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000
FXUS66 KSEW 240434
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
934 PM PDT THU MAY 23 2013

.SYNOPSIS...A SLOW MOVING COLD UPPER-LEVEL LOW WILL CONTINUE TO
PRODUCE SHOWERS ACROSS THE REGION TONIGHT. THE UPPER LOW WILL WOBBLE
AROUND THE PACIFIC NORTHWEST INTO THE MEMORIAL DAY WEEKEND AS IT
SLOWLY FILLS AND WEAKENS. THE COOL AIR MASS WILL GRADUALLY MODERATE
INTO THE WEEKEND AND SHOWERS WILL GRADUALLY DIMINISH STARTING
TONIGHT.

&&

.SHORT TERM...A CLOSED UPPER LEVEL LOW WILL CONTINUE TO SLOWLY SPIN
OVER THE REGION TONIGHT FOR ADDITIONAL LIGHT PRECIP ACROSS THE
AREA. THERE WERE A FEW THUNDERSTORMS OVER WHATCOM AND SKAGIT
COUNTIES AROUND 23Z...BUT NO ACTIVITY SINCE. SHOWERS ARE ISOLATED
OVER THE NORTHWEST INTERIOR WITH LIGHT STRATIFORM PRECIP FROM THE
COAST TO PUGET SOUND. THE CURRENT FORECAST LOOKS GOOD WITH NO
PLANNED UPDATES TONIGHT.

THE UPPER LOW CENTER WILL SHIFT INTO EASTERN WA ON FRIDAY...WITH
SCATTERED SHOWERS ACROSS WESTERN WA. TEMPERATURES ARE STILL PRETTY
COOL ALOFT WITH 500 MB TEMPS IN THE -20S. SURFACE TEMPS IN THE MID
TO UPPER 50S LOOK GOOD...WITH A FEW LOW 60S POSSIBLE.

THIS SYSTEM WILL ROTATE NORTH INTO B.C./ALBERTA OVER THE WEEKEND FOR
A MODEST WARM-UP...TEMPS ARE CLOSER TO NORMAL. THE MODELS STILL SHOW
A WEAK TROUGH OVER WESTERN WA FOR A CHANCE OF SHOWERS BUT LOOKS LIKE
JUST ISOLATED COVERAGE. SNOW LEVELS WILL RISE TO 5000-6000 FT IN THE
MOUNTAINS. 33

.LONG TERM...PREVIOUS DISCUSSION...THE GFS CONTINUES TO BRING A WEAK
SYSTEM INLAND AROUND MONDAY OR TUESDAY. THE EURO IS STARTING TO COME
AROUND TO THIS IDEA EXCEPT THAT IT SENDS THE SYSTEM SOUTH INTO
OREGON AND CALIFORNIA. HAVE RAIN LIKELY FOR A FEW PERIODS IN THE
EXTENDED BUT AM NOT CONFIDENT IN THE DETAILS. BACK TO SCATTERED
SHOWERS STARTING ABOUT WEDNESDAY. TEMPERATURES ARE LIKELY TO BE NEAR
NORMAL. BURKE

&&

.AVIATION...UPPER LEVEL LOW PRESSURE CENTERED OVER WRN WA TONIGHT
WILL VERY GRADUALLY SHIFT EWD FRIDAY. LIGHT VARIABLE FLOW ALOFT
TONIGHT...BECOMING LIGHT SWLY FLOW ON FRIDAY. MOIST AT ALL LEVELS
AND SOMEWHAT UNSTABLE. SHOWERS...DECREASING LATER TONIGHT AND
FRIDAY. THE RISK OF AN ISOLATED THUNDERSTORM IS LESS THAN 10
PERCENT. MOSTLY VFR CIGS EXCEPT MVFR UNDER RAIN BANDS OR SHOWERS.

KSEA...NW WIND 3-6 KT...BECOMING S 5-8 KT AFTER 5 AM PDT (12Z). DTM

&&

.MARINE...A 1014 MB LOW CENTER STALLED JUST W OF ASTORIA WILL WEAKEN
AND MOVE INLAND FRIDAY MORNING. SOUTHEAST/EASTERLY GRADIENT IS
STRONG ENOUGH TO SUPPORT LOW-END SMALL CRAFT WINDS IN ADMIRALTY
INLET/AND THE CENTRAL/E STRAIT OF JUAN DE FUCA THROUGH MIDNIGHT
BEFORE EASING. SE WINDS OVER THE SRN PORTION OF THE WA COASTAL
WATERS MAY ALSO REACH SMALL CRAFT CRITERIA THIS EVENING. WINDS WILL
EASE FURTHER OVERNIGHT.

A FRONT WILL APPROACH THE PACIFIC NORTHWEST FROM THE WEST MONDAY AND
WEAKEN AS IT MOVES INLAND MONDAY NIGHT. AT THIS POINT IT LOOKS LIKE
IT WILL PRODUCE SMALL CRAFT ADVISORY WINDS OVER THE COASTAL WATERS.
WEAK ONSHORE FLOW WILL DEVELOP AGAIN TUESDAY.   DTM/MCDONNAL

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL/EAST STRAIT OF JUAN DE
     FUCA...ADMIRALTY INLET...AND THE SOUTHERN HALF OF THE WA
     COASTAL WATERS THROUGH MIDNIGHT.

&&

$$

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