Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 242232
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
332 PM PDT FRI APR 24 2015

.SYNOPSIS...AN UPPER LOW OVER VANCOUVER ISLAND WILL MOVE OVER THE
AREA LATER TONIGHT. EXPECT THIS LOW TO MOVE EAST OF THE CASCADES
SATURDAY AFTERNOON. HIGH PRESSURE ALOFT WILL PREVAIL SUNDAY AND
MONDAY. ALTHOUGH...ANTICIPATE A WARM FRONT TO BRING SOME RAIN TO
THE REGION DURING THIS TIME FRAME. TEMPERATURES WILL START OUT
BELOW NORMAL ON SATURDAY BUT WILL RISE WELL ABOVE NORMAL ON
MONDAY.

&&

.SHORT TERM...
A FEW TSTMS ERUPTED OVER THE FAR NORTH INTERIOR THIS AFTERNOON. IT
LOOKS LIKE THE BEST CHANCE OF TSTMS WILL REMAIN OVER THE NORTH
INTERIOR THROUGH THIS EVENING. HOWEVER...CANNOT COMPLETELY RULE
OUT AN ISOLATED LIGHTNING STRIKE ELSEWHERE. THE THREAT OF TSTMS
SHOULD END SHORTLY AFTER SUNSET.

THE UPPER LOW SPINNING OVER VANCOUVER ISLAND WILL MOVE OVER
WESTERN WASHINGTON LATER TONIGHT. EXPECT THE LOW TO MOVE INTO
EASTERN WA SATURDAY AFTERNOON. THERE WILL BE A THREAT OF TSTMS
AGAIN ON SATURDAY BUT THE BEST CHANCE SHOULD BE OVER THE CASCADES.
ALTHOUGH...CANNOT RULE OUT AN ISOLATED TSTM OVER THE REST OF THE
INTERIOR SATURDAY AFTERNOON. AN UPPER RIDGE WILL MOVE OVER THE
REGION SATURDAY NIGHT FOR IMPROVED WEATHER CONDITIONS.

AN UPPER RIDGE WILL PREVAIL OVER THE PACIFIC NORTHWEST ON SUNDAY.
HOWEVER...A WARM FRONT WILL APPROACH FROM THE WEST DURING THE DAY.
THIS WILL RESULT IN A CHANCE OF RAIN OVER THE WESTERN PART OF THE
CWA. THERE WERE DIFFERENCES IN THE MODELS CONCERNING THE PRECIP
POTENTIAL OVER THE CWA SUNDAY NIGHT. THE GFS WAS THE DRIEST
WHEREAS THE ECMWF APPEARED THE WETTEST. HOWEVER...THE ECMWF SEEMED
TO BE BACKING OFF FROM ITS EARLIER SOLUTIONS. CONSEQUENTLY...THE
FORECAST KEPT THE HIGHEST THREAT OF RAIN OVER THE WESTERN ZONES.

THE RIDGE WILL AMPLIFY FURTHER ON MON AND THIS WILL LEAD TO A
DECREASED THREAT OF PRECIP. IT WILL ALSO BE QUITE WARM ON MON...
WITH TEMPS ACROSS MANY LOCATIONS FORECAST TO CLIMB WELL ABOVE
NORMAL.

.LONG TERM...
CONFIDENCE IN THIS PERIOD WAS VERY LOW DUE TO DISAGREEMENT BETWEEN
AND LACK OF CONSISTENCY IN THE MEDIUM RANGE MODEL SOLUTIONS. HAVE
CHOSEN TO KEEP A LOW CHANCE OF PRECIP IN THE FORECAST FOR THE MOST
PART. ALSO...DECIDED TO SHOW A COOLING TREND...WITH DAYTIME TEMPS
FALLING BACK TO NEAR NORMAL.

&&

.AVIATION...AN UPPER LOW OVER SOUTHERN VANCOUVER ISLAND WILL DRIFT
SLOWLY SOUTHEAST TONIGHT AND SATURDAY WITH WESTERLY FLOW ALOFT
BECOMING NORTHERLY. AIR MASS MOIST AND UNSTABLE...BECOMING A BIT
MORE STABLE LATER TONIGHT.

MULTIPLE CLOUD LAYERS TONIGHT AND SATURDAY WITH CEILINGS MOSTLY VFR
AND SOME DRYING IN THE LOW LEVELS ON SATURDAY. 2000-3000 FOOT
CEILINGS ARE POSSIBLE IN SHOWERS. SHOWERS SHOULD TAPER THIS EVENING
AND BE MORE ISOLATED ON SATURDAY. THERE IS SMALL CHANCE OF
THUNDERSTORMS OVER THE NORTH PART OF THE FORECAST AREA THIS EVENING.

KSEA...SOUTHERLY WINDS 10 KNOTS WITH GUSTS TO 20 KNOTS POSSIBLE
THROUGH EARLY EVENING. WINDS EASING TONIGHT. CEILINGS EXPECTED TO BE
AROUND 5000 FEET TONIGHT...POSSIBLY DOWN TO AROUND 2000 FEET IN
SHOWERS THIS EVENING. AN ISOLATED THUNDERSTORM CANNOT BE COMPLETELY
RULED OUT THIS EVENING BUT THE CHANCES ARE TOO LOW TO MENTION IN THE
TAF. SCHNEIDER

&&

.MARINE...A TROUGH OVER THE COASTAL WATERS WILL WEAKEN AND SHIFT
ONSHORE TONIGHT. SMALL CRAFT SOUTH WINDS IN PUGET SOUND AND WEST
WINDS IN THE STRAIT SHOULD EASE LATER TONIGHT AS ONSHORE FLOW
RELAXES. 10 OR 11 FOOT WEST SWELLS OVER THE COASTAL WATERS SHOULD
SUBSIDE BELOW 10 FEET LATER TONIGHT.

HIGH PRESSURE WILL BUILD OVER THE WATERS ON SATURDAY FOR LIGHTER
WINDS. A WEAKENING FRONT WILL MOVE THROUGH THE AREA SUNDAY AND
SUNDAY NIGHT. THIS SHOULD BRING SMALL CRAFT ADVISORY WINDS TO THE
COASTAL WATERS...AND POSSIBLY PARTS OF THE NORTHERN INTERIOR WATERS.

A SECOND FRONTAL SYSTEM WILL REACH THE AREA MONDAY OR TUESDAY.
MODELS ARE IN POOR AGREEMENT WITH THE DETAILS AND CONFIDENCE IN THE
WIND FORECAST FOR EARLY NEXT WEEK IS LOW. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORIES ARE IN EFFECT FOR MUCH OF THE COASTAL
     AND INLAND WATERS.

     SMALL CRAFT ADVISORY FOR ROUGH BAR IN EFFECT TIL MIDNIGHT
     TONIGHT FOR THE GRAYS HARBOR BAR.

&&

$$

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