Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 291535 CCA
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
835 AM PDT FRI AUG 29 2014

.SYNOPSIS...LOW PRESSURE ALOFT WILL DOMINATE THE WEATHER PATTERN
OVER THE REGION THROUGH THIS WEEKEND FOR COOL AND UNSETTLED
CONDITIONS. LOOK FOR A WEAK COLD FRONT TO SWEEP ACROSS THE AREA
LATER THIS MORNING. A SLIGHTLY STRONGER FRONT IS EXPECTED TO IMPACT
THE REGION ON SUNDAY.

&&

.SHORT TERM...JUST IN TIME FOR THE LABOR DAY HOLIDAY WEEKEND AND
ASSOCIATED OUTDOOR EVENTS...A CHANGE IN THE WEATHER PATTERN. MORE
ZONAL FLOW ACROSS THE NORTHERN PACIFIC WITH A HEALTHY 120 KNOT JET
AND PROGRESSIVE PATTERN. AN UPPER TROUGH WAS APPROACHING 130W THIS
MORNING WITH THE ASSOCIATED BAROCLINIC ZONE MOVING ONSHORE AT THIS
HOUR WITH SOME EMBEDDED SHOWERS. THIS SYSTEM IS TIMED TO MOVE
THROUGH THE REST OF WESTERN WA AND INTO THE CASCADES BY MIDDAY.
NESDIS NOTED THAT THE SOURCE OF THIS MOISTURE ORIGINATED FROM JAPAN
BACK ON AUGUST 21/22.

THE LOW LEVEL ONSHORE FLOW PATTERN WAS ALSO SUPPORTING A WEAK PUGET
SOUND CONVERGENCE ZONE THIS MORNING WITH SOME LIGHT RAIN/DRIZZLE.
ISSUED A NOWCAST FOR THIS MORNING PRECIPITATION.

THE NEXT SHORTWAVE IS APPARENT ON WATER VAPOR SATELLITE IMAGERY NEAR
170W THAT THE PROGS BRING ONSHORE SATURDAY PM FOR ANOTHER SURGE OF
SHOWERS. THEN THE NEXT SHORTWAVE IS NEAR 165E THAT IS DUE TO ARRIVE
SUNDAY FOR MORE SHOWERS. 00Z PROGS HAD SOME TIMING DIFFERENCES ON
THESE SYSTEMS. WILL SEE WHAT THE 12Z GUIDANCE DOES FOR FURTHER
FINE-TUNING...YET THE NAM IS SATURDAY PM AND AGAIN SUNDAY PM.
DAYTIME TEMPS SHOULD REMAIN JUST A BIT BELOW SEASONAL AVERAGES. LESS
THAN SUNNY LABOR DAY WEEKEND FORECAST LOOKS ON TRACK. BUEHNER

.LONG TERM...PREVIOUS DISCUSSION...IT APPEARED THAT THE REGION WILL
BE MORE UNDER THE INFLUENCE OF AN UPPER RIDGE ON MON. BEYOND
MON...CONFIDENCE IN THE FORECAST WAS SOMEWHAT LOW. IT LOOKS LIKE THE
THE MEDIUM RANGE SOLUTIONS MIGHT BE LEANING TOWARD HOLDING ONTO AN
UPPER TROF OVER THE AREA LONGER THAN THE PREVIOUS RUNS. DUE TO LACK
OF CONFIDENCE...THE ONLY CHANGES MADE TO THE EXTENDED WERE TO BLEND
BETTER WITH NEIGHBORS. NC

&&

.AVIATION...CLOUDY WITH A WEAK COLD FRONT CROSSING WRN WA TODAY. IN
SOME AREAS THE CIGS ARE RATHER LOW. VSBY WILL BE LOCALLY REDUCED IN
SOME AREAS OF LIGHT RAIN OR DRIZZLE. LOW LEVEL ONSHORE FLOW WILL
CONTINUE TONIGHT AND SATURDAY. THE FLOW ALOFT IS WESTERLY.

KSEA...MORNING LOW CLOUDS SHOULD LIFT UP IN THE AFTERNOON...HOWEVER
THE PUGET SOUND AREA MIGHT SEE A PERIOD OF LIGHT RAIN OR DRIZZLE
WITH THE VERY WEAK FRONT THAT WILL BE OVER THE AREA LATER THIS
MORNING AND AFTERNOON.

&&

.MARINE...A WEAK COLD FRONT WILL CROSS WESTERN WA TODAY. ONSHORE
FLOW WILL INCREASE BEHIND THE FRONT THIS EVENING AND THE FCST IS FOR
SMALL CRAFT ADVISORY WINDS IN THE CENTRAL AND EAST STRAIT OF JUAN DE
FUCA. ANOTHER WEAK SURFACE TROUGH WILL MOVE INLAND ON SUNDAY. HIGH
PRES OVER THE NE PAC WILL MAINTAIN ONSHORE FLOW ACROSS WESTERN WA
THROUGH EARLY NEXT WEEK.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY IN EFFECT UNTIL 5 AM SATURDAY FOR THE
     CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.

&&

$$

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