Winter Weather Advisory 13, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
250 PM PST SAT JAN 28 2012

.SYNOPSIS...A FRONT WILL BRING RAIN AND WIND TONIGHT AND SUNDAY. A
SECOND FRONTAL SYSTEM WILL BRING RAIN AROUND TUESDAY. HIGH PRESSURE
WILL BRING DRIER WEATHER TOWARD THE END OF THE WEEK.

&&

.SHORT TERM...A FRONTAL SYSTEM WILL BRING RAIN TONIGHT AND
SUNDAY...CHANGING TO SHOWERS SUNDAY EVENING. RAIN IS EXPECTED TO
DEVELOP AT THE COAST AROUND MIDNIGHT TONIGHT AND SPREAD OVER THE
INTERIOR IN THE EARLY MORNING HOURS. THE PRECIPITATION APPEARS TO BE
COMING IN TWO WAVES...THE WARM FRONT IN THE EARLY MORNING
HOURS...AND THE TRAILING COLD FRONT IN THE AFTERNOON.

SNOW LEVELS WILL BE BETWEEN 6000 AND 7000 FEET SUNDAY BUT SOMEWHAT
LOWER OVER THE NORTH CASCADES. THE SNOW LEVEL WILL BE AROUND 4000
FEET AT MOUNT BAKER BUT COULD RISE TO 5000 FEET FOR PART OF SUNDAY
WITH THE WARM FRONT. THIS WILL MAKE SNOW AMOUNT FORECASTING
CHALLENGING. A WINTER WEATHER ADVISORY WILL BE ISSUED FOR THE NORTH
CASCADES ABOVE 4000 FEET TO HANDLE THIS SITUATION.

THERE WILL ALSO BE SOME BREEZY TO LOCALLY WINDY CONDITIONS
WITH THIS FRONTAL SYSTEM SUNDAY BUT PROBABLY NOT QUITE ADVISORY
LEVELS.

MONDAY LOOKS LIKE A RATHER UNEVENTFUL DAY IN BETWEEN FRONTS. THE AIR
MASS WILL REMAIN MOIST WITH MODERATE ONSHORE FLOW WHICH SHOULD BE
ENOUGH TO KEEP SHOWERS AROUND. ANOTHER FRONT WILL BRING RAIN AGAIN
TUESDAY. SCHNEIDER

.LONG TERM...LONG RANGE MODELS ARE IN PRETTY GOOD AGREEMENT SHOWING
DECREASING SHOWERS WEDNESDAY AND THEN DRY WEATHER THURSDAY THROUGH
SATURDAY WITH AN UPPER LEVEL RIDGE IN CONTROL. POPS FOR THIS TIME
FRAME HAVE BEEN ADJUSTED DOWN INTO THE CHANCE CATEGORY FOR NOW. IF
FUTURE MODELS RUNS REMAIN CONSISTENT...ALL MENTION OF RAIN CAN
PROBABLY BE REMOVED FROM THE FORECAST. SCHNEIDER

&&

.HYDROLOGY...A FRONTAL SYSTEM WILL BRING BETWEEN 1.5 AND 3.5 INCHES
OF RAIN TO THE MOUNTAINS TONIGHT THROUGH SUNDAY NIGHT. AT THE SAME
TIME...SNOW LEVELS WILL RISE TO BETWEEN 6000 AND 7000 FEET OVER MUCH
OF THE AREA TONIGHT AND SUNDAY BEFORE FALLING TO AROUND 3500 FEET
SUNDAY NIGHT.

THE COMBINATION OF HEAVY RAIN AND HIGH SNOW LEVELS IS EXPECTED TO
DRIVE THE SKOKOMISH RIVER IN MASON COUNTY TO SLIGHTLY ABOVE FLOOD
STAGE SUNDAY NIGHT. A FLOOD WATCH IS IN EFFECT TO COVER THIS FOR NOW.

OTHER RIVERS FLOWING OFF THE OLYMPICS AND RIVERS FLOWING OFF THE
CASCADES SHOULD ALSO SEE SIGNIFICANT RISES SUNDAY INTO MONDAY. AT
THIS TIME NO RIVERS ARE EXPECTED TO REACH FLOOD STAGE BUT SOME MAY
COME WITHIN A FOOT OR TWO OF FLOOD STAGE...ESPECIALLY IF MORE RAIN
FALLS THAN CURRENTLY FORECAST.

OTHERWISE......FLOODING IS NOT EXPECTED THE NEXT 7 DAYS. SCHNEIDER

&&

.AVIATION...W FLOW ALOFT BECOMING SW TNGT AND SUN WITH INCREASING
MOISTURE AS A FNTL SYS MOVES SLOWLY OVER THE REGION. CIGS WILL BE
LOWEST N PART WITH SOME AREAS OF RAIN...HIGHER CIGS SOUTH PART OF
WRN WA. SFC PRES GRADIENTS WILL INCREASE THIS EVENING AS THE WARM
FRONT APPROACHES THE COAST. A COLD FRONT WILL MOVE THRU SUNDAY
AFTERNOON. AIR MASS IS STABLE WITH MOISTURE INCREASING...RAIN AT
TIMES NW COAST TODAY AND TNGT...RAIN DEVELOPING OVER THE REST OF WRN
WA AFTER MIDNIGHT TNGT. THE MTNS WILL BE OBSCURED THRU SUN.  19

KSEA...21Z TAF LOOKS GOOD NOT PLANNING ON CHANGING IT MUCH AT 00Z.

&&

.MARINE...A WARM FRONT WILL APPROACH THE COAST TONIGHT...INCREASING
SOUTHERLY WINDS OVER ALL WATERS. GALES ARE FORECAST TO DEVELOP FROM
ADMIRALTY INLET NORTH. THE COLD FRONT WILL PASS SUNDAY AND MODERATE
TO STRONG ONSHORE FLOW WILL FOLLOW MONDAY. ANOTHER FRONT FOLLOWS
TUESDAY. FCSTS HAVE NOT CHANGED MUCH FOR THE 3PM FCST PACKAGE. 19

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER WEATHER ADVISORY NORTH CASCADES ABOVE 4000 FEET THIS
     EVENING THROUGH SUNDAY NIGHT.
    .FLOOD WATCH MASON COUNTY SUNDAY MORNING THROUGH MONDAY MORNING.
PZ...GALE WARNING NORTHERN COASTAL WATERS...ENTRANCES TO THE
     STRAIT OF JUAN DE FUCA...AND ADMIRALTY INLET.
    .SMALL CRAFT ADVISORY ALL OTHER WATERS EXCEPT CENTRAL STRAIT.

WWW.WEATHER.GOV/SEATTLE

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