Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 121714
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
914 AM PST FRI FEB 12 2016

.SYNOPSIS...A COLD FRONT WILL PASS THROUGH WESTERN WASHINGTON THIS
MORNING. AN UPPER LEVEL TROUGH WILL PRODUCE SHOWERS THIS AFTERNOON
THROUGH SATURDAY MORNING. A PAIR OF WARM FRONTS WILL BRING RAIN
SATURDAY AFTERNOON THROUGH SUNDAY EVENING. WEST FLOW ALOFT WILL
MAINTAIN AN ACTIVE WEATHER PATTERN INTO EARLY NEXT WEEK.

&&

.SHORT TERM...A COLD FRONT AND UPPER LEVEL TROUGH WILL KEEP SHOWERS
IN THE FORECAST TODAY. THERE WILL BE BREEZY WINDS TOO AS THE FRONT
MOVES INLAND THIS MORNING AND LOW LEVEL ONSHORE FLOW INCREASES.
TEMPERATURES WILL BE PRETTY STEADY WITH HIGHS IN THE LOW TO MID 50S.

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 WITH SNOW LEVELS AROUND 7000 FT. THE
SKOKOMISH RIVER IS ALREADY RUNNING HIGH AND MAY NEED A FLOOD WATCH
FOR MASON COUNTY. RAIN AMOUNTS WILL BE LESS IN THE CENTRAL SOUND
SATURDAY NIGHT WITH WESTERLY DOWNSLOPE WINDS OFF THE OLYMPICS.

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 HOVER NEAR 6000 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...PREVIOUS DISCUSSION...MONDAY ONLY PROVES TO BE THE
START OF THE DIVERGENCE IN THE MODELS. STARTING TUESDAY...IT LOOKS
LIKE DOMINANT WEATHER FACTORS WILL BE A PAIR OF LOWS OUT OVER THE
PACIFIC...ONE PROGGED TO GO NORTH OF WESTERN WA INTO CANADA...THE
OTHER...WELL...THAT DEPENDS ON WHICH MODEL TO BELIEVE. AND EVEN
THEN...GFS AND ECMWF HAVE TRADED SOLUTIONS IN THE PAST 24 HOURS. GFS
NOW FAVORS WETTER SOLUTION WITH SOUTHERN LOW COMING ON SHORE OFF THE
OREGON COAST WHILE ECMWF NOW HAS LOW GOING INTO CALIFORNIA...WHICH
WOULD KEEP THE CWA NOT ENTIRELY DRY...BUT PRECIP WOULD BE MORE
SCATTERED. NEEDLESS TO SAY...THIS DOES NOT PUT A GREAT DEAL OF
CONFIDENCE IN THE EXTENDED. THUS...LIKE PREVIOUS DAYSHIFT...HAVE
OPTED FOR BROAD BRUSH POPS OVER THE AREA UNTIL A SOLUTION GELS
BETWEEN THE TWO. SMR

&&

.HYDROLOGY...RIVER FLOODING IS UNLIKELY THROUGH SATURDAY. THERE IS
SOME POTENTIAL FOR HEAVY RAIN OVER THE OLYMPICS AND NORTH CASCADES
BEGINNING SATURDAY NIGHT WHICH COULD CAUSE THE SKOKOMISH RIVER AND
POSSIBLY A FEW RIVERS IN THE NORTH CASCADES TO FLOOD EARLY NEXT WEEK.

&&

.AVIATION...AN UPPER TROUGH AXIS WILL QUICKLY MOVE EASTWARD ACROSS
WRN WA TONIGHT. IN ADVANCE OF THE TROUGH...A COLD FRONT IS CURRENTLY
MOVING ACROSS WRN WA. IT WILL MOVE EAST OF THE CASCADE CREST AROUND
20Z...OR NOON. COLDER AIR ALOFT WILL ARRIVE BEHIND THE FRONT AND
DESTABILIZE THE AIR MASS THIS AFTN AND EVNG. WITH MOIST ONSHORE
FLOW...THAT WILL LEAD TO CONVECTIVE SHOWER DEVELOPMENT. SHOWER
ACTIVITY WILL FOCUS OVER THE MTNS AND NEAR A PUGET SOUND CONVERGENCE
ZONE THAT WILL BE FURTHER NORTH THAN USUAL...FAVORING SKAGIT COUNTY
MORE THAN THE MORE TYPICAL LOCATION OVER SNOHOMISH COUNTY. WITH
CONVECTIVE SHOWERS...CIGS WILL BE VARIABLE...RANGING FROM IFR UNDER
SHOWERS...TO VFR OUTSIDE OF SHOWERS THIS AFTN. MODERATE TO STRONG SW
FLOW ALOFT TODAY...BECOMING W TONIGHT.

KSEA...COLD FRONTAL PASSAGE COMING UP SOON AROUND 18Z...OR 10 AM.
GUSTY S/SW WIND WILL FOLLOW THE FRONT FOR MUCH OF THE AFTN.
A FEW DISORGANIZED CONVECTIVE SHOWERS WILL QUICKLY PASS ACROSS THE
TERMINAL AT ANY TIME THIS AFTN AND EVNG...TEMPORARILY LOWERING CIGS
TO NEAR 020...BUT CIGS OF 030-045 WILL BE PREVALENT OUTSIDE OF
SHOWERS. HANER

&&

.MARINE...A COLD FRONT WILL SOON FINISH MOVING ACROSS THE INLAND
WATERS...WITH SOUTH AND SW GRADIENTS PREVAIL BEHIND THE FRONT THIS
AFTN AND TONIGHT. A WARM FRONT WILL SWEEP THROUGH ON SAT...BRINGING
A PERIOD OF STRONG SE GRADIENTS DURING THE DAY.
SE WINDS COULD AMOUNT TO A LOW-END GALE OVER THE COASTAL WATERS...SO
WILL BE LOOKING AT THAT MORE CLOSELY FOR THE 3 PM FORECAST UPDATE.
HANER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 6 PM PST SATURDAY FOR COASTAL WATERS
     FROM CAPE FLATTERY TO JAMES ISLAND 10 TO 60 NM-COASTAL
     WATERS FROM JAMES ISLAND TO POINT GRENVILLE 10 TO 60 NM-
     COASTAL WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER 10
     TO 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH BAR UNTIL 10 AM PST SATURDAY FOR
     GRAYS HARBOR BAR.

     SMALL CRAFT ADVISORY UNTIL 10 AM PST THIS MORNING FOR ADMIRALTY
     INLET-COASTAL WATERS FROM CAPE FLATTERY TO JAMES ISLAND OUT
     10 NM-COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE
     OUT 10 NM-COASTAL WATERS FROM POINT GRENVILLE TO CAPE
     SHOALWATER OUT 10 NM-EAST ENTRANCE U.S. WATERS STRAIT OF
     JUAN DE FUCA-NORTHERN INLAND WATERS INCLUDING THE SAN JUAN
     ISLANDS.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 PM PST SATURDAY
     FOR COASTAL WATERS FROM CAPE FLATTERY TO JAMES ISLAND OUT
     10 NM-COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE
     OUT 10 NM-COASTAL WATERS FROM POINT GRENVILLE TO CAPE
     SHOALWATER OUT 10 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 PM PST SATURDAY
     FOR WEST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.

     SMALL CRAFT ADVISORY UNTIL 1 AM PST SATURDAY FOR CENTRAL U.S.
     WATERS STRAIT OF JUAN DE FUCA.

     SMALL CRAFT ADVISORY UNTIL 6 PM PST SATURDAY FOR PUGET SOUND AND
     HOOD CANAL.

&&

$$

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