000
FXUS66 KSEW 070422
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PDT SAT SEP 6 2008
.SYNOPSIS...AN UPPER LEVEL RIDGE CONTINUES TO BRING FAIR WEATHER TO
THE PACIFIC NORTHWEST. A THERMALLY INDUCED TROUGH OF LOW PRESSURE
WILL BUILD UP THE WASHINGTON COAST SUNDAY TURNING THE SURFACE FLOW
OFFSHORE. SUNDAY AND MONDAY WILL BE WARMER WITH TEMPERATURES RUNNING
ABOVE SEASONAL NORMALS. TEMPERATURES WILL COOL AS A DISSIPATING
WEATHER SYSTEM BRUSHES THE AREA MONDAY NIGHT AND TUESDAY. HIGH
PRESSURE WITH OFFSHORE FLOW WILL BRING WARMER TEMPERATURES WEDNESDAY
AND THURSDAY.
&&
.SHORT TERM...PRETTY CLEAR SKIES OVER THE AREA WITH ONLY A FEW
STRATO-CUMULUS HERE AND THERE...MAINLY OVER THE MOUNTAINS. NORTHERLY
FLOW SHOWING UP WELL ON THE SATELLITE PIX WITH THE COASTAL STRATUS
HEADING SOUTH. GRADIENTS OFFSHORE OVER WESTERN WASHINGTON THIS
EVENING WHICH WILL HELP LIMIT STRATUS FORMATION. HOWEVER WITH
DEWPOINTS RELATIVELY HIGH AND LONGER NIGHTS...MAY END UP WITH SOME
FOG FORMATION IN AREAS WHERE THE WIND DIES OFF ENOUGH. WHATEVER FOG
DEVELOPS WILL BURN OFF FAIRLY QUICKLY SUNDAY REVEALING ANOTHER SUNNY
AND MILD DAY.
A DISSIPATING FRONT WILL APPROACH THE COASTAL WATERS MONDAY
AFTERNOON...AND THE FLOW WILL TURN ONSHORE ON THE COAST MONDAY
AFTERNOON AS THE THERMAL TROUGH SHIFT INLAND. GFS AND NAM SHOW THE
PUSH TRENDING SLIGHTLY LATER IN THE DAY THEN PREVIOUS MODEL RUNS.
WEAK NORTHWEST PUSH WILL MOVE CLOUDS IN MONDAY NIGHT...AND HEIGHTS
WILL DROP FURTHER ON TUESDAY AS A SHORTWAVE TROUGH DIGS INTO
SOUTHERN BRITISH COLUMBIA.
.LONG TERM...FROM PREVIOUS DISCUSSION...STILL NO QPF FORECASTED
THROUGH THE ENTIRE FORECAST PERIOD...AS THE TROUGH QUICKLY MOVES
INTO THE ID/MT BORDER BY WED MORNING...AND THE RIDGE BEGINS TO BUILD
AGAIN AROUND 140W. GRADIENTS BRIEFLY GO OFFSHORE AGAIN WEDNESDAY
BEFORE THE NEXT FRONTAL SYSTEM ATTEMPTS TO BREAK DOWN THE RIDGE ON
THURSDAY...LIKELY RESULTING IN ONLY SOME HIGH CLOUD COVER IN THE
LATE AFTERNOON/EVENING. WEAK FRONTAL SYSTEM WASHES OUT TO OUR EAST
ON FRIDAY...AND THE RIDGE BUILDS BACK IN ON SATURDAY. DAMICO
&&
.AVIATION...A RIDGE OF HIGH PRESSURE WILL PERSIST ALONG 130W THROUGH
SUNDAY. LIGHT NE FLOW ALOFT AND STABLE. AMS DRY...EXCEPT MOIST BELOW
1K FT WITH AREAS OF LOW STRATUS AND FOG FORMING LATER TONIGHT. MANY
OF THE TERMINALS WILL LIKELY SEE A 2-4 HOUR PERIOD OF STRATUS AND
FOG SUNDAY MORNING...AND SOME VISIBILITIES WILL LIKELY BE 1/2SM OR
LESS IN FG. WITH INCREASING OFFSHORE GRADIENTS SUNDAY
MORNING...CLOUDS/STRATUS SHOULD MIX OUT BY 17Z.
KSEA...LOW STRATUS AND FOG WILL LIKELY DEVELOP IN THE VALLEYS E OF
I-5 LATE TONIGHT...LIKELY REACHING THE TERMINAL BY 12Z-13Z. LOW
LEVEL MOISTURE WILL RAPIDLY EVAPORATE AFTER 17Z. VISIBILITIES
BETWEEN 14Z AND 17Z MAY OCCASIONALLY DROP BELOW 1/2SM FG. DTM
&&
.MARINE...OFFSHORE FLOW THROUGH SUNDAY. THE NAM ELY GRADIENT IS
CURRENTLY RUNNING WAY TOO LOW FOR KUIL-KBLI...THE GFS LOOKS MUCH
BETTER WITH -2.3 MB BY 12Z. THIS SHOULD RESULT IN STRONGER E WINDS
AT THE W ENTRANCE...POSSIBLY APPROACHING SMALL CRAFT EARLY SUNDAY
MORNING. N/NE WIND OVER THE INTERIOR WILL ALSO PICK UP ON
SUNDAY...BUT SHOULD REMAIN BELOW 20 KT THROUGH THE AFTERNOON. DTM
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.
$$
WEATHER.GOV
