Small Craft Advisory 56, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
310 AM PST MON MAR 7 2016

.SYNOPSIS...A BROAD UPPER LEVEL TROUGH WILL MOVE INTO THE AREA TODAY
BRINGING ANOTHER ROUND OF SHOWERS. A FRONT WILL REACH THE COAST
TUESDAY AFTERNOON AND SPREAD RAIN INLAND BY TUESDAY NIGHT. A WET
FRONTAL SYSTEM WILL BRING RAIN WEDNESDAY AND WEDNESDAY NIGHT. THIS
GENERALLY WET PATTERN WILL CONTINUE INTO THE WEEKEND.

&&

.SHORT TERM...SURFACE LOW PRESSURE CONTINUES TO TRACK OVER WESTERN
WASHINGTON RESULTING IN SHOWERS...MAINLY OVER THE WESTERN HALF OF
THE CWA. THOSE ARE EXPECTED TO SPREAD EASTWARD THIS MORNING AND INTO
THE AFTERNOON. SHOWERS THIS EVENING AND INTO TONIGHT WILL BE DUE
MOSTLY TO THE LINGERING UPPER LEVEL TROUGH AS IT SLOWLY MOVES EAST
TONIGHT. NEAR TERM MODELS SUGGEST A CONVERGENCE ZONE SETTING UP
RIGHT AROUND NOON...LOOKING TO MAINLY IMPACT SNOHOMISH COUNTY.
PREVIOUS SHIFT SUGGESTED CONSIDERING PUTTING THUNDER IN
FORECAST...PARTICULARLY FOR AREAS IMPACTED BY CONVERGENCE
ZONE...HOWEVER...INSTABILITY IS PRETTY MINOR AND DOES NOT LINE UP
WITH WHERE CONVERGENCE ZONE IS PROGGED TO BE...SO HAVE OPTED TO
LEAVE IT AS SHOWERS FOR NOW. MODELS HINT AT SOME DRYING MONDAY NIGHT
AND AS GREAT AS THAT SOUNDS...IT IS UNFORTUNATELY SHORT LIVED AS A
FRONTAL SYSTEM IS PROGGED TO BRING YET MORE RAIN FOR TUESDAY. THIS
FRONT MOVES THROUGH PRETTY QUICKLY...BRINGING ANOTHER BREATHER FOR
TUESDAY NIGHT AND INTO LATE WEDNESDAY MORNING.

WEDNESDAY CONTINUES TO LOOK...TO BE POLITE...UNPLEASANT. MODELS
REMAIN CONSISTENT WITH AN ATMOSPHERIC RIVER TYPE SITUATION
DEVELOPING WITH SOME PRETTY HIGH QPF VALUES OVER THE OLYMPIC
PENINSULA FOR THE WEDNESDAY EVENING TIME FRAME. WHILE JUST OUT OF
RANGE OF CURRENT FORECAST FOR HEADLINES...WOULD NOT BE SURPRISED TO
SEE SOMETHING FROM FUTURE SHIFTS FOR THAT TIME PERIOD. BUT
WAIT...THERE IS MORE. SURFACE PRESSURE GRADIENTS LOOK TO TIGHTEN
SIGNIFICANTLY WEDNESDAY AFTERNOON. CURRENT FORECAST WILL HAVE WIND
SPEEDS WEDNESDAY AFTERNOON AND EVENING JUST SHY OF HIGH WIND
CRITERIA ON THE COAST...BREEZY TO WINDY ELSEWHERE. IT IS A LITTLE TO
EARLY TO ISSUE ANYTHING REGARDING THESE WINDS JUST YET...BUT
AGAIN...LIKELY TO SEE ADDITIONAL HEADLINES REGARDING THIS FROM
FUTURE SHIFTS. THIS SYSTEM WILL LINGER INTO THURSDAY MORNING BEFORE
THINGS SCATTER OUT ONCE MORE. BY THURSDAY AFTERNOON MODELS START TO
DIVERGE IN THEIR SOLUTIONS. THE ECMWF...WHICH CLEARLY FEELS WESTERN
WASHINGTON COULD USE A DASH MORE RAINFALL...KEEPS SHOWERS OVER THE
AREA THANKS TO A WEAK SHORTWAVE TROUGH PASSING THROUGH THURSDAY
EVENING AND THURSDAY NIGHT. THE GFS ALLOWS FOR AN ALL TOO BRIEF DRY
PERIOD TO SET UP OVER WESTERN WASHINGTON FOR MUCH OF THE DAY
THURSDAY AND INTO THURSDAY NIGHT. SMR

.LONG TERM...MODELS REMAIN OUT OF SYNC AS THEY GO OUT INTO THE
EXTENDED. THE GFS WANTS TO BRING IN ANOTHER SYSTEM FOR FRIDAY
WHEREAS THE ECMWF LOOKS DRY FOR THE DAY. BOTH MODELS LOOK TO FALL IN
STEP WITH REGARDS TO AN UPPER LEVEL LOW APPROACHING THE COAST FOR
SATURDAY. THE ECMWF WANTS TO SET THIS SYSTEM UP MUCH LIKE WHAT IS
BEING ADVERTISED FOR THIS WEDNESDAY...WHILE THE GFS DOES NOT SHOW IT
TO BE THAT STRONG. TIME WILL TELL...BUT AT THIS POINT...THE PROSPECT
OF A WET WEEKEND SHOULD SURPRISE JUST ABOUT NO ONE. SMR

&&

.HYDROLOGY...THE SKOKOMISH RIVER IS HOLDING STEADY JUST ABOVE THE
OLD FLOOD STAGE OF 16.5 FT AND IS FORECAST TO SLOWLY RECEDE THROUGH
THE MORNING AND THIS AFTERNOON. WITH THE NEW FLOOD STAGE OF 17.0 FT
IN PLACE...WILL NOT BE ISSUING ANY PRODUCTS AT THIS TIME...EVEN
THOUGH THIS NEW FLOOD STAGE IS NOT YET REFLECTED ON THE AHPS PAGE.

HEAVY RAIN WEDNESDAY AND WEDNESDAY NIGHT WILL LIKELY DRIVE THE
SKOKOMISH RIVER ABOVE ITS NEW FLOOD STAGE. GIVEN QPF
FORECASTS...OTHER RIVERS MAY ALSO HAVE MINOR FLOODING FROM THIS RAIN
EVENT. BURKE/SMR

&&

.AVIATION...SOUTHWEST FLOW ALOFT OVER WESTERN WASHINGTON EARLY THIS
MORNING WILL CONTINUE TODAY AS A WEAK UPPER TROUGH MOVES ACROSS THE
REGION. WESTERLY FLOW WILL FOLLOW BEHIND THE TROUGH TONIGHT. THE AIR
MASS WILL BE FAIRLY MOIST AND BE SOMEWHAT UNSTABLE TODAY THROUGH
THIS EVENING.

AREAS OF RAIN ARE MOVING THROUGH WESTERN WASHINGTON EARLY THIS
MORNING WITH MAINLY SCT-OVC050 OVC090...AND LOCAL IFR WITH CIGS AOB
BKN010 AND VIS 3SM -RA BR. THESE CONDITIONS WILL GENERALLY CONTINUE
THROUGH EARLY EVENING AS THE AIR MASS BECOMES A BIT UNSTABLE AND
PRECIPITATION TURNS SHOWERY

KSEA...LIGHT VARIABLE WIND WILL BECOME SOUTH TO SOUTHWEST 8-14 KT
GUSTING 22 KT THIS MORNING...THEN SOUTH 6-10 KT TONIGHT. CEILING
WILL PROBABLY BE IN THE HIGH-END MVFR RANGE AT TIMES THROUGH AROUND
10 AM THIS MORNING. MCDONNAL

&&

.MARINE...ONSHORE FLOW WILL PREVAIL ACROSS WESTERN WASHINGTON
TODAY...THEN TURN OFFSHORE TONIGHT. SMALL CRAFT ADVISORY CONDITIONS
WILL CONTINUE FOR THE COASTAL WATERS AND WEST ENTRANCE STRAIT OF
JUAN DE FUCA THROUGH TONIGHT...FOR SWELL GREATER THAN 10 FT IF NOT
FOR A COMBINATION OF WIND AND SWELL. IN ADDITION MARGINAL SMALL
CRAFT ADVISORY WINDS ARE LIKELY OVER THE INLAND WATERS TODAY...AS A
RESULT OF ONSHORE FLOW AND A SOMEWHAT UNSTABLE AIR MASS.

A STRONG FRONT WILL CROSS THE COASTAL AND INLAND WATERS TUESDAY. THE
GALE WATCH FOR THE COASTAL WATERS AND WEST ENTRANCE STRAIT OF JUAN
DE FUCA HAS BEEN UPGRADED TO GALE WARNINGS...IN EFFECT FROM 9 AM
TUESDAY THROUGH TUESDAY EVENING. IN ADDITION A GALE WATCH HAS BEEN
ISSUED FOR THE EAST ENTRANCE STRAIT FOR TUESDAY AFTERNOON AND
EVENING.

A STRONGER FRONTAL SYSTEM IS LIKELY WEDNESDAY AND WEDNESDAY
NIGHT...WITH A DEEPENING SURFACE LOW TRACKING NORTH-NORTHEAST NEAR
THE OUTER EDGE OF THE OFFSHORE WATERS -- THAT IS NEAR 130W. GALES UP
TO 40 KT FOR THE COASTAL WATERS AND WEST ENTRANCE STRAIT ARE IN THE
FORECAST AT THIS TIME. GALES ARE ALSO A DECENT BET IN THE CENTRAL
STRAIT...EAST ENTRANCE...AND NORTHERN INLAND WATERS.

TIDAL LEVELS WILL BE NEAR THE MINOR TIDAL OVERFLOW THRESHOLDS
WEDNESDAY AND WEDNESDAY NIGHT...SO A STATEMENT FOR THAT MAY BE
NEEDED IN THE NEXT DAY OR SO. MCDONNAL

&&

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...GALE WATCH FROM TUESDAY MORNING THROUGH TUESDAY EVENING 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 UNTIL 6 AM PST TUESDAY 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 6 PM PST MONDAY FOR
     GRAYS HARBOR BAR.

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

     SMALL CRAFT ADVISORY UNTIL 9 PM PST MONDAY FOR WEST ENTRANCE
     U.S. WATERS STRAIT OF JUAN DE FUCA.

     SMALL CRAFT ADVISORY UNTIL 9 PM PST THIS EVENING FOR PUGET SOUND
     AND HOOD CANAL.

&&

WWW.WEATHER.GOV/SEATTLE

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML