Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 311616
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
914 AM PDT SUN AUG 31 2014

.SYNOPSIS...STRONG WESTERLY FLOW ALOFT OVER THE AREA WILL KEEP THE
WEATHER SOMEWHAT UNSETTLED TODAY. A LOW PRESSURE SYSTEM PASSING TO
OUR NORTH WILL RESULT IN A CHANCE OF LIGHT RAIN LATE TONIGHT FOR THE
COAST AND MONDAY MORNING OVER THE NORTH. HIGH PRESSURE ALOFT WILL
BUILD OVER THE REGION DURING THE AFTERNOON AND EVENING OF LABOR DAY
FOLLOWED BY A STRONGER AND COLDER SYSTEM TO IMPACT THE AREA ON
TUESDAY.

&&

.SHORT TERM...THE UPPER LEVEL JET AND STRONG WESTERLY FLOW OVER THE
REGION TODAY WILL KEEP THE THREAT OF SHOWERS IN THE FORECAST TODAY.

MODELS REMAIN IN AGREEMENT ON BRINGING A VIGOROUS SHORT WAVE TROUGH
INTO FAR NORTHERN BRITISH COLUMBIA AND BUILDING HEIGHTS OVER THE
PACIFIC NORTHWEST TONIGHT. HAVE GONE AHEAD AND UPDATED THE FORECAST
TO TAKE OUT THE THREAT OF PRECIPITATION OVER ALL BUT THE NORTH COAST
AND MOUNTAINS TONIGHT...AND THE NORTH TOMORROW MORNING. OTHERWISE
AND ELSEWHERE...LABOR DAY WILL BE A DRY DAY WITH NEAR NORMAL TEMPS
UNDER HIGH PRESSURE ALOFT.

MODELS CONTINUE TO BRING A STRONGER AND COLDER LOW PRESSURE SYSTEM
SOUTH THROUGH BRITISH COLUMBIA MONDAY...AND INTO WASHINGTON
TUESDAY. THE BEST CHANCE OF PRECIP WILL BE ACROSS THE NORTHERN
ZONES. THE MOST NOTICEABLE IMPACTS WITH THIS SYSTEM WILL BE MUCH
COOLER TEMPERATURES...DAYTIME TEMPS WILL RUN 5-10 DEGREES COOLER
THAN MONDAY. ACCORDINGLY...THE SNOW LEVEL IS EXPECTED TO FALL TO
BELOW 6000 FEET LATE TUESDAY NIGHT IN THE NORTH CASCADES...A
RAIN/SNOW MIX AT THOSE ELEVATIONS WILL NOT BE SURPRISING. LOCALLY
BREEZY CONDITIONS ARE POSSIBLE TUESDAY AFTERNOON.


.LONG TERM...FROM PREVIOUS DISCUSSION...AN UPPER RIDGE WILL BUILD
OVER THE REGION ON WED FOR THE ESTABLISHMENT OF DRY...NORTHERLY
FLOW. WED NIGHT WILL LIKELY BE THE CHILLIEST MORNING THIS
WEEK...WITH THE MIN TEMP AT MANY LOWLAND SITES PREDICTED TO BE IN
THE 40S.

EXPECT AN UPPER RIDGE TO DOMINATE THE WEATHER PATTERN OVER THE
AREA DURING MUCH OF THIS PERIOD. HOWEVER THE MEDIUM RANGE
SOLUTIONS DIFFERED ON THE STRENGTH OF THE RIDGE. BEYOND FRI...
CONFIDENCE IN THE FORECAST WAS LOW DUE TO DIFFERENCES IN THE
MEDIUM RANGE SOLUTIONS...THAT IS AN UPPER TROF VERSUS AN UPPER
RIDGE. THE ONLY CHANGES MADE WERE TO BLEND BETTER WITH
NEIGHBORING OFFICES.

&&

.AVIATION...NW FLOW ALOFT. LOW LEVEL ONSHORE FLOW. AIR IS MOIST. A
WEAK WEATHER SYSTEM WILL MOVE INTO WRN WA MONDAY. ISOLATED SHOWERS.
AREAS OF MORNING LOW CLOUDS WILL LIFT INTO THE AFTERNOON WITH
INCREASING SUNBREAKS.

KSEA...MORNING CLOUDS WILL LIFT WITH INCREASING SUNBREAKS INTO THE
AFTERNOON WITH THE DAYTIME HEATING...BUT THE AIR IS MOIST AND LOW
CLOUDS WILL DEVELOP AGAIN TONIGHT FOR ANOTHER CLOUDY MORNING ON
MONDAY.

&&

.MARINE...NO UPDATES OR CHANGES EXPECTED TO THE FORECAST THIS
MORNING. A WEAK DECAYING TROUGH WILL PASS NORTH OF THE AREA TONIGHT
ENHANCING ONSHORE FLOW THIS EVENING. WESTERLY WINDS MAY REACH
LOW-END SMALL CRAFT TO 25 KNOTS FOR A FEW HOURS THIS EVENING IN THE
CENTRAL/E STRAIT. ANOTHER STRONGER SURFACE TROUGH WILL BRING
INCREASED ONSHORE FLOW TUESDAY AND WEDNESDAY. SMALL CRAFT WINDS ARE
AGAIN LIKELY AT TIMES IN THE CENTRAL/E STRAIT.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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






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