Small Craft Advisory 58, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
910 PM PST TUE MAR 8 2016

.SYNOPSIS...A WEAK FRONT OVER WESTERN WASHINGTON WILL DISSIPATE AS
IT MOVES EAST OF THE CASCADES OVERNIGHT. A VERY STRONG FRONTAL
SYSTEM ASSOCIATED WITH A RAPIDLY DEEPENING LOW OFFSHORE WILL GIVE
RAIN AND WINDY CONDITIONS TO THE AREA WEDNESDAY NIGHT INTO THURSDAY
MORNING. DAMAGING WINDS ARE EXPECTED ON THE WASHINGTON COAST.  THE
WEATHER WILL BE WET AT TIMES INTO THE WEEKEND AS A SERIES OF
FRONTAL SYSTEMS MOVE ACROSS THE REGION.

&&

.SHORT TERM...RADAR AND SATELLITE SHOW A WEAKENING FRONTAL SYSTEM
MOVING NORTHEAST ACROSS WESTERN WASHINGTON THIS EVENING. RAINFALL
AND WIND WITH THIS FRONT IS UNIMPRESSIVE AS IT WEAKENS AND MOVES
EAST.

THE MAIN PROBLEM TONIGHT IS THE DEVELOPMENT OF A BOMBING LOW
PRESSURE SYSTEM OFFSHORE. THE LOW APPEARS TO BE HANDLED CONSISTENTLY
AND WELL BY THE MODELS. AIREPS AND CLOUD VECTORS AS WELL AS WATER
VAPOR IMAGERY NICELY SHOW A 165 TO 175 KT 300 MB JET MOVING EAST
ACROSS NORTHERN OREGON THIS MORNING. ANOTHER JET STREAK IS MOVING NE
ALONG THE FRONT WELL OFFSHORE WITH WINDS AT 300 MB SWLY AT 150 KT.
STRONG VERTICAL MOTIONS AT THE LEFT EXIT REGION OF THE SECOND JET
AND THE RIGHT ENTRANCE REGION OF THE FIRST JET NOW MOVING EAST
SUPPORT VERY RAPID LOW DEVELOPMENT AS SHOWN BY THE MODELS
WEDNESDAY AND WEDNESDAY NIGHT.

THIS LOW IS EXPECTED TO DEEPEN FROM ABOUT 1000 MB THIS EVENING TO
974 MB AS IT MOVES TO 46N 131.5W LATE WEDNESDAY AFTERNOON AND 964 MB
SHORTLY AFTER MIDNIGHT WEDNESDAY NIGHT AS IT MOVES TO 48N 130.5W.
THE WIND FIELD WITH THIS LOW WILL BE IMPRESSIVE AS STORM FORCE WINDS
DEVELOP OVER THE COASTAL WATERS EARLY WEDNESDAY EVENING AND HIGH
WINDS MOVE ONTO THE IMMEDIATE COASTLINE SHORTLY THEREAFTER. HIGH
WINDS ARE LIKELY TO CONTINUE INTO THURSDAY MORNING AS THE BENT BACK
OCCLUSION WRAPPING AROUND THE DEVELOPING LOW NICKS THE NORTHWEST
CORNER OF THE OLYMPIC PENINSULA. WINDS WILL LIKELY BE QUITE GUSTY ON
THE COAST WITH 925 MB WINDS 60-65 KT BEHIND THE WARM FRONT
SUPPORTING WINDS 30 TO 45 MPH WITH GUSTS TO 65 MPH. WINDS WILL
GRADUALLY TAPER OFF ON THURSDAY AS THE DEEP LOW MOVES SLOWLY
NORTHWARD AND PRESSURE GRADIENTS TO ITS SOUTH SLOWLY RELAX. THE HIGH
WIND WATCH FOR THE NORTH AND CENTRAL WASHINGTON COAST WAS UPGRADED
TO A WARNING THAT WILL GO FROM 3 PM PST WEDNESDAY TO 9 AM PST
THURSDAY. FLOW ALOFT WILL INTERACT WITH THE OLYMPICS TO PRODUCE
WINDY CONDITIONS OVER THE INTERIOR FROM ABOUT WHIDBEY ISLAND
NORTHWARD TO THE CANADIAN BORDER. AT THIS TIME IT APPEARS THAT THE
STRONGEST WINDS WILL OCCUR OVER THE MARINE WATERS...WITH SOME
NORMALLY WINDY SPOTS LIKE WHIDBEY ISLAND NAS...SOUTHERN PORTIONS OF
THE SAN JUANS...AND COASTAL AREAS ALONG WESTERN SKAGIT AND WHATCOM
COUNTIES SEEING ADVISORY LEVEL SOUTHEAST WINDS WEDNESDAY EVENING.

IN THE MOUNTAINS EXPECT A BURST OF HEAVY SNOWFALL ABOVE ABOUT 4000
FEET DURING THE AFTERNOON AND EVENING HOURS AHEAD OF THE INCOMING
FRONTAL SYSTEM. SNOWFALL AMOUNTS MAY BE STRONG ENOUGH TO JUSTIFY THE
ISSUANCE OF A WINTER WEATHER ADVISORY OVER PORTIONS OF THE
CASCADES...BUT WILL LET THE NEXT SHIFT

A BURST OF HEAVY RAINFALL IS EXPECTED OVER THE SOUTH SLOPES OF THE
OLYMPICS WITH 2 TO 4 INCH 12 TO 18 HOUR AMOUNTS THERE. THIS MAY
PRODUCE FLOODING ON THE NORMALLY FLOOD PRONE SKOKOMISH RIVER IN
MASON COUNTY...AND A FLOOD WATCH IS IN EFFECT FOR THAT AREA.

SHOWERY AND WINDY CONDITIONS ARE EXPECTED THURSDAY MORNING. WINDS
AND SHOWER ACTIVITY WILL GRADUALLY DECREASE AS THE DAY WEARS ON WITH
THE LOW PUSHING NORTHWARD AND SLOWLY FILLING.

FORECASTS WERE UPDATED FOR THE PERIOD WEDNESDAY AFTERNOON THROUGH
THURSDAY MORNING TO ACCOUNT FOR COASTAL WIND UPDATES AND THE
CONVERSION OF THE HIGH WIND WATCH TO A WARNING. OTHERWISE THE
FORECAST APPEARS TO BE IN GOOD SHAPE. ALBRECHT

.LONG TERM...FROM THE PREVIOUS LONG TERM DISCUSSION...IT SEEMS LIKE
EACH MODEL RUN HAS HAD DIFFERENT TIMING FOR SEVERAL SHORTWAVES THAT
AFFECT THE REGION THROUGH THE WEEKEND. IT IS HARD TO SAY WHEN THE
PERIODS OF RAIN WILL FALL VERSUS THE SCATTERED SHOWERS IN BETWEEN
THE FRONTS. EXPECT WETTER THAN NORMAL WEATHER BUT THE TIMING OF THE
FRONTS IS UP IN THE AIR. IT COULD BE BREEZY AT TIMES BUT THE FRONT
WEDNESDAY NIGHT IS THE MAIN SYSTEM THIS WEEK AND ALL THE OTHERS ARE
SO MUCH LESS INTERESTING THAT LITTLE TIME HAS BEEN SPENT ON THE
EXTENDED FORECAST.

&&

.HYDROLOGY...HEAVY RAIN WEDNESDAY NIGHT IN THE OLYMPICS WILL LIKELY
DRIVE THE SKOKOMISH RIVER ABOVE ITS NEW FLOOD STAGE ON THURSDAY AND
A FLOOD WATCH IS UP FOR MASON COUNTY. THIS FRONT GIVES THE OLYMPIC
PENINSULA ABOUT 12 TO 18 HOURS OF HEAVY RAIN AND THEN THERE IS A
FRONTAL PASSAGE BY DAYBREAK THURSDAY. RIVER FLOODING IS NOT LIKELY
EXCEPT FOR FOR THE SKOKOMISH RIVER IN MASON COUNTY.

&&

.AVIATION...A WEAK COLD FRONT WILL DISSIPATE OVER THE INTERIOR THIS
EVENING. THE FLOW ALOFT IS WESTERLY. CEILINGS ARE MAINLY VFR WITH
BKN DECK 040-050. RAIN WILL INCREASE WEDNESDAY AFTERNOON AND EVENING
AS A STRONG WARM FRONT LIFTS NORTH THROUGH WESTERN WA. STRONG GUSTY
WINDS ARE POSSIBLE ON THE COAST THROUGH WEDNESDAY NIGHT. 33

KSEA...LIGHT RAIN IN THE VICINITY TONIGHT BUT CIGS SHOULD REMAIN
VFR. A WARM FRONT WILL SPREAD MORE RAIN TO THE AREA WEDNESDAY
AFTERNOON. SURFACE WINDS WILL TURN SE TO E TO 15 KT BY 21Z. 33

&&

.MARINE...A FRONT WILL DISSIPATE OVER THE INTERIOR WATERS THIS
EVENING.

A VERY STRONG SYSTEM WILL IMPACT THE REGION WEDNESDAY AND WEDNESDAY
NIGHT. STORM FORCE WINDS ARE POSSIBLE OVER THE COASTAL WATERS AND
WEST ENTRANCE AS A DEEP 970-975 MB LOW CURLS NORTH ALONG 130W.
STRONG ONSHORE FLOW WILL CONTINUE THURSDAY MORNING AS THIS SYSTEM
MOVES INLAND OVER NORTHERN VANCOUVER ISLAND. THIS SYSTEM WILL ALSO
BRING HIGH SEAS OF 20-25 FT.

HIGH ASTRONOMICAL TIDES AND UNUSUALLY LOW SURFACE PRESSURE WILL
BRING THE THREAT OF MINOR TIDAL OVERFLOW WEDNESDAY OR WEDNESDAY
NIGHT.

DECREASING ONSHORE FLOW WILL PREVAIL BEHIND THE FRONTAL SYSTEM ON
THURSDAY. OFFSHORE FLOW WILL DEVELOP FRIDAY AS A SURFACE LOW TRACKS
TOWARDS THE OREGON COAST. A FRONTAL SYSTEM WILL REACH THE AREA ON
SATURDAY. 33

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY AFTERNOON
     FOR MASON COUNTY.

     HIGH WIND WARNING FROM 3 PM WEDNESDAY TO 9 AM PST THURSDAY FOR
     CENTRAL COAST-NORTH COAST.

     COASTAL FLOOD ADVISORY FROM 11 AM WEDNESDAY TO 4 AM PST THURSDAY
     FOR CENTRAL COAST.

PZ...SMALL CRAFT ADVISORY FOR ROUGH BAR UNTIL 4 PM PST WEDNESDAY FOR
     GRAYS HARBOR BAR.

     SMALL CRAFT ADVISORY UNTIL 2 PM 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.

     STORM WARNING FROM 2 PM WEDNESDAY TO 9 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-WEST ENTRANCE U.S.
     WATERS STRAIT OF JUAN DE FUCA.

     SMALL CRAFT ADVISORY UNTIL 4 PM PST WEDNESDAY FOR EAST ENTRANCE
     U.S. WATERS STRAIT OF JUAN DE FUCA.

     GALE WARNING FROM 4 PM WEDNESDAY TO 4 PM PST THURSDAY FOR EAST
     ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA-NORTHERN INLAND
     WATERS INCLUDING THE SAN JUAN ISLANDS.

     SMALL CRAFT ADVISORY UNTIL MIDNIGHT PST TONIGHT FOR ADMIRALTY
     INLET-NORTHERN INLAND WATERS INCLUDING THE SAN JUAN ISLANDS.

     GALE WARNING FROM 4 PM WEDNESDAY TO 6 AM PST THURSDAY FOR
     CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA.

&&

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