Small Craft Advisory 31, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
958 AM PST WED FEB 12 2014

.SYNOPSIS...WESTERN WASHINGTON WILL BE BETWEEN WEATHER SYSTEMS TODAY
FOR SCATTERED SHOWERS AND EASING WINDS. THE NEXT SYSTEM WILL BRING
MORE RAIN...MOUNTAIN SNOW...AND BREEZY TO WINDY CONDITIONS TONIGHT
AND THURSDAY. THEN ANOTHER STRONG FRONTAL SYSTEM WILL MOVE THROUGH
THURSDAY NIGHT AND FRIDAY. THE STORMY PATTERN WILL CONTINUE THIS
WEEKEND AND EARLY NEXT WEEK.

&&

.SHORT TERM...ON THE LARGE SCALE...A LARGE AND BROAD POSITIVELY
TILTED LONGWAVE TROUGH AXIS HAS BECOME ESTABLISHED OVER THE ERN PAC.
AN UPPER LOW DROPPING INTO SOUTH-CENTRAL ALASKA LATER TODAY WILL
HELP TO ANCHOR THE LONGWAVE PATTERN IN PLACE UNTIL ABOUT MON OR TUE
OF NEXT WEEK. THE LONGWAVE PATTERN IS DIRECTING A STRONG W-SW JET
STREAM INTO THE PAC NW...WITH 300 MB WINDS IN THE JET CURRENTLY
RUNNING AROUND 130 KT. THE JET SHOULD SHARPEN A BIT ON THU AND
FRI...WITH 300 MB WINDS EXPECTED TO REACH 160 KT DURING THAT TIME.
SUCH A FAST AND ENERGETIC JET WILL DIRECT WET...WINDY AND
FAST-MOVING SYSTEMS THROUGH WRN WA EVERY 24-36 HOURS UNTIL THE
LONGWAVE PATTERN STARTS TO PROGRESS EARLY NEXT WEEK. AS FOR
TIMING...STORMS ARE EXPECTED TO PASS THROUGH WRN WA TONIGHT...
FRIDAY...SATURDAY PM...AND SUNDAY PM. WHILE ALL THE STORMS WILL COME
WITH SIGNIFICANT RAINFALL...THE SUNDAY PM STORM WILL BE THE
SLOWEST-MOVING WITH THE HEAVIEST RAIN AS WELL AS THE HIGHEST FLOOD
POTENTIAL.

DRILLING DOWN TO THE DETAILS...STILL FACING STRONG ONSHORE FLOW
RIGHT NOW IN THE WAKE OF LAST NIGHT'S STORM...AND A PUGET SOUND
CONVERGENCE ZONE HAS DEVELOPED OVER SOUTH SNOHOMISH COUNTY. ONSHORE
FLOW WILL QUICKLY WEAKEN TODAY...CAUSING WINDS TO EASE AND CAUSING A
DISSIPATION OF THE CONVERGENCE ZONE EARLY THIS AFTN. A RELATIVE LULL
IN THE WEATHER IS EXPECTED THIS AFTN AND EARLY THIS EVNG OVER WRN WA.

A 988 MB LOW IS EXPECTED TO REACH HAIDA GWAII LATE TONIGHT...WITH A
TRAILING OCCLUSION CROSSING WRN WA. FAIRLY WIDESPREAD RAIN WILL
REACH THE COAST AND SW INTERIOR BETWEEN 7 PM AND 10 PM...THE SPREAD
ACROSS THE REST OF WRN WA BY MIDNIGHT. MODEST PRE-FRONTAL SOUTHERLY
AND SOUTHEASTERLY WINDS WILL DEVELOP AHEAD OF THE OCCLUDED FRONT.
THE STRONGER WINDS WILL BE THE ONSHORE WESTERLY WINDS WHICH DEVELOP
BEHIND THE FRONT LATE TONIGHT AND THU MRNG. A PUSH OF GALES IS
LIKELY THROUGH THE STRAIT...WITH THE UW WRF-GFS SHOWING ADVISORY
LEVEL WESTERLIES AFFECTING THE SOUTHERN SAN JUAN ISLANDS ARND 7 AM
ON THU MRNG. QPF AMOUNTS ARE EXPECTED TO REMAIN BELOW 1 INCH OVER
THE OLYMPICS...AND ONLY EXCEED 1 INCH BY A LITTLE OVER THE CASCADES.
THIS IS NOT ENOUGH TO CAUSE CONCERN FOR FLOODING. A RELATIVE LULL IN
THE WEATHER IS EXPECTED ON THU AFTN AND EVNG.

NEXT UP...A MATURE 975 MB LOW IS EXPECTED TO REACH HAIDA GWAII BY
12Z FRI. A STRONGER UPPER JET AT THAT TIME WILL SUPPORT A MORE
ENERGETIC TRAILING FRONT. RAIN WILL SPREAD ACROSS WRN WA ARND
MIDNIGHT ON THU NGT. RAIN WILL BE HEAVY AT TIMES INTO FRI
MRNG...WITH LOWLAND QPF OF 0.50"-1.00" COMMON. QUICK MOVEMENT OF
THIS STORM WILL KEEP QPF FROM BEING MUCH HEAVIER THAN THAT. IN TERMS
OF WIND...THIS COULD BE A SETUP WITH ADVISORY-LEVEL WINDS FOR
NORMALLY SUSPECT LOCATIONS SUCH AS THE COAST AND NORTH INTERIOR
ZONES IN THE PRE-FRONTAL ENVIRONMENT.   HANER

.LONG TERM...FROM PREVIOUS DISCUSSION...THE PROGRESSIVE STORMY
PATTERN WILL CONTINUE...AND THE MODELS ARE IN FAIRLY GOOD AGREEMENT
WITH RESPECT TO TIMING ETC. THE MOST LIKELY TIMING IS ANOTHER STRONG
FRONT MOVING THROUGH SATURDAY AND SATURDAY NIGHT...FOLLOWED BY
ANOTHER SUNDAY NIGHT AND MONDAY. ANOTHER SYSTEM ASSOCIATED WITH A
COOL UPPER TROUGH WILL LIKELY REACH THE PACIFIC NORTHWEST AROUND
TUESDAY.   MCDONNAL

&&

.HYDROLOGY...AT 9 AM...THE SKOKOMISH RIVER NEAR POTLATCH WAS AT 16.5
FEET...OR JUST A SMIDGE ABOVE FLOOD STAGE. THE RIVER LEVEL WAS STILL
RISING...BUT RATE OF RISE HAS STARTED TO SLOW. IN OTHER WORDS...THE
HYDROGRAPH CURVE IS SHOWING EARLY SIGNS OF TURNING OVER. NO
HYDROLOGICALLY SIGNIFICANT RAIN IS EXPECTED FOR THE REMAINDER OF
TODAY...SO THIS WILL HELP THE RIVER START TO HEAD DOWN...FALLING
BELOW FLOOD STAGE BY LATE THIS AFTERNOON. A FLOOD WARNING IS IN
EFFECT AND WILL REMAIN IN EFFECT UNTIL A FEW HOURS AFTER THE RIVER
DROPS BACK BELOW 16.5 FEET.

THE NEXT STORM WILL ARRIVE TONIGHT. RAINFALL AMOUNTS OVER MOUNTAIN
HEADWATERS IS NOT EXCEED TO EXCEED 1 INCH BY MUCH. RISES CAN BE
EXPECTED ON AREA RIVERS...BUT THIS MUCH RAIN IS NOT EXPECTED TO
CAUSE FLOODING.

THE NEXT RAIN-PRODUCING STORMS ON FRIDAY AND ON SAT PM WILL BRING
HEAVY RAINFALL RATES WITH RISES ON AREA RIVERS...BUT THE FAST
MOVEMENT OF THESE STORMS WILL LIMIT RAINFALL DURATION TO THE POINT
OF CAUSING LITTLE CONCERN FOR FLOODING ON AREA RIVERS.

A SLOWER MOVING FRONT WITH HEAVY RAIN WILL ARRIVE AROUND SUNDAY
NIGHT. RIVERS WILL ALREADY BE RUNNING HIGH FROM THIS WEEK'S
SUCCESSION OF STORMS...SO THE LONG DURATION OF HEAVIER RAINFALL ON
SUNDAY NIGHT AND MONDAY MAY BE ENOUGH TO CAUSE A FEW RIVERS IN
WESTERN WASHINGTON TO REACH FLOOD STAGE. IT IS STILL TOO EARLY TO
SAY WHICH RIVERS ARE MORE LIKELY TO REACH FLOOD STAGE...BUT THOSE
WITH SENSITIVITIES TO RIVER FLOODING WILL WANT TO CHECK BACK LATE
THIS WEEK AND OVER THE WEEKEND.     HANER

&&

.AVIATION...STRONG WESTERLY FLOW ALOFT WILL CONTINUE INTO THE
WEEKEND RESULTING IN A VERY ACTIVE WEATHER PATTERN OVER THE REGION.
STRONG POST-FRONTAL ONSHORE FLOW HAS CLEARED OUT THE CLOUD COVER
OVER LARGE REGIONS OF W WA. SHOWER ACTIVITY HAS DIMINISHED. THE ONLY
EXCEPTION OVER THE LOWLANDS IS A PUGET SOUND CONVERGENCE ZONE OVER
NORTH PUGET SOUND. STRONG WEST FLOW ALOFT WILL KEEP THE MOUNTAINS
OBSCURED. W-SW SURFACE WINDS REMAIN QUITE GUSTY OVER THE
INTERIOR...BUT WILL DIMINISH RAPIDLY THIS AFTERNOON AS A SURFACE
RIDGE MOVES BRIEFLY OVER W WA. MVFR CIGS CAN BE EXPECTED IN THE
CONVERGENCE ZONE AND IN SPOTS AROUND THE INTERIOR. OTHERWISE CIGS
WILL BE ABOVE 3000 FEET OVER THE LOWLANDS.

KSEA...VFR CONDITIONS SHOULD PREVAIL AT KSEA TODAY...ALTHOUGH SPOTTY
LOW LEVEL MOISTURE AROUND THE REGION COULD STILL PRODUCE A BRIEF CIG
NEAR 2000 FEET. THE CONVERGENCE ZONE OVER N SEATTLE SHOULD REMAIN
NORTH OF THE TERMINAL. GUSTY SURFACE WINDS SW15G25KT WILL CONTINUE
THROUGH ABOUT 20Z THEN DIMINISH AS A SURFACE RIDGE MOVES OVER W WA.
WINDS WILL REMAIN SOUTHERLY. KAM

&&

.MARINE...STRONG POST-FRONTAL ONSHORE FLOW THIS MORNING WILL WEAKEN
RAPIDLY THIS AFTERNOON AS A SURFACE RIDGE MOVES BRIEFLY OVER THE
AREA. ONLY GALES LEFT ARE FOR THE CENTRAL/EAST STRAIT AND THEY
SHOULD EASE INTO SCA WINDS THIS AFTERNOON.

THE NEXT SURFACE LOW OUT NEAR 50N/140W IS HEADED TOWARD QUEEN
CHARLOTTE SOUND. MODELS HAVE BEEN CONSISTENT. THE LOW WILL CROSS QC
SOUND AROUND 12Z WHILE THE TRAILING SURFACE TROUGH CROSSES W WA.
MESO-MODELS DO NOT SHOW MUCH SIGNIFICANT S FLOW AHEAD OF THE
SYSTEM...BUT THE 06Z ARW-WEST SHOWS A BURST OF POTENTIAL GALE WINDS
ALONG THE COAST...THROUGH THE STRAIT AND OVER THE N INLAND WATERS
LATE TONIGHT ROUGHLY 12Z-15Z OR SO. WILL PROBABLY ISSUE A GALE FOR
THESE AREAS IN THE AFTERNOON PACKAGE. SMALL CRAFT ADVISORIES ARE
ALREADY IN PLACE TO BRIDGE BETWEEN THE CURRENT CONDITIONS AND THE
POTENTIAL GALE LATE TONIGHT.

GALE WATCH IS ALREADY UP FOR THE STRONGER FRONTAL SYSTEM EXPECTED
LATE THURSDAY NIGHT INTO FRIDAY MORNING.

THIS ACTIVE WEATHER PATTERN LOOKS LIKE IT WILL CONTINUE THROUGH THIS
WEEKEND...WITH TWO MORE SYSTEMS...AND POSSIBLY INTO EARLY NEXT WEEK.
KAM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER STORM WARNING FOR THE NORTH CASCADES TIL NOON.
     WINTER WEATHER ADVISORY FOR THE CENTRAL CASCADES TIL NOON.
     WINTER WEATHER ADVISORY IN EFFECT THIS EVENING AND
      THURSDAY FOR THE NORTH AND CENTRAL CASCADES.

PZ...GALE WARNING CENTRAL AND EAST STRAIT.
     SMALL CRAFT ADVISORY REMAINING WATERS.
     GALE WATCH MOST WATERS THURSDAY NIGHT AND FRIDAY.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.

&&

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

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
1141 AM PST WED FEB 12 2014

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0800 AM     HEAVY RAIN       1 W HUMPTULIPS          47.23N 123.98W
02/12/2014  M3.10 INCH       GRAYS HARBOR       WA   CO-OP OBSERVER

            24 HOUR RAINFALL TOTAL.

1135 AM     HEAVY RAIN       HOODSPORT               47.41N 123.14W
02/12/2014  M2.75 INCH       MASON              WA   TRAINED SPOTTER

            24 HOUR RAINFALL TOTAL.

&&

JSMITH