Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 260340
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
840 PM PDT MON AUG 25 2014

.SYNOPSIS...HIGH PRESSURE ALOFT OVER THE REGION WILL CONTINUE THE
SUNNY WARM WEATHER TO WESTERN WASHINGTON TUESDAY AND WEDNESDAY. A
PACIFIC WEATHER SYSTEM IS FORECAST TO APPROACH THE AREA THURSDAY AND
FRIDAY RESULTING IN SOME CLOUDS AND THE START TO A COOLING TREND.
THE SYSTEM IS EXPECTED TO MOVE ONSHORE OVER THE HOLIDAY WEEKEND
BRINGING A CHANCE OF SHOWERS THAT WILL CONTINUE INTO EARLY NEXT WEEK.

&&

.SHORT TERM...POSITIVE TILTED UPPER RIDGE IS NOW AROUND 130W WITH
THE UPSTREAM UPPER TROUGH NEAR 150W. MUCH MORE ZONAL FLOW ACROSS THE
NW PACIFIC FOR A DEVELOPING MORE PROGRESSIVE PATTERN. NORTHERLY FLOW
ALOFT OVER WA THIS EVENING.

STRATUS AND FOG WAS HUGGING THE BEACHES THIS EVENING AND HAS FILLED
IN ACROSS THE COASTAL WATERS. 00Z KUIL RAOB SHOWS THE TOP OF THE
MARINE LAYER A LITTLE UNDER 2000 FT.

THE 00Z PROGS IN THUS FAR CONTINUE THE TREND OF SAGGING THE UPPER
RIDGE DOWN OVER WA TUESDAY FOR WHAT WILL PROBABLY BE THE WARMEST DAY
OF THE WEEK. 850 MB TEMPS PEAK AT ABOUT 16 DEGREES C TUESDAY
AFTERNOON. THE RIDGE WILL TEND TO SUPPRESS THE MARINE LAYER AND WITH
MAINLY NW LIGHT LOW LEVEL ONSHORE FLOW...THE STRATUS AND FOG WILL
NOT MAKE TOO MUCH INLAND PROGRESSION BY TUESDAY MORNING.

THE UPPER RIDGE CONTINUES INLAND WEDNESDAY AS IT FLATTENS AND THE
FLOW ALOFT BECOMES MORE ZONAL. LOW LEVEL ONSHORE FLOW SHOULD BEGIN
TO RISE A BIT EACH DAY WEDNESDAY AND THURSDAY RESULTING IN GREATER
INLAND PROGRESSION OF MARINE CLOUDS EACH MORNING. COMBINED WITH
SAGGING HEIGHTS ALOFT...DAYTIME HIGHS SHOULD BE DROP A FEW DEGREES
EACH DAY AS WELL. MADE A FEW SUBTLE ADJUSTMENTS TO THE SHORT TERM
SKY AND FREEZING LEVEL GRIDS TO REFLECT MORE CURRENT CONDITIONS.
OTHERWISE NO CHANGES TO THE FORECAST PACKAGE. BUEHNER

.LONG TERM...FROM THE PREVIOUS DISCUSSION...THE MODELS HAVE STAYED
CONSISTENT IN THE LONGER RANGE. THEY SHOW THE UPPER LEVEL FLOW
BACKING TO SOUTHWEST ON FRIDAY AS AN OFFSHORE UPPER TROUGH
APPROACHES THE REGION. ONSHORE FLOW WILL INCREASE...AND MARINE LAYER
STRATUS WILL PROBABLY PUSH FAR INLAND THURSDAY NIGHT. THE TROUGH
SHOULD REACH THE AREA SATURDAY AND MOVE INLAND SUNDAY FOR A CHANCE
OF SHOWERS...BUT PRECIPITATION AMOUNTS WILL PROBABLY NOT BE VERY
SIGNIFICANT EXCEPT PERHAPS ON SATURDAY NIGHT OR SUNDAY IN THE
MOUNTAINS. A CHANCE OF SHOWERS WILL CONTINUE OFF AND ON THROUGH THE
BEGINNING OF NEXT WEEK. JSMITH

&&

.AVIATION...UPPER LEVEL RIDGING OVER THE PAC NW IS LEADING TO A DRY
AND STABLE AIR MASS ACROSS WESTERN WA. THE FLOW ALOFT IS NORTHERLY.
LOW LEVEL STRATUS IS HUGGING THE COAST THIS EVENING AND WILL PUSH
INLAND OVERNIGHT MAINLY AFFECTING THE COAST AND STRAIT...IFR
CONDITIONS POSSIBLE. THE INTERIOR WILL LIKELY REMAIN CLEAR WITH VFR
CONDITIONS EXPECTED. LOW CLOUDS WILL BURN BACK TO THE COASTAL WATERS
TUE AFTERNOON. OTHERWISE...THE RIDGE WILL REMAIN OVERHEAD ON TUE FOR
MORE DRY WEATHER.

KSEA...VFR CONDITIONS WILL PREVAIL WITH LIGHT N/NE WINDS AT THE
SURFACE. 33

&&

.MARINE...HIGH PRES OVER THE NE PAC WILL MAINTAIN ONSHORE FLOW
ACROSS WESTERN WA THROUGH WED. HIGHEST WIND AND WAVES WILL BE FOUND
THROUGH THE CENTRAL AND EAST STRAIT OF JUAN DE FUCA DURING THE
AFTERNOON AND EVENING HOURS. A WEAK COLD FRONT WILL CROSS WESTERN WA
ON THU...FOLLOWED BY ANOTHER FRONT FRI NIGHT OR SAT. THESE FRONTS
WILL INCREASE THE WESTERLY ONSHORE PUSH THROUGH THE STRAIT. 33

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA
TONIGHT.

&&

$$

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





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