Gale Watch 6, NWS Seattle, WA

AREA FORECAST DISCUSSION...CORRECTED AVIATION SECTION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST TUE JAN 24 2012

.SYNOPSIS...STRONG MOIST WESTERLY FLOW WILL KEEP SHOWERS OVER
WESTERN WASHINGTON TODAY...AND THEN A WEAK FRONT WILL BRING MORE
STEADY RAIN TONIGHT. SNOW WILL CONTINUE IN THE MOUNTAINS. SHOWERS
WILL BEGIN TO DECREASE THURSDAY...AND AN UPPER RIDGE WILL BRING DRY
WEATHER FRIDAY AND SATURDAY. EXPECT A RETURN TO TYPICAL WET JANUARY
WEATHER SUNDAY INTO EARLY NEXT WEEK.

&&

.SHORT TERM...IR SATELLITE IMAGERY SHOWS A STREAM OF MOISTURE OVER
THE ERN PAC DIRECTED INTO WRN WA. A STRONG 150 KT WLY JET IS
CONTINUING TO PRODUCE OROGRAPHICALLY ENHANCED PRECIPITATION ALONG
THE W SLOPES OF THE CASCADES...ADDING TO WHAT THE MOUNTAINS HAD THE
PAST 24 HOURS. THE SNOW LEVEL HAS DROPPED TO AROUND 2000-3000 FEET
THIS MORNING SO MOST THE PRECIPITATION WILL FALL AS SNOW IN THE
MOUNTAINS AND PASSES. GIVEN THE STRONG 850 MB WLY WINDS OVER 30 KT
AND QPF UP TO THREE QUARTERS OF AN INCH...HIGH RATIOS CAN BE
EXPECTED WITH A DOUBLING OF QPF LIKELY. SNOWFALL AMOUNTS OF 11-17
INCHES SEEMS REASONABLE AS INDICATED IN THE WINTER WEATHER ADVISORY
WHICH REMAINS IN EFFECT UNTIL 6 AM THURSDAY.

RAIN FELL IN THE LOWER ELEVATIONS YESTERDAY AFFECTING LOWER RIVER
BASINS BELOW THE SNOW LEVEL. THE SKOKOMISH RIVER BASIN WAS
PARTICULARLY AFFECTED CAUSING IT SPIKE ABOVE FLOOD STAGE OVERNIGHT.
A FLOOD WARNING REMAINS IN EFFECT. SEE THE LATEST HYDRO DISCUSSION
BELOW AND THE LATEST FLOOD STATEMENT FOR DETAILS.

RAIN AT TIMES WILL CONTINUE ACROSS THE LOWLANDS TODAY...TAPERING TO
SHOWERS FOR A TIME THIS AFTERNOON. ANOTHER WAVE WITH A CLOSED
SURFACE LOW REFLECTION WILL MOVE NEAR OR ACROSS THE AREA TONIGHT. AS
MENTIONED ABOVE THE SNOW WILL CONTINUE IN THE MOUNTAINS. RAIN WILL
PICK BACK ACROSS THE LOWLANDS LATER TONIGHT AND THURSDAY REGARDLESS
OF THE TRACK. WIND WILL NOT BE A BIG ISSUE WITH THIS SYSTEM EVEN IF
THE 12Z NAM IS CORRECT TAKING THE 1012 MB INTO S VANCOUVER ISLAND.
GRADIENTS MAY COME UP JUST ENOUGH FOR SOME BORDERLINE GALES IN THE
STRAIT AND COAST BUT LAND AREAS WILL BE JUST BREEZY. SINCE THE LOW
IS NOT DEEPENING AND THE CENTRAL PRESSURE IS THAT LOW I WOULD EXPECT
NO MORE THAN BREEZY CONDITIONS IN THE 15 TO 25 MPH RANGE.

RAIN OR SHOWERS DECREASE BEHIND THE WAVES ON THURSDAY WITH HIGH
PRESSURE AT THE SURFACE AND ALOFT QUICKLY BUILDING INTO THE AREA
LATER IN THE DAY. THE AREA SHOULD BE DRY THURSDAY NIGHT AND FRIDAY
AS THE RIDGE MOVE OVER THE PAC NW. EXPECT COLDER OVERNIGHT LOWS DUE
TO CLEAR SKIES AND LIGHT FLOW...MOST AREAS IN THE 20S TO NEAR 30.
PATCHY NIGHT AND MORNING FOG IS LIKELY FRIDAY AND SATURDAY BUT
EXPECT MOSTLY SUNNY SKIES IN THE AFTERNOON.  MERCER

.LONG TERM...FROM PREVIOUS DISCUSSION...THE UPPER RIDGE OFFSHORE
SHOULD KEEP MOST OF WESTERN WASHINGTON DRY THROUGH SATURDAY...BUT
THE FRONTAL SYSTEM MOVING INTO BRITISH COLUMBIA WILL BRING CLOUD
COVER AND MAYBE A LITTLE RAIN TO THE COAST AND NORTHWEST INTERIOR.
THE MODELS ARE IN FAIRLY GOOD AGREEMENT THROUGH EARLY NEXT WEEK.
THEY SHOW A WET AND RATHER COOL PATTERN WITH FRONTAL SYSTEMS MOVING
THROUGH THE REGION IN WESTERLY FLOW ALOFT...PROBABLY SATURDAY NIGHT
AND SUNDAY AND THEN AGAIN AROUND MONDAY NIGHT. THE SNOW LEVEL WILL
GENERALLY BE 3000 FT OR BELOW SO MORE SNOW WILL PILE UP IN THE
MOUNTAINS. MCDONNAL

&&

.HYDROLOGY...THE SKOKOMISH RIVER REACHED ABOVE FLOOD STAGE EARLY
THIS MORNING AND A FLOOD WARNING HAD TO BE ISSUED FOR MINOR
FLOODING. AT 8 AM HYDROGRAPHS INDICATE THE SKOKOMISH NEAR POTLATCH
IS PROBABLY NEAR PEAK STAGE AND SHOULD BEGIN TO FALL THIS AFTERNOON.
SEE THE LATEST FLOOD STATEMENT FOR THE LATEST DETAILS REGARDING
FLOODING ON THE SKOKOMISH RIVER.

UP TO 3.5 INCHES FELL OVER THE SOUTH SLOPES OF THE OLYMPICS AND UP
TO 2.0 INCHES OVER THE HIGHER TERRAIN OF SOUTHWEST WASHINGTON THE
PAST 24 HOURS. THIS CAUSED RISES ON RIVERS ACROSS THAT PART OF THE
FORECAST AREA AND ESPECIALLY ON FLOOD-PRONE RIVERS. BESIDES THE
SKOKOMISH RIVER...RISES ON OTHER RIVER ARE NOT LIKELY TO PUSH THEM
OVER FLOOD STAGE.

THE THREAT OF FLOODING WILL EASE FROM HERE OUT. THE UPCOMING PATTERN
OF LESS PRECIPITATION AND LOWER SNOW LEVELS DOES NOT PRODUCE
FLOODING IN WESTERN WASHINGTON. SO AFTER THE IMMEDIATE THREAT IS
OVER...THERE IS NO FORESEEABLE FLOOD THROUGH FOR THE NEXT 7 DAYS.
MERCER/MCDONNAL

&&

.AVIATION...CORRECTED TO ADD MENTION OF TONIGHTS COLD FRONT. STRONG
WEST FLOW ALOFT COMBINED WITH SW ONSHORE FLOW WILL KEEP THE AIR MASS
OVER W WA MOIST THROUGH THIS EVENING...WITH FREQUENT SHOWERS. A MIX
OF MVFR CIGS AND VFR CIGS BKN-OVC030-050 WILL CONTINUE...WITH
VISIBILITY MAINLY VFR...BUT OCCASIONALLY DROPPING TO 3-5SM AROUND
HEAVIER SHOWERS. THE MOUNTAINS WILL BE MAINLY OBSCURED.

A 1012 MB SURFACE LOW AND ASSOCIATED COLD FRONT WILL MOVE ACROSS W
WA TONIGHT...WITH RAIN DEVELOPING AFTER 04Z.

KSEA...A MIX OF MVFR AND VFR CIGS BKN-OVC030-050 WILL CONTINUE TODAY
AS FREQUENT SHOWERS CROSS THE TERMINAL. SW SURFACE WINDS WILL
CONTINUE 5 TO 15 KT. KAM

&&

.MARINE...SW ONSHORE FLOW WILL CONTINUE TODAY BEHIND LAST NIGHTS
FRONTAL SYSTEM. THE AN APPROACHING UPPER LEVEL SHORTWAVE TROUGH
EMBEDDED THE BAROCLINIC BAND OFFSHORE WILL INTENSIFY
TODAY...DEVELOPING A 1012 MB SURFACE LOW PER THE 12Z NAM...AND A
1016 MB LOW PER THE 12Z GFS. MODEL TIMING AND TRACK ARE
SIMILAR...BRINGING THE LOW TO THE VANCOUVER ISLAND COAST JUST N OF
CAPE FLATTERY AROUND 06Z TONIGHT. WILL GO WITH THE DEEPER NAM
SOLUTION HOWEVER AND AND INCREASE WINDS TO SOLID SCA LEVELS TONIGHT.
WILL AWAIT THE 12Z WRF-GFS MODEL AND REVISIT THE STRENGTH ISSUE IN
THE AFTERNOON FORECAST. STRONG ONSHORE FLOW DEVELOPS IMMEDIATELY
BEHIND THE SYSTEM TONIGHT...THEN WEAKENS STEADILY THROUGH THURSDAY
AS A SURFACE HIGH BUILDS INLAND.

A LARGE WESTERLY SWELL CONTINUES TO REACH THE COASTAL WATERS. SWELLS
OF 25 TO 29 FT ARE LIKELY ON THE COASTAL WATERS TODAY...GRADUALLY
SUBSIDING TONIGHT. HAZARDOUS SEAS WILL REMAIN AN ISSUE INTO
THURSDAY...AND A HIGH SURF WARNING CONTINUES FOR THE COAST TODAY.
KAM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WATCHES AND/OR WARNINGS FOR PORTIONS OF THE FORECAST
     AREA.

     HIGH SURF WARNING UNTIL 4 AM PST THURSDAY FOR CENTRAL THE
     COAST.

     WINTER WEATHER ADVISORY FOR THE CENTRAL AND NORTHERN CASCADES
     TODAY AND TONIGHT.

     COASTAL FLOOD WATCH IN EFFECT FOR LA PUSH AND THE QUILEUTE
     TRIBE LOWER VILLAGE FROM 9 AM PST THIS MORNING THROUGH LATE
     TONIGHT.

PZ...SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE COAST...WEST
     ENTRANCE TO THE STRAIT...AND PUGET SOUND AND HOOD CANAL.

     SMALL CRAFT ADVISORY FOR ROUGH BAR UNTIL 6 PM PST THURSDAY
     FOR THE GRAYS HARBOR BAR.

WWW.WEATHER.GOV/SEATTLE

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