000
FXUS66 KSEW 092151
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PDT FRI MAY 9 2008

.SYNOPSIS...A COLD FRONT WILL MOVE OVER WESTERN WASHINGTON BY
SATURDAY NIGHT. A COOL UPPER LEVEL TROUGH WILL BE OVER THE AREA
SUNDAY. A WEAK RIDGE WILL BUILD INTO THE REGION MONDAY FOLLOWED BY A
WARM FRONT NEXT TUESDAY. AN UPPER LEVEL RIDGE WILL BUILD OVER THE
PACIFIC NORTHWEST NEXT WEDNESDAY.

&&

.SHORT TERM...SORRY TO SAY THAT ANOTHER COLD FRONT FOLLOWED BY A
COOL UPPER LEVEL TROUGH IS ON TAP FOR THE WEEKEND. THE FRONT SEEMS
TO BE HOLDING TOGETHER JUST FINE AND IS NEAR 130W THIS AFTERNOON. AN
INCREASING CHANCE OF RAIN IN THE FORECAST FOR SATURDAY...BECOMING
LIKELY ON THE COAST AND IN THE OLYMPICS AND NORTH CASCADES...BUT NOT
LIKELY UNTIL EVENING FOR THE REST OF WESTERN WA. SHOWING TEMPS NOT
TOO AWFULLY COOL WITH JUST THE CHANCE POPS ARND PUGET SOUND BECAUSE
I THINK WE MAY SEE JUST A VERY LITTLE LIGHT RAIN AMOUNTING TO ONLY A
HUNDREDTH OR TWO. SATURDAY NIGHT WITH THE UPPER TROF MOVG OVER WRN
WA LIGHT RAIN OR SHOWERS ARE LIKELY...AND WILL PROBABLY FINISH OFF
WITH A PSCZ. SCATTERED AIR MASS HIT OR MISS SHOWERS UNDER THE COOL
UPPER TROF FOR SUNDAY WITH HIGHS IN THE 50S OVER WRN WA...A GOOD
FIVE DEGREES BELOW NORMAL. UPPER LEVEL HEIGHTS RECOVER INTO MONDAY
AS WEAK HIGH PRES BUILDS INTO THE AREA BUT IT ISN`T MUCH OF A RIDGE.
THE GFS TAKES A WARM FRONT INTO B.C. BY DAYBREAK TUE AND THE MODELS
HAVE BEEN PUTTING PRECIP OVER WRN WA AS WELL WITH THAT FEATURE. 19

.LONG TERM...THE WARM FRONT LIFTS NORTH LATE TUESDAY NIGHT. GFS HAS
THE 500MB HEIGHTS RISING TO 576DAM AT DAYBREAK WED THEN WELL INTO
THE 580`S...AND PEAKING AROUND 590 WEDNESDAY NIGHT. A GOOD WARM
RIDGE FOR A CHANGE WITH PRECIP FROM A FRONTAL SYSTEM DIRECTED AT
B.C. BETWEEN THE CHARLOTTES AND VRILS THRU WED NIGHT. THIS RIDGE
COULD GIVE THE INTERIOR OF WESTERN WA TEMPS WELL INTO THE
80S...ALTHOUGH FOR NOW WE ARE JUST SHOWING TEMPS IN THE INTERIOR IN
THE 70S. IT HAS BEEN SUCH A COOL SPRING EVEN SOMETHING 10 OR 15
DEGREES ABOVE AVERAGE FOR A COUPLE OR THREE DAYS SEEMS GOOD ENUF FOR
NOW. 19

&&


.AVIATION...SCT CLOUDS AROUND 5-6 KT FT THROUGH THIS EVENING...THEN
BKN-OVC CIGS 10-12K FT DEVELOPING AFTER 08Z. A WEAK SURFACE FRONT
WILL REACH THE COAST AROUND 16-18Z...THEN PUSH INLAND AND DISSIPATE.
LIGHT RAIN ALONG THE COAST BY 15Z WILL SPREAD INLAND DURING THE
AFTERNOON IN THE FORM OF SHOWERS. CIGS WILL LOWER THROUGH THE
AFTERNOON WITH TEMPO MVFR AFTER 20Z.

AT KSEA....W-NW WIND 4-8 KT...BECOMING S WIND 2-4 KT AFTER 04Z. DTM

&&

.MARINE...A WEAK FRONT WILL MOVE INTO THE COASTAL WATERS SATURDAY
MORNING (PIC10) AND DISSIPATE OVER THE INLAND WATERS DURING THE
AFTERNOON (PIC11). OTHERWISE...ONSHORE FLOW WILL PREVAIL THE NEXT
SEVERAL DAYS. A BURST OF SMALL CRAFT WESTERLIES ARE LIKELY SATURDAY
EVENING. DTM

&&

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

$$

WEATHER.GOV/SEATTLE