Heavy Snow in Washington, November 26 to 27, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
340 PM PST MON NOV 26 2007

.SYNOPSIS...A STRONG COLD FRONT WILL PASS THROUGH WESTERN WASHINGTON
EARLY THIS EVENING SPREADING RAIN INLAND WITH SNOW IN THE MOUNTAINS.
IT WILL ALSO KICK UP THE WIND THIS EVENING...ESPECIALLY ACROSS
NORTHERN AREAS. SHOWERS WILL PERSIST INTO TUESDAY AND TUESDAY
NIGHT...MAINLY OVER THE MOUNTAINS. ANOTHER FRONT WILL BRING A ROUND
OF RAIN TO THE REGION LATER WEDNESDAY INTO WEDNESDAY
NIGHT...TAPERING TO SHOWERS THURSDAY. DRIER AND COOL WEATHER IS
EXPECTED FRIDAY INTO THE WEEKEND.

&&

.SHORT TERM...SURFACE LOW AND COLD FRONT LURKING JUST OFFSHORE AND
BOTH WILL MOVE ACROSS THE AREA THIS EVENING. EXPECTING STRONG
WESTERLY FLOW TO DEVELOP IN THE WAKE OF THIS SYSTEM WITH STRONG
WINDS FLOWING DOWN THE STRAIT AND INTO THE NW INTERIOR PART OF
WESTERN WASHINGTON. ISSUED A WIND ADVISORY FOR THIS REGION TO COVER
THE ENHANCEMENT.  WILL BE BREEZY OTHER AREAS AS WELL...JUST NOT HIGH
ENOUGH TO HEADLINE WITH AN ADVISORY.

SNOW HAS ALREADY SPREAD INTO THE OLYMPICS AND WILL BEGIN IN THE
CASCADES ANY MOMENT NOW IF IT HASNT ALREADY. THIS IS A FEW HOURS
SLOWER THAN INITIALLY FORECAST BUT NOT EXPECTING IT TO AFFECT THE
ACCUMULATIONS MUCH. WHEN I UPDATE THE OLYMPIC SNOW ADVISORY I WILL
PUSH THE EXPIRE TIME BACK A COUPLE OF HOURS. STILL EXPECTING 5-8
INCHES IN THE OLYMPICS AND AROUND OR A LITTLE OVER A FOOT IN THE
CASCADES.

FOR TUESDAY WE WILL END UP IN A COOL AND UNSTABLE AIR MASS WITH A
DECENT RESIDUAL WESTERLY FLOW. THEREFORE WE WILL END UP WITH A BIT
OF SUNSHINE AND SCATTERED SHOWERS. SHOWERS WILL BE MOST NUMEROUS IN
THE CASCADES WHERE THE WEST FLOW WILL ENHANCE THE SHOWER POTENTIAL.

TUESDAY NIGHT WE WILL HAVE A BRIEF BREAK BETWEEN THE OUTGOING AND
INCOMING SYSTEMS. WITH ENOUGH BREAKS IN THE CLOUD COVER WE SHOULD
DROP DOWN TO AND BELOW FREEZING BEFORE THE CLOUDS FROM THE NEXT
SYSTEM BLANKET THE AREA. THIS SYSTEM WILL BEGIN AS A WARM ADVOCATIVE
PRECIPITATION EVENT THE A SURFACE LOW WILL DEVELOP JUST SOUTH OF
VANCOUVER ISLAND AND DRIFT SOUTHEAST THROUGH THURSDAY. THIS WHOLE
SETUP WILL NEED TO BE WATCHED VERY CAREFULLY. AT THIS POINT IT LOOKS
LIKE A PREDOMINATELY COLD RAIN EVENT FOR THE LOWLANDS WITH LOW SNOW
LEVELS FOR THE MOUNTAINS...BUT AIR MASS IS BORDERLINE COLD ANS THE
SYSTEM IS REALLY TAKING HOLD AT NIGHT. IF THE LOW TAKES A BIT MORE
OF A SOUTHERLY TRACK OR IS JUST A BIT COLDER...LIKE EARLIER PROGGED
IT WILL BE A DIFFERENT STORY. HAVE LEANED TOWARD CLIMATOLOGY WITH
THIS EVENT NOW AND LEFT IT AS RAIN. STAY TUNED WITH THIS ONE.
CERNIGLIA

.LONG TERM...FOR FRIDAY THROUGH SATURDAY IT IS A BIT OF A MESSY
FORECAST TO DEAL WITH. LOOKS AS THOUGH WE WILL HAVE A WEAK TROUGH
EXTENDING ACROSS THE REGION WITH SOME POTENTIAL EAST OR NORTH...IE
CONTINENTAL FLOW...ACROSS THE AREA. THIS WILL PROVIDE A COLD AIR
MASS AND IF THE TROUGH IS NOT ALL THAT ACTIVE...ONLY PARTLY CLOUDY
SKIES. ECMWF IS HINTING AT SOME FRAZIER VALLEY OUTFLOW SO THAT WILL
NEED TO BE WATCHED FOR TEMPERATURE FORECAST. BASICALLY LOOKS PARTLY
CLOUDY...DRY AND COOL/COLD.  BEYOND THAT THINGS GET REALLY MESSY IN
THE MODEL WORLD AND CONFIDENCE IS RATHER LOW. POTENTIAL FOR A STRONG
SYSTEM TO MOVE INTO REGION LATE SUNDAY INTO MONDAY SO THAT IS IN THE
FORECAST. WHAT FORM WITH THAT TAKE????   CERNIGLIA

&&

.AVIATION...THE VIGOROUS CDFNT WAS JUST OFF THE COAST AND IS
EXPECTED TO MOVE ONSHORE BETWEEN 00Z AND 01Z. THIS FRONT SHOULD BE E
OF THE CASCADES BY 07Z. PRECIP WAS ALREADY FALLING ON THE
COAST...AND WILL OVERSPREAD THE REST OF THE AREA BY 01Z. CIGS
CONTINUED TO LOWER...AND WILL BE MOSTLY IN THE 2-4K FT RANGE BY 06Z.
THE PRECIP WILL DECREASE AND BECOME MOSTLY CONFINED TO THE CASCADES
BETWEEN 06Z AND 12Z.

A PGTSND CONVERGENCE ZONE /PSCZ/ WILL QUICKLY DEVELOP BEHIND THE
FRONT AND SHOULD BE ROUGHLY LOCATED FROM PORT LUDLOW TO KPAE EWD TO
THE CASCADES. THE PSCZ IS EXPECTED TO BE QUASISTATIONARY BUT WILL
REMAIN N OF KBFI. THE CDFNT WILL USHER IN A COLDER AIR MASS...THUS
THERE MAY BE A RAIN/SNOW MIX WITH THE HEAVIER SHOWERS WITHIN THE
PSCZ AFTER 08Z. HOWEVER THE SNOW WILL MOST LIKELY OCCUR AT OR ABOVE
500 FEET...WITH ONLY A DUSTING OF SNOW ANTICIPATED AT THIS LEVEL.

AT KSEA...FROPA IS STILL EXPECTED ABOUT 04Z. CIGS WILL CONTINUE TO
LOWER AND SHOULD BE NEAR 2K FT BY 03Z. SLY WINDS WILL INCREASE TO
10-15 KT AND BECOME GUSTY...BECMG SW BEHIND THE CFDNT. CIGS SHOULD
LIFT TO NEAR 4K FT AFTER 06Z AND WINDS WILL SLOLY DIMINISH.

&&

.MARINE....THE GALE WARNING ISSUED EARLIER WAS EXPANDED TO INCLUDE
ALL WATERS. THE SURFACE LOW NW OF CAPE FLATTERY HAS DEEPENED MORE
THAN WHAT THE NUMERICAL WEATHER MODELS INDICATED. THE LOW WAS NEAR
1006 MB AT THIS TIME BASED ON OBSERVATIONS ALONG AND W OF VANCOUVER
ISLAND AND THE WA COAST. PRESSURES WERE STARTING TO RISE MORE
STRONGLY W OF THE CDFNT BUT THE PROBLEM STILL CONCERNED HOW MUCH
PRES DIFFERENCE WILL DEVELOP BETWEEN THE RISE/FALL COUPLET. HAVE
BUMPED UP SPEEDS CLOSER TO STORM FORCE CRITERIA IN THE STRAIT
OR INTO THE 35 TO 45 KNOT RANGE BEHIND THE COLD FRONT. WILL HAVE TO
MONITOR THE ISALLOBARIC OR PRESSURE CHANGE TRENDS CLOSELY THE NEXT
FEW HOURS.

THE FRONT WILL EXIT THE AREA LATER TONIGHT WITH GENERALLY W TO NW
FLOW ACROSS THE AREA. WILL NEED TO WATCH WINDS THRU THE GEORGIA
STRAIT LATER TONIGHT AND TUE MORNING. IF GALE FORCE WINDS DEVELOP
THERE AND PERSIST FOR 3 TO 6 HOURS...THERE COULD BE SOME COASTAL
FLOODING AT SANDY POINT BUT IF AND ONLY IF CONDITIONS COINCIDE WITH
THE HIGH TIDE AT 1630Z OR 0830 AM TUE.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
1. HEAVY SNOW WARNING NORTH AND CENTRAL CASCADES
2. SNOW ADVISORY OLYMPIC MOUNTAINS
3. GALE WARNING ALL WATERS
4. WIND ADVISORY NORTHWEST INTERIOR...SAN JUANS...ISLAND COUNTY AND
THE EVERETT AND VICINITY REGION. SMALL CRAFT ADVISORY ADMIRALTY
INLET AND PUGET SOUND/HOOD CANAL

WEATHER.GOV/SEATTLE

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
436 PM PST MON NOV 26 2007

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0429 PM     SNOW             5 NNW SHELTON           47.29N 123.13W
11/26/2007  E0.8 INCH        MASON              WA   TRAINED SPOTTER

            SNOW ESTIMATED TO BE LESS THAN AN INCH. SNOW FALLING FOR
            45 MINUTES. TEMPERATURE 35 DEGREES.

&&

GRUB