Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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033
FXUS66 KSEW 130546
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
946 PM PST FRI FEB 12 2016

.SYNOPSIS...A LOW PRESSURE SYSTEM WILL OFF THE COAST WILL MOVE
ACROSS THE AREA OVERNIGHT. LOOK FOR WARM FRONTS TO BRING RAIN...
LOCALLY HEAVY...TO THE AREA SATURDAY AFTERNOON THROUGH SUNDAY.
MOIST WESTERLY FLOW ALOFT WILL CONTINUE THROUGH MONDAY.

&&

.SHORT TERM...
SHOWERS WERE INCREASING OVER THE FORECAST AREA AHEAD OF A LOW
PRESSURE TROF /SURFACE AND ALOFT/. THE TROF WILL MOVE ACROSS THE
REGION OVERNIGHT.

MEANWHILE...THERE WAS A PERSISTENT BAND OF SHOWERS /LOCALLY HEAVY/
OVER WHATCOM COUNTY THAT WAS IMPACTING THE MOUNT BAKER SKI AREA.
SNOW HAS BEEN FALLING AT A RATE OF ABOUT ONE INCH PER HOUR SINCE
6 PM PST. THUS FAR...ABOUT FOUR INCHES OF SNOW HAS FALLEN IN THE
MOUNT BAKER SKI AREA NEAR THE 4000 FOOT LEVEL. AN ADDITIONAL...6
TO 11 INCHES OF SNOW IS LIKELY BY LATE SATURDAY MORNING.
THEREFORE...A WINTER WEATHER ADVISORY WAS ISSUED FOR THE NORTH
CASCADES ABOVE 3500 FEET.

THERE WILL BE A BREAK IN THE ACTION SATURDAY MORNING...THEN RAIN
INCREASING TOWARD THE AFTERNOON AND EVENING AS THE NEXT WARM FRONT
MOVES IN. THIS IS ANOTHER JUICY SYSTEM AND RAIN WILL BE HEAVY AT
TIMES ALONG THE COAST...AT LEAST ANOTHER 1 INCH OF RAIN EXPECTED.
THE OLYMPICS MAY SEE 1-3 INCHES OF RAIN WITH SNOW LEVELS RISING TO
AROUND 6000 FEET. RAIN AMOUNTS WILL BE LESS IN THE CENTRAL SOUND
SATURDAY NIGHT WITH WESTERLY DOWNSLOPE WINDS OFF THE OLYMPICS.
RAIN AMOUNTS IN THE SEATTLE METRO WILL BE 0.25-0.50 INCHES THROUGH
SATURDAY NIGHT.

MOIST WESTERLY FLOW WILL PREVAIL SUNDAY AND MONDAY AS A ANOTHER WARM
FRONT STALLS THEN SHIFTS NORTH INTO SOUTHERN BRITISH COLUMBIA. THE
AIR MASS WILL REMAIN MILD WITH TEMPS MAINLY IN THE 50S. SNOW LEVELS
WILL RANGE FROM 5000-7000 FT AND RAIN WILL AGAIN BE HEAVY AT TIMES
ALONG THE COAST AND IN THE MOUNTAINS. A FEW RIVERS IN THE NORTH
CASCADES WILL RISE CLOSE TO FLOOD STAGE. 33

.LONG TERM FROM THE PREV DISCUSSION...
MOIST WESTERLY FLOW WILL CONTINUE THROUGH TUESDAY BUT MODELS
DISAGREE ON WHETHER THE WARM FRONTAL BAND WILL FIZZLE OUT OR NOT.
THE GFS IS CURRENTLY WETTER THAN THE ECMWF. BOTH THE GFS AND ECMWF
SHOW AN UPPER LEVEL TROUGH DIGGING OFFSHORE THEN MOVING INLAND ON
WEDNESDAY OR THURSDAY. BUT AGAIN THE GFS IS MUCH WETTER WITH THE
TROUGH. THE ECMWF BRING THE TROUGH INLAND FARTHER SOUTH WITH
LITTLE IMPACT OVER WESTERN WA. FOR NOW WILL CONTINUE WITH A BLEND
OF THE MODELS THROUGH THIS POINT. THE FORECAST DETAILS REMAIN LOW
THROUGH THE END OF NEXT WEEK AS THE MODEL SOLUTIONS DIVERGE. 33

&&

.AVIATION...AN UPPER TROUGH AXIS WILL MOVE THROUGH THE AREA
OVERNIGHT. MOISTURE INCREASING WITH THE AIR MASS BECOMING SLIGHTLY
UNSTABLE. LEADING EDGE OF THE RAIN AHEAD OF THE NEXT WARM FRONT
MOVING QUICKLY ACROSS THE EASTERN PACIFIC REACHING WESTERN
WASHINGTON 18Z-21Z SATURDAY.

CEILINGS LOWERING OVERNIGHT WITH THE TROUGH AXIS WITH AREAS OF MVFR
CEILINGS WITH SHOWERS. AFTER SOME IMPROVEMENT SATURDAY MORNING
CEILINGS WILL LOWER AGAIN BACK DOWN TO MVFR LATE SATURDAY
AFTERNOON INTO THE EVENING HOURS.

KSEA...SC DECK AOA 5000 FEET INTO THE EARLY MORNING HOURS. TEMPORARY
CEILINGS 2000-3000 FEET WITH PASSING SHOWERS 09Z-13Z. STEADY
RAIN BEGINNING ABOUT 20Z WITH CEILINGS SETTLING INTO THE 3500-
4500FOOT RANGE UNTIL LATE SATURDAY AFTERNOON INTO SATURDAY
EVENING WHEN CEILINGS LOWER TO 1000-2000 FEET. SOUTHERLY WINDS 6 TO
10 KNOTS BECOMING SOUTHEAST SATURDAY MORNING. FELTON

&&

.MARINE...MODERATE SOUTHERLY GRADIENTS WILL PREVAIL TONIGHT.
A WARM FRONT WILL CROSS THE WATERS SATURDAY AFTERNOON AND
EVENING...PRECEDED BY A PERIOD OF STRONG SE GRADIENTS 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
...FOLLOWED BY A PUSH OF SW GRADIENTS ON SUNDAY AFTERNOON AND SUNDAY
NIGHT. MODERATE SOUTHERLY GRADIENTS WILL PREVAIL MON AND TUE. FELTON

&&

.HYDROLOGY...
THERE IS POTENTIAL FOR HEAVY RAIN OVER THE OLYMPICS SATURDAY
NIGHT 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 WILL BE ISSUED. 33

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER WEATHER ADVISORY IN EFFECT UNTIL 10 AM SATURDAY FOR
 THE CASCADES OF WHATCOM AND SKAGIT COUNTIES ABOVE 3500 FEET.

 FLOOD WATCH IN EFFECT THROUGH SUNDAY MORNING FOR MASON COUNTY.

PZ...SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE COASTAL WATERS...
 WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA...AND THE PUGET
 SOUND.

  SMALL CRAFT ADVISORY FOR ROUGH BAR IN EFFECT UNTIL 9 PM
 SATURDAY FOR THE GRAYS HARBOR BAR.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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