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000
FXUS66 KSEW 122230
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 PM PDT SUN MAY 12 2013

.SYNOPSIS...A WEAKENING COLD FRONT IS OVER WESTERN WASHINGTON...
SCATTERED SHOWERS WILL OCCASIONALLY MOVE THROUGH WESTERN WASHINGTON
TONIGHT. A STRONGER WEATHER SYSTEM WILL REACH THE AREA MONDAY.
SHOWERS AND ISOLATED THUNDERSTORMS WITH BREEZY WEATHER IS EXPECTED
FOR MONDAY AFTERNOON AND EVENING. COOL UNSETTLED WEATHER WILL
PERSIST THROUGH THE WEEK AND INTO NEXT WEEKEND.

&&

.SHORT TERM...A COLD FRONT IS STILL HUNG UP OVER WESTERN
WASHINGTON...IT SEEMS TO BE WEAKENING BUT RADAR STILL SHOWS AREAS OF
SHOWERS THIS AFTERNOON. AN UPPER SHORTWAVE TROUGH AND A DECENT SURGE
OF ONSHORE FLOW WILL ACCOMPANY THE NEXT ROUND OF PRECIP MONDAY...AND
AS RAIN TURNS TO SHOWERS AND ISOLD TSTMS GRADIENTS WILL PICK UP FOR
BREEZY WEATHER BY MONDAY EVENING. WEAK RIDGING WILL ARRIVE TUESDAY
WITH SCATTERED SHOWERS DECREASING.

.LONG TERM...WEAK DISTURBANCES IN A ZONAL WEATHER PATTERN BRING A
LITTLE RAIN OR SHOWERS TO THE AREA AT TIMES THROUGH THE WEEK AHEAD.
UPPER HEIGHTS FALL OFF THROUGH THE WEEK...SLOWLY AT FIRST AND THEN
PERHAPS A LITTLE MORE SIGNIFICANTLY NEXT WEEKEND. THE ECMWF
ESPECIALLY HAS TRENDED A BIT COOLER AND WETTER FOR THE WED-SUN
PERIOD AND THE POPS HAVE BEEN ADJUSTED TO GIVE THE WETTER AREAS A
FORECAST OF SHOWERS LIKELY. A CAMPING TRIP TO THE COAST OR THE
MOUNTAINS CAN PROBABLY COUNT ON BLUE TARP WEATHER AT TIMES.

&&

.AVIATION...A LONGWAVE UPPER TROUGH AXIS IS LOCATED NEAR 140W...WITH
MODERATE SW FLOW ALOFT OVER WRN WA. A DISSIPATING FRONTAL BOUNDARY
WAS LOCATED NEAR THE COAST THIS AFTERNOON...ALIGNED WITH THE FLOW
ALOFT. AS THE FRONT DISSIPATES...RAIN AND SHOWERS WILL DECREASE IN
COVERAGE THIS EVNG. HOWEVER...A MURKY AIR MASS WILL MEAN AREAS OF
IFR AND MVFR CIGS...MOST NOTABLY ALONG THE COAST AND OVER THE NORTH
INTERIOR...WHERE HIGH DEWPOINT AIR (TD`S IN THE UPPER 50S) INTERACTS
WITH COOLER WATERS FOR MORE LOW CLOUDS. ON MON...A SHARP UPPER
TROUGH WILL PASS WRN WA LATE IN THE AFTN. LOTS OF LIFT ACTING ON AN
INCREASINGLY MOIST AND UNSTABLE ATMOSPHERE COULD LEAD TO A FEW
THUNDERSTORMS ON MON AFTN AND EVNG. ALSO EXPECTING GUSTY S/SW WINDS
LATE MON AFTN...ENHANCED BY CONVECTIVE OUTFLOWS.

KSEA...OTHER THAN THE POSSIBILITY OF A STRAY SPRINKLE...RAIN AND
SHOWERS ARE GENERALLY DONE FOR THIS EVNG AND OVERNIGHT. CIGS WILL
SETTLE INTO THE 020-030 RANGE AFT 05Z GIVEN THE MOIST AIR MASS. ON
MON...A SHARP UPPER TROUGH WILL ARRIVE...LEADING TO AN INCREASINGLY
MOIST AND UNSTABLE AIR MASS...AND THE POSSIBILITY OF THUNDERSTORMS
LATE IN THE AFTN. SFC WINDS REMAINING SOUTHERLY...BECOMING GUSTY IN
THE 22Z-02Z TIME FRAME ON MON AFTN AS CONVECTIVE OUTFLOWS ENHANCE
THE S/SW SFC WIND.      HANER

&&

.MARINE...SMALL CRAFT SOUTHERLIES CONTINUE OVER NORTH PUGET SOUND AT
THIS TIME BUT WILL SETTLE DOWN THIS EVNG.

A STRONG SURFACE TROUGH WILL SWEEP ACROSS THE WATERS MONDAY
AFTERNOON AND EVENING. SOUTHERLY WINDS IN ADVANCE OF THE FRONT WILL
INCREASE ACROSS THE COASTAL WATERS STARTING EARLY MON MORNING...THEN
SPREAD INLAND BY EARLY AFTN. A COLD FRONT WILL SWEEP INLAND LATE IN
THE AFTN...POSSIBLY ACCOMPANIED BY SOME LIGHTNING...THEN FOLLOWED BY
AN INCRS IN SW WIND. THESE WINDS COULD BE ENHANCED FURTHER BY
CONVECTIVE OUTFLOW. LOOKS LIKE A SOLID SMALL CRAFT EVENT FOR ALL
WATERS.

HIGH PRES WILL BUILD BACK INTO THE WATERS ON TUE. A WEAKER FRONTAL
SYSTEM IS EXPECTED TO MOVE INTO THE COASTAL WATERS GIVING POSSIBLE
SMALL CRAFT ADVISORY CONDITIONS THERE TUE NIGHT INTO EARLY WED.
HANER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY PUGET SOUND AND HOOD CANAL UNTIL 8 PM.

&&

$$

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