High Wind and Strong Wind in Washington, December 17, 2012

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST SUN DEC 16 2012

CORRECTED TO ADD MARINE SECTION.

.SYNOPSIS...A DEEP 974 MB LOW CENTERED ABOUT 100 NM WSW OF CAPE
FLATTERY AT 8 PM WILL MOVE EAST ACROSS THE CENTRAL PUGET SOUND AREA
OVERNIGHT THEN EAST OF THE CASCADES MONDAY MORNING. THE SYSTEM WILL
BRING THE POTENTIAL FOR DAMAGING WINDS ACROSS THE LOWLANDS AND HEAVY
SNOW TO THE MOUNTAINS TONIGHT AND MONDAY. LOOK FOR SHOWERY WEATHER
TO PREVAIL IN THE WAKE OF THE OCCLUDED FRONT THAT WILL MOVE ACROSS
THE REGION MONDAY MORNING. THE SNOW LEVELS WILL ALSO FALL TO NEAR
SEA LEVEL MONDAY NIGHT AS A COLDER AIR MASS SETTLES OVER THE AREA.
HIGHER PRESSURE ALOFT WILL SLOWLY BUILD IN FROM THE WEST DURING THE
DAY TUESDAY.

&&

.SHORT TERM...INFRARED SATELLITE IMAGERY SHOWS WHAT APPEARS TO BE A
974 MB LOW CENTER MAYBE A BIT FARTHER SOUTH THAN EARLIER THOUGHT...
NEAR 47.2N 128.5W. THE LOW WILL MOVE EAST TO NEAR DESTRUCTION ISLAND
BY MIDNIGHT THEN ACROSS WHIDBEY ISLAND OR SO ON ITS TRACK INTO THE
CASCADES BY LATE TONIGHT. THE LOW IS COMPLEX AND MAY HAVE SEVERAL
CENTERS.

A BENT BACK OCCLUSION IS TRYING TO DEVELOP TO THE WEST OF THE LOW.
THIS FEATURE WILL WRAP AROUND AND CLIP THE SOUTHERN HALF OF THE
FORECAST AREA...FROM GRAYS HARBOR COUNTY TO MT RAINIER DURING THE
LATE NIGHT AND MORNING HOURS.

THE UPPER LEVEL DIVERGENCE TO THE NORTHEAST OF A 160 KT JET STREAK
HAS ALLOWED THE LOW TO DEEPEN TODAY. BUT THE JET STREAK IS SINKING
OFF TO THE SOUTHEAST TOWARD FAR SOUTHERN OREGON. SO THE LOW IS
PEAKING NOW AND WILL GRADUALLY SPIN DOWN AS IT MOVES ACROSS THE AREA
LATE TONIGHT AND ACROSS THE CASCADES MONDAY MORNING.

EASTERLY UPSLOPE FLOW AGAINST THE OLYMPICS IN ADVANCE OF THE LOW
COMBINED WITH STRONG PRESSURE FALLS PRODUCED UNEXPECTED HEAVY SNOW
ALONG THE CENTRAL HOOD CANAL AREA WITH A PUBLIC REPORT OF 6 INCHES
IN SEABECK. OTHER REPORTS ACROSS THE HOOD CANAL AREA WERE ON
THE ORDER OF AN INCH OR TWO. A SHORT FUSED WINTER STORM WARNING WAS
ISSUED AND WILL BE MAINTAINED UNTIL THE LOW MOVES BY AND SCOURS OUT
ANY COLD AIR LEFT IN THAT AREA. EARLIER THERE WAS SOME SNOW ON THE
COAST...MIXES TO SNOW THIS EVENING AROUND PORT ANGELES...AND A FEW
REPORTS OF SNOW JUST NORTH OF BLAINE. THE SNOW LEVEL PER DUAL POL
RADAR AT CAMANO ISLAND IS NOW 1350 FT AND IS NEAR 2500 FEET ON THE
COAST...SO SNOW REPORTS SHOULD BECOME MORE RARE OVER THE NEXT FEW
HOURS...EXCEPT AROUND CENTRAL HOOD CANAL UNTIL ABOUT 2 AM. EXPECT
THE SNOW LEVEL IN THE INTERIOR TO RISE TO AROUND 2500 FT AS THE LOW
PASSES LATE TONIGHT THEN FALL BACK TO 1500 FT MON AFTERNOON AND DOWN
TO NEAR SEA LEVEL LATE MON NIGHT.

LATER TONIGHT INTO MONDAY MORNING...STRONG ONSHORE FLOW WITH LIKELY
HIGH WIND SOUTH AND COAST AND THROUGH THE STRAIT CONTINUES MON
MORNING WITH CONDITIONS GRADUALLY IMPROVING DURING THE DAY. THE
STRONGEST GUSTS ARE LIKELY ALONG THE CENTRAL COAST WITH THE BENT
BACK OCCLUSION AND ALONG THE WEST SIDE OF WHIDBEY ISLAND WHERE
PRESSURE RISES CAUSING FUNNELING OF THE WEST WIND THROUGH THE STRAIT
HIT.

HEAVY SNOW AND STRONG WINDS WILL KEEP BLIZZARD CONDITIONS GOING OVER
THE OLYMPICS AND THE CENTRAL CASCADES THROUGH EARLY AFTERNOON AT
LEAST. WITH SLIGHTLY LIGHTER WINDS OVER THE NORTH CASCADES...JUST
WINTER STORM CONDITIONS THERE. 1 TO 3 FT OF SNOW IS EXPECTED TONIGHT
THROUGH MON NIGHT IN THE CASCADES WITH ABOUT 1-1.5 FT IN THE
OLYMPICS.

WILL BE REFRESHING THE WIND AND WINTER STATEMENTS AS NEEDED OVER THE
NEXT SEVERAL HOURS AS CONDITIONS CHANGE.

SHOWERS ARE EXPECTED ACROSS THE LOWLANDS MONDAY AFTERNOON AND MONDAY
NIGHT. SNOWFALL WILL NOT EASE UNTIL MONDAY NIGHT IN THE CASCADES
GIVEN THE OROGRAPHIC FLOW. SNOW LEVELS WILL BE VERY LOW...500 FEET
OR LESS...SO THE LOWLANDS COULD VERY WELL SEE A MIX OF RAIN/SNOW
SHOWERS MONDAY NIGHT THROUGH TUESDAY. HIGHS/LOWS TUESDAY WILL ONLY
BE IN THE 30S. IF ANY CONVERGENCE ZONE FORMS THEN SOME LOCALIZED
LOWLAND ACCUMULATION IS POSSIBLE. ALBRECHT

.LONG TERM...FROM THE AFTERNOON FORECAST DISCUSSION...A WARM FRONT
AND TRAILING COLD FRONT WILL BRING MORE RAIN AND MOUNTAIN SNOW TO
THE AREA WEDNESDAY. MODELS HAVE SHIFTED TOWARD SHOWING A PERIOD OF
COOLER AND SHOWERY WEATHER THURSDAY THROUGH NEXT WEEKEND. THIS MEANS
SNOW LEVELS MAY BE LOWER THAN PREVIOUSLY THOUGHT...GOOD NEWS FOR
SNOW IN THE MOUNTAINS.  MERCER

&&

.HYDROLOGY...FROM THE AFTERNOON FORECAST DISCUSSION...FLOODING IS
NOT EXPECTED ON AREA RIVERS THROUGH THE END OF THE WEEK. MERCER

&&

.AVIATION...A DEEP SURFACE LOW ABOUT 100 NM OFF THE NORTH WASHINGTON
COAST AT 03Z WILL PUSH A STRONG FRONT THROUGH WESTERN WASHINGTON
OVERNIGHT. THE DEEP SURFACE LOW WILL BE INTO THE FRASER RIVER VALLEY
OF SOUTHWEST B.C. BY DAYBREAK. A SIGNIFICANT SURGE OF WINDS WILL
OCCUR AS THE LOW MOVES THROUGH MONDAY MORNING. STRONG ONSHORE
GRADIENTS BEHIND THE LOW WILL LEAD TO VERY WINDY CONDITIONS ACROSS
THE INTERIOR DURING THE EARLY MORNING HOURS...BEFORE GRADUALLY
EASING IN THE AFTERNOON. STEADY PRECIPITATION HAS ALREADY
TRANSITIONED TO SHOWERS AT THE COAST AT 04Z...AND STRATIFORM PRECIP
WILL TURN OVER TO SHOWERS OVER THE INTERIOR OVERNIGHT.

KSEA...RAIN TURNING TO SHOWERS OVERNIGHT AND BECOMING QUITE WINDY
FOR SEVERAL HOURS FROM ABOUT 4-10AM...AND THEN A PSCZ SHOULD SET UP
NORTH OF SEATTLE. MVFR CEILINGS OVERNIGHT...OCCASIONALLY BECOMING
VFR AS PRECIP TURNS MORE SHOWERY. COLD AIR ALOFT WILL MOVE IN BEHIND
THIS SYSTEM. SOME WET SNOW COULD MIX IN TONIGHT AND ON MONDAY. AS
THE AIR MASS BECOMES UNSTABLE WE MAY SEE ICE PELLET OR GRAUPEL
SHOWERS. 27

&&

.MARINE...A DEEP 974 MB LOW OVER THE COASTAL WATERS WILL SLOWLY FILL
AS IT MOVES EAST THROUGH THE INLAND WATERS LATE TONIGHT AND ACROSS
THE CASCADES MONDAY MORNING. STORM WARNINGS ARE IN EFFECT FOR THE
COAST AND THROUGH THE STRAIT WHILE GALE WARNINGS ARE IN EFFECT FOR
THE REMAINDER OF THE INLAND WATERS. MARINERS SHOULD STAY OFF THE
WATERS.

VERY STRONG ONSHORE FLOW BEHIND THE LOW WILL SLOWLY RELAX MONDAY
AFTERNOON. ALBRECHT

&&

.AVALANCHE...A FAST APPROACHING VERY STRONG STORM WILL CAUSE AN
SIGNIFICANTLY INCREASING AVALANCHE DANGER LATE SUNDAY THROUGH EARLY
MONDAY. VERY STRONG WINDS AND HEAVY SNOWFALL AT SLIGHTLY WARMING
TEMPERATURES WILL ADD SIGNIFICANT LOADS OVER THE 1-3 FEET OF LOW
DENSITY SNOW RECEIVED THIS PAST WEEK. A HIGH AVALANCHE DANGER SHOULD
DEVELOP ON MOST STEEP SLOPES BY LATER SUNDAY AND SUNDAY NIGHT
THEREFORE BACKCOUNTRY TRAVEL IN AVALANCHE TERRAIN IS NOT RECOMMENDED
LATER SUNDAY AFTERNOON THROUGH EARLY MONDAY. AN AVALANCHE WATCH IS
CURRENTLY IN EFFECT AND WILL BE UPGRADED TO A WARNING LATER SUNDAY.
PLEASE SEE NWAC.US FOR DETAILS. KRAMER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...BLIZZARD WARNING IN EFFECT FOR THE CENTRAL CASCADES AND
       OLYMPICS THROUGH 6 PM MONDAY.

     WINTER STORM WARNING IN EFFECT FOR THE NORTH CASCADES THROUGH
       6 PM MONDAY.

     WINTER STORM WARNING FOR THE HOOD CANAL AREA THROUGH 4 AM
       MONDAY.

     HIGH WIND WARNING IN EFFECT FOR THE NORTH AND CENTRAL COAST
       THROUGH 4 PM MONDAY.

     HIGH WIND WARNING FOR THE WESTERN AND EASTERN STRAIT OF JUAN
       DE FUCA...ADMIRALTY INLET...SAN JUANS ISLANDS...WESTERN
       SKAGIT COUNTY...TACOMA AND VICINITY...AND THE LOWER CHEHALIS
       VALLEY THROUGH 4 PM MONDAY AFTERNOON.

     HIGH SURF ADVISORY CENTRAL AND NORTH COAST.

     COASTAL FLOOD ADVISORY FOR MINOR TIDAL OVERFLOW COAST TONIGHT
       AND INTERIOR WATERS MONDAY MORNING.

PZ...STORM WARNING COASTAL WATERS AND STRAIT OF JUAN DE FUCA.

     GALE WARNING ALL REMAINING WATERS.

     SMALL CRAFT ADVISORY SEVERE BAR CONDITIONS GRAYS HARBOR BAR.

&&

WWW.WEATHER.GOV/SEATTLE

FOR THE GRAPHICAL AFD...VISIT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML