Small Craft Advisory 831, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
840 PM PDT SAT OCT 1 2011

.SYNOPSIS...AFTER SHOWERS TAPER TONIGHT...SUNDAY WILL BE MOSTLY DRY
WITH SOME SUN. A SERIES OF FRONTAL SYSTEMS WILL ARRIVE SUNDAY NIGHT
THROUGH TUESDAY IN A COOL WET WEATHER PATTERN. MONDAY AND TUESDAY
WILL LIKELY BE WET AND BREEZY. THE PATTERN WILL BECOME MORE SHOWERY
LATER IN THE WEEK...WITH DRYING POSSIBLE BY THE WEEKEND.

&&

.SHORT TERM...A WEAK SHORT WAVE MOVING THROUGH IN MOIST UNSTABLE
SOUTHWEST FLOW ALOFT THIS EVENING WILL BRING SCATTERED SHOWERS.
THESE SHOULD TAPER AFTER MIDNIGHT AS THE WAVE SHIFTS NORTHEAST OF
THE AREA. SUNDAY LOOKS GENERALLY DRY IN BETWEEN SYSTEMS. THE
NEXT...STRONGER FRONTAL SYSTEM WILL SPREAD RAIN TO THE COAST LATE
SUNDAY. WITH THE SYSTEM COMING IN NEGATIVELY TILTED...RAINS SHOULD
HOLD OFF UNTIL SUNDAY NIGHT FOR THE INTERIOR. THERE WILL ALSO BE
SOME BREEZY WINDS IN THE USUAL SOUTHEAST SUCKER LOCATIONS LATE
SUNDAY AND SUNDAY NIGHT. AFTER A SHOWERY DAY MONDAY...ANOTHER
FRONTAL SYSTEM WILL BRING RAIN AND WIND TUESDAY. RECENT MODEL TRENDS
HAVE BEEN TO SLOW DOWN THE TUESDAY FRONT AS IT STRETCHES AND THE
MAIN ENERGY DIVES SOUTH TOWARDS CALIFORNIA BUT IT STILL LOOKS LIKE
THERE WILL BE SOME RAIN AND WIND LATER IN THE DAY. CURRENT FORECAST
GENERALLY ON TRACK. NO UPDATES PLANNED THIS EVENING. SCHNEIDER

.LONG TERM...PREVIOUS DISCUSSION...AFTER THE FRONT PASSES TUESDAY
NIGHT OR WEDNESDAY MORNING FLOW ALOFT BECOMES MORE NORTHWESTERLY AND
THERE WILL BE A COOLING AND DRYING TREND. HIGH TEMPERATURES
WEDNESDAY MAY NOT REACH 60 DEGREES. THIS IS ALSO WHEN THE SNOW LEVEL
FALLS TO 5000 FEET OR LOWER...SO PEAKS AND HIGHER PASSES ARE LIKELY
TO SEE SOME SNOW.

MODELS SLOWLY RAISE HEIGHTS INTO THE WEEKEND BUT ARE NOT QUITE DRY
ENOUGH TO TAKE CHANCE POPS OUT OF THE EXTENDED FORECAST. IF THIS
TREND CONTINUES FRIDAY AND SATURDAY HAVE THE POTENTIAL TO BE DRY.
BURKE

&&

.AVIATION...AN UPPER LEVEL DISTURBANCE OVER WESTERN WASHINGTON WILL
WEAKEN AS IT LIFTS NORTHEAST THIS EVENING. CEILINGS ARE GENERALLY
VFR WITH ONLY LOCALIZED MVFR IN SCATTERED SHOWERS THIS EVENING. THIS
WILL BE REPLACED BY MORE WIDESPREAD MVFR CEILINGS OVERNIGHT AS THE
ATMOSPHERE STABILIZES WITH WEAK HIGH PRESSURE BUILDING INTO THE
AREA. BY DAYBREAK...CEILINGS ARE EXPECTED TO BE MOSTLY IN THE
015-030 RANGE. DEVELOPING OFFSHORE FLOW ON SUNDAY AHEAD OF AN
APPROACHING FRONT WILL HELP SCOUR OUT THE LOW LEVELS AS HIGH AND MID
LEVEL MOISTURE INCREASES.

KSEA...VFR CEILINGS THIS EVENING ARE EXPECTED TO LOWER BACK TO MVFR
OVERNIGHT. AN AREA OF SHOWERS OVER SW WASHINGTON THIS EVENING IS
MOVING NE AND COULD TEMPORARILY LOWER CEILINGS TO MVFR LATE THIS
EVENING. OTHERWISE...A STABILIZING ATMOSPHERE WILL LEAD TO THE
REDEVELOPMENT OF MVFR CEILINGS OVERNIGHT IN THE 1500-2500 FOOT
RANGE. DEVELOPING OFFSHORE FLOW ON SUNDAY AHEAD OF THE NEXT FRONT
WILL LEAD TO A DRIER BOUNDARY LAYER...WITH VFR EXPECTED BY 18Z AND
CONTINUING THROUGH THE DAY. LIGHT SOUTHEAST WIND
OVERNIGHT...BECOMING LIGHT AND VARIABLE ON SUNDAY.

&&

.MARINE...WEAK HIGH PRESSURE WILL MOVE OVER THE WATERS TONIGHT AND
EARLY SUNDAY FOR LIGHT WINDS. FORECAST MODELS CONTINUE TO SHOW A
WEATHER SYSTEM NOW NEAR 41N 139W DEVELOPING INTO A 985 MB LOW OVER
THE OFFSHORE WATERS BY LATE SUNDAY...THEN WEAKENING TO 990 MB AS IT
MOVES TOWARD HAIDA GWAII MONDAY EVENING. A TRAILING COLD FRONT WILL
MOVE ACROSS THE WATERS SUNDAY NIGHT FOLLOWED BY A STRONG SURFACE
TROUGH ON MONDAY. THIS IS EXPECTED TO PRODUCE GALE FORCE WINDS FOR
THE COASTAL WATERS AND SMALL CRAFT ADVISORY WINDS FOR MUCH OF THE
NORTHERN INLAND WATERS.

ANOTHER FRONT IS EXPECTED ON TUESDAY. THE MODELS SEEM TO BE TRENDING
WEAKER WITH THIS SYSTEM...WITH MOST OF THE ENERGY ASSOCIATED WITH IT
PASSING TO OUR SOUTH. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WATCH SUNDAY EVENING THROUGH MONDAY AFTERNOON FOR THE
     WASHINGTON COASTAL WATERS.

FOR AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION PLEASE SEE
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML (ALL LOWERCASE)