FXUS66 KSEW 150525
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
930 PM PST MON DEC 14 2009
.SYNOPSIS...RAIN WILL TAPER OFF OVERNIGHT AS A WARM FRONT MOVES
THROUGH WESTERN WASHINGTON. FREEZING RAIN AND SNOW WILL CONTINUE IN
WESTERN WHATCOM COUNTY OVERNIGHT AS COOL AIR CONTINUES TO FLOW DOWN
THE FRASER. PERIODS OF HEAVY SNOW WILL FALL IN THE MOUNTAINS THROUGH
TUESDAY. A SERIES OF FRONTAL SYSTEMS WILL AFFECT THE REGION THROUGH
THE WEEK.
&&
.SHORT TERM...FREEZING RAIN AND SNOW CONTINUE UP ARND BELLINGHAM
THIS EVENING...AND LIGHT SNOW AT EAST SOUND ON ORCAS SO COLD FRASER
AIR EXTENDS TO AT LEAST THE NRN SAN JUANS...AND BLI-YWL HAS REACHED
-15MB. SNOW AND WIND IN THE MOUNTAINS...STRONG ELY GRADIENT WITH GAP
WIND THRU THE CASCDS GVG AREAS LOW VSBY IN THE PASSES. ON AVERAGE A
FOOT OF NEW SNOW OUGHT TO FALL IN THE MTNS TNGT WITH THIS FIRST
SURGE OF WARM ADVECTION. EASTERLY GRADIENTS HAVE BEEN QUITE
STRONG...GVG FULL GALE DESTRUCTION AND TATOOSH AND DUNGENESS SPIT
REACHED EAST 40MPH. COLD HEAVY RAIN AT SHELTON...DROPPED THE SNOW
ADVISORY FOR HOOD CANAL...WET SNOW ON THE HILLS BUT ANY DECENT SNOW
ACCUMULATION WILL GNLY BE ABV 1500FT ON THE EAST SLOPES OF THE
OLYMPICS OVERNIGHT...HERE IS SEATTLE THE FREEZING LEVEL HAS RISEN TO
1000M ON THE PROFILER SO THE TREND IS BACK TO MILD TEMPS AND PERIODS
OF RAIN...WITH THE EXCEPTION OF UP ARND KBLI AND THE NRN SAN JUANS
TNGT. 19
.LONG TERM...PREV...HAVE LIKELY POPS FOR THE THURSDAY NIGHT SYSTEM.
THEN ON FRIDAY HAVE A MORE SHOWERY SITUATION AND HAVE PUT IN CHANCE
POPS...WITH LIKELIES FOR THE MOUNTAINS. ONE MORE SYSTEM ON SATURDAY
BRINGS ANOTHER BATCH OF LIKELY POPS. THEN BOTH THE GFS AND THE EURO
SHOW A SMALL DRYING TREND...THE GFS IS KIND OF DRY OVER THE PACIFIC
NORTHWEST AND THE EURO SHUNTS THE MOISTURE INTO BRITISH COLUMBIA.
ANYWAY HAVE GIVEN CHANCE POPS TO THE SUNDAY-MONDAY PERIOD. BURKE
&&
.HYDROLOGY...A TRANSITION TO A WETTER PATTERN WILL BEGIN TONIGHT
THROUGH AT LEAST THE MIDDLE OF THE WEEK AS A SERIES OF PACIFIC
FRONTAL SYSTEMS SWEEP THROUGH WESTERN WASHINGTON. INITIALLY SNOW
LEVELS REMAIN LOW WITH HEAVY SNOW EXPECTED TONIGHT THROUGH TUESDAY
AFTERNOON IN THE MOUNTAINS. SNOW LEVELS WILL RISE TO AROUND 4000 FT
ON WEDNESDAY AS ANOTHER SYSTEMS REACHES THE REGION. THE FLOOD
POTENTIAL LOOKS LOW AT THE MOMENT AS RIVERS HAVE BEEN RUNNING LOW
WITH LITTLE TO NO PRECIPITATION ACROSS THE REGION SINCE LATE
NOVEMBER. NO FLOOD CONCERNS FOR THE GREEN RIVER.
MODELS TRY TO BUILD AN UPPER LEVEL RIDGE ACROSS THE PACIFIC
NORTHWEST BEGINNING ABOUT SUNDAY...WITH A BREAK IN THE WEATHER
POSSIBLE. THE RIDGE WILL BREAK DOWN EARLY NEXT WEEK BUT EXACT TIMING
REMAINS UNCLEAR AS BOTH THE GFS AND ECMWF DIFFER. BURKE
&&
.AVIATION...WARM FRONT OFFSHORE REACHING THE COAST AROUND 09Z AND
MOVING THROUGH THE INTERIOR BY 13Z. STRONG EASTERLY GRADIENTS OUT
AHEAD OF THE FRONT KEEPING CEILINGS AROUND 3000 FEET OVER THE
INTERIOR WITH VISIBILITIES AS LOW AS 1-3SM IN MODERATE RAIN. THE
EXCEPTION TO THIS IS UP NEAR KBLI WHERE NORTHEASTERLY OUTFLOW WINDS
ARE KEEPING TEMPERATURES BELOW FREEZING RIGHT NEAR THE SURFACE AND
THE PRECIPITATION IS IN THE FORM OF FREEZING RAIN. FREEZING RAIN
WILL CONTINUE AT KBLI UNTIL THE FRONT PASSES. CEILINGS LOWERING DOWN
TO THE 1000 TO 2000 FOOT RANGE RIGHT WITH AND BEHIND THE FRONT
TUESDAY MORNING. CEILINGS LIFTING BACK UP TO NEAR 3000 FEET MIDDAY
TUESDAY WITH THE RAIN FROM THE NEXT SYSTEM BEGINNING LATE IN THE
AFTERNOON. FELTON
KSEA...CEILINGS RUNNING AROUND 3000 FEET UNTIL RIGHT BEFORE THE
FRONT PASSES AROUND 12Z. CEILINGS LOWERING DOWN TO 1000 TO 200 FEET
WITH AND JUST BEHIND THE FRONT. CEILINGS WILL LIFT BACK UP TO NEAR
3000 FEET MIDDAY WITH RAIN FROM THE NEXT SYSTEM BEGINNING AROUND 00Z
WED. EASTERLY WINDS 10 TO 15 KNOTS BECOMING SOUTHEAST 10 KNOTS OR
LESS AFTER 12Z. FELTON
&&
.MARINE...A WARM FRONT WILL MOVE INTO THE AREA FROM THE SOUTHWEST
AND PASS THROUGH THE INLAND WATERS LATE TONIGHT. STRONG EASTERLY
GRADIENTS AHEAD OF THE FRONT...KUIL-KBLI PEAKED AT -8.7 MB AT 03Z
WHILE CROSS CASCADE GRADIENT IS UP TO -11 MB AT 04Z. GALE FORCE
WINDS OVER THE COASTAL WATERS AND THROUGH THE STRAIT WILL EASE
BEHIND THE FRONT TUESDAY MORNING. OVER THE NORTHERN INLAND WATERS
OUTFLOW NORTHEASTERLY WINDS CONTINUE WITH KBLI-CYWL AT -13.6 MB AT
04Z. SMALL CRAFT ADVISORY NE WINDS WILL CONTINUE UNTIL THE FRONT
PASSES. SMALL CRAFT ADVISORY WINDS WILL ALSO CONTINUE IN ADMIRALTY
INLET UNTIL THE FRONT MOVES BY TO THE EAST. EXPECT WINDS TO DIMINISH
EARLY TUE...THEN PICK UP AGAIN LATE IN THE DAY THROUGH TUE NIGHT AS
YET ANOTHER WARM FRONT MOVES NE THROUGH THE WATERS.
A SERIES OF WARM FRONTS ASSOCIATED WITH LOWS MOVING THROUGH THE EAST
PACIFIC TOWARD THE QUEEN CHARLOTTE ISLANDS WILL MOVE THROUGH THE
WATERS WED THROUGH THU NIGHT.
A LESS ACTIVE TIME IS SEEN FRI THROUGH NEXT WEEKEND. EXTENDED MARINE
FORECASTS GENERALLY FOLLOW THE ECMWF...THAT KEEPS LOWER PRES MOVING
N AND WEST OF THE AREA IN LIEU OF THE 12Z GFS THAT MOVES LOW PRES
SYSTEMS INTO OREGON. FELTON/ALBRECHT
&&
.AVALANCHE...COLD WEATHER THE PAST WEEK GENERALLY CREATED WEAK
SURFACE SNOW LAYERS. A FRONT SHOULD CAUSE INCREASING STRONG
WINDS...INCREASING MODERATE TO HEAVY SNOW AND WARMING TEMPERATURES
MONDAY AFTERNOON AND NIGHT. THIS SHOULD BUILD INCREASING DEEP
UNSTABLE LAYERS ON SOME SLOPES. NATURAL OR TRIGGERED AVALANCHES
SHOULD BECOME LIKELY MONDAY NIGHT AND TO PERSIST TUESDAY MORNING. AN
AVALANCHE WARNING IS NOW IN EFFECT FOR MONDAY NIGHT FOR BACK COUNTRY
AREAS OF THE OLYMPICS AND CASCADES.
ANOTHER FRONT IS CURRENTLY EXPECTED TO CAUSE RENEWED HIGH AVALANCHE
DANGER TUESDAY AFTERNOON AND TUESDAY NIGHT. PLEASE VISIT WWW.NWAC.US
FOR DETAILS. FERBER
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...A WINTER WEATHER ADVISORY IS IN EFFECT FOR WESTERN WHATCOM
COUNTY TONIGHT.
A WINTER STORM WARNING IS IN EFFECT FOR THE OLYMPICS AND
CASCADES THROUGH TUESDAY.
AN AVALANCHE WATCH IS IN EFFECT FOR THE OLYMPICS AND
CASCADES TONIGHT.
PZ...GALE WARNING COAST AND STRAIT OF JUAN DE FUCA.
.SMALL CRAFT ADVISORY CAMANO ISLAND TO POINT ROBERTS AND
ADMIRALTY INLET.
.SMALL CRAFT ADVISORY GRAYS HARBOR BAR FOR ROUGH BAR CONDITIONS.
$$
