Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 031914 AAA
AFDSEW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SEATTLE WA
1215 PM PDT MON AUG 3 2015

.SYNOPSIS...A LOW PRESSURE SYSTEM ALOFT WILL PREVAIL OVER THE
REGION THROUGH MIDWEEK. THIS COMBINED WITH LOW LEVEL ONSHORE FLOW
WILL RESULT IN COOLER WEATHER. DAYTIME TEMPERATURES WILL REMAIN
ABOVE NORMAL ACROSS MUCH OF THE AREA TODAY...BUT WILL BE NEAR
NORMAL TUESDAY AND WEDNESDAY.

&&

.UPDATE...TEMPS AT A NUMBER OF PLACES WERE RUNNING 5-10 DEGREES
COOLER THAN AT THE SAME TIME YESTERDAY...THANKS TO INCREASED ONSHORE
FLOW AND THE PRESENCE OF CLOUDS. FORECAST WAS UPDATED ACCORDINGLY.

&&

SHORT TERM... STRATUS BLANKETED MUCH OF THE COAST THIS MORNING WHILE
THE INTERIOR /EAST OF THE OLYMPIC RANGE/ WAS BLANKETED BY MID AND
HIGH CLOUDS. THERE WERE A FEW SPRINKLES FALLING FROM THE ALTOCUMULUS
CLOUDS. IN CONTRAST...SKIES WERE MOSTLY SUNNY OVER THE OLYMPICS...
MUCH OF THE STRAIT OF JUAN DE FUCA...AND PARTS OF THE NORTHWEST
INTERIOR. ANTICIPATE CLEARING FROM THE WEST THIS MORNING...WITH
SKIES BECOMING MOSTLY SUNNY OVER MUCH OF THE CWA THIS AFTERNOON. THE
EXCEPTION WILL BE THE COAST...WHERE STRATUS WILL PERSIST OVER SOME
AREAS.

MEANWHILE...AN UPPER LEVEL TROF WILL MOVER OVER THE REGION DURING
THE DAY TODAY. THE MAIN IMPACT THIS SYSTEM WILL HAVE ON OUR
WEATHER WILL BE TO STRENGTHEN THE SURFACE ONSHORE PRESSURE
GRADIENT. THIS WILL RESULT IN COOLER TEMPS.

LOW CLOUDS WILL BECOME MORE WIDESPREAD ALONG THE COAST TONIGHT
THEN  PUSH DOWN THE STRAIT AND THROUGH THE CHEHALIS GAP
OVERNIGHT. STRATUS WILL LIKELY FILL IN ACROSS MOST THE LOWLANDS
WITH A CLOUDY START TO THE DAY ON TUESDAY. UPPER HEIGHTS WILL BE
LOWER AND THE INCREASED MARINE INFLUENCE SHOULD HOLD HIGH
TEMPERATURES TO THE 70S OVER THE INTERIOR...NEAR AVERAGE FOR EARLY
AUGUST. THIS PATTERN WILL REPEAT ON WEDNESDAY. MERCER/05

.LONG TERM FROM THE PREV DISCUSSION...
THE UPPER LOW SHOULD START TO MIGRATE EWD THURSDAY WITH WEAK
RIDGING ON FRIDAY. ONSHORE FLOW WILL BE LIGHTER WITH LESS CLOUDS
AND SLIGHTLY WARMER TEMPERATURES. HIGHS MAY REACH THE LOW 80S
TOWARD THE END OF THE WEEK.

MODELS DISAGREE ON THE PATTERN THIS NEXT WEEKEND. SOLUTIONS RANGE
FROM A WEAK AND DRY SPLIT TROUGH TO A MORE CONSOLIDATED LOW. MOST
SOLUTIONS SHOW SOME QPF OVER THE PAC NW SO WILL LEAVE THE SHOWERS
IN  THE FORECAST. ONSHORE FLOW WILL PROBABLY PICK UP WITH
MODERATING DAYTIME TEMPERATURES. MERCER

&&

.AVIATION...AN UPPER LEVEL TROUGH WILL APPROACH FROM THE NORTHWEST
TODAY AND TONIGHT BRINGING SW FLOW ALOFT. A WEAK COLD FRONT WILL
APPROACH THE COAST TODAY...THEN MOVE INLAND TONIGHT. THE MAIN EFFECT
OF THE FRONT WILL BE TO SPREAD A DEEP STRATUS LAYER INLAND TONIGHT
AS WELL AS INCREASE LOW LEVEL ONSHORE FLOW.

VISIBLE SATELLITE IMAGERY THIS MORNING SHOWS A STRIP OF SHALLOW
STRATUS ALONG THE NORTH COAST OF THE OLYMPIC PENINSULA AROUND PORT
ANGELES...AND A MORE EXTENSIVE AREA OF STRATUS FROM THE WESTERN
STRAIT OF JUAN DE FUCA AND ALONG THE WASHINGTON COAST TO WELL
OFFSHORE. IN THE INTERIOR THERE IS JUST ABUNDANT MID AND HIGH
CLOUDINESS. EXPECT THE STRATUS IN THE STRAIT TO BURN OFF...BUT THE
STRATUS ALONG THE COAST WILL GENERALLY REMAIN OVER THAT AREA. ACROSS
THE INTERIOR...MID AND HIGH LEVEL MOISTURE...REMNANTS OF OLD
MONSOONAL MOISTURE ORIGINATING IN THE DESERT SOUTHWEST...WILL
CONTINUE TO STREAM INTO THE AREA.

ONSHORE FLOW WILL INCREASE RAPIDLY THIS EVENING AS A FRONT NOW OVER
NW VANCOUVER ISLAND SWINGS SE ACROSS THE AREA. WITH THE INCREASE IN
ONSHORE FLOW...EXPECT STRATUS WITH BASES 040-050 TO SPREAD INLAND
THEN BASES WILL LOWER TO AROUND 020 OVERNIGHT. STRATUS BASES AROUND
010-015 TODAY AND THIS EVENING WILL LIKELY LOWER TO 007-010 LATER
TONIGHT INTO TUE MORNING. ALBRECHT

KSEA...GOOD VFR CONDITIONS WITH ONLY MID AND HIGH CLOUDS WILL
CONTINUE TODAY. EXPECT LIGHT SOUTH TO SOUTHWESTERLY WIND THROUGH
THIS EVENING. ALBRECHT

&&

.MARINE...HIGH PRESSURE WELL OFFSHORE COMBINED WITH LOWER PRESSURE
EAST OF THE CASCADES IS GIVING ONSHORE FLOW TO THE AREA. THE ONSHORE
FLOW WILL INCREASE LATE THIS AFTERNOON LATE THIS AFTERNOON AS A COLD
FRONT NOW OVER NORTHERN VANCOUVER ISLAND MOVES SOUTHEAST ACROSS THE
WATERS. THE STRONG ONSHORE FLOW WILL THEN CONTINUE THROUGH ABOUT
WEDNESDAY BEFORE GRADUALLY WEAKENING LATER IN THE WEEK.

SMALL CRAFT ADVISORY WINDS CONTINUE THIS MORNING OVER THE CENTRAL
AND EASTERN PORTIONS OF THE STRAIT OF JUAN DE FUCA. WINDS WILL
RAPIDLY INCREASE LATE THIS AFTERNOON AND WILL REACH 30 TO 40 KNOTS
THERE THIS EVENING...THEN WILL SLOWLY RELAX EARLY TUESDAY MORNING. A
SMALL CRAFT ADVISORY IS IN EFFECT FOR THOSE WATERS THROUGH MID
AFTERNOON AND A GALE WARNING IS IN EFFECT FOR LATE THIS AFTERNOON
THROUGH TONIGHT. GALE FORCE WINDS WILL LIKELY REDEVELOP TUESDAY
EVENING. A SMALL CRAFT ADVISORY HAS BEEN ISSUED FOR ADMIRALTY INLET
STARTING AT 5 PM THIS AFTERNOON AS NORTHWEST WINDS INCREASE WITH THE
INFLOW THROUGH THE STRAIT OF JUAN DE FUCA.

SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE COASTAL WATERS BEYOND
10 NM FROM THE COASTLINE AS NW PRESSURE GRADIENTS INCREASE THROUGH
TUESDAY MORNING. WINDS IN THE COASTAL WATERS WILL RELAX MIDDAY
TUESDAY. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING IN EFFECT FROM 3 PM THIS AFTERNOON TIL 5 AM
 TUESDAY FOR THE CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.

     SMALL CRAFT ADVISORY IN EFFECT FROM 5 PM THIS AFTERNOON TIL
 11 AM TUESDAY FOR THE COASTAL WATERS FROM CAPE FLATTERY TO
 CAPE SHOALWATER FROM 10 OUT TO 60 NM.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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


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