Small Craft Advisory 659, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST THU MAR 3 2011

.SYNOPSIS...THE WEATHER WILL REMAIN SHOWERY AND COOL THROUGH
TONIGHT. EXPECT A BREAK BETWEEN WEATHER SYSTEMS FRIDAY...BEFORE RAIN
AND BREEZY CONDITIONS RETURN FRIDAY NIGHT. SCATTERED SHOWERS AND
COOL TEMPERATURES WILL BE THE RULE THIS WEEKEND AND EARLY NEXT WEEK.

&&

.SHORT TERM...MOIST SOUTHWEST FLOW ALOFT ACROSS THE PACIFIC
NORTHWEST WITH A DEEP UPPER LOW IN THE NORTHEAST PACIFIC. A SMALL
SHORTWAVE IS MOVING INTO THE CASCADES TODAY...AND ANOTHER
DISTURBANCE...A COMMA CLOUD OR SO CALLED INSTANT OCCLUSION IS AT
128W AT 9AM. THIS DISTURBANCE WILL REACH THE COAST LATER THIS
AFTERNOON AND MOVE INLAND ACROSS WRN WA TONIGHT...GIVING ANOTHER
ROUND OF SHOWERS. THE AIR IS COOL WITH A LOW SNOW LEVEL...AND A FEW
OF THE SHOWERS MAY HAVE ICE PELLETS OR GRAUPEL OR WET SNOW IN THE
FOOTHILLS. A WEAK UPPER RIDGE AND OFFSHORE FLOW WILL SHIFT OVER
WESTERN WA FRIDAY MORNING FOR A DRY PERIOD...AND IT MAY REMAIN DRY
TIL FRIDAY EVENING. FRIDAY NIGHT WILL BE WET AND BREEZY AS ANOTHER
WELL DEVELOPED BUT NOT PARTICULARLY STRONG FRONTAL SYSTEM MOVES
TROUGH THE REGION. THE LATEST NAM HAS A VERY TYPICAL LOOKING FRONT
OVER WESTERN WA FRIDAY NIGHT...WITH THE FROPA NEAR THE COAST BY
MIDNIGHT. 19

.LONG TERM...THE MODELS AGREE THAT THE NEXT FRONTAL SYSTEM UPSTREAM
MOVE INLAND ACROSS OREGON AND NORTHERN CALIFORNIA ON SUNDAY...
LEAVING WESTERN WASHINGTON IN THE COOL LESS ACTIVE AREA NORTH OF THE
JET. THE GFS AND THE EUROPEAN MODEL ALSO SHOW ANOTHER SYSTEM
OFFSHORE EARLY NEXT WEEK SPLITTING AND PRETTY MUCH FALLING APART
BEFORE IT REACHES THE AREA. SO THERE IS A GOOD CHANCE THAT WE WILL
NOT SEE ANOTHER WELL ORGANIZED FRONT ARRIVING BEFORE TUESDAY
NIGHT...AND TEMPERATURES WILL LIKELY REMAIN A LITTLE BELOW NORMAL.
THE CURRENT FORECAST FOR SUNDAY THROUGH WEDNESDAY LOOKS GOOD.
MCDONNAL

&&

.HYDROLOGY...NO FLOODING IS EXPECTED ON RIVERS IN THE FORECAST AREA
DURING THE NEXT TEN DAYS...INCLUDING THE GREEN RIVER. SNOW LEVELS
WILL REMAIN LOW AND HYDROLOGICALLY SIGNIFICANT PRECIPITATION IS NOT
EXPECTED.  MCDONNAL

&&

.AVIATION...A LOW PRES TROUGH OVER THE PAC NW WILL FLATTEN TONIGHT.
AN EMBEDDED WEAK SURFACE TROUGH WILL MOVE THROUGH WRN WA LATE TODAY
THROUGH EARLY THIS EVENING. MODERATE SW FLOW ALOFT OVER WA
TODAY...BECOMING LIGHT SLY FLOW TONIGHT. THE ATMOSPHERE WILL REMAIN
MOIST AND SLIGHTLY UNSTABLE THIS AFTERNOON AND EARLY EVENING.

KSEA...S/SE WIND 6-12 KT...BECOMING SW 10-14 KT AROUND 03Z AS A WEAK
TROUGH PASSES THROUGH PUGET SOUND. DTM

&&

.MARINE...A WEAK SURFACE TROUGH APPROACHING THE COASTAL WATERS WILL
INCREASE SE GRADIENTS TODAY. THIS WILL RESULT IN LOW END SMALL CRAFT
WINDS ACROSS THE COASTAL WATERS AND ENTRANCES AS THE TROUGH MOVES
CLOSER. THE TROUGH SHOULD PUSH THROUGH PUGET SOUND THIS
EVENING...WITH WINDS 15-20 KT...COULD POSSIBLY REACH SMALL CRAFT
CRITERIA.

ANOTHER FRONT APPROACHING THE COASTAL WATERS FRIDAY WILL INCREASE SE
GRADIENTS ONCE AGAIN. EXPECT AT LEAST SMALL CRAFT WINDS LATER FRIDAY
INTO SATURDAY...WITH GALES A POSSIBILITY OVER THE COASTAL WATERS AND
ENTRANCES. DTM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY COAST AND ENTRANCES THROUGH THIS AFTERNOON.
    .SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR ROUGH GRAYS HARBOR
     BAR CONDITIONS THRU THIS EVENING.

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