Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 190424
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
930 PM PDT FRI JUL 18 2014

.SYNOPSIS...CLOUDS WILL INCREASE OVER WESTERN WASHINGTON TONIGHT AS
A WEATHER SYSTEM BRUSHES WESTERN WASHINGTON AS IT MOVES INTO BRITISH
COLUMBIA. THE SYSTEM WILL BRING SHOWERS TO MAINLY THE NORTH COAST
AND THE NORTH CASCADES THROUGH SATURDAY. SUNDAY AND MONDAY WILL BE
PARTLY SUNNY. AN UPPER LEVEL LOW WILL PRODUCE SHOWERS ON WEDNESDAY.

&&

.SHORT TERM...A WEATHER SYSTEM MOVING INTO BRITISH COLUMBIA WILL SAG
JUST FAR ENOUGH SOUTH TO GIVE SOME PRECIP TO WESTERN WA LATE TONIGHT
AND SATURDAY. PRECIP IS THE MOST LIKELY ON THE NORTH COAST AND IN
THE NORTH CASCADES. UPPER HEIGHTS FALL OF GRADUALLY OVER THE
WEEKEND...THERE IS LOW LEVEL ONSHORE FLOW...SO CLOUDS AND COOL
WEATHER ARE A GOOD BET. SOME AREAS OF NIGHT AND MORNING DRIZZLE ARE
NOT A BAD BET...ESPECIALLY AROUND DAYBREAK SUNDAY. FOR SUNDAY
AFTERNOON AND MONDAY...EXPECT PARTLY SUNNY SKIES. THE AIR WILL WARM
AND DRY MON AND TUE AND HEIGHTS RISE A LITTLE AS AN UPPER TROUGH
MOVES TOWARD THE AREA AND THE FLOW BACKS AROUND FROM WESTERLY SUNDAY
NIGHT TO MORE SLY BY TUE.

.LONG TERM...AN UPPER LOW WILL MOVE TOWARD THE PACNW ON TUESDAY AND
MOVE RIGHT OVER WA ON WED. SHOWERS ARE LIKELY FOR BOTH THE LOWLANDS
AND MOUNTAINS ON WED. THE UPPER LOW WILL MOVE EAST OF THE CASCADES
WEDNESDAY NIGHT AND THURSDAY...WITH WEAK HIGH PRESSURE BUILDING
TOWARD THE END OF THE WEEK.

&&

.AVIATION...WEST TO NORTHWEST FLOW ALOFT WILL PREVAIL TONIGHT AND
SATURDAY WITH A WEAK UPPER LEVEL DISTURBANCE MOVING ONSHORE DURING
THE DAY SATURDAY. AT THE SURFACE...ONSHORE FLOW WILL CONTINUE WITH
HIGH PRESSURE OFFSHORE AND LOWER PRESSURE INLAND. THE AIR MASS IS
STABLE WITH A MID LEVEL DECK OVER THE INTERIOR AND LOW CLOUDS NEAR
THE COAST.

LOW CLOUDS ALONG THE COAST MOVING INLAND OVERNIGHT BUT AT THIS POINT
THE IFR CEILINGS LOOK TO ONLY MAKE IT DOWN THE STRAIT A BIT AND INTO
THE LOWER CHEHALIS VALLEY. SC DECK IN THE 1500-2500 FOOT RANGE
DEVELOPING OVER THE INTERIOR 12Z-15Z SATURDAY MORNING AND REMAINING
UNTIL AROUND NOON AS AN UPPER LEVEL WEATHER SYSTEM MOVES
INTO THE AREA. CEILINGS LIFTING DURING THE AFTERNOON INTO THE
2500-3500 FOOT RANGE.

KSEA...MID LEVEL CLOUDS TONIGHT INTO EARLY SATURDAY MORNING. SC DECK
DEVELOPING AROUND 12Z WITH CEILINGS NEAR 2000 FEET. CEILINGS LIFTING
BACK UP TO NEAR 3500 FEET IN THE AFTERNOON. SOUTHERLY WIND 4-8 KNOTS
TONIGHT. SOUTHWEST WIND INCREASING TO 10 TO 20 KNOTS SATURDAY.
FELTON

&&

.MARINE...ONSHORE FLOW IN THE PROCESS OF PEAKING AT 04Z THIS EVENING
WITH GALE FORCE WEST WINDS IN THE CENTRAL AND EASTERN STRAIT OF JUAN
DE FUCA WITH SMALL CRAFT ADVISORY WESTERLY WINDS TO THE ADJACENT
INLAND WATERS.

A WEAK UPPER TROUGH WILL MOVE THROUGH THE WATERS SATURDAY. SMALL
CRAFT ADVISORY SOUTHERLY WINDS ARE POSSIBLE FOR SOME OF THE WATERS
AS THIS SYSTEM MOVES THROUGH.

AN ONSHORE FLOW PATTERN WILL PREVAIL SUNDAY THROUGH WEDNESDAY WITH
HIGH PRESSURE OFFSHORE AND LOWER PRESSURE INLAND. SCHNEIDER/FELTON

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.
    .SMALL CRAFT ADVISORY NORTHERN INLAND WATERS...ADMIRALTY INLET...
     AND COASTAL WATERS ZONES PZZ150 AND PZZ170.

&&

$$

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






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