FXUS66 KSEW 262254
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PST THU NOV 26 2009

.SYNOPSIS...A WEAK FRONT WILL REMAIN JUST SOUTH OF THE AREA WHILE AN 
UPPER TROUGH MOVES ACROSS THE REGION EARLY FRIDAY MORNING.  THE 
SOUTHERN END OF A WARM FRONT WILL APPROACH THE NORTHWEST FRIDAY 
NIGHT BRINGING A THREAT OF RAIN INTO SUNDAY.  A WEAK COLD FRONT WILL 
DROP SOUTHEAST THROUGH THE AREA MONDAY.  BEHIND THIS FRONT AN UPPER 
LEVEL RIDGE WILL BUILD OVER THE EASTERN PACIFIC TUESDAY FOR WHAT 
LOOKS TO BE THE BEGINNING OF AN EXTENDED PERIOD OF DRY WEATHER. 

&&

.SHORT TERM...THE COLD FRONT IS JUST SOUTH OF THE FORECAST AREA AS 
THE WEAK SURFACE LOW GRADUALLY MOVES TO THE NE TOWARD THE NORTH 
OREGON COAST.  THIS WILL PASS BY TO THE SOUTH TONIGHT AS THE 
ASSOCIATED UPPER TROUGH APPROACHES THE COAST.  UNTIL THE UPPER 
TROUGH AXIS PASSES BY FRIDAY MORNING THE ENTIRE AREA IS UNDER THE 
THREAT OF AT LEAST SOME SHOWERS.  THEN AS THE SYSTEM CONTINUES TO 
MOVE OFF TO THE EAST THE SHOWER THREAT COMES TO AN END LATER FRIDAY 
MORNING WITH THE LIKELIHOOD OF SOME SUN BREAKING THROUGH THE CLOUD 
COVER AT TIMES DURING THE AFTERNOON.  TEMPERATURES SEASONAL. 

FRIDAY NIGHT INTO SATURDAY WE ARE STILL LOOKING AT WARM ADVECTION 
MOVING INTO THE REGION FROM HERE UP THE BRITISH COLUMBIA COAST.  OUR 
AREA REMAINS ON THE SOUTHERN EDGE OF THE SIGNIFICANT WARM ADVECTION 
AND AS SUCH THE GRADIENT OF THE RAIN THREAT RANGES FROM HIGH TO THE 
NORTH TO NEARLY NON-EXISTENT TO THE SOUTH.  PRECIPITATION AMOUNTS 
ARE EXPECTED TO BE LIGHT OVERALL.  

THIS WARM ADVECTION PATTERN CONTINUES INTO SUNDAY...HOWEVER UPPER 
HEIGHTS RISE A BIT AND THE BULK OF THE MOISTURE ROLLS BY TO THE 
NORTH SO THE THREAT OF RAIN IS REDUCED WHEN COMPARED TO SATURDAY.  
THERE IS A POSSIBILITY THAT MOST OF THE AREA COULD END UP RAIN FREE 
THAT DAY.  CERNIGLIA

.LONG TERM...A MAJOR AND LIKELY WELCOME CHANGE IN THE WEATHER 
PATTERN BEGINS TO TAKE SHAPE MONDAY.  A WEAK COLD FRONT IS FORECAST 
TO SLIDE SE ACROSS THE REGION OR POSSIBLY JUST BRUSH BY...THEN AN 
UPPER LEVEL RIDGE WILL BUILD OVER THE EASTERN PACIFIC AND THE 
WESTERN EDGE OF THE NORTH AMERICA.  AFTER THE WEAK FRONT MOVES 
BY...DRY WEATHER WILL TAKE HOLD TUESDAY AND LIKELY CONTINUE THROUGH 
AT LEAST THURSDAY AND ONE MODEL IS EVEN SUGGESTING IT MIGHT CONTINUE 
INTO NEXT WEEKEND.  WE ALREADY DRIED OUT THE FORECAST TUESDAY ONWARD 
YESTERDAY SO I JUST EXTENDED THAT TREND INTO THURSDAY.  CERNIGLIA 

&&

.HYDROLOGY...THE BAROCLINIC BAND SHIFTED SOUTHEAST ACROSS THE REGION 
A BIT QUICKER THAN ANTICIPATED AND THIS HAD A POSITIVE AFFECT ON 
LIMITING THE FLOODING TO JUST TWO RIVERS...AND THOSE WERE MINOR.  
MANY OTHER RIVERS HAD SIGNIFICANT RISES BUT REMAINED JUST BELOW 
FLOOD STAGE.  SO AFTER WE DROP THE TWO WARNINGS WE HAVE UP NOW AS 
THEY AREA RECEDING...THE THREAT OF FLOODING WILL PRETTY MUCH BE OVER 
FOR THIS EVENT.

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

BEYOND THAT THE FORECAST IS DRY WELL INTO NEXT WEEK AND LIKELY INTO 
THE FOLLOWING WEEKEND.  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...A WEAK 1010 MB SURFACE LOW WILL TRACK INTO NRN OREGON 
THIS EVENING ALLOWING THE FRONTAL BAND OVER SRN WA TO FINALLY PUSH 
EWD. THE UPPER TROUGH WILL FOLLOW LATER TONIGHT WITH LIGHT FLOW 
ALOFT. RESIDUAL MOISTURE AND WEAK ONSHORE SURFACE GRADIENTS WILL 
RESULT IN WIDESPREAD LOW MVFR AND IFR CIGS/VIS TONIGHT. LOW CLOUDS 
AND FOG WILL HANG IN THROUGH AT LEAST MIDDAY FRI.

KSEA...N/NE WIND 5 TO 8 KT...BECOMING S 3-6 KT BY 12Z FRI MORNING. 
DTM

&&

.MARINE...ONSHORE FLOW WILL REMAIN MODERATELY STRONG OVER THE 
COASTAL WATERS THROUGH FRI BEHIND A FRONTAL SYSTEM PUSHING INLAND 
TONIGHT. WILL CONTINUE THE SMALL CRAFT WINDS THROUGH FRI...BUT IT 
DOES APPEAR WINDS START TO COME DOWN LATE IN THE DAY. SWELL ALSO 
REMAINS ABOVE 10 FT THROUGH THE PERIOD. WINDS ACROSS THE INTERIOR 
WILL REMAIN BELOW 20 KT THROUGH FRI.

A WARM FRONT LIFTS ACROSS WRN WA ON SAT. THE BEST CHANCE FOR SMALL 
CRAFT CONDITIONS WILL BE OVER THE COASTAL WATERS. WINDS WILL COME UP 
ACROSS THE INTERIOR...POSSIBLY MARGINAL SMALL CRAFT WINDS AT THE 
ENTRANCES TO THE STRAIT AND MAYBE THE N INTERIOR. DTM

&&

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

PZ...SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR. 
     SMALL CRAFT ADVISORY COAST.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS WEST ENTRANCE.

$$

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