Gale Warning 6, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
935 PM PST TUE JAN 8 2013

.SYNOPSIS...A VIGOROUS FRONTAL SYSTEM WILL CONTINUE TO BRING RAIN
AND WINDY CONDITIONS TO WESTERN WASHINGTON TONIGHT. THE FRONT WILL
MOVE INLAND WEDNESDAY. A COLD UPPER TROUGH WILL MOVE OVER THE AREA
WEDNESDAY NIGHT AND THURSDAY. THE SNOW LEVEL WILL DROP BELOW 500
FEET WEDNESDAY NIGHT AND THURSDAY WITH SCATTERED SNOW SHOWERS
POSSIBLE.

&&

.SHORT TERM...FRONTAL SYSTEM OVER THE REGION TONIGHT FOR RAIN AND
BLUSTERY WEATHER. THE OLM-BLI GRADIENT HAS BEEN AROUND 5MB THIS
EVENING AND THE WIND ADVISORIES ARE WORKING OUT WELL FOR MANY AREAS.
PRECIP AMOUNTS HAVE RANGED UP TO SEVERAL INCHES IN THE WETTEST SPOTS
IN THE MOUNTAINS AND THE RIVERS WILL RISE THROUGH WEDNESDAY
MORNING...THERE IS A FLOOD WATCH OUT FOR SOME AREAS AND A WARNING
FOR THE SKOKOMISH RIVER IN MASON COUNTY.

THE SNOW LEVEL IN THE NORTH CASCADES IS ABOUT 4500FT AROUND MT BAKER
WHERE THE HIGHER ELEVATIONS ARE GETTING 1-2 INCHES OF WET SNOW AN
HOUR...BUT IT HAS BEEN RAINING ON THE MAIN CASCADE PASSES. THE RAIN
IN THE MOUNTAINS WILL TURN TO SNOW SHOWERS WED AND BY WED NIGHT THE
SNOW LEVEL WILL DROP BELOW 1000FT FOR A CHANCE OF SCATTERED HILLTOP
SNOW SHOWERS IN THE LOWLANDS. THE 00Z NAM FORECAST HAS SOME PRECIP
IN THE PSCZ AREA WED NITE AND AN 850MB TEMP OF -6 TO -7C. THE 12
HOUR PRECIP TOTAL FROM THE NAM FOR 7PM WED TO 7AM THU SHOWS THAT
SKAGIT COUNTY MIGHT HAVE AN EVEN BETTER CHANCE FOR SNOW THAN THE
PSCZ AREA...PERHAPS SKAGIT COUNTY WILL SEE AN AREA OF HEAVIER
SHOWERS THAT SET UP ALONG THE LEADING EDGE OF SOME COLDER AIR
LEAKING OUT OF BRITISH COLUMBIA WED NITE AND THU...WORTH KEEPING AN
EYE ON AND A GOOD IDEA TO INSPECT THE 12Z WED CYCLE OF THE MODELS
INCLUDING THE UW MESOSCALE SOLUTIONS. THE 1000-850MB THICKNESS SHOWS
IT WILL BE COOL ENOUGH FOR SNOW SHOWERS WED NIGHT AND THU AND
CERTAINLY COOLER FROM SEATTLE NORTH THAN ALONG THE COAST. 19

.LONG TERM...PREVIOUS DISCUSSION...LONG RANGE MODELS CONTINUE TO BE
IN POOR AGREEMENT WITH EACH OTHER AND WITH LITTLE RUN TO RUN
CONSISTENCY. THE TREND TODAY HAS BEEN TO SPLIT THE NRN STREAM ON
SATURDAY WHICH WOULD TAKE SHORT WAVE ENERGY AND LOW PRESSURE FURTHER
OFF THE COAST. 00Z CANADIAN/ECMWF MODELS WERE QUITE STRONG AND
CONSOLIDATED WITH THIS SYSTEM...DIGGING THE LOW DOWN RIGHT OVER US
WITH IMPRESSIVE QPF. THE LATEST RUNS WOULD IMPLY ONLY LIGHT
PRECIPITATION AND MORE FOCUSED TOWARD THE COAST. MODELS ARE CLEARLY
UNSTABLE WITH ANY OF THE SOLUTIONS THE PAST COUPLE DAYS STILL
PLAUSIBLE. IT DOES APPEAR COLD ENOUGH OVER THE AREA SO THAT ANY
PRECIPITATION THAT DOES FALL SHOULD BE MOSTLY AS SNOW.

THE SHORT WAVES DIVES SWD SATURDAY NIGHT AND SUNDAY. THE 12Z/18Z
MODEL TREND IS TO MIGRATE THE RIDGE EWD AND KEEP THE AREA DRY BUT
STILL COOL. SOME 00Z MODEL RUNS FROM LAST NIGHT SHOWED ADDITIONAL
SHORT WAVE ENERGY DRIVING SWD POSSIBLY BRINGING MORE SHOWERS/ OR
MIXED PRECIPITATION TO THE AREA SUNDAY INTO EARLY NEXT WEEK. KEPT
SOME CHANCE POPS JUST IN CASE BUT THE LATEST TREND IS CLEARLY TOWARD
DRIER. MERCER

&&

.HYDROLOGY...THE RIVERS WILL RISE SHARPLY TONIGHT AND THE SKOKOMISH
RIVER HAS THE BEST CHANCE TO GET OVER FLOOD STAGE...SO A WARNING HAS
BEEN ISSUED FOR THAT RIVER. A FEW OTHER RIVERS ARE STILL WORTH
WATCHING BUT THE RAIN HAS NOT BEEN ESPECIALLY HEAVY EXCEPT FOR THE
NORMAL WETTEST SPOTS IN THE MOUNTAINS. THE RAIN WILL TURN TO
SHOWERS ON WED WITH THE SNOW LEVEL FALLING SHARPLY WED NITE. A
FAIRLY DRY AND COLDER PATTERN WILL BE IN PLACE FOR THU THROUGH EARLY
NEXT WEEK. 19

&&

.AVIATION...WESTERLY FLOW ALOFT WILL GRADUALLY TURN SOUTHWESTERLY
TONIGHT AS UPPER LEVEL TROUGH DIGS SOUTH OFF THE COAST. A STRONG
COLD FRONT WILL MOVE THROUGH THE AREA TONIGHT. AIR MASS MOIST AND
STABLE.

CEILINGS MOSTLY IN THE 1000-2500 FOOT RANGE THIS EVENING WITH SOME
HIGHER CEILINGS NORTH OF KNUW. LOCAL VISIBILITIES 3-5SM IN LIGHT
RAIN. LITTLE CHANGE IN THE CEILINGS AND VISIBILITIES EXPECTED
OVERNIGHT WITH A STRONG COLD FRONT NOT MOVING THROUGH THE AREA UNTIL
AFTER 12Z WEDNESDAY. GUSTY SOUTHERLY WINDS WILL CONTINUE AS WELL
UNTIL AFTER THE COLD FRONT PASSAGE. SLOW IMPROVEMENT ON THE CEILINGS
BEHIND THE COLD FRONT WEDNESDAY AFTERNOON.

STRONG WINDS ALOFT CONTINUING OVERNIGHT WITH SOUTHWEST WINDS 35 TO
45 KNOTS AT 2000 FEET INCREASING TO 60 KNOTS AROUND 5000 FEET. WINDS
ALOFT EASING AFTER 15Z WEDNESDAY.

KSEA...CEILINGS AROUND 2000 FEET THROUGH WEDNESDAY MORNING.
SOUTHWEST WIND 15 TO 20 KNOTS GUSTING TO 30 KNOTS EASING AFTER 12Z
WEDNESDAY TO 10-15 KNOTS. STRONGER WINDS IN THE LOWER LEVELS WILL
KEEP THE POTENTIAL FOR LOW LEVEL WIND SHEAR UNTIL 12Z WEDNESDAY AS
WELL. FELTON

&&

.MARINE...A STRONG COLD FRONT WILL MOVE THROUGH THE WATERS EARLY
WEDNESDAY MORNING WITH THE PARENT 995 MB LOW MOVING INLAND JUST
NORTH OF THE NORTHERN TIP OF VANCOUVER ISLAND. GALE FORCE WINDS ARE
EXPECTED OVER MOST OF THE WATERS UNTIL THE COLD FRONT PASSAGE. WINDS
EASING BEHIND THE FRONT EXCEPT IN THE CENTRAL AND EASTERN STRAIT
WITH A SURGE OF WESTERLIES BEHIND THE FRONT. POST FRONTAL ONSHORE
FLOW WILL RAPIDLY DIMINISH ON WED AFTERNOON AS A BROAD TROUGH OF LOW
PRES DIGS DOWN OVER THE REGION. BY THURSDAY THERE IS THE POTENTIAL
FOR SMALL CRAFT ADVISORY WINDS ON THE COASTAL WATERS. SMALL CRAFT
ADVISORY NORTHERLY FLOW IS POSSIBLE OVER THE NORTHERN WATERS ON SAT
AS HIGH PRES BUILDS OVER BRITISH COLUMBIA AND A LOW DIGS DOWN OFF
THE WASHINGTON COASTLINE. FELTON/SMR

&&

.AVALANCHE...A STRONG WARM FRONT HAS DEVELOPED FURTHER TUESDAY
HELPING TO SLOW THE EASTWARD MOVEMENT. THIS HAS ALLOWED SIGNIFICANT
SNOW TO BE DEPOSITED IN THE PASSES DUE TO COOLING EAST FLOW. HEAVY
SNOW AT WARMING TEMPERATURES ELSEWHERE AND THE IMPENDING CHANGE FROM
SNOW TO RAIN IN THE LOWER CASCADE PASSES IS LEADING TO A
SIGNIFICANTLY INCREASING AVALANCHE DANGER. INCREASING NATURAL
AVALANCHES ARE LIKELY LATER TUESDAY AND TUESDAY NIGHT. AS A RESULT
THE EXISTING AVALANCHE WARNING HAS BEEN EXTENDED TO ALL ZONES ALONG
THE WEST SLOPES OF THE WA CASCADES AND CONTINUES IN THE OLYMPICS.

KRAMER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNING SKOKOMISH RIVER.
     .WIND ADVISORY FOR ALL LOWLAND ZONES EXCEPT THE STRAIT OF JUAN
DE FUCA ZONES TIL 4 AM PST WEDNESDAY MORNING.
    .WINTER STORM WARNING FOR THE NORTH CASCADES THROUGH NOON PST
     WEDNESDAY.
    .WINTER WEATHER ADVISORY FOR THE CENTRAL CASCADES THROUGH 10 PM
     THIS EVENING.
PZ...GALE WARNING COASTAL WATERS...ADMIRALTY INLET AND PUGET SOUND
     AND HOOD CANAL.
     GALE WARNING STRAIT OF JUAN DE FUCA AND NORTHERN INLAND WATERS
     FROM 4 PM PST THIS AFTERNOON UNTIL 4 AM PST WEDNESDAY.
    .SMALL CRAFT ADVISORY FOR STRAIT OF JUAN DE FUCA AND NORTHERN
     INLAND WATERS UNTIL 4 PM PST THIS AFTERNOON.
    .SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS GRAYS HARBOR BAR.

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