Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 230331
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
830 PM PDT MON SEP 22 2014

.SYNOPSIS...A WEAK FRONT OFFSHORE WILL MOVE INLAND TONIGHT THEN
DISSIPATE OVER THE INTERIOR. A STRONGER FRONT WILL ARRIVE LATE
TUESDAY NIGHT AND WEDNESDAY BRINGING RAIN AND LOCALLY WINDY
CONDITIONS. AN UPPER TROUGH WILL BRING MOSTLY CLOUDY SKIES AND A
CHANCE OF SHOWERS LATE WEDNESDAY THROUGH FRIDAY.

&&

.SHORT TERM...CLOUDS ARE INCREASING ACROSS WESTERN WASHINGTON
TONIGHT AS A WEAK FRONT MOVES INLAND AND DISSIPATES. SO FAR THIS
FRONT HAS NOT EVEN RAINED ON THE COAST THOUGH THERE HAVE BEEN
SPRINKLES OVER THE SOUTHWEST. THOUGH THIS PARTICULAR FRONT IS NOT A
BIG RAIN PRODUCER IT DOES HERALD A CHANGE IN THE WEATHER OVER THE
NEXT FEW DAYS.

ANOTHER WAVE WILL ARRIVE FROM THE SOUTHWEST TUESDAY AND RAIN WILL
DEVELOP MORE OR LESS EVERYWHERE. THE PARENT FRONT ASSOCIATED WITH A
LOW OFFSHORE WILL MOVE INLAND TUESDAY NIGHT AND WEDNESDAY MORNING
GIVING HIGH POPS AND A FAIR AMOUNT OF RAIN...ESPECIALLY IN THE
OLYMPICS AND NORTH CASCADES. LATER WEDNESDAY AND THURSDAY THE
PRECIPITATION WILL BECOME MORE SHOWERY. BURKE

.LONG TERM...PREVIOUS DISCUSSION...THE OFFSHORE UPPER TROUGH MOVES
EASTWARD ONTO THE WEST COAST LATE IN THE WEEK. THE GLOBAL MODELS
THEN HAVE A TOUGH TIME DETERMINING WHETHER OR NOT THE TROUGH WILL
CUT OFF INTO AN UPPER LOW OVER THE SOUTHWEST OR INTERMOUNTAIN WEST
PER THE GFS OR PREVIOUS MODEL SOLUTIONS...OR WILL GENERALLY LINGER
OVER THE PACIFIC NW THROUGH SATURDAY AS ADVERTISED BY THE LATEST
ECMWF. IF THE LATEST ECMWF VERIFIES...ANY UPPER RIDGE OVER THE
WEEKEND WILL BE FLAT AND SHORT LIVED AND WILL BE RAPIDLY FOLLOWED BY
MOIST ZONAL FLOW. WITH THE INCREASED UNCERTAINTY IN THE EXTENDED
FORECAST...WILL INDICATE MOSTLY CLOUDY CONDITIONS WITH A CHANCE OF
RAIN ACROSS THE AREA AND TEMPERATURES NEAR CLIMATOLOGICAL VALUES.
ALBRECHT

&&

.AVIATION...A BROAD UPPER LEVEL TROUGH WILL REMAIN OFFSHORE OF THE
PACIFIC NORTHWEST THROUGH TUESDAY WITH INCREASING SOUTHWEST FLOW
ALOFT OVER WESTERN WASHINGTON. THE AIR MASS IS SOMEWHAT UNSTABLE AND
MOISTURE WILL INCREASE AT ALL LEVELS TOWARD MORNING. SHOWERS EARLY
ON TUESDAY WILL TURN TO MORE WIDESPREAD RAIN BY TUESDAY NIGHT AS A
WARM FRONT LIFTS NORTHWARD TOWARD THE REGION. MOSTLY VFR CEILINGS
EARLY ON TUESDAY ARE EXPECTED TO BECOME MVFR AFTER 21Z AS RAIN
INCREASES. A TRAILING COLD FRONT WILL MOVE ACROSS THE AREA EARLY
WEDNESDAY MORNING.

KSEA...MAINLY VFR CEILINGS OF 3K TO 6K FEET EXPECTED OVERNIGHT WITH
A FEW SHOWERS PASSING THROUGH. SHOWER COVERAGE IS EXPECTED TO
INCREASE EARLY TUESDAY...THEN BECOME MORE STEADY RAIN WITH
DETERIORATING CEILINGS TO MVFR AS A WARM FRONT LIFTS TOWARD THE AREA
TUESDAY EVENING. WIND BECOMING SOUTH TO SOUTHEAST 10 KNOTS OR LESS.

&&

.MARINE...A SURFACE LOW WILL DEEPEN TO AROUND 973 MILLIBARS AS IT
APPROACHES 46N 137W LATE TUESDAY AFTERNOON. AN ASSOCIATED WARM FRONT
WILL LIFT NORTHWARD ACROSS THE WATERS TUESDAY EVENING WITH A
TRAILING COLD FRONT MOVING THROUGH EARLY WEDNESDAY. THE SURFACE LOW
OFFSHORE WILL GRADUALLY FILL WEDNESDAY EVENING THROUGH FRIDAY AS IT
SENDS A SERIES OF WEAKER IMPULSES ONSHORE. WINDS OVER THE COASTAL
WATERS COULD REACH GALE FORCE AHEAD OF AND NEAR THE WARM FRONT.
SMALL CRAFT ADVISORY WINDS ARE EXPECTED AT THE STRAIT ENTRANCES AS
WELL AS THE NORTHERN INLAND WATERS TUESDAY AFTERNOON THROUGH TUESDAY
NIGHT. SMALL CRAFT ADVISORY WINDS ARE POSSIBLE FOR PUGET SOUND
FOLLOWING THE PASSAGE OF THE COLD FRONT ON WEDNESDAY MORNING. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY COASTAL WATERS THROUGH TUESDAY AFTERNOON.
     GALE WATCH COASTAL WATERS TUESDAY NIGHT.

&&

$$

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YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
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