Debris Flows in Washington, January 17 to 19, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
920 AM PST SUN JAN 17 2010

.SYNOPSIS...A STORM SYSTEM DEVELOPING OFF THE SOUTHERN OREGON COAST
WILL DEEPEN AND MOVE NORTH THROUGH EARLY MONDAY BRINGING RAIN AND
WINDS TO THE REGION.  FOLLOWING THAT A SERIES OF STORMS WILL AFFECT
THE WEST COAST...EACH ONE A LITTLE FURTHER SOUTH THEN THE PREVIOUS
ONE.  A COOLER MORE SHOWERY REGIME IS EXPECTED AFTER THE MIDDLE OF
THE WEEK.

&&

.SHORT TERM...WE HAVE A BIT OF A BREAK AT THE MOMENT AS THE AIR MASS
RELOADS.  A FRONT SWUNG THROUGH EARLIER WITH THE STEADY RAIN HAVING
PRETTY MUCH ENDED.  THERE ARE A FEW BRIEF SHOWERS FLOATING
AROUND...BUT THE NEXT ROUND OF STEADY RAINS WILL HOLD OFF UNTIL
LATER IN THE DAY.  TEMPERATURES HAVE JUMPED SEVERAL DEGREES THIS
MORNING WITH THE WIND AND THE BREAK IN THE RAIN SO HAD TO ADJUST
THAT AS WELL.

THE NEXT ITEM OF INTEREST IS A DEVELOPING LOW THAT IS ROUNDING THE
BASE OF THE TROUGH OFF THE SOUTHERN OREGON COAST.  THIS STORM WILL
DEEPEN THROUGH THE DAY AS IT BEGINS TO HEAD NORTH.  WATER VAPOR
IMAGERY SHOWS A NICE DARK SLOT ON THE BACK SIDE OF THIS FEATURE SO
DEEPENING IS ONGOING AND IT ALSO SHOWS THE DUEL LOW NATURE OF THE
SYSTEM.  DEEPENING IS EXPECTED TO CONTINUE OVER THE NEXT 18 HOURS
THEN AS IT MOVES INTO OUR NEIGHBORHOOD IT SHOULD BEGIN THE FILLING
PROCESS ALTHOUGH IT WILL STILL BE RATHER DEEP WITH A STRONG PRESSURE
GRADIENT BETWEEN IT AND WESTERN WASHINGTON.

WHAT IS EXPECTED WITH THIS STORM...RAIN SPREADING NORTH ACROSS THE
AREA LATER TODAY.  THE WESTPORT PROFILER SHOWED THE SNOW LEVEL
RISING WHILE IT WAS RAINING AND AT THE LAST OB WAS OVER 5000 FEET SO
RAIN WILL BE THE RULE FOR THE MOUNTAINS AS WELL.  THE BIGGEST
CONCERN WITH THE SYSTEM IS HOW MUCH WIND WE WILL END UP WITH.  EVEN
THROUGH THE CENTRAL PRESSURE OF THE STORM WILL BE LOW...AROUND 970
MB...THE CENTER IS WELL OFFSHORE WHICH IS A STRIKE AGAINST IT.  THE
MODELS DO INDICATE THE BENT BACK OCCLUSION WILL WRAP AROUND THE
UNDERSIDE OF THE STORM AND MOVE ACROSS THE REGION EARLY MONDAY
MORNING WHICH WILL SERVE TO ENHANCE THE WINDS OVER THE REGION.  AT
THIS POINT THE PRIMARY LAND TARGETS ARE THE COAST...WESTERN
STRAIT...THE OLYMPIC MOUNTAINS AND PARTS OF THE NW INTERIOR.
PRELIMINARY THOUGHTS IS THAT WE WILL NEED A WIND ADVISORY FOR THE NW
INTERIOR AND A HIGH WIND WARNING OTHER MENTIONED AREAS.  I WILL GO
OVER THE LATEST GUIDANCE THIS MORNING AND MAKE IT FINAL THIS
AFTERNOON.

AFTER THAT SYSTEM VACATES THE AREA...ANOTHER WILL FOLLOW ON IT HEELS
TUESDAY.  WHILE IT WILL LIKELY BE A BIT DEEPER...THIS ONE WILL BE
FURTHER OFFSHORE AND FURTHER SOUTH WHEN IT BEGINS FILLING AND THUS
HAVE LESS OF AN IMPACT ON THE REGION.  SO LESS RAIN AND LESS WIND
OVERALL.  CERNIGLIA

.LONG TERM...BY MIDWEEK...A 190+ KNOT JET STREAM IS AIMED AT THE
L.A. BASIN.  WITH THE MAIN STORM TRACK SO FAR SOUTH...THIS LEAVES
RELATIVELY WEAK SYSTEMS TO PINWHEEL AROUND THE BROAD UPPER LEVEL
TROUGH OVER THEN NORTHEAST PACIFIC AND BRING SHOWERS TO THE REGION
AT TIMES.  SNOW LEVELS WILL BE LOWER THAN WHAT THEY HAVE BEEN
RECENTLY...BUT MOISTURE WILL NOT BE ALL THAT PLENTIFUL. 27/CERNIGLIA

&&

.HYDROLOGY...THE SEVERAL WEATHER SYSTEMS ARE NOT EXPECTED TO PRODUCE
ANYWHERE CLOSE TO THE RAINFALL OBSERVED LAST WEEK.  SO SIGNIFICANT
FLOODING PROBLEMS ARE NOT EXPECTED ALTHOUGH THE SKOKOMISH RIVER WILL
NEED TO BE WATCHED AS IT IS STILL RUNNING HIGH.  WITH A SOMEWHAT
COOLER AND MORE SHOWERY REGIME EXPECTED FOR MUCH OF THE UPCOMING
WEEK...ADDITIONAL FLOODING PROBLEMS ARE NOT ANTICIPATED IN THE
FORESEEABLE FUTURE.  FLOODING IS NOT EXPECTED ON THE GREEN RIVER FOR
THE NEXT 10 DAYS.

THE RECENT RAINFALL THOUGH WILL MAINTAIN A THREAT OF LOCAL
LANDSLIDES. THE USGS LANDSLIDE INDEX INDICATES THAT THE GROUND IS
SUFFICIENTLY WET.  EVEN WITH THE HEAVY RAINFALL OVER...IT IS GOING
TO TAKE AT LEAST A FEW DAYS UNTIL THE THREAT OF ANY ISOLATED
LANDSLIDES WILL END.  CERNIGLIA

&&

.AVIATION...A FRONT OVER THE INTERIOR OF  W WA WILL DISSIPATE TODAY.
THE AIR MASS WILL REMAIN MOIST AND STABLE. MOIST SW FLOW ALOFT WILL
CONTINUE TO BRING AREAS OF LIGHT RAIN UP OVER W WA TODAY. A STRONG
UPPER LEVEL TROUGH AND SURFACE LOW WILL MOVE ACROSS THE OFFSHORE
WATERS TONIGHT BRINGING MORE RAIN...AND STRONG WINDS TO THE COAST
AND NORTH INTERIOR. LOW LEVEL WINDS ALOFT...BETWEEN FL025 AND FL050
WILL RISE TO S 40-60 KT TONIGHT.

KSEA...THE FRONT DISSIPATING OVER THE AREA WILL NOT BE MUCH OF A
FACTOR TODAY. MOIST SW FLOW ALOFT HOWEVER WILL CONTINUE TO BRING
AREAS OF LIGHT RAIN ACROSS THE TERMINAL AT TIMES...WHICH COULD DROP
VIS/CIGS BRIEFLY TO AROUND 3SM -RA/BKN025. OTHERWISE SEE LITTLE
CHANGE FROM CIGS BKN040-050. RAIN AND LOW LEVEL WINDS ALOFT WILL
INCREASE TONIGHT AS A STRONG UPPER LEVEL TROUGH/SURFACE LOW MOVE N
OFFSHORE. WILL FIGURE ON CIGS LOWERING BACK TO MVFR TONIGHT...WITH
FL050 WINDS RISING TO S 50-60KT 06Z-15Z. SURFACE WINDS WILL REMAIN S
TODAY. KAM

&&

.MARINE...MODELS AGREE ON BRINGING A DEEP LOW NORTHWARD ACROSS
THE OFFSHORE WATERS...ABOUT 170 NM W OF THE COAST...AT AROUND 973 MB
TONIGHT. SMALL DIFFERENCES BETWEEN THE MODELS IN TRACK AND PRESSURE
MAY SPELL THE DIFFERENCE BETWEEN HIGH END GALES ON THE COAST OR
STORM FORCE WINDS. HAVE LEFT IT AT GALES FOR THE COAST FOR NOW BUT
WILL CONSIDER A STORM WARNING AFTER THE WRF-GFS GUIDANCE ARRIVES.
GALES OVER THE INLAND WATERS OF NW WA LATE TONIGHT ARE A GOOD BET SO
HAVE CONVERTED THE WATCH TO A GALE WARNING. WILL LEAVE THE SMALL
CRAFT ADVISORIES FOR THE INTERIOR UP AS A RAMP-UP TRANSITION TO
GALES LATE TONIGHT. SOME SPOTS STILL HAVE SCA WINDS GOING AFTER THIS
MORNINGS FRONT...BUT THEY MOSTLY SHOULD EASE FOR A WHILE THIS
AFTERNOON. THIS SYSTEM COULD PRODUCE HIGH ENOUGH SWELL TO MERIT A
HIGH SURF ADVISORY FOR THE COAST MONDAY...HOWEVER PERIODS WILL BE
SHORT WHICH WILL REDUCE THE SWELL ENERGY.

HIGH ASTRONOMICAL TIDES AND LOW PRESSURE OVER THE AREA MONDAY
MORNING FROM THE APPROACHING WILL MOSTLY LIKELY CONTINUE THE
POSSIBILITY OF MINOR TIDAL OVERFLOW FLOODING OVER INLAND AREAS.
STRONG WINDS AND WAVE ACTION WILL LIKELY EXACERBATE THE PROBLEM.
WILL LET THIS MORNINGS ADVISORY EXPIRE...THEN REISSUE IT THIS
AFTERNOON FOR THE NEXT ROUND OF HIGH TIDES MONDAY MORNING. KAM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...HIGH WIND WATCH NORTH/CENTRAL COAST..WESTERN STRAIT OF JUAN DE
     FUCA AND OLYMPICS FOR TONIGHT/MON MORNING.
    .COASTAL FLOOD ADVISORY THIS MORNING ALONG THE INLAND WATERS OF
     WESTERN WASHINGTON.
PZ...GALE WARNING COAST AND WEST ENTRANCE TO THE STRAIT.
    .SMALL CRAFT ADVISORY CENTRAL AND EAST STRAIT...NORTH
     INLAND WATERS AND ADMIRALTY INLET.
    .SMALL CRAFT ADVISORY IN EFFECT FOR ROUGH GRAYS HARBOR BAR.
    .GALE WARNING CENTRAL STRAIT...EAST ENTRANCE...NORTH
     INLAND WATERS AND ADMIRALTY INLET LATER TONIGHT INTO MON.

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