Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 141600
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PDT MON APR 14 2014

.SYNOPSIS...HIGH PRESSURE WILL BE IN CONTROL TODAY FOR DRY WEATHER.
ONSHORE FLOW WILL DEVELOP THIS AFTERNOON AND INCREASE THIS EVENING
WITH A WEAK FRONT MOVING THROUGH THE AREA ON TUESDAY. A SERIES OF
WEATHER SYSTEMS WILL MOVE ACROSS THE AREA LATE THIS WEEK...BRINGING
MOSTLY CLOUDY CONDITIONS WITH A CHANCE OF SHOWERS.

&&

.SHORT TERM...AN UPPER RIDGE OVER THE AREA WILL SHIFT INLAND TODAY
WITH INCREASING LOW LEVEL ONSHORE FLOW. IT WILL BE ANOTHER MOSTLY
SUNNY DAY WITH HIGH CLOUDS...BUT THE ONSHORE FLOW WILL RESULT IN A
FEW DEGREES OF COOLING.

LOW CLOUDS WILL DEVELOP TONIGHT AS ONSHORE FLOW BECOMES MODERATE TO
STRONG. THERE COULD ALSO BE A FEW SHOWERS LATER TONIGHT AS THE LOW
LEVELS BECOME MOIST. THE BEST CHANCE FOR SHOWERS WILL BE OVER THE
MOUNTAINS AND PERHAPS IN A PUGET SOUND CONVERGENCE ZONE.

A WEAK FRONT WILL BRING MORE WIDESPREAD SHOWERS ON TUESDAY. CLOUDS
AND ONSHORE FLOW WILL RESULT IN AROUND 10 DEGREES OF FURTHER COOLING
ON TUESDAY.

AN UPPER RIDGE WILL BUILD OVER THE AREA ON WEDNESDAY. LOW LEVEL FLOW
WILL REMAIN ONSHORE...KEEPING HIGHS NEAR NORMAL WITH MOSTLY CLOUDY
SKIES. THE MODELS HINT AT WARM ADVECTION BRINGING SPOTTY LIGHT RAIN
BUT IT WILL PROBABLY BE A MOSTLY DRY DAY. SCHNEIDER

.LONG TERM...PREVIOUS DISCUSSION...THE GFS/CANADIAN/ECMWF SOLUTIONS
ALL GENERALLY AGREE THAT A RATHER WET LOOKING COLD FRONT WILL MOVE
ACROSS THE AREA LATE THURSDAY INTO THURSDAY NIGHT. LIKELY POPS ARE
INDICATED FOR THIS SYSTEM. THEN FOR FRI THROUGH NEXT
WEEKEND...MODELS GENERALLY SHOW LOW AMPLITUDE RIDGING ON THE WEST
COAST WITH SYSTEMS MOVING ENE AND CLIPPING AT LEAST THE COASTAL
AREAS AT TIMES. SOME SHOW SYSTEMS REMAINING FARTHER OFFSHORE WHILE
OTHERS DRIVE SYSTEMS INLAND. THE CURRENT BROAD BRUSH FORECAST WILL
BE MAINTAINED. ALBRECHT

&&

.HYDROLOGY...RIVER FLOODING IS UNLIKELY FOR THE NEXT 7 DAYS.

THE EXCEPTION IS THE NORTH FORK OF THE STILLAGUAMISH RIVER EAST OF
THE SR 530 LANDSLIDE NEAR OSO WHERE A FLOOD WARNING REMAINS IN
EFFECT UNTIL FURTHER NOTICE. FLOODING CONTINUES FOR THIS RIVER AS A
RESULT OF WATER POOLED BEHIND THE DEBRIS DAM THAT PARTIALLY BLOCKS
THE RIVER.

THE NORTH FORK OF THE STILLAGUAMISH NEAR ARLINGTON AND THE POOL
UPSTREAM OF THE SR 530 SLIDE WILL VERY SLOWLY FALL TODAY AS DRY
WEATHER CONTINUES. THE RIVER AND UPSTREAM POOL ARE FORECAST TO RISE
ABOUT A FOOT TUESDAY AS A WEAK FRONT BRINGS RAIN AT TIMES...THEN
RESUME A SLOW DOWNWARD TREND.

AT THIS TIME...THE MOST SIGNIFICANT SYSTEMS ARE EXPECTED LATE
TONIGHT AND TUESDAY...GIVING A QUARTER TO A HALF INCH OF RAIN TO THE
SLIDE AREA...AND ON THURSDAY...GIVING ANOTHER QUARTER TO HALF AN
INCH OF RAIN TO THE SLIDE AREA.

LIGHT SHOWERS AT OTHER TIMES THIS WEEK WILL NOT GIVE HYDROLOGICALLY
SIGNIFICANT RAINFALL TO THE SLIDE AREA...BUT WILL KEEP CONDITIONS
WET. SCHNEIDER

&&

.AVIATION...SOUTHWESTERLY FLOW ALOFT TODAY WILL BECOME MORE WESTERLY
TONIGHT. AT THE SURFACE STRONG ONSHORE FLOW WILL DEVELOP THIS
AFTERNOON AND CONTINUE INTO THE EVENING. AIR MASS IS DRY AND STABLE
BUT MID AND HIGH CLOUDS WILL INCREASE THIS AFTERNOON AS A FRONT
MOVES TOWARD THE COAST. LOW LEVEL MOISTURE WILL INCREASE ALONG THE
COAST LATE THIS AFTERNOON THEN SPREAD INLAND OVERNIGHT.

VFR CONDITIONS WILL PREVAIL OVER THE AREA TODAY. LATE IN THE
AFTERNOON SOME MVFR CEILINGS WILL DEVELOP ALONG THE COAST. THESE
WILL SPREAD INLAND OVERNIGHT WITH RAIN BECOMING LIKELY ON THE COAST.

KSEA...VFR TODAY AND THIS EVENING. CEILINGS 3-5K FT DEVELOPING LATE
TONIGHT. LIGHT AND VARIABLE WIND WILL BECOME SOUTHERLY 4-8 KT LATER
THIS MORNING. WIND WILL BECOME SOUTHWEST THIS AFTERNOON AND INCREASE
TO 10G16KT THIS EVENING. CHB

&&

.MARINE...STRONG ONSHORE FLOW WILL DEVELOP THIS AFTERNOON. THIS WILL
BRING GALE FORCE WINDS TO THE CENTRAL AND EAST STRAIT TONIGHT WITH
30-40 KT WINDS IN THE FORECAST. WINDS OVER ALL OTHER WATERS SHOULD
REACH SMALL CRAFT ADVISORY STRENGTH. WARNINGS AND ADVISORIES ARE ALL
NOW POSTED.

MODERATE ONSHORE FLOW WILL CONTINUE TUESDAY. FLOW SHOULD WEAKEN
CONSIDERABLY WEDNESDAY AS WEAK HIGH PRES BUILDS OVER THE AREA.
ANOTHER SYSTEM WILL ARRIVE AROUND THURSDAY WITH SMALL CRAFT ADVISORY
WINDS LIKELY OVER AT LEAST SOME WATERS. CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNING NORTH FORK OF THE STILLAGUAMISH RIVER EAST OF THE
     SR 530 LANDSLIDE.
PZ...GALE WARNING CENTRAL AND EAST STRAIT.
     SMALL CRAFT ADVISORY ALL OTHER WATERS.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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






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