High Wind in Washington, February 7, 2013

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
905 PM PST WED FEB 6 2013

.SYNOPSIS...RAIN OUT AHEAD OF AN APPROACHING WEATHER SYSTEM WILL
CONTINUE TO SPREAD OVER THE AREA TONIGHT. THE FRONT WILL MOVE
THROUGH WESTERN WASHINGTON THURSDAY MORNING. AN UPPER LEVEL TROUGH
WILL MOVE THROUGH THE REGION LATER THURSDAY WITH THE TROUGH BEING
REPLACED BY A RIDGE ON FRIDAY. THE RIDGE WILL REMAIN IN PLACE
THROUGH THE WEEKEND WITH A WEAK SYSTEM MOVING THROUGH THE RIDGE
BRUSHING THE COAST ON SATURDAY.

&&

.SHORT TERM...CURRENT RADAR IMAGERY SHOWS ANOTHER ROUND OF SHOWERS
MAKING THEIR WAY INLAND FROM THE COAST AND SLOWLY SPREADING EASTWARD
IN ADVANCE OF THE FRONT EXPECTED TO PASS THROUGH WESTERN WASHINGTON
TOMORROW MORNING. SWITCHING OVER TO CURRENT IR SATELLITE
IMAGERY...THE FRONT REMAINS OFF THE COAST AS ASSOCIATED DUAL LOW
PRESSURE CENTERS ARE VERY SLOW TO MOVE. INHERITED FORECAST PROGS THE
COLD FRONT REACHING THE COAST AROUND 12Z AND THE CASCADES BETWEEN
15Z AND 18Z. GIVEN THIS MOTION...OR DISTINCT LACK THEREOF...AM
INCLINED TO AGREE WITH THIS.

FREEZING LEVELS ON 00Z KUIL SOUNDING REMAIN CONSISTENT...NOT
IDENTICAL BUT DEFINITELY CLOSE...SO DO NOT IMAGINE ANY FLUCTUATION
IN SNOW LEVELS OVERNIGHT AND INTO THURSDAY MORNING...REMAINING
AROUND 2500 FEET. SHIFT IN FLOW ALOFT TO MORE SOUTHERLY DIRECTION
MAY LIMIT SNOW AMOUNTS FOR AREAS UNDER WINTER WEATHER
ADVISORY...HOWEVER STILL LOOK TO MEET LOW END CRITERIA OR JUST SHY
OF THAT. MOUNT BAKER SHOULD GET THE HIGHEST NEW SNOW AMOUNTS WITH A
LITTLE MORE THAN A FOOT OF NEW SNOW POSSIBLE. THAT SAID...WILL LEAVE
THE ADVISORY IN PLACE.

BEHIND THE FRONT UPPER LEVEL TROUGH DIGGING SOUTH LEAVING WESTERN
WASHINGTON WITH LIGHT FLOW ALOFT BUT IN THE TROUGH POSITION. THIS
WILL KEEP SHOWERS IN THE FORECAST INTO THURSDAY EVENING.

UPPER LEVEL RIDGE BUILDING INTO THE BRITISH COLUMBIA COAST THURSDAY
NIGHT INTO FRIDAY MORNING WITH A DRY NORTH NORTHEASTERLY FLOW ALOFT
OVER WESTERN WASHINGTON. SURFACE GRADIENTS GOING LIGHT THURSDAY
NIGHT AND REMAINING LIGHT INTO FRIDAY MORNING WITH AREAS OF FOG
FORMING IN THE EARLY MORNING HOURS ON FRIDAY.

UPPER LEVEL RIDGE REMAINING IN PLACE FRIDAY INTO SATURDAY BUT A
WEAKENING SYSTEM WILL RIDE OVER THE TOP OF THE RIDGE FRIDAY NIGHT
AND SLIDE BY TO THE WEST SATURDAY MORNING. ALL OF THE MODELS SHOW
SOME VERY LIGHT PRECIPITATION ALONG THE COAST FOR SATURDAY MORNING.
WITH THE SYSTEM MOVING OVER THE TOP OF THE RIDGE...THERE WILL NOT BE
MUCH LEFT OF IT BY THE TIME IT APPROACHES THE AREA. HOWEVER...GIVEN
THE GOOD MODEL AGREEMENT...CHANCE POPS SEEMS LIKE A GOOD STARTING
POINT. FOR THE REMAINDER OF THE AREA THE WEAK WARM ADVECTION
COMBINED WITH THE LIGHT SURFACE GRADIENTS HAS A GOOD CHANCE OF
CREATING WIDESPREAD LOW CLOUDS OR FOG SATURDAY MORNING. WHILE THE
SUN HAS A LITTLE BIT OF JUICE THIS TIME OF YEAR WITH THE LIGHT FLOW
AT THE LOWER LEVELS IT WILL BE TOUGH TO GET RID OF THE LOW LEVEL
MOISTURE LEAVING SATURDAY A CLOUDY DAY FOR THE MOST PART. SMR/FELTON

.LONG TERM...PREVIOUS DISCUSSION...ONCE AGAIN THE MODELS ARE IN
DISAGREEMENT IN THE MONDAY THROUGH WEDNESDAY. FOR SUNDAY THERE IS
GOOD AGREEMENT WITH AN UPPER LEVEL RIDGE OVER THE AREA AND LIGHT
ONSHORE SURFACE GRADIENTS. AS HAS BEEN THE CASE FOR AT LEAST THE
LAST 4 MODEL RUNS THE DIFFERENCES BEGIN ON MONDAY. THE GFS KEEPS THE
UPPER LEVEL RIDGE INTACT OVER WESTERN WASHINGTON WHILE THE ECMWF
WEAKENS THE RIDGE WITH A WARM FRONT MOVING OVER THE RIDGE INTO
WESTERN WASHINGTON. THE ECMWF CONTINUES WITH WETTER PATTERN ON
TUESDAY AND HAS AN EVEN STRONGER SYSTEM ARRIVING ON WEDNESDAY. THE
GFS KEEPS A RIDGE OVER WESTERN WASHINGTON THROUGH THE WHOLE TIME.
THE CANADIAN IS MORE IN LINE WITH THE ECMWF AND THE GFS ENSEMBLES DO
NOT ADD CONFIDENCE TO THE GFS SOLUTION BEING CORRECT. AT THIS POINT
A BROAD BRUSH CHANCE OF RAIN FORECAST WILL CONTINUE FOR THE MONDAY
THROUGH WEDNESDAY TIME FRAME. FELTON

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THE NEXT 7 DAYS.

&&

.AVIATION...A FRONTAL SYSTEM ASSOCIATED WITH A LOW OVER THE COASTAL
WATERS WILL MOVE ONSHORE SHORTLY AFTER MIDNIGHT THEN THROUGH THE
INTERIOR OF WESTERN WASHINGTON DURING THE EARLY MORNING HOURS.
STRONG SW WINDS ALOFT WILL BECOME WESTERLY AND DIMINISH THURSDAY
MORNING. STABLE CONDITIONS ALOFT WILL BECOME UNSTABLE BEHIND THE
FRONT. A MOIST AIR MASS AHEAD OF THE FRONT WILL GRADUALLY DRY LATER
THURSDAY.

CONDITIONS THIS EVENING ARE MVFR ON THE COAST WITH PRECIPITATION
AHEAD OF THE INCOMING FRONT. BRIEF OFFSHORE FLOW IN THE INTERIOR
HAS ALLOWED CONDITIONS TO IMPROVE TO VFR. CONDITIONS WILL
DETERIORATE OVER THE INTERIOR LATER THIS EVENING AS THE FRONTAL BAND
MOVES ONSHORE THEN INTO THE INTERIOR.

SHOWERS WILL GIVE VFR TO OCCASIONAL MVFR CONDITIONS ON THURSDAY.
EXPECT POORER CONDITIONS AND HEAVIER SHOWERS NEAR THE MOUNTAINS AND
ALONG THE COAST. CONDITIONS WILL GRADUALLY IMPROVE THURSDAY NIGHT AS
HIGH PRESSURE BUILDS INTO THE REGION AND FLOW AT THE SURFACE AND
ALOFT BECOMES MORE NORTHERLY. ALBRECHT

KSEA...SOUTHEAST WIND 8-12 KT WILL SHIFT TO SSW AND INCREASE TO 12
TO 20 KT 09Z-11Z WITH FRONTAL PASSAGE. WIND WILL GRADUALLY DIMINISH
DURING THE MORNING HOURS. EXPECT A PERIOD OF LIGHT TO OCCASIONALLY
MODERATE RAIN 07-11Z THAT WILL BECOME SHOWERY WITH THE FRONTAL
PASSAGE. CIGS AROUND 045 WILL FALL TO 020 09-11Z THEN GRADUALLY
IMPROVE DURING THE DAY THU. ALBRECHT

&&

.MARINE...A MODERATE TO STRONG FRONTAL SYSTEM OVER THE COASTAL
WATERS IS ASSOCIATED WITH A 1002 MB LOW JUST OFF THE CENTRAL WA
COAST. THE LOW AND ITS ASSOCIATED BENT BACK OCCLUSION WILL LIFT
NORTHEAST ACROSS THE FAR NORTHERN COASTAL WATERS OVERNIGHT. THE COLD
FRONT ASSOCIATED WITH THIS SYSTEM WILL MOVE ONSHORE SHORTLY AFTER
MIDNIGHT AND THROUGH THE INLAND WATERS BY 4 AM. POST FRONTAL SHOWERS
LATE TONIGHT AND EARLY THURSDAY MORNING  WILL BE ACCOMPANIED BY A
PERIOD OF GUSTY SOUTHWEST WINDS THAT WILL GRADUALLY DIMINISH DURING
THE DAY THURSDAY AS HIGH PRES BUILDS INTO THE INLAND WATERS.

WITH THE FRONT ENTERING THE COASTAL WATERS AND THE APPEARANCE OF A
BENT BACK OCCLUSION ON SATELLITE IMAGERY...GALE WARNINGS WILL BE
MAINTAINED OVER THE COASTAL WATERS AND AT THE WEST ENTRANCE OF THE
STRAIT. WINDS BRIEFLY HIT GALE FORCE AT SMITH ISLAND AT THE EAST
ENTRANCE OF THE STRAIT EARLIER THIS EVENING BEFORE DIMINISHING
SOMEWHAT. EXPECT PRESSURE GRADIENTS AND WINDS TO INCREASE AGAIN
OVERNIGHT AS THE OFFSHORE FRONT MOVES THROUGH...AS SHOWN BY THE 00Z
NAM12 SOLUTION...SO A GALE WARNING WAS HOISTED FOR THE EAST ENTRANCE
TO THE STRAIT OVERNIGHT. SMALL CRAFT ADVISORIES WILL BE MAINTAINED
OVER ALL THE WATERS EARLY THURSDAY MORNING WITH POST FRONTAL
SOUTHWEST FLOW AND SHOWERS. WHILE WINDS WILL DIMINISH OVER THE
COASTAL WATERS DURING THE DAY ON THURSDAY...SMALL CRAFT ADVISORY
CONDITIONS FOR HAZARDOUS SEAS WILL CONTINUE THROUGH THURSDAY EVENING.

HIGH PRESSURE WILL GIVE MAINLY LIGHT WINDS OVER THE WATERS LATE
THURSDAY THROUGH THE WEEKEND. ALBRECHT.

&&

WA...WINTER WEATHER ADVISORY FOR THE OLYMPICS ABOVE 2500 FEET UNTIL
     NOON THURSDAY.

     WINTER WEATHER ADVISORY FOR THE CASCADES ABOVE 2500 FEET
     TONIGHT THROUGH NOON THURSDAY.

PZ...GALE WARNING IN EFFECT FOR THE COASTAL WATERS...THE WEST
     ENTRANCE TO THE STRAIT OF JUAN DE FUCA...AND EAST ENTRANCE TO
     THE STRAIT.

     SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE REMAINING WATERS.

     SMALL CRAFT ADVISORY IN EFFECT FOR ROUGH GRAYS HARBOR BAR
     CONDITIONS UNTIL 9 PM THURSDAY.

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