Small Craft Advisory 20, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
842 AM PST TUE JAN 26 2016

.SYNOPSIS...A FRONT WILL BRUSH BY THE AREA TODAY...ACCOMPANIED BY
LIGHT TO MODERATE RAIN. RAIN WILL DECREASE TONIGHT. A VIGOROUS
COLD FRONT WILL MOVE SLOWLY ACROSS THE AREA WEDNESDAY NIGHT INTO
THURSDAY BRINGING A PERIOD OF HEAVY RAIN TO THE OLYMPIC PENINSULA
AND NORTH CASCADES. A LOW PRESSURE CENTER WILL PASS NORTH OF THE
AREA ON FRIDAY...WITH A TRAILING FRONT BRINGING RAINY AND WINDY
CONDITIONS. OVER THE WEEKEND...AN UPPER TROUGH OVER THE WESTERN
U.S WILL BRING COOL AND SOMETIMES SHOWERY WEATHER TO THE PACIFIC
NORTHWEST.

&&

.SHORT TERM...AN UPPER RIDGE WILL HANG OUT OVER THE ROCKIES
THROUGH WED...WITH A LONGWAVE TROUGH OUT AROUND 150W-160W. THIS
SPELLS SW FLOW ALOFT FOR TODAY AND TOMORROW OVER WRN WA. A
SHORTWAVE TROUGH IS SCOOTING BY TO OUR NW THIS MORNING...ENHANCING
THE STRENGTH OF LOW-MID LEVEL SW FLOW...AND CONTRIBUTING TO SOME
WARM ADVECTION LIFT AND RAIN. THIS FEATURE WILL QUICKLY SCOOT OUT
THIS AFTN...CAUSING THE COVERAGE OF RAIN TO DECREASE. BY THE PM
COMMUTE...THE SEATTLE METRO AREA SHOULD BE MOSTLY RAIN-FREE...WITH
LINGERING PRECIP MAINLY CONFINED TO THE COAST AND MTNS.

A SHORTWAVE RIDGE WITHIN THE SW FLOW WILL LEAD TO A LULL OR BREAK
IN THE RAIN FROM LATE THIS EVENING INTO WED MORNING.

WILL THEN BE WATCHING A VIGOROUS COLD FRONT APPROACH FROM THE
PACIFIC ON WED AFTN. THIS FRONT WILL BE PROGRESSIVE...IN OTHER
WORDS IT WILL BE MOVING QUICKLY AND STEADILY ACROSS WRN WA.
HOWEVER...IT WILL BRING ABOUT 6-9 HOURS OF INTENSE PRECIP TO THE
OLYMPIC MTNS AND NORTH CASCADES. SEE THE HYDROLOGY SECTION FOR
RIVER IMPACTS. JUST IN ADVANCE OF THE FRONT ON WED NGT...SW 850 MB
WINDS OF 50-65 KT AND A RICHLY MOIST AIR MASS (PW VALUES ARND
1-1.25 INCHES) WILL SUPPORT THE BRIEF BUT INTENSE PRECIP.

THE COLD FRONT WILL ESSENTIALLY BASH DOWN THE UPPER RIDGE OVER THE
ROCKIES ON THU...WITH MORE ZONAL FLOW SETTING UP. THE JET STREAM
WILL SINK TO OUR SOUTH OVER OREGON FOLLOWING THE FRONT ON
THU...AND A QUICK-MOVING SHORTWAVE RIDGE LATER THU NOW LOOKS LIKE
IT WILL AFFORD A WELL-DEFINED BREAK OF RAIN-FREE WEATHER ON THU
AFTN AND EVNG. 	HANER

.LONG TERM...FROM PREVIOUS DISCUSSION...A BRIEF BREAK IN
PRECIPITATION IS POSSIBLE THURSDAY EVENING AS AN INSTANT OCCLUSION
DEVELOPS FROM THE SOUTHWEST OREGON COAST TO A VIGOROUS AND
DEVELOPING LOW THAT CURLS NORTHEASTWARD ALONG ABOUT 132W. THE
OCCLUSION WILL LIFT NORTH ACROSS WESTERN WASHINGTON LATE THURSDAY
NIGHT AND FRIDAY MORNING AND WILL BE ACCOMPANIED AND FOLLOWED BY
WINDY CONDITIONS. RAIN FRIDAY MORNING WILL TURN TO SHOWERS LATER
FRIDAY THROUGH SATURDAY.

UPPER LEVEL TROUGHING WILL GIVE COOLER CONDITIONS NEXT WEEKEND WITH
A CHANCE OF SHOWERS. SNOW LEVELS WILL GRADUALLY LOWER TO 1000-2000
FEET BY SUNDAY NIGHT OR MONDAY. ALBRECHT

&&

.AVIATION...SOUTHWEST FLOW ALOFT OVER WESTERN WASHINGTON THIS
MORNING WILL CONTINUE THROUGH TONIGHT. THE AIR MASS WILL REMAIN
MOIST BELOW 12000 FT AS A WARM FRONT LIFTS NORTH AND WEAKENS OVER
THE AREA.

WIDESPREAD MVFR AND LOCAL IFR CONDITIONS THIS MORNING WILL PROBABLY
DETERIORATE SLIGHTLY DURING THE DAY IN -RA AND BR. THERE SHOULD BE
MARGINAL IMPROVEMENT TONIGHT AS THE WARM FRONT WEAKENS AND
PRECIPITATION GENERALLY DECREASES.

KSEA...SOUTHEAST TO SOUTH WIND 5-12 KT. MCDONNAL

&&

.MARINE...A WARM FRONT OVER WESTERN WASHINGTON TODAY WILL SLOWLY
LIFT NORTH AND WEAKEN TONIGHT. SMALL CRAFT ADVISORY CONDITIONS DUE
TO WIND AND SWELL WILL CONTINUE FOR THE COASTAL WATERS AND WEST
ENTRANCE STRAIT OF JUAN DE FUCA. SMALL CRAFT ADVISORY WINDS OVER THE
INLAND WATERS SHOULD EASE MIDDAY.

A STRONGER FRONTAL SYSTEM WILL MOVE THROUGH THE FORECAST AREA LATE
WEDNESDAY THROUGH THURSDAY...WITH GALES LIKELY OVER THE WATERS WITH
THE PROBABLE EXCEPTION OF THE CENTRAL STRAIT AND PUGET SOUND. A GALE
WARNING IS BEING ISSUED THIS MORNING FOR THE COASTAL WATERS...WITH A
GALE WATCH FOR THE WEST ENTRANCE STRAIT AND THE INLAND WATERS.

ANOTHER SYSTEM WILL ARRIVE FRIDAY WITH WIDESPREAD SMALL CRAFT
ADVISORY WINDS AND POSSIBLY GALES. THERE IS STILL CONSIDERABLE
DIFFERENCE ON THIS FEATURE BETWEEN VARIOUS MODELS...SO CONFIDENCE
ON FORECAST SPECIFICS IS RATHER LOW.

WESTERLY SWELL OF 10-15 FEET WITH A PERIOD OF 15 TO 18 SECONDS WILL
PREVAIL OVER THE COASTAL WATERS THROUGH WEDNESDAY. WINDS OFFSHORE
WILL GENERATE A LARGER SWELL TRAIN NEAR 20 FEET WHICH SHOULD IMPACT
THE COAST WEDNESDAY NIGHT. A HIGH SURF ADVISORY IS IN EFFECT FOR THE
CENTRAL COAST TO ADDRESS THE POSSIBLE BEACH EROSION AROUND THE OCEAN
SHORES NORTH JETTY. AN ADVISORY MAY EVENTUALLY BE NEEDED FOR THE
NORTH COAST AS WELL. MCDONNAL

&&

.HYDROLOGY...FLOODING IS LIKELY STARTING WEDNESDAY NIGHT AND
CONTINUING INTO FRIDAY MORNING ON THE SKOKOMISH RIVER IN MASON
COUNTY. THE SKOKOMISH RIVER AT POTLATCH MAY REACH MAJOR FLOOD STAGE
THURSDAY MORNING. THE FLOODING WILL BE CAUSED BY RAINFALL AMOUNTS OF
3 TO 6 INCHES AND SNOW LEVELS OVER 7000 FEET WEDNESDAY NIGHT
THROUGH THURSDAY MORNING.

THERE IS A 20 TO 30 PERCENT CHANCE THAT THE FRONT WILL SLOW AND
CAUSE AND CAUSE FLOODING ON OTHER RIVERS FLOWING OFF THE OLYMPICS
AND THE NORTH CASCADES. BUT MODELS APPEAR TO BE KEEPING THE FRONT
PROGRESSIVE ENOUGH TO KEEP RIVERS SUCH AS THE SATSOP...NOOKSACK...
AND SKAGIT BELOW FLOOD STAGE.

ELSEWHERE OVER WESTERN WASHINGTON...RIVER FLOODING IS NOT EXPECTED
FOR THE NEXT 7 DAYS. 	HANER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WATCH FROM WEDNESDAY EVENING THROUGH LATE THURSDAY NIGHT
     FOR HOOD CANAL AREA-LOWER CHEHALIS VALLEY AREA-OLYMPICS.

     HIGH SURF ADVISORY FROM 4 PM WEDNESDAY TO 4 AM PST THURSDAY FOR
     CENTRAL COAST.

PZ...SMALL CRAFT ADVISORY UNTIL 4 AM PST WEDNESDAY FOR COASTAL WATERS
     FROM CAPE FLATTERY TO JAMES ISLAND 10 TO 60 NM-COASTAL
     WATERS FROM CAPE FLATTERY TO JAMES ISLAND OUT 10 NM-COASTAL
     WATERS FROM JAMES ISLAND TO POINT GRENVILLE 10 TO 60 NM-
     COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE OUT 10
     NM-COASTAL WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER
     10 TO 60 NM-COASTAL WATERS FROM POINT GRENVILLE TO CAPE
     SHOALWATER OUT 10 NM-WEST ENTRANCE U.S. WATERS STRAIT OF
     JUAN DE FUCA.

     GALE WARNING FROM 4 AM WEDNESDAY TO 4 AM PST THURSDAY FOR
     COASTAL WATERS FROM CAPE FLATTERY TO JAMES ISLAND 10 TO 60
     NM-COASTAL WATERS FROM CAPE FLATTERY TO JAMES ISLAND OUT 10
     NM-COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE 10
     TO 60 NM-COASTAL WATERS FROM JAMES ISLAND TO POINT
     GRENVILLE OUT 10 NM-COASTAL WATERS FROM POINT GRENVILLE TO
     CAPE SHOALWATER 10 TO 60 NM-COASTAL WATERS FROM POINT
     GRENVILLE TO CAPE SHOALWATER OUT 10 NM.

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

     GALE WATCH FROM WEDNESDAY AFTERNOON THROUGH LATE WEDNESDAY NIGHT
     FOR EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA-
     NORTHERN INLAND WATERS INCLUDING THE SAN JUAN ISLANDS.

     SMALL CRAFT ADVISORY UNTIL NOON PST TODAY FOR ADMIRALTY INLET-
     EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA-NORTHERN
     INLAND WATERS INCLUDING THE SAN JUAN ISLANDS.

     GALE WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY NIGHT
     FOR WEST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.

&&

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