Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 282230
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 PM PDT THU APR 28 2016

.SYNOPSIS...WEAK UPPER LEVEL RIDGE MOVING EAST OF THE AREA THIS
EVENING. A FRONT AND ITS UPPER TROUGH WILL BRING SHOWERS LATE
TONIGHT AND FRIDAY. A STRONG UPPER RIDGE WILL BRING DRY WARMER
WEATHER SATURDAY THROUGH MONDAY. A CHANCE OF PRECIPITATION WILL
RETURN TUESDAY THROUGH THURSDAY OF NEXT WEEK.

&&

.SHORT TERM...SATELLITE IMAGERY SHOWS A LOT OF SC OVER WESTERN
WASHINGTON THIS AFTERNOON WITH A WEAK FRONT WELL OFFSHORE. RADAR
NOT PICKING UP ANY SHOWER ACTIVITY AS OF 22Z/3PM. TEMPERATURES AT
3 PM WERE IN THE MID 50S TO MID 60S.

FRONT OFFSHORE WILL CONTINUE TO APPROACH TONIGHT WITH THE UPPER
LEVEL RIDGE CONTINUING TO MOVE EAST. AIR MASS SLIGHTLY UNSTABLE
LATE THIS AFTERNOON INTO THIS EVENING SO A LIGHT SHOWER OVER THE
HIGHER TERRAIN CAN NOT BE RULED OUT. ONSHORE FLOW AT THE LOWER
LEVELS TONIGHT WITH A SURFACE RIDGE OUT AHEAD OF THE FRONT. BEST
CHANCES FOR SHOWERS AFTER MIDNIGHT ALONG THE COAST AND IN A WEAK
CONVERGENCE ZONE OVER NORTHERN SNOHOMISH AND SOUTHERN SKAGIT
COUNTY. LOWS TONIGHT WILL BE IN THE 40S TO NEAR 50.

FRONT MOVING THROUGH WESTERN WASHINGTON FRIDAY MORNING INTO THE
EARLY AFTERNOON HOURS. POSSIBLE CONVERGENCE CONTINUING NEAR THE
EAST ENTRANCE OF THE STRAIT OF JUAN DE FUCA. SHOWERS WILL DECREASE
IN THE AFTERNOON HOURS ESPECIALLY WEST OF PUGET SOUND. HIGHS ON
FRIDAY WILL BE COOL...MOSTLY IN THE 50S.

SHOWER CHANCES DECREASING QUICKLY FRIDAY NIGHT AS AN UPPER LEVEL
RIDGE BUILDS OFF THE COAST. LOW LEVEL ONSHORE FLOW STILL KEEPING
MOSTLY CLOUDY SKIES OVER MOST OF THE AREA. LOWS WILL BE MOSTLY IN
THE 40S.

UPPER LEVEL RIDGE BEGINNING TO NOSE IN OVER WESTERN WASHINGTON ON
SATURDAY WITH 500 MB HEIGHTS UP TO THE LOWER TO MID 570 DECAMETERS
BY 00Z SUNDAY. SURFACE GRADIENTS REMAINING NORTHWESTERLY ALL DAY
SO EVEN THOUGH TEMPERATURES ALOFT WARM UP HIGHS ON SATURDAY WILL
ONLY MOSTLY BE IN THE 60S WITH THE WARMER LOCATIONS IN THE LOWER
70S.

SURFACE GRADIENTS TURN OFFSHORE OVERNIGHT SATURDAY NIGHT INTO
SUNDAY MORNING WITH A THERMALLY INDUCED TROUGH DEVELOPING ALONG
THE COAST. WINDS FROM 850 MB TO THE SURFACE ALSO TURNING EASTERLY.
TEMPERATURES ALOFT WARMING WITH THE MODEL 850 MB TEMPERATURES
PLUS 10 TO PLUS 13C AT 00Z MONDAY. HIGHS WILL WARM ON SUNDAY INTO
THE 70S AND LOWER 80S.

.LONG TERM...EXTENDED MODELS IN GOOD AGREEMENT WITH THE LOW LEVEL
OFFSHORE FLOW WEAKENING ON MONDAY WITH THE GRADIENTS TURNING
WEAKLY ONSHORE ALONG THE COAST IN THE AFTERNOON. THIS WILL COOL
THE HIGH TEMPERATURES DOWN ALONG THE COAST WHILE OVER THE INTERIOR
MONDAY LOOKS TO BE THE WARMEST DAY IN THIS MINI HEAT WAVE WITH
HIGHS IN THE 70S AND LOWER 80S. SPLITTING FRONT APPROACHING THE
COAST ON TUESDAY WITH A SMALL CHANCE OF SHOWERS OVER THE AREA. LOW
LEVEL FLOW TURNS ONSHORE FOR THE ENTIRE AREA ON TUESDAY. THIS
CHANCE IN THE LOW LEVEL FLOW WILL LOWER HIGH TEMPERATURES AROUND
10 DEGREES. WHAT IS LEFT OF THE FRONT MOVING THROUGH THE AREA
TUESDAY NIGHT. UPPER LEVEL TROUGH WILL REMAIN OFF THE COAST
TUESDAY NIGHT THROUGH THURSDAY KEEPING A CHANCE OF SHOWERS IN THE
FORECAST. WITH THE LOW LEVEL ONSHORE FLOW TEMPERATURES WILL
CONTINUE TO COOL DOWN WITH 60S EXPECTED WEDNESDAY AND THURSDAY.
FELTON

&&

.AVIATION...AN UPPER TROUGH AXIS WILL PASS WRN WA ON FRI
MORNING. AIR MASS SOMEWHAT MOIST AND STABLE TODAY...BECOMING MORE
MOIST AND MORE UNSTABLE ON FRI. SHOWERS AND FAIRLY WIDESPREAD IFR
CONDS EXPECTED FRI MORNING. SHOWERS ENDING AND GRADUAL CLEARING FRI
AFTN AND EVNG...FIRST NEAR THE WATERS. LIGHT AND VARIABLE FLOW ALOFT
TODAY...BECOMING LIGHT NW ON FRI.

KSEA...PUGET SOUND CONVERGENCE ZONE MAY SLIP JUST SOUTH OF THE
TERMINAL THIS EVNG...BRINGING A SHIFT TO NORTHERLY WINDS ARND
02Z. NLY WINDS WOULD LAST FOR 2-4 HOURS. THE PASSAGE OF A FRONT ON
FRI MORNING WILL ENHANCE MOIST LOW-LEVEL ONSHORE FLOW...BRINGING IFR
CIGS ON FRI MORNING IN THE 1000-2000 FOOT RANGE...ALONG WITH A FEW
HOURS OF RAIN. CIGS LIFTING ON FRI AFTN TO NEAR 030-040...THEN
SCATTERING OUT ON FRI EVNG.     HANER

&&

.MARINE...A FRONT WILL PASS EASTWARD ACROSS THE WATERS ON FRI
MORNING...ENHANCING ONSHORE FLOW THIS EVENING AND AGAIN ON FRI EVNG.
A TURN TO NORTHERLY ONSHORE FLOW IS EXPECTED ON SATURDAY. NORTHERLY
OFFSHORE FLOW IS EXPECTED ON SUNDAY. NORTHERLIES COULD REACH SMALL
CRAFT STRENGTH IN PUGET SOUND ON SUNDAY PM.     HANER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...SMALL CRAFT ADVISORY UNTIL 8 AM PDT FRIDAY FOR EAST ENTRANCE
     U.S. WATERS STRAIT OF JUAN DE FUCA.

     SMALL CRAFT ADVISORY UNTIL 10 PM PDT THIS EVENING FOR WEST
     ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.

     SMALL CRAFT ADVISORY UNTIL 8 AM PDT FRIDAY FOR CENTRAL U.S.
     WATERS STRAIT OF JUAN DE FUCA.

&&

$$

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