Heavy Snow in Washington, December 18 to 20, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
845 PM PST TUE DEC 18 2007

.SYNOPSIS...SHOWERS WILL CONTINUE TONIGHT. RAIN AND WIND WILL
INCREASE WEDNESDAY AS A STRONG COLD FRONT MOVES ASHORE. HEAVY SNOW
WILL FALL IN THE MOUNTAINS. THURSDAY WILL BE SHOWERY AND FRIDAY WILL
LIKELY BE DRY. THE NEXT STORM WILL ARRIVE SATURDAY AFTERNOON.

&&

.SHORT TERM...SHOWERS CONTINUE THIS EVENING WITH NORTHWEST INTERIOR
AND COAST GETTING THE BRUNT. THERE IS ALSO SNOW FALLING IN THE
MOUNTAINS. IN FACT MOUNT BAKER HAS RECEIVED ANOTHER 12 INCHES SINCE
9 AM. WILL KILL THE SNOW ADVISORY AND JUST GO WITH THE HEAVY SNOW
WARNING...AND WILL ALSO EXTEND HEAVY SNOW WARNING INTO THURSDAY.
GUSTY WINDS THIS EVENING SHOULD STAY IN THE 20G30 MPH RANGE AND
SHOULD DIMINISH AFTER MIDNIGHT.

WEDNESDAY WILL BE WET AND WINDY IN WESTERN WASHINGTON. RAIN WILL
SPREAD OVER THE AREA DURING THE DAY AND TURN TO SHOWERS IN THE
AFTERNOON. THE MOUNTAINS WILL CONTINUE TO GET HEAVY SNOW...WITH
PROBABLY 1-2 FEET NEW SNOW WEDNESDAY AND ANOTHER FOOT OR SO ON
THURSDAY. WINDS SHOULD BE JUST BELOW HIGH WIND CATEGORY. MM5-GFS HAD
A FEW SPOTS IN THE 1000MB WIND FIELD WITH 35 KNOTS...BOTH ON THE
COAST AND OVER THE NW INTERIOR. THESE WERE CONCENTRATED IN THE
12Z-15Z TIME. WOULD NOT RULE OUT A FEW REPORTS OF HIGH WIND DURING
THIS PERIOD WHEN THE PRESSURE GRADIENT IS STRONGEST. BUT WILL STAY
WITH THE WIND ADVISORY FOR NOW. PUGET SOUND AREA IN PARTICULAR WILL
PROBABLY NOT SEE WINDY CONDITIONS UNTIL THE AFTERNOON.

SHOWERS TAPER THURSDAY...AND THURSDAY NIGHT LOOKS PRETTY DRY. BURKE

LONG TERM...PREVIOUS DISCUSSION...LOOKS LIKE WE MAY SEE A BIT OF A
BREAK IN THE WEATHER ON FRIDAY AS AN UPPER LEVEL RIDGE SHIFTS EAST
OVER THE AREA. HOWEVER...THIS BREAK WILL BE BRIEF AS YET ANOTHER
SYSTEM HEADS TOWARD THE NORTHWEST. LOOKS LIKE THIS NEXT FRONT WILL
PASS THROUGH WESTERN WA LATE FRIDAY INTO SATURDAY...ALTHOUGH EXACT
TIMING IS STILL IN QUESTION AS THE EURO IS ABOUT 12 HRS FASTER THAN
THE GFS. SHOWERS ON SUNDAY...THEN ANOTHER SYSTEM HEADING TOWARD THE
QUEEN CHARLOTTES SUNDAY EVENING INTO MONDAY BRINGING MORE WET
WEATHER TO THE AREA. AGAIN...THE EURO IS MUCH FASTER. CHRISTMAS DAY
EURO HAS DEEP UPPER LEVEL TROUGH THROUGH THE WEST WHILE GFS HAS
NEARLY ZONAL FLOW. WILL JUST STICK WITH SHOWERS LIKELY FOR NOW. 33

&&

.AVIATION...LOW PRESSURE CENTER HAS NOW MOVED INLAND OVER SRN B.C.
WITH A QUICK ONSHORE SURGE OF WIND. WIND SHOULD HELP TO LIFT FOG AND
CIGS BELOW 010 OUT THE FEW PLACES WHERE THOSE CONDITIONS
REMAIN...SUCH AS KBLI. AFTER 08Z...AN OFFSHORE WEATHER SYSTEM WILL
START TO HAVE MORE INFLUENCE...SENDING A FRONT ACROSS WRN WA LATE
WED MORNING. LOOKING FOR A PERIOD OF SOMEWHAT STRONG SOUTHERLIES TO
ACCOMPANY THE WED MORNING FRONT. GOOD MIXING WILL LEAD TO CIGS MOST
COMMONLY IN THE 015-025 RANGE.

KSEA...SOUTHWESTERLY SURGE OF WIND UNDERWAY BEHIND A LOW CENTER THAT
HAS MOVED INTO SRN B.C.. GOOD MIXING LIFTED OUT THE LOWEST CIGS UP
TO NEAR 015. ANOTHER FRONT WILL CROSS KSEA AROUND 18Z WED. THIS WILL
BE ACCOMPANIED BY STRONG WINDS ALOFT...21060KT AT 5000 FT AND
19045KT AT 2000 FT...PEAKING AROUND 18Z. CIGS AND VSBYS WILL ALSO BE
LOWEST IN RAIN AROUND THE FROPA. POST-FRONTAL SHOWERY PATTERN
CONTINUES WED AFTERNOON WITH CIGS BOUNCING AROUND 020-030. HANER

&&

.MARINE...WESTERLY AND SOUTHWESTERLY ONSHORE SURGE UNDERWAY BEHIND A
LOW CENTER THAT HAS MOVED INTO SRN B.C.. OVERNIGHT...PRES GRADIENTS
WILL LEAN BACK OFFSHORE IN ADVANCE OF ANOTHER FRONT THAT WILL REACH
THE COAST AROUND THE MIDDLE OF WED MORNING. STRONG SOUTHERLIES WILL
ACCOMPANY THE FRONT WITH GALES EXPECTED OVER ALL WATERS EXCEPT THE
CENTRAL STRAIT. LOOKING FOR HIGH-END GALES ALONG THE COAST AND FOR
THE NORTH INTERIOR AND LOW-END GALES FOR PUGET SOUND...PEAKING
AROUND THE TIME OF FROPA. FROPA WILL REACH THE COAST AROUND 8 AM AND
THE INLAND WATERS AROUND 11 AM. HANER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
.HEAVY SNOW WARNING FOR THE OLYMPICS AND CASCADES THROUGH THU.
.WIND ADVISORY FOR ALL LOWLANDS EXCEPT COAST AND EAST STRAIT.
.GALE WARNING ALL WATERS EXCEPT CENTRAL STRAIT OF JUAN DE FUCA.
.SMALL CRAFT ADVISORY CENTRAL STRAIT.
.SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.