Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 290354
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 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...ONSHORE FLOW AND AN APPROACHING FRONTAL SYSTEM WILL
KEEP SKIES CLOUDY TONIGHT. A FEW SHOWERS ARE STARTING TO DEVELOP IN
SNOHOMISH COUNTY WHERE THERE IS LOW LEVEL CONVERGENCE. SHOWERS WILL
INCREASE IN COVERAGE FRIDAY MORNING AS THE COLD FRONT MOVES
INLAND...BUT OVERALL THIS SYSTEM DOES NOT LOOK TOO IMPRESSIVE. THE
INFRARED SATELLITE SHOWS SOME SIGNS OF SPLITTING AS THIS FRONT
APPROACHES. SHOWERS WILL TAPER OFF FRIDAY EVENING AS THE TRAILING
UPPER LEVEL TROUGH EXITS. IT WILL BE ANOTHER COOL DAY WITH
TEMPERATURES MAINLY IN THE MID TO UPPER 50S.

SATURDAY IS STILL LOOKING DRY AND MILD AS AN UPPER LEVEL RIDGE
PUSHES INLAND. NORTHERLY FLOW SHOULD HELP SCOUR OUT THE MORNING LOW
CLOUDS. FORECAST MAX TEMPS ARE BACK IN THE 60S...A FEW DEGREES ABOVE
NORMAL.

THE UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION ON SUNDAY FOR
ANOTHER DRY DAY. LOW LEVEL OFFSHORE FLOW WILL INCREASE AS A THERMAL
TROUGH FORMS ALONG THE COAST. THE DRY OFFSHORE FLOW WILL HELP BOOST
TEMPS INTO THE 70S TO LOWER 80S...ESPECIALLY ACROSS THE INTERIOR AND
COAST. THE COOL SPOTS WILL BE THE STRAIT AND SAN JUANS WITH HIGHS IN
THE MID 60S TO LOWER 70S. 33

.LONG TERM...PREVIOUS DISCUSSION...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 FRIDAY MORNING.
AIR MASS SOMEWHAT MOIST AND STABLE TODAY...WITH MOISTURE AND
INSTABILITY INCREASING AS TROUGH AXIS PASSES THROUGH FRIDAY. SHOWERS
AND FAIRLY WIDESPREAD IFR CIGS EXPECTED FRIDAY MORNING. SHOWERS
ENDING AND GRADUAL CLEARING FRI AFTN AND EVNG FROM WEST TO EAST.
LIGHT AND VARIABLE FLOW ALOFT TODAY...BECOMING LIGHT NW ON FRI.

KSEA...NOT SEEING PSCZ DEVELOP AS PREVIOUS SHIFT THOUGHT...SO
GENERALLY EXPECTING SOUTHWEST WINDS THIS EVENING SHIFTING TO THE
SOUTHEAST TONIGHT WITH CIGS REMAINING VFR THROUGH TONIGHT. THE
PASSAGE OF A FRONT FRI MORNING WILL ENHANCE MOIST LOW-LEVEL ONSHORE
FLOW...BRINGING IFR CIGS EARLY 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/SMR

&&

.MARINE...A FRONT WILL PASS EASTWARD ACROSS THE WATERS FRIDAY
MORNING...ENHANCING ONSHORE FLOW THIS EVENING AND AGAIN FRIDAY
EVENING. SMALL CRAFT ADVISORIES REMAIN IN PLACE FOR CENTRAL AND
EASTERN STRAIT...AND CURRENT OBS LOOK LIKE THE ADVISORY LOOKS GOOD
FOR CENTRAL STRAIT. EASTERN STRAIT LOOKS TO HAVE FALLEN BELOW
CRITERIA...BUT WILL KEEP ADVISORY UP FOR EVENING FORECAST. WILL
LIKELY NEED ANOTHER ROUND OF ADVISORIES FOR MOST WATERS FOR
FRIDAY...BUT WILL WAIT AND ISSUE WITH EARLY MORNING FORECAST
PACKAGE. 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/SMR

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT.

&&

$$

WWW.WEATHER.GOV/SEATTLE

ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION CAN BE SEEN AT
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