Heavy Snow in Washington, February 18 to 19, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 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 IN THE
ACTIVE PATTERN THAT HAS PREVAILED FOR THE PAST WEEK AND A HALF.

&&

.SHORT TERM...THE NEXT FRONTAL SYSTEM IS MOVING TOWARD THE
WASHINGTON COASTAL WATERS EARLY THIS MORNING. IN THE MEANTIME WE
STILL HAVE SCATTERED SHOWERS OVER WESTERN WASHINGTON...BUT IT HAS
BEEN A RELATIVELY QUIET NIGHT WEATHER WISE. TEMPERATURES AT 2 AM
WERE IN THE UPPER 30S TO MID 40S IN THE LOWLANDS. ANOTHER 3 OR 4
INCHES OF SNOW HAS FALLEN IN THE MOUNTAINS WITH THE SNOW LEVEL
AROUND 2000 FT.

THE LEADING EDGE OF PRECIPITATION WITH THE APPROACHING STORM CAN BE
SEEN JUST OFFSHORE IN RADAR IMAGERY... AND IT WILL SPREAD TO THE
COAST IN THE NEXT FEW HOURS AND INLAND TO THE CASCADE CREST BY LATE
MORNING. STEADY RAIN WILL CHANGE TO SHOWERS TONIGHT AS THE UPPER
TROUGH FOLLOWS THE FRONT. BUT SNOW WILL CONTINUE IN THE CASCADES IN
STRONG MOIST WESTERLY FLOW...AND A PUGET SOUND CONVERGENCE ZONE
COULD DEVELOP OVER THE NORTH PUGET SOUND AREA.

THIS FRONTAL SYSTEM -- WHICH IS ASSOCIATED WITH A SOUTHWESTERLY 120
KT JET -- SHOULD DEVELOP FURTHER AS IT MOVES INTO THE AREA
TODAY...BUT WITH RESPECT TO WIND AND PRECIPITATION AMOUNTS IT PACKS
A LITTLE LESS PUNCH THAN THE LAST COUPLE FRONTS. THE AIR MASS WITH
IT IS A BIT COOLER THOUGH. THE SNOW LEVEL WILL RISE TO AROUND 3000
FT AHEAD OF THE FRONT...AND FALL TO 1000 TO 1500 FT TONIGHT IN ITS
WAKE. THERE IS ALSO A CHANCE OF THUNDERSTORMS...AND FOR NOW WE HAVE
ADDED THAT TO THE COAST AND COASTAL WATERS TONIGHT.

THE THREAT OF HIGH WIND -- BY DEFINITION SUSTAINED WINDS 40 MPH OR
GUSTS 60 MPH -- LOOKS TO BE LOW WITH THIS SYSTEM...BUT IT WILL BE
WINDY ENOUGH FOR A WIND ADVISORY AT THE COAST AND IN THE NORTH
INTERIOR. THAT ADVISORY WAS ISSUED MONDAY AFTERNOON...WHICH IS IN
EFFECT THROUGH 3 PM TODAY. IT WILL BE BREEZY TO WINDY ELSEWHERE IN
THE FORECAST AREA.

RAINFALL TODAY AND TONIGHT WILL BE ROUGHLY 0.25 TO 1 INCH IN THE
LOWLANDS. WATER EQUIVALENT PRECIPITATION AMOUNTS IN THE MOUNTAINS
WILL BE 1 TO 2.5 INCHES...TRANSLATING TO AROUND ANOTHER 10 TO 25
INCHES OF SNOW. A WINTER STORM WARNING REMAINS IN EFFECT FOR THE
CASCADES THROUGH TONIGHT...WITH A SNOW ADVISORY IN EFFECT FOR THE
OLYMPICS THROUGH THIS EVENING.

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 ALSO 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...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. 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 0.5 TO 2 INCHES OF RAIN WILL FALL IN THE RIVER BASINS OF
SOUTHWEST WASHINGTON TODAY THROUGH WEDNESDAY...AND THE RIVERS THAT
HAVE FLOODED OR CAME CLOSE TO FLOODING WILL STILL BE AT RISK. SO THE
FLOOD WATCH REMAINS IN EFFECT THROUGH LATE WEDNESDAY -- FOR THE TIME
BEING -- FOR MASON...THURSTON...LEWIS...GRAYS HARBOR COUNTIES. WE
MAY NEED TO EVENTUALLY EXTEND THE FLOOD WATCH FURTHER...AS ANOTHER
STORM WILL MOVE THROUGH WEDNESDAY NIGHT AND THURSDAY.

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

&&

.AVIATION...STRONG WESTERLY FLOW ALOFT WILL CONTINUE THROUGH TODAY.
AIR MASS STABILIZING TODAY AHEAD OF FRONT THEN BECOMING SOMEWHAT
UNSTABLE AGAIN BEHIND THE FRONT. SURFACE FLOW WILL TURN SOUTHEAST
THIS MORNING AND INCREASE AS ANOTHER FRONT REACHES THE AREA. ONSHORE
FLOW WILL RESUME LATER THIS AFTERNOON BEHIND THE FRONT.

SHOWER ACTIVITY HANGING TOUGH EARLY THIS MORNING. LANGLEY HILL RADAR
SHOWS LEADING EDGE OF THE PRECIPITATION AHEAD OF THE APPROACHING
FRONT MOVING INTO KHQM AT 11Z. STEADY RAIN WILL SPREAD OVER THE
ENTIRE AREA THIS MORNING WITH THE FRONT MOVING THROUGH THIS
AFTERNOON. CEILINGS GENERALLY IN THE 3000-4000 FOOT RANGE WILL LOWER
INTO THE 2000-3000 FOOT RANGE 15Z-18Z AS THE RAIN INCREASES WITH
AREAS OF VISIBILITIES 3-5 SM. FRONTAL PASSAGE NEAR MIDDAY ALONG THE
COAST AND 21Z-00Z OVER THE INTERIOR. PLENTY OF POST FRONTAL SHOWERS
BUT WITH THE WESTERLY FLOW ALOFT CENTRAL SOUND WILL BE RAIN SHADOWED
ALLOWING SOME IMPROVEMENT IN THE CEILINGS POST FRONTAL.

KSEA...CEILINGS IN THE 3500 TO 5000 FEET RANGE EARLY THIS MORNING.
RAIN DEVELOPING AT THE TERMINAL 15Z-18Z WITH CEILINGS LOWERING DOWN
INTO THE 2000-3000 FOOT RANGE WITH VISIBILITIES 3-5 SM. SOUTHERLY
WINDS 8-12KT INCREASING TO 12G22KT AFTER 18Z. CEILINGS IMPROVING
BACK UP TO NEAR 5000 FEET BEHIND THE FRONT TONIGHT WITH GUSTY
SOUTHWESTERLY WINDS CONTINUING. FELTON

&&

.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 AND POST
FRONTAL THERE COULD BE GALE WESTERLIES IN THE STRAIT.

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. FELTON

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER STORM WARNING CASCADES THROUGH TONIGHT.
     WINTER WEATHER ADVISORY OLYMPICS THROUGH THIS EVENING.
     WIND ADVISORY NORTH COAST...CENTRAL COAST...NORTH INTERIOR
       TODAY.

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