FXUS66 KSEW 272254
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PST FRI NOV 27 2009

.SYNOPSIS...THE SOUTHERN END OF A WARM FRONT WILL EDGE INTO WESTERN 
WASHINGTON LATE TONIGHT INTO SATURDAY NIGHT THEN LIFT NORTH SUNDAY.  
A WEAK COLD FRONT WILL SLIDE THROUGH THE REGION MONDAY FOR A CHANCE 
OF SHOWERS.  THIS WILL BE FOLLOWED BY AN UPPER LEVEL RIDGE WHICH IS 
EXPECTED TO PROVIDE DRY WEATHER THROUGH MOST OF THE COMING WEEK. 

&&

.SHORT TERM...SKIES CLEARED OUT NICELY TODAY FOR SUNSHINE AND MILD 
TEMPERATURES.  HOWEVER ON THE WESTERN HORIZON MID AND HIGH CLOUDS 
ARE APPROACHING AND WILL SPREAD EAST ACROSS WESTERN WASHINGTON 
TONIGHT.  

THE HIGHER CLOUDS ARE THE ADVANCE NOTICE THAT WARM ADVECTION IS 
BEGINNING TO TAKE HOLD...WHICH WILL STRENGTHEN SATURDAY WITH 
ADDITIONAL MOISTURE.  AS A RESULT WE HAVE SOME RAIN...SNOW IN THE 
MOUNTAINS...SATURDAY INTO SATURDAY NIGHT.  THE THREAT WILL BE 
GREATEST OVER NORTHERN AREAS WHILE THE FAR SE PART OF OUR FORECAST 
AREA...CENTRAL AND EASTERN LEWIS COUNTY...COULD END UP DRY THROUGH A 
LARGE PART OF THIS EVENT.  AMOUNTS WILL BE LIGHT WHERE IT DOES RAIN 
AND SNOW AMOUNTS WILL RANGE FROM A INCH SOUTH TO POSSIBLY NEAR A 
FOOT OVERALL AT MT BAKER.  

THIS WHOLE AREA OF WARM ADVECTION WILL LIFT NORTH THROUGH SUNDAY 
DIMINISHING THE THREAT OF PRECIPITATION AND ALLOWING THE CLOUDS TO 
THIN OUT DURING THE DAY.  THIS THINNING CLOUD COVER AND THE MOISTURE 
LEFT BEHIND WILL ALLOW A GOOD AMOUNT OF FOG TO FORM SUNDAY NIGHT AND 
LINGER INTO MONDAY.  

ON MONDAY A WEAK COLD FRONT WILL EITHER BARELY SLIDE THROUGH THE 
AREA OR BRUSH BY TO THE NORTH FOR A CHANCE OF A FEW SHOWERS...AGAIN 
MAINLY NORTH.  THERE IS EXPECTED TO BE A MIX OF CLOUDS AND SUN WITH 
SEASONABLE TEMPERATURES.  CERNIGLIA

.LONG TERM...THE OVERALL PATTERN WILL CONTINUE TO MAKE A MAJOR SHIFT 
AND AN UPPER LEVEL RIDGE WILL BUILD OVER THE EASTERN PACIFIC AND 
BLEED OVER INTO THE WEST COAST.  THIS WILL BRING ABOUT A MUCH DRIER 
PATTERN FOR THE REGION NEXT WEEK.  

THERE IS A BUNDLE OF ENERGY THAT THE VARIOUS LONG RANGE MODELS TRY 
TO GRAB ONTO AND MOVE EAST EITHER THROUGH OR OVER THE RIDGE.  
HOWEVER...EACH RUN AND MODEL IS DIFFERENT WITH THE 
TRACK...DEPTH...AND WHAT DAY THIS WILL MOVE THROUGH THE WESTERLIES.  
IN EACH CASE THE RIDGE POSITION IS PRETTY MUCH LOCKED IN WITH THIS 
FEATURE PLOWING THROUGH OR OVER THE TOP OF IT.  IF THIS COMES TO 
PASS IN SOME FORM IT COULD BRING A CHANCE OF SHOWERS TO THE AREA FOR 
ONE DAY.  FOR NOW WILL CONTINUE TO GO WITH THE DRY FORECAST AS THIS 
IS WHAT IS THE MOST PROBABLE SOLUTION FOR NOW.  CERNIGLIA 

&&

.HYDROLOGY...THE WARM ADVECTION SYSTEMS THAT WILL SPREAD LIGHT 
PRECIPITATION OVER WESTERN WASHINGTON THIS WEEKEND WILL BE RATHER 
WEAK AND AS A RESULT WILL NOT PRODUCE ENOUGH RAIN TO CAUSE ANY RIVER 
PROBLEMS.  

BEYOND THAT...THE FORECAST IS DRY WELL INTO NEXT WEEK.  AS A RESULT 
NO NEW FLOODING IS EXPECTED THROUGH NEXT WEEK AND AREA RIVERS WILL 
RETURN TO LOWER FLOW LEVELS.  

NO FLOODING IS EXPECTED ON THE GREEN RIVER THROUGH NEXT WEEK.  
CERNIGLIA

&&

.AVIATION...STILL CLEAR SKIES ACROSS A GOOD PART OF WRN WA THIS 
AFTERNOON WITH HIGH PRES OVER THE AREA. BKN SC HAS FILLED IN OVER 
THE COASTAL WATERS AND REMAINS SE OF THE OLYMPICS AND NR WEST SLOPES 
OF THE CASCADES. FAIRLY DRY AIR MASS TODAY WILL MOISTEN UP TNGT AND 
SAT AS A WARM FRONT BRUSHES THE REGION. FOR SAT AMS MOIST AND STABLE 
WITH AREAS OF LIGHT RAIN MNLY NORTH AND OVER THE MTNS. NO BIG 
CHANGES TO THE TAFS XCP WILL SHOW LESS RAIN KPAE SOUTH...BUT STILL 
FAIRLY LIKELY THAT CIGS AND VSBY WILL DECREASE THRU SAT AFTERNOON 
AND NIGHT WITH THE WARM FRONT...PROBABLY LOOKING AT CONDITIONS 
LOWERING TO 3-5SM -DZ OVC010 SAT NITE. 19

KSEA...NO BIG UPDATES TO THE TAF...AFTER THE WARM FRONT MOVES OVER 
THE AREA SAT AREAS OF LIGHT RAIN WILL DEVELOP BUT SEA TAC MIGHT NOT 
GET MORE THAN A FEW HUNDREDTHS. THEN...CONDITIONS SHOULD BOTTOM OUT 
SAT NITE AND SUN MORNING AS LOW LEVEL MOISTURE PERSISTS AND SFC HIGH 
PRES BUILDS BACK OVER THE REGION IN THE WAKE OF THE WARM FRONT. 

&&

.MARINE...EXPECTING A GOOD 25KT SLY WIND SATURDAY AS THE WARM FRONT 
MOVES INTO B.C. AND BRUSHES WRN WA...STRONGEST WIND WILL BE COAST 
AND SAN JUANS SATURDAY. THE 4KM WRFGFS SHOWS AN AREA OF SSE WIND 
30KT FROM LUMMI ISLAND TO CHERRY POINT TO JUST OUTSIDE OF BIRCH BAY 
SAT. AFTER THE WARM FRONT HIGH PRES WILL BUILD OVER THE REGION THRU 
SUN NIGHT...THEN OVER B.C. GVG NE FLOW BY TUE. 19

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.    

PZ...SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR. SMALL CRAFT 
ADVISORY COASTAL WATERS AND WEST ENTRANCE.

$$

WWW.WEATHER.GOV/SEATTLE

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