003
FXUS66 KSEW 111527
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
827 AM PDT TUE AUG 11 2026
SYNOPSIS
ZONAL FLOW ALOFT AND ONSHORE FLOW WILL MAINTAIN SEASONABLE
CONDITIONS WITH MORNING CLOUDS AND AFTERNOON SUNSHINE AGAIN TODAY.
AN UPPER LEVEL TROUGH WILL DIG INTO THE REGION WEDNESDAY, BRINGING
COOLER TEMPERATURES ALONGSIDE SHOWERS AND THUNDERSTORMS OVER THE
NORTH CASCADES WEDNESDAY AND THURSDAY. WARMER CONDITIONS WILL RETURN
BY THE WEEKEND AS UPPER RIDGING REBUILDS OVER THE REGION.
SHORT TERM /TODAY THROUGH THURSDAY/
NO FORECAST UPDATES ANTICIPATED THIS MORNING. PREVIOUS DISCUSSION
FOLLOWS WITH MODIFIED AVIATION PORTION. 27
MARINE STRATUS NOT QUITE AS SUCCESSFUL AS IT WAS 24 HOURS AGO ON ITS
EASTWARD PROGRESSION, ALTHOUGH NOW IS NOT THE TIME TO SELL IT SHORT
AS ADDITIONAL ADVANCEMENT IS LIKELY THIS MORNING, AS HINTED AT BY
STRATUS GETTING INTO WHIDBEY ISLAND AS WELL AS NORTHERN PORTIONS OF
SNOHOMISH COUNTY. MORNING TEMPERATURES PRETTY MUCH EVEN KEEL WITH
THOSE FROM THIS TIME YESTERDAY.
ONE LAST DAY OF THE CURRENT WEATHER PATTERN, ZONAL FLOW ALOFT AND
ONSHORE WINDS, STRONGEST IN THE AFTERNOON AND EVENING. DAYTIME TEMPS
WILL DEPEND ON HOW MUCH ADDITIONAL EASTWARD PROGRESS MARINE STATUS
MAKES. AS STATED ABOVE, SINCE IT IS A LITTLE BIT SHY OF WHAT IT WAS
YESTERDAY, SHOULD SEE AN EARLIER BURN OFF AND AS SUCH PERHAPS A
DEGREE OR TWO OF WARMING.
UPPER LEVEL TROUGH FOR WEDNESDAY IS STILL ON TRACK AS MODELS WANT TO
DIG THIS FEATURE A LITTLE FURTHER SOUTH THAN PREVIOUS RUNS. FOR THE
THUNDERSTORM RISK TO OLYMPICS, IT MAKES SENSE, AS SOME MODEL
SOLUTIONS HAD BEEN HINTING AT THAT AND HAVE CONSISTENTLY SHOWN THE
INSTABILITY WILL BE THERE FOR IT...SO HAVE ALLOWED THAT CHANGE TO
SEEP INTO THE FORECAST. BEST CHANCES FOR PRECIP STILL FAVOR THE
HIGHER TERRAINS OF THE AREA AND WITH A MORE SOUTHERN TRACK NOW
PROGGED, THIS WILL ALLOW FOR SHOWER/THUNDERSTORM CHANCES TO SAG DOWN
INTO THE CASCADES OF SNOHOMISH COUNTY AND MAYBE EVEN THE FAR
NORTHEASTERN CORNER OF KING COUNTY. THIS SYSTEM DOES NOT LINGER AND
ANY PRECIP/LIGHTNING THREAT SHOULD BE WRAPPED UP BY MIDNIGHT
WEDNESDAY NIGHT.
A GENERAL TROUGH PATTERN REMAINS OVER THE PAC NW THURSDAY AND LATEST
SOLUTIONS SEEM TO BE TRYING VERY HARD TO BRING IN WRAP AROUND
MOISTURE...BUT COVERAGE LOOKS VERY SPLOTCHY AT BEST. AN ARGUMENT
COULD BE MADE FOR THE TERRAIN OF THE CASCADES...BUT SOLUTIONS THAT
INCLUDE THE OLYMPICS HAVE A HARDER TIME MAKING THEIR CASE
CONVINCING. LEFT IT IN FORECAST FOR NOW, BUT IF NO ACTIVITY OCCURS
THERE WEDNESDAY. THE CHANCES FOR THURSDAY WOULD LIKELY BE NIL.
DAYTIME HIGHS WEDNESDAY WILL TAKE A SLIGHT TUMBLE, WITH THE INTERIOR
LOWLANDS IN THE LOWER TO MID 70S AND THE COAST AROUND THE MID TO
UPPER 60S. THURSDAY WASTES NO TIME REBOUNDING, HOWEVER, AS UPPER 70S
TO LOWER 80S RETURN INLAND...ALTHOUGH NO SIGNIFICANT CHANGE FOR THE
COAST.
18
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
THE UPPER LEVEL TROUGH SLOWLY CYCLES OUT OF THE AREA FRIDAY AS AN
UPPER LEVEL RIDGE BUILDING OVER THE ROCKIES ENDS UP BEING THE
PRIMARY WEATHER DRIVER FOR THE WEEKEND INTO NEXT MONDAY. WHILE THIS
MAY NOT ADVANCE THE WARMING SEEN ON THURSDAY, INTERIOR DAYTIME HIGHS
WILL LINGER IN THE UPPER 70S TO LOWER 80S FOR THE REMAINDER OF THE
FORECAST PERIOD AS THE COAST CONTINUES TO FAVOR MID TO UPPER
60S...WITH A FEW SPOTS GETTING UP TO 70. EARLIER SOLUTIONS SHOWED A
STRONGER WARMING TREND DURING THIS TIME, WHICH WOULD HAVE ELEVATED
FIRE WEATHER CONCERNS FOR THE END OF THE FORECAST CYCLE. WILL NOT
BACK AWAY FROM THIS THINKING JUST YET, BUT IF THIS SOMEWHAT COOLER
SOLUTIONS PERSISTS, DAYTIME RH VALUES WOULD REMAIN NORTH OF 40 PCT,
WHICH, GIVEN THE TIME OF YEAR, IS NOT TERRIBLE.
18
AVIATION
WESTERLY FLOW ALOFT CONTINUES WITH ONSHORE FLOW IN THE LOW LEVELS.
LIFR/IFR STRATUS EXTENDS PARTIALLY INLAND FROM THE COAST. IT IS
EXPECTED TO BURN BACK TO NEAR THE IMMEDIATE COAST BY MIDDAY. LOW
CLOUDS WILL PUSH BACK INLAND AGAIN TONIGHT AHEAD OF AN APPROACHING
TROUGH LATE TONIGHT WITH IFR OR LOW MVFR CEILINGS LIKELY WEDNESDAY
MORNING ACROSS MUCH OF THE REGION.
KSEA...SCATTERED LOW CLOUDS IN THE VICINITY OF THE TERMINAL WILL
CONTINUE TO DISSIPATE WITH VFR EXPECTED FOR THE REMAINDER OF THE
DAY. LOW CLOUDS ARE EXPECTED TO RETURN ON WEDNESDAY MORNING, BUT
CEILINGS WILL MORE LIKELY FALL INTO MVFR CATEGORY. SURFACE WINDS
W/SW UNDER 7 KNOTS VEERING N/NW AGAIN LATE AFTERNOON BEFORE BACKING
S/SW AGAIN TONIGHT. 27
MARINE
BROAD SURFACE HIGH PRESSURE WILL REMAIN CENTERED OVER THE OFFSHORE
WATERS WITH LOWER PRESSURE EAST OF THE CASCADES THROUGH MUCH OF THE
WEEK AHEAD. 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.
STRONGER ONSHORE FLOW WILL DEVELOP AT TIMES THROUGHOUT THE WEEK AS A
SERIES OF WEAK SYSTEMS PASSES TO THE NORTH OF THE AREA. THIS MAY
BRING ADDITIONAL RISKS OF GALES ALONG THE CENTRAL AND EASTERN STRAIT
AT TIMES.
SEAS ACROSS THE COASTAL WATERS WILL PRIMARILY PERSIST BETWEEN 2-4
FEET TODAY ARE EXPECTED TO INCREASE TO 5-7 FEET NEAR MIDWEEK. SEAS
WILL THEN SUBSIDE BACK TO 3-5 FEET HEADING INTO THE WEEKEND.
14
FIRE WEATHER
A DRY, ONSHORE FLOW PATTERN WITH SEASONABLE TEMPERATURES AND
PERSISTENT GOOD TO EXCELLENT OVERNIGHT RH RECOVERIES WILL CONTINUE
TODAY. ENSEMBLES CONTINUE TO VERY CONFIDENTLY SHOW AN UPPER LEVEL
SHORTWAVE CLIPPING THE AREA WEDNESDAY, WITH SOME VARIABILITY IN THE
STRENGTH OF THE SHORTWAVE, AS RECENT MODELS HAVE BROUGHT THE
SHORTWAVE A BIT MORE SOUTH OVER THE CWA. THIS WILL CONTINUE THE
SCENARIO OF THUNDERSTORM POTENTIAL WEDNESDAY AFTERNOON AND EVENING
FOR THE NORTHERN AND CENTRAL CASCADES. LATEST GUIDANCE SHOWS
GENERALLY A 20-30% PROBABILITY OVER THE WHATCOM, SKAGIT AND
SNOHOMISH CASCADES THROUGH LATE WEDNESDAY EVENING. WARMER AND
CONTINUED DRY CONDITIONS REMAIN ON TRACK THROUGH THE SECOND HALF OF
THE WEEK, ALTHOUGH THE WARMING SEEMS TO BE CAPPED IN THE LATEST
SOLUTIONS. IT IS A LITTLE EARLY TO BACK AWAY FROM EXPECTING WARMER
AND DRY CONDITIONS INTO THE START OF NEXT WEEK...RESULTING IN
ELEVATED FIRE WEATHER CONCERNS. IF CURRENT SOLUTIONS REMAIN
CONSISTENT, DAYTIME RH VALUES MAY NOT TAKE THE HIT INITIALLY
EXPECTED IN THIS TIME FRAME, STAYING ABOVE 40 PCT FOR THE MAJORITY
OF W WA. STAY TUNED.
18
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT EARLY THIS MORNING FOR
CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE
U.S. WATERS STRAIT OF JUAN DE FUCA.
SMALL CRAFT ADVISORY FROM 5 PM THIS AFTERNOON TO 5 AM PDT
WEDNESDAY FOR CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-
EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.
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