Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 250408
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
910 PM PDT FRI APR 24 2015

.SYNOPSIS...AN UPPER LOW WILL MOVE THROUGH THE AREA TONIGHT AND
SATURDAY. HIGH PRESSURE WILL BUILD SOMEWHAT ON SUNDAY...BUT A WARM
FRONT WILL REACH THE AREA LATE IN THE DAY. TEMPERATURES WILL WARM
SUNDAY AND MONDAY BEFORE A COLD FRONT REACHES THE AREA.

&&

.SHORT TERM...AN UPPER LOW PRESSURE SYSTEM IS OVER THE AREA TONIGHT
AND THE LOW WILL SAG SLOWLY THROUGH WA THROUGH SATURDAY. SCATTERED
SHOWERS WILL CONTINUE...WITH A SLIGHT CHANCE OF MAINLY AFTERNOON
TSTMS ON SAT. SHOWERS TONIGHT SHOULD BE MORE NUMEROUS OVER THE
ADMIRALTY INLET AREA AND EAST INTO SNOHOMISH COUNTY. AN UPPER RIDGE
WILL SHIFT OVER THE PACIFIC NORTHWEST ON SUNDAY WITH A WARM FRONT
APPROACHING OFFSHORE. THE WARM FRONT SHOULD REACH THE LATE SUNDAY
AFTERNOON AND EVENING BUT WILL BREAK UP AND GRADUALLY DRY UP INTO
MONDAY AS THE FLOW ALOFT TURNS MORE SOUTHERLY AND UPPER LEVEL
HEIGHTS RISE A BIT MORE. MONDAY SHOULD SEE TEMPS CLIMB ABOVE NORMAL
IN THE WARM SECTOR BEHIND THE WARM FRONT AND AHEAD OF THE COLD FRONT
WHICH SHOULD BE CROSSING 130W LATE MONDAY AFTERNOON OR EVENING.

.LONG TERM....PREVIOUS DISCUSSION...CONFIDENCE IN THIS PERIOD WAS
VERY LOW DUE TO DISAGREEMENT BETWEEN AND LACK OF CONSISTENCY IN THE
MEDIUM RANGE MODEL SOLUTIONS. HAVE CHOSEN TO KEEP A LOW CHANCE OF
PRECIP IN THE FORECAST FOR THE MOST PART. ALSO...DECIDED TO SHOW A
COOLING TREND...WITH DAYTIME TEMPS FALLING BACK TO NEAR NORMAL.

&&

.AVIATION...AN UPPER LOW OVER SOUTHERN VANCOUVER ISLAND WILL DRIFT
SLOWLY SOUTHEAST TONIGHT AND SATURDAY WITH WESTERLY FLOW ALOFT
BECOMING NORTHERLY SATURDAY MORNING. AIR MASS MOIST AND
UNSTABLE...BECOMING A BIT MORE STABLE LATER TONIGHT.

MULTIPLE CLOUD LAYERS TONIGHT AND SATURDAY BETWEEN 4500 AND 8000
FEET. 2000-3000 FOOT CEILINGS ARE POSSIBLE IN SHOWERS TONIGHT INTO
THE EARLY MORNING HOURS SATURDAY. SHOWERS WILL BECOME MORE ISOLATED
ON SATURDAY.

KSEA...SOUTHERLY WINDS 8 TO 12 KNOTS EASING SATURDAY MORNING.
CEILINGS EXPECTED TO BE AROUND 5000 FEET AT TIMES THROUGH SATURDAY
AFTERNOON. FELTON

&&

.MARINE...A TROUGH OVER THE COASTAL WATERS WILL WEAKEN AND SHIFT
ONSHORE TONIGHT. 10 OR 11 FOOT WEST SWELLS OVER THE COASTAL WATERS
WILL SUBSIDE BELOW 10 FEET LATER TONIGHT.

HIGH PRESSURE WILL BUILD OVER THE WATERS ON SATURDAY FOR LIGHTER
WINDS. A WEAKENING FRONT WILL MOVE THROUGH THE AREA SUNDAY AFTERNOON
AND EVENING. THIS SHOULD BRING SMALL CRAFT ADVISORY WINDS TO
THE COASTAL WATERS...AND POSSIBLY PARTS OF THE NORTHERN INTERIOR
WATERS.

A SECOND FRONTAL SYSTEM WILL REACH THE AREA TUESDAY. MODELS ARE IN
POOR AGREEMENT WITH THE DETAILS AND CONFIDENCE IN THE WIND FORECAST
FOR EARLY NEXT WEEK IS LOW. FELTON/SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY COASTAL WATERS EXCEPT ZONE 150.
    .SMALL CRAFT ADVISORY NORTHERN INLAND WATERS.
    .SMALL CRAFT ADVISORY GRAYS HARBOR BAR FOR ROUGH BAR.

&&

$$

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




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