641
FXUS66 KSEW 142119
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
219 PM PDT FRI AUG 14 2026
SYNOPSIS
AN UPPER LEVEL TROUGH OVER THE AREA TODAY WILL BRING CHANCES OF
THUNDERSTORMS ACROSS THE MOUNTAINS AND CRITICAL FIRE WEATHER
CONDITIONS. THUNDERSTORM POTENTIAL WILL CONTINUE ALONG THE CASCADES
ON SATURDAY, BUT WILL WANE THROUGHOUT THE WEEKEND AS AN UPPER
LEVEL RIDGE STARTS TO BUILDS INTO THE AREA FROM THE SOUTHEAST.
ANOTHER UPPER LEVEL TROUGH WILL MOVE INTO THE REGION EARLY NEXT
WEEK. UNCERTAINTY THEN INCREASES IN THE FORECAST HEADING INTO
MIDWEEK AS GUIDANCE REMAINS SPLIT BETWEEN A WARMER, DRIER PATTERN
AND A COOLER, WETTER ONE.
SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/
LATEST SATELLITE IMAGERY SHOWS STRATUS DRAPED INLAND ALONG THE
COAST, WHILE IT SCATTERS OUT ACROSS THE INTERIOR THIS AFTERNOON.
RADAR ALSO SHOWS SOME DEVELOPMENT OF SOME ISOLATED SHOWERS AND
THUNDERSTORMS ALONG THE SOUTHERN CASCADES THIS AFTERNOON. WITH A
WEAK UPPER LEVEL TROUGH REMAINING OVER THE AREA TODAY, EXPECT
ANOTHER ROUND OF THUNDERSTORMS ALONG THE OLYMPICS AND CASCADES THIS
AFTERNOON AND EVENING AS CONDITIONS OVER THE HIGHER TERRAIN BECOME
INCREASINGLY UNSTABLE. CRITICAL FIRE WEATHER CONDITIONS ARE EXPECTED
AGAIN ACROSS THE MOUNTAINS AS ANY THUNDERSTORMS THAT DO DEVELOP
COULD PRODUCE ABUNDANT LIGHTNING AND GUSTY, ERRATIC WINDS AND
NOT MUCH IN THE WAY OF RAIN AS CONDITIONS REMAIN VERY DRY ACROSS
THE REGION. THE EXCEPTION REMAINS ANY STORMS THAT REMAIN
STATIONARY OVER AN AREA, WHICH WILL NEED TO BE MONITORED FOR
ENHANCED RAINFALL, ESPECIALLY IN THE VICINITY OF ANY BURN SCARS.
AFTERNOON HIGHS WILL BE IN LOW 80S ACROSS THE INTERIOR AND 60S
ALONG THE COAST IN STRATUS.
THE UPPER LEVEL TROUGH WILL WEAKEN ACROSS THE AREA TONIGHT, ALLOWING
FOR A RIDGE TO BUILD INTO THE AREA FROM THE SOUTHEAST OVER THE
WEEKEND. SOUTHWESTERLY FLOW WILL DEVELOP ALOFT AND WILL HELP TO
PUSH SMOKE OUT OF THE AREA THIS WEEKEND. LOW LEVEL FLOW WILL REMAIN
ONSHORE, ALLOWING FOR MARINE STRATUS TO PUSH INLAND DURING THE
OVERNIGHT PERIODS BOTH SATURDAY AND SUNDAY. WHILE OVERALL THUNDERSTORM
CHANCES WILL PRIMARILY WANE THROUGHOUT THE WEEKEND, ANOTHER
ROUND OF THUNDERSTORMS WILL BE POSSIBLE ACROSS THE CASCADES ON
SATURDAY AFTERNOON AND EVENING AS THE AIR MASS BECOMES UNSTABLE
DURING THE AFTERNOON HOURS AND SOME MONSOONAL MOISTURE WORKS
ITS WAY UP INTO THE REGION. BY SUNDAY, ANY THUNDERSTORMS THAT DO
DEVELOP WILL MOSTLY BE CONFINED TO THE CASCADE CREST AND AREAS
EAST OF THE CREST. AFTERNOON HIGHS OVER THE WEEKEND WILL BE IN
THE UPPER 70S TO LOW 80S ACROSS THE INTERIOR AND IN THE MID TO
UPPER 60S ALONG THE COAST, WHILE OVERNIGHT LOWS WILL BE IN THE
50S.
14
LONG TERM /MONDAY THROUGH FRIDAY/
THE FIRST PART OF NEXT WEEK REMAINS TO FOLLOW A RATHER TYPICAL
PATTERN OF ONSHORE LOW-LEVEL FLOW MAINTAINING MORNING CLOUDS, WITH
SOME CLEARING IN THE AFTERNOON. A PASSING TROUGH AROUND TUESDAY
COULD PROVIDE A REINFORCING PUSH OF CLOUDS AND KNOCK TEMPERATURES A
FEW DEGREES COOLER THAN NORMAL. OTHERWISE, ENSEMBLE GUIDANCE BEGINS
TO SPREAD A BIT LARGER TOWARD THE MIDDLE OF NEXT WEEK WITH A FAIRLY
EVEN SPLIT BETWEEN A COOLER TROUGH PATTERN AND A WARMER (NEAR
NORMAL) PATTERN UNDER ZONAL FLOW OR A WEAK RIDGE. IN ANY EVENT,
THERE'S NOT A SIGNIFICANT SIGNAL FOR ANY PRECIPITATION OF NOTE.
AVIATION
STRATUS HAS CLEARED ACROSS THE INTERIOR WITH GENERALLY VFR
CONDITIONS. HOWEVER, SOME THUNDERSTORMS WILL CONTINUE TO DEVELOP OFF
THE MOUNTAINS, MOSTLY OVER THE CASCADES, THIS AFTERNOON AND EVENING.
OTHERWISE, STRATUS WILL SLOWLY RETREAT TO THE COAST THIS AFTERNOON.
ANOTHER SURGE OF STRATUS IS LIKELY LATER TONIGHT THROUGH SATURDAY
MORNING FOR MOST OF THE AREA, WITH IFR CEILINGS AND VISIBILITY
EXPECTED FOR MOST TERMINALS.
KSEA...VFR THROUGH THE REMAINDER OF THE DAY. SOME THUNDERSTORMS WILL
DEVELOP WELL EAST OF THE TERMINAL AREA AND CONTINUE INTO THE
EVENING, BUT IS NOT EXPECTED AT KSEA ITSELF. WINDS PREDOMINANTLY
FROM THE SOUTHWEST, BECOMING WEST/NORTHWEST (BUT 5 KT OR LESS) THIS
EVENING AROUND 02Z. A RETURN TO LIGHT SOUTHWEST WINDS THEN FOLLOWS
OVERNIGHT, ALONG WITH THE RETURN OF LOW STRATUS AROUND 12Z TONIGHT
WITH IFR/LIFR CONDITIONS INTO THE MORNING TOMORROW.
MARINE
HIGH PRESSURE REMAINING OFF THE COAST OF CALIFORNIA WILL KEEP
WINDS OVER THE COASTAL WATERS LIGHT THROUGH SATURDAY. HIGH
PRESSURE WILL THEN REBUILD OFFSHORE BRITISH COLUMBIA AND MOVE
SOUTHWARD ON SUNDAY AND REMAIN SITUATED OFF THE PACIFIC NORTHWEST
INTO NEXT WEEK. THIS WILL BRING THE RETURN OF NORTHWESTERLY WINDS
TO THE COASTAL WATERS. DIURNALLY DRIVEN WESTERLY WINDS DOWN THE
STRAIT OF JUAN DE FUCA WILL OCCUR EACH AFTERNOON AND EVENING
OVER THE NEXT SEVERAL DAYS, WITH WINDS APPROACHING SMALL CRAFT
ADVISORY STRENGTH AT TIMES.
SEAS WILL PRIMARILY REMAIN BETWEEN 3 TO 6 FT THROUGH THE
WEEKEND AND THROUGH MUCH WEEK.
14
FIRE WEATHER
A RED FLAG WARNING REMAINS IN EFFECT FOR THE OLYMPICS AND CASCADES
THROUGH THIS EVENING FOR ANOTHER ROUND OF CONVECTION. SIMILARLY
TO THURSDAY, MOST OF THE STORMS ARE NOT EXPECTED TO PRODUCE MUCH
IN THE WAY OF WETTING RAINS. GIVEN THE DRY CONDITIONS, ANY STORMS
THAT DO DEVELOP COULD HAVE GUSTY AND ERRATIC OUTFLOW WINDS, WHICH
COMBINED WITH THE LIGHTNING AND THE DRY CONDITIONS PRESENT, COULD
PRODUCE NEW FIRE STARTS. WHILE MOST STORMS WILL NOT PRODUCE MUCH
RAIN, THERE REMAINS A SMALL CHANCE OF FLASH FLOODING IN ANY STORMS
THAT REMAIN STATIONARY OVER AN AREA AND PRODUCE ENHANCED RAINFALL,
ESPECIALLY OVER BURN SCARS.
ELEVATED FIRE WEATHER CONDITIONS WILL CONTINUE ACROSS THE CASCADES
INTO SATURDAY WITH CHANCES OF THUNDERSTORMS POSSIBLE AGAIN ALONG
THE CASCADE CREST ON SATURDAY AFTERNOON AND EVENING. OVERALL
CHANCES FOR CONVECTION WILL DECREASE THROUGH THE WEEKEND, HOWEVER,
AS AN UPPER LEVEL RIDGE STARTS TO BUILD INTO THE AREA FROM THE
SOUTHEAST. BY SUNDAY, EXPECT CONVECTION TO MAINLY BE CONFINED TO
THE CASCADE CREST AND AREAS EAST OF THE CREST. ANOTHER UPPER
LEVEL TROUGH WILL MOVE INTO THE AREA NEXT WEEK AND COULD BRING
SOME ADDITIONAL ELEVATED FIRE WEATHER CONCERNS TO WESTERN
WASHINGTON AT TIMES.
14
SEW WATCHES/WARNINGS/ADVISORIES
WA...RED FLAG WARNING UNTIL 9 PM PDT THIS EVENING FOR EAST PORTION
OF THE OLYMPIC MOUNTAINS-WEST PORTION OF THE OLYMPIC
MOUNTAINS-WEST SLOPES OF THE CENTRAL CASCADES GENERALLY
ABOVE 1500 FEET-WEST SLOPES OF THE NORTH CASCADES
GENERALLY ABOVE 1500 FEET.
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT SATURDAY FOR CENTRAL U.S.
WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE U.S. WATERS
STRAIT OF JUAN DE FUCA.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page