Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 210428
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
928 PM PDT SAT SEP 20 2014

.SYNOPSIS...HIGH PRESSURE ALOFT OVER THE REGION WILL MOVE EAST
WITH TIME...ALLOWING A WEAK LOW PRESSURE SYSTEM TO MOVE ACROSS
THE AREA ON MONDAY. A STRONGER SYSTEM WILL IMPACT THE REGION THE
MIDDLE OF THE UPCOMING WEEK...PROMISING WET AND BREEZY CONDITIONS.

&&

.SHORT TERM...
AN UPPER RIDGE OVER THE REGION WILL CONTINUE MOVING EAST...
ALLOWING A BROAD UPPER TROF OVER THE NORTHEAST PACIFIC TO
APPROACH THE REGION. LOOK FOR THE LOW LEVEL OFFSHORE FLOW TO
BECOME ONSHORE BY MIDDAY SUNDAY. THIS WILL ALLOW STRATUS TO SURGE
NORTH ALONG THE COAST SUNDAY MORNING. EXPECT INCREASING CLOUDS
SUNDAY NIGHT ACROSS THE CWA DUE TO STRENGTHENING LOW LEVEL ONSHORE
FLOW AND THE APPROACHING UPPER TROF.

EXPECT A SHORT WAVE TROF TO MOVE ACROSS THE AREA ON MON. THE
ASSOCIATED OCCLUDED FRONT WILL LIKELY DISSIPATE AS IT MOVES
ONSHORE. THE BEST CHANCE OF PRECIP WILL BE ON THE COAST WITH THIS
SYSTEM.

A STRONGER AND WETTER LOW PRESSURE SYSTEM WILL IMPACT THE REGION
ON TUE FOR A BETTER THREAT OF RAIN ACROSS THE ENTIRE CWA AS WELL
AS AN INCREASE IN WIND.

.LONG TERM FROM THE PREV DISCUSSION...
TUESDAY NIGHT AND WEDNESDAY WILL BE THE PERIOD OF TIME WHEN
WESTERN WA IS LIKELY TO HAVE PERIOD OF RAIN AS A STRONGER FRONTAL
SYSTEM MOVES SLOWLY THROUGH THE REGION. THERE MIGHT BE TWO SURGES
OF FAIRLY STRONG SLY FLOW ALOFT...ONE TUESDAY EVENING...AND
ANOTHER LATER WED OR WED NIGHT AND TUE-THU DO NOT LOOK LIKE A GOOD
TIME TO BE CAMPING OR HIKING...ESPECIALLY IN THE OLYMPICS. THERE
WILL BE A BROAD UPPER TROUGH CENTERED AROUND 140W TUESDAY. GFS
HEIGHT FALLS ASSOCIATED WITH THE FRONTAL SYSTEM STRETCH AND PETER
OUT IN THE GFS WHICH WAS NOT NEARLY AS WET AS THE ECMWF. BOTH
MODELS SHOWED THE HEAVIEST RAIN COAST AND OLYMPICS. AFTER A WET
PERIOD...THE MAIN UPPER TROUGH IS LIKELY TO DROP SOUTH THU AND FRI
INTO CALIF/NV. THE GFS AND EURO SOLUTIONS DIVERGED LATE IN THE
WEEK...THE EURO KEPT A WEAKENING UPPER TROUGH OVER THE WEST WITH A
CHANCE OF SHOWERS WHILE THE GFS WAS FASTER WITH AN APPROACHING
UPPER RIDGE WITH A BETTER PROSPECT FOR DRY WEATHER BY NEXT
WEEKEND.

&&

.AVIATION...SOUTHWEST FLOW ALOFT WITH AN UPPER LEVEL TROUGH OVER THE
NORTHEAST PACIFIC AND AN UPPER LEVEL RIDGE OVER THE ROCKIES. AT THE
SURFACE...A TROUGH ALONG THE COAST WILL SHIFT INLAND SUNDAY. AIR
MASS DRY AND STABLE.

STRATUS PUSHING NORTH UP THE WEST COAST SHOULD REACH THE WASHINGTON
COAST SUNDAY MORNING AS ONSHORE FLOW DEVELOP. THERE SHOULD ALSO BE
SOME FOG SUNDAY MORNING IN SHELTERED VALLEYS.

KSEA...CLEAR SKIES. NORTHERLY WIND 4-8 KNOTS WILL BECOME SOUTHERLY
SUNDAY. SCHNEIDER

&&

.MARINE...OFFSHORE FLOW WILL SWITCH TO ONSHORE SUNDAY AS A TROUGH
ALONG THE COAST MOVES INLAND. A WEAK FRONT WILL MOVE THROUGH THE
WATERS ON MONDAY. A STRONGER FRONTAL SYSTEM WILL ARRIVE TUESDAY AND
WEDNESDAY. THIS SYSTEM COULD BRING GALE SOUTHERLY WINDS TO THE
COASTAL WATERS. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE COASTAL WATERS
     AND STRAIT OF JUAN DE FUCA.


&&

$$

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