139
FXUS66 KSEW 061814
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
1114 AM PDT SAT JUN 6 2026
SYNOPSIS
LOW PRESSURE WILL MOVE DIRECTLY OVER WESTERN WASHINGTON TODAY,
BRINGING WIDESPREAD SHOWERS WITH THE CHANCE FOR ISOLATED
THUNDERSTORMS THIS AFTERNOON AND EVENING. ANY STORMS THAT DEVELOP
WILL BE CAPABLE OF LIGHTNING, GUSTY WINDS, AND BRIEF PERIODS OF
HEAVY RAIN. WHILE THE THREAT FOR THUNDER ENDS THIS EVENING, A
GENERALLY TROUGHY PATTERN WILL KEEP WEATHER COOL AND UNSETTLED FOR
THE FIRST HALF OF THE UPCOMING WEEK. A WARMING AND DRYING TREND
TAKES HOLD LATE NEXT WEEK.
SHORT TERM /TODAY THROUGH MONDAY/
GENERAL INSTABILITY ASSOCIATED WITH THE LEADING EDGE OF SUCH A
FEATURE COUPLED WITH COLD AIR ALOFT WILL CERTAINLY LEAD TO
ANOTHER DAY OF THUNDERSTORM POTENTIAL...AND MODELS AND SPC
OUTLOOK HAS RIGHTLY LOCKED ON TO THIS. HOWEVER, THERE ARE SOME
OFFSETTING FACTORS THAT LOOK TO LIMIT THE AMOUNT OF ACTIVITY
THAT MAY SPRING UP THIS AFTERNOON AND EARLY EVENING. FIRST,
WHILE THERE IS COLD AIR ALOFT, THE AIR AT THE SURFACE IS NOT
TERRIBLY TOASTY EITHER AS DAYTIME HIGHS ARE PROGGED TO REMAIN
LARGELY IN THE MID TO UPPER 50S. IN TURN, THESE COOLER SURFACE
CONDITIONS WILL KEEP ANY LI AND AVAILABLE CAPE PRETTY LOW. THESE
OFFSETTING FACTORS ACTUALLY SERVE TO HELP HIGHLIGHT WHERE THE
BETTER CHANCES FOR THUNDER WILL EMERGE...MAINLY AROUND PUGET
SOUND, THE SOUTH SOUND AREA AND THE SW INTERIOR/CHEHALIS VALLEY.
NBM PROBTHUNDER VALUES ECHO THIS, BUT MIGHT BE A LITTLE TOO
GENEROUS...AT TIMES INDICATING A 30-40 PCT CHANCE FOR THUNDER IN
THESE AREAS. TO TAKE INTO ACCOUNT OFFSETTING FACTORS, TRIMMED
TO ALLOW 30 PCT TO BE THE ROOF AND EVEN THAT BEING LIMITED TO
THE 2-6 PM PDT WINDOW. THIS UPPER LOW EJECTS OUT OF THE AREA
OVERNIGHT TONIGHT, TAKING THE BULK OF ACTIVITY WITH IT, ALTHOUGH
AND POTENTIAL FOR THUNDER LOOKS TO WRAP UP BY SUNSET OR MAYBE
AN HOUR AFTER.
A SHORTWAVE RIDGE FOLLOWING IN THE WAKE OF THE AFOREMENTIONED LOW
WILL BRING A FEW DEGREES OF WARMING AS DAYTIME HIGHS CREEP INTO THE
UPPER 50S TO LOWER 60S BUT IS NOT STRONG ENOUGH TO REMOVE MUCH OF
THE MOISTURE IN THE AREA. CLOUDS LOOK TO REMAIN IN PLACE, ALBEIT
WITH SOME BREAKS...AND EVEN AN ISOLATED SHOWER OR TWO WILL BE
POSSIBLE, MAINLY IN THE CASCADES.
A FRONTAL SYSTEM REACHES THE COASTLINE SUNDAY NIGHT BUT HESITATES TO
PUSH INLAND UNTIL MONDAY AFTERNOON...WHEN THE BEST CHANCES FOR
RAINFALL EMERGE. TEMPS TAKE A MINOR HIT TO REFLECT THIS, ONLY
DROPPING A DEGREE OR TWO FROM SUNDAY'S HIGHS, BUT STILL REMAINING
WITHIN THE UPPER 50S TO LOWER 60S. NO THUNDERSTORM THREAT APPEARS TO
ACCOMPANY THIS FRONTAL PASSAGE AT THIS TIME.
18
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/
A SERIES OF UPPER LEVEL LOWS WILL KEEP TROUGHY CONDITIONS OVER W WA
INTO THE FIRST HALF OF THE UPCOMING WEEK...AND AS SUCH KEEP COOLER
TEMPERATURES AND THE CHANCES FOR PRECIPITATION IN THE FORECAST. AS
THESE SEEM TO FOLLOW ONE RIGHT AFTER THE OTHER, IT WILL BE DIFFICULT
TO DIFFERENTIATE FROM RAINS ASSOCIATED WITH THE UPPER LOW EXITING
MONDAY NIGHT AND THE FRESH SYSTEM ENTERING INTO THE AREA TUESDAY
INTO WEDNESDAY. LATEST FORECAST AND MODEL DATA SUGGEST A BRIEF DIP
IN POPS TUESDAY NIGHT INTO EARLY WEDNESDAY MORNING, BUT WILL NEED TO
MONITOR FUTURE RUNS TO SEE IF CONSISTENCY WILL BUILD CONFIDENCE IN
THIS WINDOW OR IF IT SHIFTS ABOUT BOTH IN AREAL TERMS AND
TEMPORALLY. COOLER DAYTIME HIGHS WILL REMAIN THE RULE FOR BOTH OF
THESE DAYS WITH TUESDAY STILL RANGING IN THE UPPER 50S TO LOWER 60S
WHILE WEDNESDAY SEES A SLIGHT WARMING WITH LOWER 60S AREA-WIDE.
AS THIS ALL HAPPENS OVER LAND, UPPER LEVEL RIDGING WILL CONTINUE TO
BUILD OVER THE EASTERN PACIFIC. ONCE THIS FEATURE STARTS MOVING
EASTWARD WEDNESDAY NIGHT, MODELS DO SHOW IT BEGINNING TO SCOUR OUT
ANY LINGERING MOISTURE...ALTHOUGH HOW QUICKLY VARIES MODEL TO MODEL.
WIDE AGREEMENT THAT THURSDAY AND FRIDAY WILL BE DRY THANKS TO THIS
FEATURE AS ITS IMPACTS SPREAD EASTWARD AND THE WARMING TREND FOR
THESE TWO DAYS STARTING TO SHOW SIGNS OF BEING ABLE TO LEAP OVER
TALL BUILDINGS IN A SINGLE BOUND. DAYTIME HIGHS THURSDAY SEE PLENTY
OF UPPER 60S TO LOWER 70S FOR THE INTERIOR AND FRIDAY JUMPS FURTHER
WITH MID 70S TO NEAR 80 EXPECTED...MAKING UP THE DISTANCE FROM BELOW
NORMAL TO ABOVE NORMAL VERY QUICKLY.
18
AVIATION
AN UPPER TROUGH AXIS OVER THE COASTAL WATERS THIS MORNING WILL SHIFT
INLAND ACROSS THE INTERIOR THIS AFTERNOON THEN EAST OF THE CASCADES
TONIGHT. WESTERLY FLOW ALOFT WILL BECOME NORTH TO NORTHWESTERLY
TONIGHT. A COMBINATION OF DAYTIME HEATING AND COOL TEMPERATURES
ALOFT WILL DESTABILIZE THE AIR MASS THIS AFTERNOON FOR SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS. LOW LEVEL CONVERGENCE WILL
ENHANCE THIS ACROSS CENTRAL PUGET SOUND. SHOWER COVERAGE WILL
DIMINISH THIS EVENING. MVFR CEILINGS CAN BE EXPECTED AROUND HEAVIER
SHOWERS AND/OR ISOLATED THUNDERSTORMS. REMNANT LOW LEVEL MOISTURE
AND LIGHT SURFACE WINDS WILL LEAD TO GREATER COVERAGE OF MVFR
CEILINGS ACROSS THE REGION ON SUNDAY MORNING. THIS WILL GRADUALLY
LIFT TO VFR SUNDAY AFTERNOON.
KSEA...TEMPO MVFR CEILINGS EXPECTED AROUND SOME OF THE HEAVIER
SHOWERS TODAY. CONFIDENCE IN THUNDERSTORM ACTIVITY IN THE VICINITY
OF THE TERMINAL HAS INCREASED AND IS THUS REFLECTED IN A PREVAILING
LINE FOR 23Z IN THE TAF. GUSTY AND ERRATIC WINDS CAN BE EXPECTED
AROUND ANY STORMS THAT DO DEVELOP. MORE PREDOMINANT MVFR CEILINGS
ARE EXPECTED SUNDAY AM AS REMNANT LOW LEVEL MOISTURE REMAINS IN THE
AREA. THESE WILL LIFT TO VFR SUNDAY AFTERNOON. SURFACE WINDS
SOUTHWESTERLY 9 TO 13 KNOTS THIS MORNING INTO THE AFTERNOON. THE
CONVERGENCE ZONE IS EXPECTED TO SHIFT INTO THE VICINITY OF THE
TERMINAL FOR FEW HOURS THIS EVENING FOR A BRIEF TO SWITCH TO NW-NE
WINDS. WINDS WILL SWITCH BACK TO PREVAILING SOUTHERLIES AFTER 06Z.
27
MARINE
A WEAK TROUGH OVER THE COASTAL WATERS THIS MORNING WILL SHIFT INLAND
TONIGHT AS WEAK HIGH PRESSURE BUILDS OVER THE COASTAL WATERS.
ANOTHER TROUGH AND ASSOCIATED FRONTAL SYSTEM WILL APPROACH THE OUTER
COASTAL WATERS SUNDAY EVENING THEN SLOW AND DISSIPATE. ONSHORE FLOW
WILL INCREASE TUESDAY AND WEDNESDAY AS BROAD HIGH PRESSURE GRADUALLY
EXPANDS INTO THE COASTAL AND OFFSHORE WATERS. ONSHORE WEAKENS LATE
NEXT WEEK AS THERMALLY INDUCED LOW PRESSURE BEGINS TO EXPAND
NORTHWARD ACROSS WESTERN OREGON.
COASTAL SEAS ARE EXPECTED TO REMAIN BELOW 10 FEET THROUGH THE
PERIOD.
27
FIRE WEATHER
ALTHOUGH LIGHTNING WILL BE POSSIBLE TODAY AND RAINFALL AMOUNTS MAY
NOT QUITE MAKE IT UP TO THE 0.25 IN THRESHOLD SEPARATING WET AND DRY
STORMS, MIN RH VALUES EXCEEDING 60 PCT SHOULD LIMIT ANY FIRE WEATHER
CONCERNS TODAY. AS THE GENERALLY TROUGHY PATTERN REMAINS IN PLACE
OVER W WA IN THE FIRST HALF OF THE UPCOMING WEEK, AGAIN, SOME
LIMITING MOISTURE IS EXPECTED TO REMAIN IN PLACE.
AS UPPER LEVEL RIDGING BUILDS INTO THE AREA STARTING THURSDAY,
CONDITIONS, INCLUDING FUELS, WILL NEED TO BE MONITORED AS
TEMPERATURES ARE EXPECTED TO CLIMB TO ABOVE NORMAL VALUES ENTERING
INTO THE WEEK 2 TIME PERIOD.
18
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 5 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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