TO MID 70S.
MODELS STILL IN GOOD AGREEMENT WITH THE TRAILING COLD FRONT
MOVING INTO WESTERN WASHINGTON WEDNESDAY BRINGING RAIN AND
LOCALLY GUSTY WINDS. RAIN OUT AHEAD OF THE COLD FRONT REACHING
THE COAST TUESDAY NIGHT. RAINFALL AMOUNTS OVER AN INCH ALONG THE
COAST, 1.5 TO 2.5 INCHES IN THE OLYMPICS WITH A HALF INCH TO AN
INCH INLAND AND IN THE CASCADES. IT'S POSSIBLE SEATTLE GETS
MORE RAIN FROM THIS SYSTEM IN LESS THAN 24 HOURS THAN ALL OF THE
LAST TWO AND A HALF MONTHS. HIGHS IN THE LOWER TO MID 60S.
SEATTLE FORECAST HIGH OF 65 IS THE NORMAL HIGH FOR OCTOBER 3RD
THROUGH 5TH.
MODELS HAVING TROUBLE WEDNESDAY NIGHT INTO FRIDAY WITH THE
ASSOCIATED UPPER LEVEL LOW LOCATION. THE GFS DROPS THE LOW FAR
ENOUGH SOUTH FOR THE SHOWER ACTIVITY TO COME TO AN END FRIDAY.
THE ECMWF HAS THE LOW FURTHER NORTH KEEPING SHOWERS OVER THE
AREA INTO THE END OF THE WEEK. ENSEMBLE SOLUTIONS FAVORING THE
GFS SOLUTION BUT NOT ENOUGH TO COMPLETELY DRY OUT THE FORECAST
FRIDAY. AT THIS POINT WILL GO WITH SHOWERS THURSDAY AND SLIGHT
CHANCE OF SHOWERS FRIDAY. CONFIDENCE NOT REAL HIGH IN THIS
SCENARIO. SNOW LEVELS GETTING AS LOW AS 7000 FEET LATER THURSDAY
INTO FRIDAY. HIGHS REMAINING COOL, IN THE 60S THURSDAY AND
FRIDAY. FELTON
AVIATION
AN UPPER LEVEL LOW WILL TRACK TO THE EAST OF THE AREA TODAY,
SWITCHING TO NORTHWESTERLY WINDS ALOFT. CEILINGS ARE A BIT OF A
MIXED BAG, THROUGH MOST LOCATIONS SHOWING MVFR TO VFR CEILINGS AS A
WEAK DISTURBANCES MAKES ITS WAY ACROSS WESTERN WASHINGTON.
THE BULK OF THE PRECIPITATION HAS PROGRESSED EAST TOWARDS THE
CASCADES, THROUGH A FEW ISOLATED SHOWERS REMAIN AND SHOWERS MAY
LINGER OVER THE CENTRAL PUGET SOUND AREA AS A CONVERGENCE ZONE
DEVELOPS. CEILINGS ARE EXPECTED TO SCATTER AND MOST TERMINALS SHOULD
SEE VFR CONDITIONS BY THIS AFTERNOON. STRATUS AND POTENTIALLY SOME
AREAS OF FOG IN THE TYPICAL FOG-PRONE LOCATIONS IS EXPECTED TO
DEVELOP LATE TONIGHT INTO SUNDAY MERING.
WINDS TODAY REMAIN SOUTHWEST 6-12 KT FOR MOST. WINDS HAVE BEEN A BIT
ERRATIC THROUGH THE PUGET SOUND WITH WINDS GOING BACK AND FORTH
BETWEEN N AND S, BUT AFTER 18Z SHOULD GENERALLY REMAIN S/SW BEFORE
BEGINNING TO TURN BACK NORTHERLY AFTER 00-03Z SUN.
WINDS LOOK TO RETURN TO S OVERNIGHT INTO SUNDAY.
KSEA...MVFR CEILINGS PRESENT WITH THE COLD FRONT PASSING THROUGH
THIS MORNING, ALONG WITH OFF AND ON SHOWERS IN AND AROUND THE
TERMINAL. TIMEFRAME FOR IMPROVEMENT TO VFR IS 18-21Z. CONVERGENCE
ZONE LIKELY TO KEEP SHOWERS MAINLY NORTH AND EAST OF THE TERMINAL.
VFR CONDITIONS LOOK TO CONTINUE UNTIL SUNDAY MORNING WHEN LOW
STRATUS BRING A CHANCE TO RETURN TO MVFR CIGS. WINDS VARIABLE THIS
MORNING BUT BECOMING MORE SW AFTER 18Z. WINDS MAY START TO TURN MORE
N/NW BETWEEN 00-06Z SUN.
MARINE
AN UPPER LEVEL LOW IS SWINGING A COLD FRONT THROUGH THE INTERIOR
WATERS THIS MORNING. SHOWERS WILL CONTINUE TO PROGRESS OVER THE
STRAIT OF JUAN DE FUCA AND INTERIOR WATERS THIS MORNING. THE THREAT
OF THUNDER WITH THIS ACTIVITY REMAINS LOW AT 15-20%. A STRONGER PUSH
OF WESTERLIES IS LIKELY IN WAKE OF THE COLD FRONT THIS AFTERNOON AND
EVENING IN THE CENTRAL/EAST STRAIT OF JUAN DE FUCA; THUS HAVE
REISSUED A SMALL CRAFT ADVISORY IN THESE AREAS FOR TONIGHT.
ADDITIONAL SYSTEMS WILL PASS NORTH OF THE WATERS SUNDAY AND MONDAY,
WITH WINDS DECREASING AND REMAINING LIGHT OUT OF THE NORTH. MODELS
HAVE A STRONGER LOW PRESSURE SYSTEM TRACKING OVER THE COASTAL WATERS
AROUND MIDWEEK, WHICH WILL BRING AN INCREASED RISK OF UPPER-END
SMALL CRAFT WINDS AND GALE-FORCE GUSTS (ESPECIALLY IN THE EAST
STRAIT OF JUAN DE FUCA AND FAR SOUTHERN COASTAL WATERS).
SEAS AT 4-6 FT THROUGH TUESDAY, PEAKING AT 9-11 FT WITH THE SYSTEM
PASSING THROUGH MIDWEEK NEXT WEEK.
HPR
FIRE WEATHER
SLIGHT CHANCE OF THUNDERSTORMS TODAY FROM THE PUGET SOUND
EASTWARD WILL KEEP FIRE WEATHER CONCERNS ELEVATED. THUNDERSTORM
THREAT ENDING QUICKLY THIS EVENING. BEGINNING SUNDAY A COOLER
AND EVENTUALLY WETTER PATTERN DEVELOPING OVER WESTERN WASHINGTON
EASING FIRE WEATHER CONCERNS. SYSTEM ARRIVING WEDNESDAY BRINGING
WETTING RAINS TO MOST OF THE AREA. THE OLYMPICS COULD SEE AS
MUCH AS TWO AND A HALF INCHES OF RAIN. COOL AND UNSETTLED
WEATHER FOR THE LATTER HALF OF NEXT WEEK KEEPING FIRE WEATHER
CONCERNS AT A MINIMUM. FELTON
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 1 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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