Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 302159
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PDT SAT MAY 30 2015

.SYNOPSIS...AFTER MOSTLY CLEAR SKIES TONIGHT...HIGH AND MID LEVEL
CLOUDS WILL INCREASE SUNDAY AS AN UPPER TROUGH MOVES TOWARD
CALIFORNIA. SHOWERS ARE LIKELY OVER THE AREA MONDAY THROUGH TUESDAY
AS THE TROUGH LIFTS NORTHEAST. ANOTHER WEAK TROUGH WILL BRING A
CHANCE OF SHOWERS WEDNESDAY AND THURSDAY. CONDITIONS WILL WARM AND
DRY HEADING INTO NEXT WEEKEND.

&&

.SHORT TERM...SUNNY DAY OVER WESTERN WASHINGTON WILL END WITH HIGHS
IN THE 70S...60S NEAR THE WATER. ONSHORE GRADIENTS ARE INCREASING
AND STRATUS WILL RETURN OVERNIGHT. AREAL EXTENT OF STRATUS WILL
PROBABLY BE SIMILAR TO TODAY AND IT WILL ALSO RETREAT BACK TOWARD
THE COAST DURING THE DAY. HOWEVER HIGH AND MID CLOUDS WILL ALSO BE
INCREASING FROM THE SOUTH AFTER MIDNIGHT TONIGHT AS AN UPPER TROUGH
MOVES TOWARD NORTHERN CALIFORNIA. CLOUDS WILL EVENTUALLY COVER THE
AREA LATER SUNDAY AND HIGHS WILL BE SIMILAR TO TODAY.

THERE IS DIVERGENCE ALOFT SUNDAY NIGHT INTO MONDAY THOUGH THE
PATTERN IS NOT AS THUNDERSTORM-FRIENDLY AS IT SEEMED YESTERDAY. ANY
THUNDERSTORMS ARE LIKELY TO BE CONFINED TO THE CASCADES THOUGH
PERHAPS THE LOWLANDS WILL SEE ONE OR TWO...ESPECIALLY IN THE SOUTH.
THERE WILL BE A GENERAL CHANCE OF SHOWERS EVERYWHERE ON MONDAY.
HIGHS WILL LOWER AS HEIGHTS FALL...MAINLY IN THE 60S.

TUESDAY HAS THE BEST CHANCE FOR SOME RAIN. THE UPPER TROUGH SWINGS
NORTH OVER WASHINGTON AND MODELS HAVE SHOWER ACTIVITY EVERYWHERE.
HAVE LIKELY POPS MONDAY NIGHT AND TUESDAY OVER THE LOWLANDS WITH
CATEGORICAL POPS IN THE MOUNTAINS. TUESDAY IS ALSO LIKELY TO BE THE
COOLEST DAY OF THE WEEK WITH HIGHS IN THE LOW 60S. BURKE

.LONG TERM...AFTER TUESDAY A SLOW WARMING AND DRYING TREND BEGINS
THOUGH THERE IS A WEAK TROUGH OVER THE AREA THROUGH THURSDAY. BY
FRIDAY THE SHOWER CHANCE IS ONLY IN THE CASCADES AND WESTERN
WASHINGTON SHOULD SEE HIGHS BACK IN THE LOW 70S. SATURDAY LOOKS DRY
EVERYWHERE WITH HIGHS IN THE MID 70S. BURKE

&&

.AVIATION...AN UPPER LEVEL LOW OVER CENTRAL BRITISH COLUMBIA
COMBINED WITH AN UPPER LEVEL RIDGE OVER THE SW U.S. WILL GIVE LIGHT
WSW FLOW ALOFT OVER W WA THROUGH SUNDAY. THE AIR MASS ALOFT IS DRY
AND STABLE AND NO CONVECTION IS EXPECTED OVER THE AREA THROUGH
SUNDAY AFTERNOON. GOOD VFR CONDITIONS WILL CONTINUE THIS EVENING
EXCEPT ALONG THE COAST AS IFR/LOW MVFR STRATUS BEGINS PUSHING
INLAND.

INCREASING ONSHORE FLOW LATE THIS AFTERNOON AND EVENING WILL BRING
ANOTHER SURGE OF MARINE MOISTURE TO THE W WA INTERIOR LATE TONIGHT
AND SUNDAY MORNING. THE MARINE LAYER WILL BE SHALLOW ONCE AGAIN WITH
CIGS 005-015 AND TOPS 015-020. IT LOOKS LIKE IT WILL HAVE ABOUT THE
SAME COVERAGE SUNDAY MORNING AS THIS MORNING...COVERING THE COAST
AND MOST OF THE INTERIOR LOWLANDS EXCEPT FOR AROUND THE BELLINGHAM
AREA AND THE E PUGET SOUND LOWLANDS E OF ABOUT BELLEVUE. THE STRATUS
SHOULD BURN OFF BACK TO THE COAST BY AROUND MIDDAY...WITH JUST HIGH
CLOUDS OVERHEAD SUNDAY AFTERNOON.

KSEA...GOOD VFR CONDITIONS WILL CONTINUE THROUGH 12Z. SURFACE WINDS
WILL REMAIN SW 4-8 KT THROUGH 00Z THEN SHIFT TO WESTERLY 3-7 KT. THE
WINDS WILL BECOME MORE LIGHT AND VARIABLE AFTER ABOUT 04Z...BUT
COULD BECOME NW TO 5 KT AT TIMES.

ONSHORE FLOW WILL BRING ANOTHER SURGE OF STRATUS TO KSEA AFTER 12Z.
IT LOOKS LIKE A SIMILAR EVENT TO THIS MORNING WITH CIGS AROUND 010
AND TOPS 011-015. KAM

&&

.MARINE...A SURFACE RIDGE WELL OFFSHORE COMBINED WITH LOWER PRES E
OF THE CASCADES WILL GIVE LIGHT TO MODERATE ONSHORE FLOW THROUGH THE
WEEKEND. WESTERLY FLOW THROUGH THE STRAIT HAS NOT WEAKENED QUITE AS
MUCH AS EXPECTED THIS AFTERNOON SO A SCA WILL BE IN EFFECT THROUGH
LATE TONIGHT. WINDS SHOULD TOP OUT IN THE 20-30 KT RANGE IN THE
CENTRAL/E STRAIT. WINDS OVER THE REMAINING WASHINGTON WATERS ARE
EXPECTED TO REMAIN 20 KT OR LESS THROUGH SUNDAY. ONSHORE FLOW
THROUGH THE STRAIT IS EXPECTED TO WEAKER SUNDAY AFTERNOON AND SUNDAY
NIGHT TOPPING OUT BELOW SCA LEVELS.

AN UPPER LEVEL LOW MOVING IN FROM THE SW WILL SHIFT THE ONSHORE
PRESSURE GRADIENTS TO A SW DIRECTION MONDAY MORNING. SOUTHERLY WINDS
OVER THE PUGET SOUND UP THROUGH THE NORTHERN INLAND WATERS WILL
INCREASE BUT AT THIS POINT ARE EXPECTED TO REMAIN BELOW SCA LEVELS.
KAM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EAST STRAIT OF JUAN DE FUCA.

&&

$$

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