Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 300411
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PDT SAT AUG 29 2015

.SYNOPSIS...A FRONT WILL BRING RAIN AT TIMES TO WESTERN WASHINGTON
TONIGHT BEFORE CHANGING TO SHOWERS. ADDITIONAL WEAKER FRONTS WILL
REACH THE AREA THROUGH THE MIDDLE OF NEXT WEEK AS A LARGE TROUGH
TAKES UP RESIDENCE OVER THE REGION. HIGH PRESSURE MAY BUILD OVER
THE AREA NEXT WEEKEND.

&&

.SHORT TERM...WINDS CONTINUE TO EASE THIS EVENING WITH JUST BREEZY
SW WINDS EXPECTED THE REST OF TONIGHT. A FRONTAL BAND FEATURE IS
BRINGING RENEWED RAINFALL TO WRN WA AS IT PUSHES VERY SLOWLY
INLAND. THIS FEATURE HAS PRODUCED LOCALLY HEAVY RAIN WITH NEARLY A
HALF INCH OF RAIN REPORTED AT SHELTON FROM 7-8 PM. RADAR SHOWS
STEADY RAIN INCREASING ALONG THE I-5 CORRIDOR WHICH MAY BE HEAVY AT
TIMES INTO THE EARLY MORNING HOURS. THE FORECAST WAS UPDATED TO
INCREASE RAINFALL COVERAGE...POPS...AND AMOUNTS FOR THE REST OF
TONIGHT.

THE TROUGH AXIS WILL SHIFT OVER WRN WA ON SUNDAY WITH A TRANSITION
OVER TO SHOWERS DURING THE MORNING. SW FLOW ALOFT WILL PROBABLY RAIN
SHADOW MUCH OF GREATER PUGET SOUND WITH ONLY LIGHT RAIN AMOUNTS
EXPECTED. HIGHS WILL REMAIN A LITTLE BELOW AVERAGE...STRUGGLING TO
REACH OUT OF THE UPPER 60S EVEN WITH PARTIAL SUNSHINE.

THE LARGE SCALE UPPER LOW REMAIN OVER PUGET SOUND INTO EARLY NEXT
WEEK. ANOTHER FRONTAL SYSTEM SHOULD BRING MORE RAIN INTO WRN WA
SUNDAY NIGHT AND MONDAY. HIGHS WILL REMAIN COOL IN THE UPPER 60S.
MERCER

.LONG TERM...FROM PREVIOUS DISCUSSION...SHORTWAVES WILL CONTINUE TO
ROTATE THROUGH THE AREA IN THE MEAN UPPER LEVEL TROUGH THROUGH
FRIDAY WITH A GOOD CHANCE OF SHOWERS. THE COOLEST AIR ALOFT WORKS
OVER THE AREA BY ABOUT WED NIGHT WHEN THE SNOW LEVEL MIGHT BE AROUND
5000FT IN THE NORTH CASCADES. A RIDGE AND WARMER AIR WILL LIKELY
BUILD OVER THE AREA FOR NEXT WEEKEND.

&&

.AVIATION...FRONTAL SYSTEM OVER THE AREA TONIGHT WILL SHIFT EAST
OF THE AREA AFTER MIDNIGHT. NARROW BAND OF HEAVY RAIN EMBEDDED IN
THE FRONT WITH CEILINGS 1500-2500 FEET AND VISIBILITIES 2-4SM. THIS
BAND OF HEAVIER PRECIPITATION WILL BE EAST OF THE AREA BY 07Z.
BEHIND THE FRONT WEAK LOW LEVEL ONSHORE FLOW WITH SCATTERED SHOWERS.
MULTIPLE CLOUD LAYERS FROM 2500 FEET TO 8000 FEET WITH CEILINGS
MOSTLY IN THE 4000-5000 FOOT RANGE THROUGH SUNDAY.

KSEA...BAND OF HEAVY RAIN WILL MOVE EAST OF THE TERMINAL BY 07Z.
UNTIL THEN VISIBILITIES AS LOW AS 2 SM. BRIEF CEILINGS NEAR 1000
FEET. CEILINGS FOR THE MOST PART IN THE 1500-2500 FOOT RANGE.
CEILINGS LIFTING BACK UP TO NEAR 4000 FEET AFTER MIDNIGHT. LITTLE
CHANGE THROUGHOUT THE DAY ON SUNDAY. BRIEF WESTERLY WINDS 8 TO 12
KNOTS WILL SHIFT BACK TO SOUTHWEST 07Z-09Z AND REMAIN SOUTH
SOUTHWESTERLY THROUGH SUNDAY. FELTON
&&

.MARINE...THE STRONG SURFACE LOW THAT MOVED NORTH THROUGH THE
COASTAL WATERS OF WASHINGTON THIS AFTERNOON HAS WELL NORTH OF
THE AREA. WINDS WILL CONTINUE TO EASE OVERNIGHT INTO SUNDAY MORNING.
SMALL CRAFT ADVISORY WINDS OVER THE COAST...ADMIRALTY INLET AND
NORTHERN INLAND WATERS WILL DROP BELOW SMALL CRAFT ADVISORY AFTER
MIDNIGHT.

AN ADDITIONAL SET OF WEAKER SYSTEMS WILL MOVE THROUGH THE WATERS
MONDAY AND TUESDAY STRENGTHENING SOUTHWESTERLY AND SOUTHERLY WINDS
MAINLY FOR THE COASTAL WATERS BUT ALSO SOME OF THE INTERIOR WATERS.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...SMALL CRAFT ADVISORY UNTIL MIDNIGHT COAST...ADMIRALTY
     INLET AND NORTHERN INLAND WATERS.

&&

$$

WWW.WEATHER.GOV/SEATTLE

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML


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