Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 131140
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
340 AM PST SAT FEB 13 2016

.SYNOPSIS...A PAIR OF WARM FRONTS WILL BRING RAIN...LOCALLY HEAVY AT
TIMES...TO THE AREA THIS AFTERNOON THROUGH SUNDAY. MOIST WESTERLY
FLOW ALOFT WILL CONTINUE THROUGH MONDAY.

&&

.SHORT TERM...CURRENT RADAR SHOWS THAT SHOWERS OVER WESTERN
WASHINGTON CONTINUE TO SCATTER OUT THIS EARLY MORNING...ALTHOUGH
SEEING SOME DECENT MODERATE RAINFALL ECHOES OVER WESTERN SKAGIT
COUNTY. PRECIP IS EXPECTED TO CONTINUE TO TAPER OFF THROUGHOUT THE
MORNING BEFORE THE FIRST OF A PAIR OF WARM FRONTS STARTS TO MOVE
INTO THE AREA THIS AFTERNOON. THIS AND ITS SEQUEL FRONT...WARM FRONT
PART 2 THE REVENGE...WILL KICK OFF A VERY WET AND ACTIVE PATTERN FOR
THIS WEEKEND.

PART 1 IS EXPECTED TO BRING MODERATE TO HEAVY RAINFALL MAINLY ALONG
THE COAST AND OVER THE OLYMPIC PENINSULA WITH 18-HOUR QPF TOTALS
EXCEEDING ONE INCH OVER MUCH OF THAT AREA. THE CASCADES JOIN IN BY
THE EVENING...BUT QPF AMOUNTS THERE ARE A BIT MORE SPREAD OUT...A
FEW SMALL BULLSEYES AS OPPOSED TO ONE BIG ONE. HOWEVER...IT DOES
LOOK LIKE SNOW WILL BE A BIT OF A CONCERN FOR HIGHER ELEVATIONS OF
CASCADES...MAINLY AROUND MT BAKER AND MT RAINIER. INHERITED WINTER
WEATHER ADVISORY FOR MT BAKER NEEDED TO BE EXTENDED...NOW IN EFFECT
THROUGH EARLY SUNDAY MORNING. STAGGERED FROM THAT IS THE ADVISORY FOR
MT RAINIER...KICKING OFF LATE THIS AFTERNOON AND CONTINUING UNTIL
LATE SUNDAY MORNING.

PART 2 LOOKS TO BE A BIGGER PROBLEM FOR THE CASCADES LATE SUNDAY
AFTERNOON WITH WIDESPREAD QPF VALUES BETWEEN 0.75 AND 1 INCH.
CONDITIONS WARM...AS PER THE NAME...TAKING RISK OF SNOW GENERALLY
OFF THE TABLE...BUT INHERITED HYDRO OUTLOOK ILLUSTRATES WELL THAT A
FLOOD RISK MAY EXIST. CURRENT HYDROGRAPHS FOR RIVERS IN WHATCOM AND
SKAGIT COUNTIES ARE FORECAST TO STAY UNDER FLOOD STAGE...BUT JUST
BARELY. ANY HANG UP TO THIS SECOND FRONT OR INCREASE IN MOISTURE
WILL CERTAINLY TIP THE BALANCE...EVEN THOUGH IMPACT MAY NOT BE FELT
TIL THE MONDAY/TUESDAY TIME FRAME. THAT SAID...AT THIS TIME...WILL
LEAVE OUTLOOK IN PLACE AND LEAVE ANY WATCH DECISION FOR A LATER
TIME.  SMR

.LONG TERM...COULD IT BE THAT GFS AND ECMWF ARE BEGINNING TO
COALESCE. GENERALLY STARTING TO LOOK THAT WAY...ALTHOUGH SOME OF THE
DETAILS ARE OFF. FLAT RIDGING LOOKS TO BE IN PLACE FOR THE START OF
NEXT WEEK...BUT ENOUGH MOISTURE PRESENT TO LEAVE POPS IN...ALBEIT A
BIT MORE SCATTERED. THIS ALIGNMENT IN MODELS ONLY SEEMS TO HOLD
THROUGH TUESDAY...AS MODELS SEEM TO DISAGREE ON HOW QUICKLY THE
RIDGE EXITS WEDNESDAY AND IS REPLACED BY AN INCOMING TROUGH. ECMWF
IS FASTER WITH THE FEATURE BY ABOUT 6 HOURS. FORTUNATELY...THEY DO
AGREE ON THE TRACK OF THE UPPER LOW...UNLIKE MOST OF THE PREVIOUS
RUNS...SIGNALING A WET SECOND HALF OF THE UPCOMING WEEK. SMR

&&

.AVIATION...UPPER LEVEL TROUGH AXIS JUST EAST OF THE AREA EARLY
THIS MORNING WITH WEST NORTHWESTERLY FLOW ALOFT. WARM FRONT MOVING
THROUGH WESTERN WASHINGTON TONIGHT WITH RAIN OUT AHEAD OF THE FRONT
ARRIVING ON THE COAST LATE MORNING AND SPREADING INLAND MIDDAY.
AIR MASS STABILIZING WITH INCREASING MOISTURE LATER THIS
MORNING INTO THE EVENING HOURS.

SCATTERED TO BROKEN CLOUD DECKS AROUND 2000 FEET...4500 FEET AND
7000 FEET EARLY THIS MORNING. LOWER LAYERS BECOMING PREDOMINANTLY
SCATTERED LATER THIS MORNING. CEILINGS IN THE 3500-5000 FOOT RANGE
LATE MORNING INTO THE AFTERNOON HOURS WITH RAIN. CEILINGS
DETERIORATING TO 1000-2000 FEET LATE AFTERNOON AND EVENING HOURS WITH
LOCAL VISIBILITIES 2-4SM IN RAIN.

KSEA...SC DECK AROUND 2500 FEET BROKEN AT TIMES THROUGH 16Z. RAIN
BEGINNING AROUND 20Z WITH CEILINGS NEAR 4000 FEET. CEILINGS
LOWERING TO AROUND 2000 FEET 02Z-06Z TONIGHT WITH REDUCED
VISIBILITIES IN RAIN. WINDS SOUTHERLY 8 TO 12 KNOTS. FELTON

&&

.MARINE...A WARM FRONT WILL CROSS THE WATERS LATER THIS AFTERNOON
INTO TONIGHT WITH SMALL CRAFT ADVISORY WINDS OVER MOST OF THE
WATERS. ANOTHER FRONT WILL CROSS THE WATERS ON SUNDAY FOR ANOTHER
ROUND OF SMALL CRAFT WINDS. ONSHORE GRADIENTS WILL FOLLOW THE FRONT
SUNDAY NIGHT AND CONTINUE INTO TUESDAY. A LARGE SURFACE LOW WILL
DEVELOP WELL WEST OF THE OFFSHORE WATERS TUESDAY NIGHT AND
WEDNESDAY. FELTON

&&

.HYDROLOGY...THERE IS POTENTIAL FOR HEAVY RAIN OVER THE OLYMPICS
TONIGHT WHICH MAY PUSH THE SKOKOMISH RIVER IN MASON COUNTY OVER
FLOOD STAGE. A FLOOD WATCH IS IN EFFECT.

A WARM FRONT WILL STALL OVER SOUTHERN B.C. OR WESTERN WA SUNDAY
THROUGH MONDAY...POSSIBLY INTO TUESDAY. HEAVY RAIN IS FORECAST IN
THE NORTH CASCADES AND A FEW RIVERS WILL BE CLOSE TO FLOOD STAGE. A
HYDROLOGIC OUTLOOK HAS BEEN ISSUED. 33/SMR

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER WEATHER ADVISORY IN EFFECT UNTIL 4 AM SUNDAY FOR
 THE CASCADES OF WHATCOM AND SKAGIT COUNTIES ABOVE 3500 FEET.

     WINTER WEATHER ADVISORY IN EFFECT FROM 4 PM THIS AFTERNOON
     UNTIL 10 AM SUNDAY FOR THE CASCADES OF PIERCE AND LEWIS
     COUNTIES ABOVE 5000 FEET.

 FLOOD WATCH IN EFFECT THROUGH SUNDAY MORNING FOR MASON COUNTY.

PZ...PZ...SMALL CRAFT ADVISORY ALL WATERS EXCEPT CENTRAL STRAIT.

     SMALL CRAFT ADVISORY FOR ROUGH BAR GRAYS HARBOR BAR.

&&

$$

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