Winter Storm Watch 10, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
945 AM PDT TUE MAR 13 2012

.SYNOPSIS...A COLD UPPER TROUGH WILL BRING RAIN AND SNOW SHOWERS TO
WESTERN WASHINGTON TODAY WITH A FEW THUNDERSTORMS. ANOTHER VIGOROUS
FRONTAL SYSTEM WILL MOVE THROUGH THE AREA WEDNESDAY...FOLLOWED
QUICKLY BY YET ANOTHER WEDNESDAY NIGHT AND THURSDAY...FOR WET AND
OCCASIONALLY WINDY WEATHER AND LOTS MORE SNOW IN THE MOUNTAINS.
SHOWERY WEATHER...AND SOME SUN BREAKS...ARE LIKELY THIS WEEKEND.

&&

.SHORT TERM...SHOWERS WILL CONTINUE TODAY...TAPERING THIS EVENING AS
AN UPPER TROUGH OVER THE AREA SHIFTS INLAND. THE AIR MASS IS COLD
ENOUGH THAT HEAVIER SHOWERS WILL MIX WITH OR BE ALL SNOW THIS
MORNING. LOCAL ACCUMULATIONS OF AN INCH OR TWO ARE POSSIBLE BUT MOST
AREAS WILL NOT SEE MUCH AND ROADS WILL PROBABLY STAY MOSTLY WET. THE
AIR MASS WILL ALSO BE UNSTABLE TODAY WITH ISOLATED THUNDERSTORMS
POSSIBLE. HIGHS WILL BE CLOSE TO 10 DEGREES BELOW NORMAL.

AFTER A BRIEF LULL TONIGHT...THE NEXT IN A SERIES OF FRONTAL SYSTEMS
WILL SPREAD RAIN ACROSS THE AREA WEDNESDAY MORNING. THE AIR MASS
WILL BE COLD ENOUGH FOR PRECIPITATION TO START OUT AS SNOW IN SOME
SPOTS BEFORE CHANGING TO RAIN. THE FAVORED UPSLOPE HOOD CANAL AREA
LOOKS LIKE IT COULD GET HEAVY SNOW IN THE MORNING BEFORE TURNING
OVER TO RAIN. A WINTER STORM WATCH MAY BE ISSUED FOR THIS LATER
TODAY. IT ALSO LOOKS LIKE ADVISORY LEVEL WINDS WILL OCCUR IN THE
USUAL SOUTHEAST SUCKER LOCATIONS WEDNESDAY...COAST AND NORTH
INTERIOR.

A WARMER AND WETTER FRONTAL SYSTEM WILL MOVE ONSHORE AFTER MIDNIGHT
WEDNESDAY NIGHT/THURSDAY MORNING. THIS SYSTEM LOOKS A NOTCH STRONGER
THAN THE WEDNESDAY ONE. ANOTHER ROUND OF ADVISORY LEVEL WINDS IS A
GOOD BET WITH SOME SOUTHEAST SUCKER LOCATIONS PERHAPS APPROACHING
HIGH WIND.

FOR THE MOUNTAINS...SNOW LEVELS WILL BE FAIRLY LOW ON WEDNESDAY WITH
FRONT NUMBER ONE AND SEVERAL INCHES OF SNOW SHOULD ACCUMULATE
DURING THE DAY. SNOW LEVELS WILL RISE ON THURSDAY...PROBABLY ABOVE
PASS LEVEL BY AFTERNOON...BUT HEAVY SNOW WILL CONTINUE AT HIGHER
LOCATIONS. A WINTER STORM WATCH IS CURRENTLY IN EFFECT FOR THE
WEDNESDAY AND THURSDAY PERIOD. SCHNEIDER

.LONG TERM...PREVIOUS DISCUSSION...FOR THE LAST FEW DAYS THE LONGER
RANGE MODELS HAVE BEEN IN ROUGH AGREEMENT THAT THERE WILL BE A
TRANSITION FROM THE VERY STORMY PATTERN THIS WEEK TO A COOL AND
SHOWERY BUT DRIER PATTERN OVER THE WEEKEND. THE RECENT RUNS SHOWS
THIS TRANSITION OCCURRING A BIT MORE SLOWLY...WITH FRIDAY NOW
LOOKING MORE WET THAN PREVIOUSLY EXPECTED AS A SHORTWAVE TROUGH
MOVES THROUGH. THE CHANGE I HAVE MADE IS TO BOOST POPS FOR FRIDAY TO
LIKELY. IT STILL LOOKS LIKE A LARGER UPPER TROUGH WILL MOVE OVER THE
REGION THIS WEEKEND...AND IT WILL BE COOL WITH MORE SCATTERED
SHOWERS AND PROBABLY SOME SUN BREAKS.   MCDONNAL

&&

.HYDROLOGY...PREVIOUS DISCUSSION...AS DISCUSSED ABOVE THE
PRECIPITATION FROM THE WEDNESDAY AND THURSDAY STORMS WILL BE
SUBSTANTIAL...WITH GENERALLY 2 TO 5 INCHES IN THE MOUNTAINS DURING A
48-HOUR PERIOD. THE HEAVIEST AMOUNTS WILL OCCUR OVER THE SOUTH
SLOPES OF THE OLYMPICS...AND THE MEAN AREAL PRECIPITATION OVER THE
SKOKOMISH RIVER BASIN WILL LIKELY EXCEED 3 INCHES. EVEN WITH
RELATIVELY LOW SNOW LEVELS DURING MOST OF THE EVENT...THIS COULD BE
ENOUGH TO DRIVE THIS UNIQUELY FLOOD-PRONE RIVER TO FLOOD STAGE ON
THURSDAY.

FLOODING IS NOT EXPECTED ON ANY OTHER RIVER IN THE FORECAST AREA
DURING THE NEXT 7 DAYS.   MCDONNAL

&&

.AVIATION...AN ACTIVE PATTERN WILL PERSIST FOR THE NEXT 24 HOURS. AN
UPPER TROUGH AXIS OVER WRN WA THIS MORNING WILL EXIT EAST OF THE
CASCADES THIS AFTN. ANOTHER TROUGH WILL BRUSH BY WRN WA ON WED
MORNING. MDT SW FLOW ALOFT TODAY...BECOMING STRONG ON WED. THE AIR
MASS WILL BE MOIST AND UNSTABLE TODAY...BECOMING STABLE ON WED
MORNING. THE MOIST AND UNSTABLE AIR TODAY WILL LEAD TO NUMEROUS
CONVECTIVE SHOWERS...WHICH ALSO ENTAILS HIGHLY VARIABLE CIGS AND
VSBYS...ESPECIALLY CONSIDERING MANY PASSING SHOWERS ALSO CONTAIN OR
ARE MIXED WITH SNOW. SHOWER COVERAGE WILL BE AT A RELATIVE MIN FROM
00Z-06Z THIS EVNG.

KSEA...HIGHLY VARIABLE CIGS AND VSBYS IN PASSING SHOWERS TODAY. ANY
OF THE SHOWERS WILL CONTAIN AT LEAST A MIXTURE OF SNOW WITH
RAIN...IF NOT OUTRIGHT SNOW...BUT DURATION OF INDIVIDUAL ROUNDS OF
SNOW SHOULD NOT EXCEED 30 MINUTES...AND AIR TEMPS WILL REMAIN ABOVE
FREEZING...SO SURFACE ACCUMULATIONS SHOULD ONLY BE BRIEF. LOOKS LIKE
A 6-HOUR REPRIEVE IN PRECIP THIS EVNG CENTERED ARND 06Z. ANOTHER
WEATHER SYSTEM ON WED...CONTAINING STRONG WINDS ALOFT. WINDS AT 020
WILL APPROACH 50 KNOTS ARND 18Z ON WED. WED WILL FEATURE A FULL DAY
OF MAINLY IFR CIGS AND PRECIP...PERHAPS BEGINNING AS A MIX WITH SNOW
UNTIL 18Z-20Z ON WED.       HANER

&&

.MARINE...A WARM FRONT WILL LIFT ACROSS THE WATERS EARLY WED
MORNING...BRINGING GALE FORCE WINDS TO EAST- AND SOUTHEAST-PRONE
LOCALES. A 975 MB LOW WILL MOVE TO NEAR QUEEN CHARLOTTE SOUND ON THU
MORNING...LEADING TO ANOTHER ROUND OF GALES IN SOUTHEAST-WIND-PRONE
LOCALES.        HANER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER STORM WATCH FOR THE CASCADES AND OLYMPICS WEDNESDAY
      THROUGH THURSDAY.
PZ...GALE WARNING COAST...WEST ENTRANCE...EAST ENTRANCE...NORTHERN
      INLAND WATERS...AND ADMIRALTY INLET.
     SMALL CRAFT ADVISORY CENTRAL STRAIT AND PUGET SOUND.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.

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

WWW.WEATHER.GOV/SEATTLE

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
1020 AM PDT TUE MAR 13 2012

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

1019 AM     SNOW             W EASTSOUND             48.70N 122.91W
03/13/2012  M0.8 INCH        SAN JUAN           WA   TRAINED SPOTTER

            STILL SNOWING.

&&

GRUB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
1040 AM PDT TUE MAR 13 2012

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

1039 AM     SNOW             5 WSW PUYALLUP          47.17N 122.38W
03/13/2012  M1.5 INCH        PIERCE             WA   TRAINED SPOTTER

&&

GS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
1107 AM PDT TUE MAR 13 2012

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

1104 AM     SNOW             BONNEY LAKE             47.19N 122.17W
03/13/2012  M3.6 INCH        PIERCE             WA   PUBLIC

            ELEVATION 630 FEET. FLURRIES NOW. SPOTTER IS PIERCE 94.

&&

GRUB