Avalanche in Washington, February 24, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
230 PM PST SAT FEB 24 2007

.SYNOPSIS...A COLD UPPER LEVEL TROUGH WILL REMAIN OFF THE COAST
THROUGH MIDWEEK...BRINGING COOL AND SHOWERY WEATHER.

&&

.SHORT TERM...SHOWERS HAVE TAPERED OR MOVED INTO THE CASCADES. TEMPS
ARE MAINLY IN THE MID 40S THOUGH THERE IS A COLD POCKET IN KITSAP
AND MASON COUNTIES. SHOWERS WILL CONTINUE TONIGHT AND INDEED FOR
MOST OF THE WEEK. IN LIGHT OF THE COLD POCKET WEST OF PUGET
SOUND...HAVE KEPT A MIX OF RAIN AND SNOW IN THE SHOWERS THERE.
MODERATE TO STRONG SE WINDS HAVE SCOURED OUT THE COLD AIR ELSEWHERE
AND SHOWERS TONIGHT SHOULD BE JUST RAIN. SNOW IN THE MOUNTAINS OF
COURSE AND IN COORDINATION WITH NWAC WILL KEEP THE SNOW ADVISORY
GOING UNTIL 10 PM TONIGHT FOR 4-6 MORE INCHES.

BUT THE SHOWERS CONTINUE...THE COLD AIR REMAINS...WITH A 520 DM LOW
SPINNING JUST OFF THE COAST FOR THE NEXT TWO DAYS THEN MOVING INLAND
TUESDAY. EACH NIGHT THE TEMPS COULD BE COLD ENOUGH FOR SNOW SHOWERS
NEARLY EVERYWHERE. HAVE KEPT THEM OUT OF THE SEATTLE METRO ZONE IN
DEFERENCE TO URBAN HEAT ISLAND EFFECT BUT SEE NO REASON IT WOULD NOT
SNOW NEARLY ANYWHERE ELSE. SO HAVE MIXED WITH SNOW WORDING EACH
NIGHT STARTING SUNDAY NIGHT AND CONTINUING THROUGH TUESDAY NIGHT.

DAYTIME TEMPS WILL REACH THE MID 40S SO MOST SNOW SHOWERS SHOULD END
BY MID MORNING. AT THIS TIME NOT EXPECTING ANY SIGNIFICANT
ACCUMULATIONS BUT A GOOD SHOWER IN A COLD POCKET COULD DROP 3 INCHES
HERE OR THERE. BURKE

.LONG TERM...LITTLE CHANGE WEDNESDAY AS UPPER TROUGH TAKES THE SLOW
TRAIN EAST THROUGH CWA. SLOW INCREASE IN HEIGHTS AFTER THAT WITH
WHAT LOOKS LIKE A SOLID RAIN EVENT SHAPING UP FOR FRIDAY. MORE
SHOWERS SATURDAY. BURKE

&&

.AVIATION...THE WARM FRONT CONTINUES TO MOVE TO THE EAST ACROSS THE
PUGET SOUND REGION THIS AFTERNOON AND ACROSS THE CASCADES THIS
EVENING. A BREAK IN CLOUDS STARTING TO SHOW ALONG THE COAST AND IS
EXPECTED TO MOVE INLAND LATER THIS EVENING. STILL PLENTY OF SHOWERS
OFFSHORE TO DEAL WITH TONIGHT AND SUNDAY AS UPPER LEVEL LOW REMAINS
TO THE WEST OF VANCOUVER ISLAND. EXPECT GENERAL CONDITIONS TO REMAIN
MOSTLY VFR OVERNIGHT WITH MVFR CONDITIONS IN HEAVIER SHOWERS. SUNDAY
APPEARS SHOWERY WITH A FEW SUNBREAKS AT TIMES AND NOT AS BREEZY. FOR
SEA-TAC TONIGHT...CIGS GENERALLY 030-045. SOME SHOWERS AROUND WITH
POSSIBLE CIGS 020-030 AND MIN VSBY 5SM -SHRA. WINDS TO REMAIN
SOUTHERLY 7 TO 12 MPH.      PRANGE

.AVALANCHE...PLENTY OF LOW DENSITY SNOW RECEIVED DURING PAST FEW
DAYS IS BEING LOADED AND STRESSED BY INCREASINGLY DENSE AND SLIGHTLY
WARMER WIND DRIVEN SNOWFALL. THOUGH VISIBILITY POOR, FIELD REPORTS
FROM SKI PATROL INDICATE RAPIDLY GROWING CORNICES AND SOME EASY SKI
TRIGGERED SLABS RELEASING UP TO 2-3 FEET, MAINLY IN WIND AFFECTED
TERRAIN. THIS SNOWPACK SENSITIVITY APPEARS TO BE VERIFYING AVALANCHE
WARNING FOR INCREASINGLY UNSTABLE SNOWPACK, ESPECIALLY ABOVE 4-5000
FEET. AS WE TURN MORE SHOWERY LATER SATURDAY, EXPECT SLIGHT DECREASE
IN DANGER AND WILL ALLOW WARNING TO EXPIRE TONIGHT. HOWEVER, WITH
MORE SNOWFALL ACCOMPANYING ANOTHER, THOUGH WEAKER, SYSTEM SUNDAY,
EXPECT ONLY A LIMITED DECREASE IN THE DANGER THROUGH THE WEEKEND
WITH DANGER LEVELS HOVERING JUST BELOW WARNING CRITERIA. NO DOUBT
THERE IS SOME QUALITY POWDER OUT THERE, JUST HOPE THAT BACK COUNTRY
TRAVELERS ADJUST THEIR ROUTES, AND BE A LITTLE MORE CONSERVATIVE FOR
AWHILE. FOR DETAILS SEE WWW.NWAC.US.    MOORE

THIS SECTION IS PROVIDED IN PARTNERSHIP WITH THE USDA FOREST SERVICE
NW WEATHER AND AVALANCHE CENTER.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
    ...GALE WARNING FOR THE COAST...WEST ENTRANCE...EAST ENTRANCE...
        ADMIRALTY INLET...AND THE NORTHERN INLAND WATERS...
    ...SMALL CRAFT ADVISORY CENTRAL STRAIT...PUGET SOUND AND HOOD
       CANAL
    ...SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS GRAYS
       HARBOR BAR...

WEATHER.GOV/SEATTLE