Gale Watch 17, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
910 PM PST THU MAR 8 2012

.SYNOPSIS...A COLD FRONT WILL MOVE ONTO THE COAST ON FRIDAY THEN
PUSH INLAND AND WEAKEN FRIDAY EVENING. ANOTHER FRONT WILL MOVE
ACROSS THE AREA LATER SATURDAY. A DEEP UPPER LEVEL TROUGH WILL BRING
COOL AND WET WEATHER TO THE AREA SUNDAY THROUGH THE MIDDLE OF NEXT
WEEK.

&&

.SHORT TERM...A RIDGE OF HIGH PRESSURE AT THE SURFACE AND ALOFT OVER
EASTERN WASHINGTON GAVE OFFSHORE FLOW AND NICE EARLY SPRING WEATHER
TO THE AREA. LOWER TO MID 60S WERE COMMON ALONG THE COAST AND IN THE
INTERIOR FROM ABOUT SEATTLE SOUTHWARD WHILE MID AND UPPER 50S
DOMINATED OVER THE INTERIOR NORTH OF SEATTLE.

ONSHORE FLOW IS RAPIDLY INCREASING AHEAD OF AN INCOMING COLD FRONT
THAT IS SITTING OVER THE OFFSHORE WATERS. WITH THIS FRONT STRATUS
AND BREEZY SOUTH WINDS HAVE SPREAD NORTHWARD ALONG THE COAST. IN THE
INTERIOR HIGH CLOUDS AND SOUTH WINDS ARE INCREASING SOMEWHAT AS
SOUTHERLY PRES GRADIENTS RISE. WITH THE INCREASE IN CLOUD COVER
TONIGHT AND THE INCREASING SOUTHERLY BREEZES...TEXT AND GRIDDED
FORECASTS WERE UPDATED FOR THE TONIGHT PERIOD TO RAISE MINIMUM
TEMPERATURES A FEW DEGREES OVERNIGHT AND TO INCREASE POPS LATER
TONIGHT ALONG THE COASTAL ZONES.

WHILE THE FRONT WILL BE WEAKENING AS IT PUSHES INLAND...IT WILL BE
ACCOMPANIED BY CLOUDS AND SOME LIGHT RAIN. RAIN WILL SPREAD ONSHORE
AND INTO THE NORTHERN INTERIOR DURING THE MORNING HOURS THEN INTO
THE INTERIOR FROM ABOUT SEATTLE SOUTHWARD MAINLY IN THE AFTERNOON.
POPS WILL BE LOWER TO THE LEE OF THE OLYMPICS WHERE SOUTHWESTERLY
FLOW ALOFT INTERACTS WITH THE TERRAIN. PRECIPITATION AMOUNTS OVER
THE NORTH CASCADES AS FORECAST BY THE MESOSCALE MODELS SUGGEST THAT
LOCALLY HEAVY SNOW COULD FALL AT LOCATIONS LIKE MOUNT BAKER ABOVE
ABOUT 3500 TO 4000 FEET. THE WINTER STORM WARNING FOR THE NORTH
CASCADES WILL BE MAINTAINED FOR NOW.

ANOTHER FRONT...CURRENTLY JUST WEST OF 150W...WILL MOVE ONTO THE
COAST SATURDAY AFTERNOON AND INTO THE INTERIOR BY SATURDAY EVENING.
THIS FRONT WILL BRING SHOWERS TO THE LOWLANDS AND ANOTHER ROUND OF
SNOW TO THE MOUNTAINS...MOST LIKELY ADVISORY AMOUNTS OVER THE
OLYMPICS AND NORTH CASCADES.

A COLD UPPER LEVEL TROUGH WILL SETTLE OVER THE AREA ON SUNDAY FOR
MORE SHOWERS AND COOLER WEATHER. SNOW LEVELS DROP TO ONLY A FEW
HUNDRED FEET SUN NIGHT AND SOME HIGHER HILLTOP AREAS IN THE LOWLANDS
MAY SEE A RAIN/SNOW MIX. A LACK OF ORGANIZATION AND GENERALLY
ONSHORE FLOW SUGGESTS THAT ANY SNOW THAT DOES FALL ON THE HIGHER
LOWLAND HILLS WILL PRODUCE SPOTTY LIGHT ACCUMULATIONS...OR MORE
LIKELY JUST A MIX OR WET SNOW. ALBRECHT

.LONG TERM...PREVIOUS LONG TERM DISCUSSION FOLLOWS...AN ACTIVE
WEATHER PATTERN WILL CONTINUE ACROSS THE PAC NW THROUGH EARLY NEXT
WEEK. MONDAY LOOKS ESPECIALLY WINDY IF THE LATEST GFS AND ECMWF
VERIFY. BOTH MODELS BRING A 980 MB LOW INTO WESTERN WA MON AFTERNOON
- HIGH WIND POSSIBLE ALONG THE COAST AND NORTH INTERIOR. ANOTHER WET
SYSTEM WILL ARRIVE ON WED...WITH MORE SHOWERS THU AND FRI. TOUGH TO
TIME EVERYTHING COMING IN BUT WILL KEEP HIGH POPS THROUGH THE
EXTENDED FORECAST FOR NOW. TEMPS WILL ALSO REMAIN NEAR TO BELOW
NORMAL. 33

&&

.HYDROLOGY...THE THREAT OF RIVER FLOODING DURING THE NEXT SEVEN DAYS
IS LOW. 33

&&

.AVIATION...AN UPPER RIDGE OVER THE REGION WILL CONTINUE MOVING
E...ALLOWING AN UPPER TROF OFFSHORE TO APPROACH THE AREA. INCREASING
SW FLOW ALOFT AND LOW LEVEL SLY FLOW. ANTICIPATE CIGS OF 1-2K FT
OVER THE COAST OVERNIGHT. ACROSS THE INTERIOR...VFR CONDITIONS WILL
PERSIST BUT CIGS WILL GRADUALLY LOWER OVERNIGHT.

KSEA...VFR CONDITIONS WILL PREVAIL OVERNIGHT.

&&

.MARINE...
A WEAK COLD FRONT OFFSHORE WILL MOVE ACROSS THE AREA ON FRI. EXPECT
A STRONGER FRONTAL SYSTEM TO IMPACT THE AREA ON SATURDAY. THERE IS
THE POSSIBILITY THAT A NEAR 980 MB LOW WILL REACH VANCOUVER ISLAND
ON MON FOR GALE FORCE WINDS ACROSS THE AREA.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER STORM WATCH FROM FRIDAY AFTERNOON THROUGH LATE FRIDAY
     NIGHT FOR WEST SLOPES NORTHERN CASCADES AND PASSES ABOVE 3500
     FEET.

PZ...SMALL CRAFT ADVISORY IN EFFECT FOR ALL WATERS EXCEPT THE
     WESTERN AND CENTRAL STRAIT OF JUAN DE FUCA.
&&

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