High Wind in Washington, February 18, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
930 AM PST TUE FEB 18 2014

.SYNOPSIS...ANOTHER STORM WILL BRING WIND AND RAIN TO WESTERN
WASHINGTON TODAY AND TONIGHT...AND HEAVY SNOW IN THE MOUNTAINS. THE
NEXT FRONT WILL MOVE THROUGH WEDNESDAY NIGHT AND THURSDAY WITH MORE
WIND... RAIN...AND MOUNTAIN SNOW. THERE IS A CHANCE OF SHOWERS AT
TIMES FRIDAY THROUGH MONDAY...BUT THIS PERIOD WILL BE A BREAK FROM
THE ACTIVE PATTERN THAT HAS PREVAILED FOR THE PAST WEEK AND A HALF.

&&

.SHORT TERM...A PROGRESSIVE UPPER TROUGH AXIS IS LOCATED OUT AROUND
135W...WITH A 120 KT UPPER JET SCOOPING THROUGH THE TROUGH AND
ACROSS WRN WA. LOTS OF UPPER LEVEL DIVERGENCE AND LARGE-SCALE LIFT
PRECEDES THE TROUGH AXIS. IR SAT IMAGERY SHOWS COOLING CLOUD TOPS
OVER THE AREA...ANOTHER SIGN OF STRONG LIFT. THE LIFT IS LEADING TO
A WIDESPREAD PRECIP SHIELD WHICH HAS OVERSPREAD WRN WA...ASIDE FROM
A RAIN SHADOW NEAR ADMIRALTY INLET. AROUND 1 INCH OF RAIN IS
EXPECTED ALONG THE I-5 CORRIDOR OF SW WA FROM KOLM ON SOUTH. WITH
THE FREEZING LEVEL NEAR 3000 FEET...THIS IS LEADING TO HEAVY SNOW IN
THE MTNS. 10 TO 25 INCHES OF SNOW ARE FORECAST FOR THE MTNS...WITH
THE HIGHER AMOUNTS FOR THE VOLCANOES...THOUGH THE PASSES ARE
CERTAINLY GETTING SIGNIFICANT SNOW. A WINTER STORM WARNING AND AN
AVALANCHE WARNING ARE IN EFFECT FOR THE CASCADES. THE 12Z GFS SHOWS
A PRESSURE FALL CENTER MOVING EAST ALONG THE U.S./CANADIAN BORDER
THIS AFTN...WITH THE FRONTAL WAVE GRADUALLY DEVELOPING INTO A CLOSED
SFC LOW AS IT MOVES EAST OF THE CASCADES. A QUICK SHOT OF S-SW 850
MB WINDS OF 60-70 KT WILL SPREAD ACROSS SW WA OVER THE NEXT FEW
HOURS IN ADVANCE OF A STRENGTHENING COLD FRONT...WITH THE 12Z NAM
SHOWING 925 MB WINDS REACHING 45-55 KT. THE KPDX-KBLI GRADIENT WAS
+6.8 MB AT 17Z AND STRENGTHENING. THESE THINGS ALL POINT TO A WINDY
LATE MORNING AND EARLY AFTERNOON. WIND ADVISORIES ARE IN EFFECT FOR
THE COAST AND NORTH INTERIOR...WHICH SEEMS WISE.

A COLD FRONT WILL CROSS WRN WA THIS AFTN. IN ITS WAKE...THE SNOW
LEVEL WILL FALL TO 1000 TO 1500 FT TONIGHT. THERE IS ALSO A CHANCE
OF THUNDERSTORMS IN THE POST-FRONTAL CONVECTIVE REGIME. THE OFFICIAL
FORECAST ALREADY REFLECTS THAT FOR THE COAST AND COASTAL WATERS
TONIGHT.        HANER

REMAINDER OF SHORT TERM SECTION FROM PREVIOUS DISCUSSION...
WEDNESDAY WILL BE ANOTHER DAY BETWEEN FRONTAL SYSTEMS...WITH COOL
MOIST NORTHWEST FLOW ALOFT. HIGHS WILL BE IN THE LOWER TO MID
40S...THE SNOW LEVEL WILL ONLY BE AROUND 1500 FT...AND IT WILL BE
SOMEWHAT BREEZY STILL. THERE WILL BE SOME SHOWERS AND PROBABLY SOME
SUN BREAKS IN THE LOWLANDS. ANOTHER 3 TO 7 INCHES OF SNOW WILL FALL
IN THE MOUNTAINS IN MORE SHOWERY PRECIPITATION.

THEN ANOTHER FRONTAL SYSTEM -- AND THE LAST REALLY VIGOROUS ONE IN
THIS SERIES OF RECENT STORMS -- WILL MOVE THROUGH WEDNESDAY NIGHT
AND THURSDAY. IT WILL ALSO BE ASSOCIATED WITH ANOTHER 120 KT JET OUT
OF THE WEST-NORTHWEST. THIS WILL BE A WINDY PERIOD. LOWLAND RAIN
SHOULD BE MAINLY 0.25 TO 0.75 INCH...WITH WATER EQUIVALENT
PRECIPITATION IN THE MOUNTAINS 0.75 TO 2 INCHES. THE SNOW LEVEL WILL
BE 1500 TO 2500 FT. SOME OF THE HIGHER TERRAIN OF THE WESTERN
WASHINGTON LOWLANDS -- IE ELEVATIONS ABOVE 1000 FT -- COULD HAVE
PRECIPITATION AS SNOW OR A MIX...BUT ACCUMULATIONS ARE UNLIKELY.
MCDONNAL

.LONG TERM...FROM PREVIOUS DISCUSSION...DRIER NORTHWEST FLOW ALOFT
WILL PREVAIL OVER THE REGION FRIDAY THROUGH SUNDAY...AHEAD OF AN
UPPER RIDGE MOVING TOWARD THE AREA FROM WELL OFFSHORE. HOWEVER THE
MODELS AGREE BROADLY THAT THERE WILL BE SOME WEAK SHORTWAVES IN THE
UPPER FLOW...AND THESE FEATURES WILL BRING A CHANCE OF SHOWERS AT
TIMES. THERE IS NOT VERY GOOD AGREEMENT ON THE TIMING OF THESE
SYSTEMS...OR WHAT PARTS OF THE FORECAST AREA ARE LIKELY TO RECEIVE
PRECIPITATION. WE HAVE DECIDED TO ADD A CHANCE OF SHOWERS TO THE
FORECAST FRIDAY THROUGH SUNDAY IN RATHER BROAD BRUSH FASHION. THE
DAYS...ESPECIALLY THIS WEEKEND... HAVE A GOOD CHANCE OF BEING PARTLY
SUNNY. THE UPPER RIDGE WILL MOVE INLAND SUNDAY NIGHT OR MONDAY...AND
A WEAK SYSTEM MOVING OVER THE RIDGE COULD BRING SOME LIGHT
PRECIPITATION.

ALL IN ALL...THIS PERIOD WILL CERTAINLY BE A BREAK IN THE ACTIVE
WEATHER PATTERN THAT BEGAN ON FEBRUARY 8.   MCDONNAL

&&

.HYDROLOGY...FLOOD WARNINGS REMAIN IN EFFECT FOR THE SKOKOMISH RIVER
AND POINTS ALONG THE CHEHALIS AND SKOOKUMCHUCK RIVERS. THE LOWEST
REACHES OF THE CHEHALIS RIVER ARE NOT YET AT FLOOD STAGE. FLOODING
THERE WILL OCCUR AS THE FLOOD WAVE FROM THE RAINFALL SUNDAY NIGHT
MOVES DOWNSTREAM. SEVERAL OTHER SPOTS FLOODED OR NEARLY FLOODED WITH
THE LAST ROUND OF HEAVY RAIN INCLUDING THE CHEHALIS RIVER NEAR
DOTY...THE SKOOKUMCHUCK AT CENTRALIA...AND THE DESCHUTES RIVER.

ANOTHER 1 TO 2 INCHES OF RAIN WILL FALL IN SOUTHWEST WASHINGTON
TODAY AND THE RIVERS THAT ARE RUNNING HIGH WILL STILL BE AT RISK.
THE FLOOD WATCH REMAINS IN EFFECT THROUGH LATE WEDNESDAY FOR
MASON... THURSTON...LEWIS...GRAYS HARBOR COUNTIES. ANOTHER STORM
WILL AFFECT THE AREA WEDNESDAY NIGHT SO THE FLOOD WATCH MAY
EVENTUALLY BE EXTENDED.

A DRIER WEATHER PATTERN WILL DEVELOP ON FRIDAY AND RIVERS WILL BEGIN
RECEDING. MCDONNAL/BURKE

&&

.AVIATION...STRONG WESTERLY FLOW ALOFT WILL CONTINUE TODAY THEN TURN
MORE NORTHWESTERLY TONIGHT. A FRONT WILL MOVE THROUGH THE AREA
TODAY. SURFACE FLOW WILL BE SOUTHEAST THIS MORNING THEN BECOME
ONSHORE BEHIND THE FRONT THIS AFTERNOON AND EVENING. MOIST AND
STABLE AIR MASS TODAY WILL BECOME SOMEWHAT UNSTABLE BEHIND THE FRONT.

CEILINGS WILL BECOME SOLIDLY MVFR THIS MORNING OVER ALL AREAS. IN
POST FRONTAL WESTERLY FLOW ALOFT THERE SHOULD BE SOME IMPROVEMENT IN
THE CEILINGS TO MOSTLY VFR. SCATTERED SHOWERS AND ISOLATED THUNDER
THIS AFTERNOON AND EVENING WILL OCCASIONALLY DIP CEILINGS TO MVFR.

KSEA...CEILINGS IN THE 3500 TO 5000 FEET RANGE THIS MORNING WILL
LOWER TO THE 2000-3000 FOOT RANGE WITH VISIBILITIES 3-5 SM BY 18Z.
SOUTHERLY WINDS 8-12KT INCREASING TO 12G22KT AFTER 18Z. CEILINGS
IMPROVING TO NEAR 5000 FEET BEHIND THE FRONT TONIGHT WITH GUSTY
SOUTHWESTERLY WINDS CONTINUING. CHB

&&

.MARINE...A FRONT ASSOCIATED WITH A 983 MB LOW MOVING INTO HAIDA
GWAII WILL MOVE THROUGH THE WATERS TODAY WITH GALE FORCE WINDS OVER
THE COASTAL WATERS...ENTRANCES TO THE STRAIT...AND NORTHERN INLAND
WATERS. OTHER WATERS WILL HAVE SMALL CRAFT ADVISORIES. POST FRONTAL
THERE COULD BE GALE WESTERLIES IN THE STRAIT BUT FOR NOW THE
FORECAST IS 20-30 KT.

ANOTHER FRONT WILL MOVE THROUGH THE WATERS WEDNESDAY NIGHT AND
THURSDAY MORNING. THIS ONE COULD ALSO PRODUCE GALES.

SWELL WILL REMAIN IN THE TEENS OVER THE COASTAL WATERS FOR THE NEXT
FEW DAYS AS THE SERIES OF STORMS CONTINUES INTO THE MIDDLE OF THE
WEEK. BEGINNING FRIDAY HIGH PRESSURE WILL BUILD AND WINDS WILL BE
LIGHTER. CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WIND ADVISORY COAST AND NORTH INTERIOR.
     WINTER STORM WARNING CASCADES.
     WINTER WEATHER ADVISORY OLYMPIC MOUNTAINS.
     FLOOD WATCH IN GRAYS HARBOR...MASON...THURSTON AND LEWIS
      COUNTIES.

PZ...GALE WARNING COAST...ENTRANCES...NORTHERN INLAND WATERS TODAY.
     SMALL CRAFT ADVISORY OTHER WATERS TODAY.
     SMALL CRAFT ADVISORY FOR ROUGH BAR GRAYS HARBOR BAR.

&&

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