Small Craft Advisory 699, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
252 PM PDT TUE MAY 3 2011

.SYNOPSIS...ISOLATED SHOWERS WILL END THIS EVENING AS HIGH PRESSURE
CONTINUES TO BUILD INTO THE REGION. WEDNESDAY WILL BE MOSTLY SUNNY.
A WEAK WEATHER SYSTEM WILL ARRIVE THURSDAY. WET WEATHER IS LIKELY BY
THE WEEKEND AS A STRONGER SYSTEM ARRIVES.

&&

.SHORT TERM...A FEW SHOWERS LEFT ON THE RADAR...MAINLY ALONG THE
KING/SNO COUNTY LINE AT 2PM...OVER DABOB BAY...A FEW IN SKAGIT
COUNTY AND THE CASCADES. PARTLY CLOUDY SKIES TONIGHT AFTER THE
SHOWERS END. AN UPPER RIDGE BUILDS OVER WA THRU WED AND THEN WEAKENS
AND PROGRESSES EAST TO IDAHO WED EVENING AS A WEAK UPPER TROF AND
FRONT APPROACH THE AREA. THU COULD BE A DRIPPY DAY WITH AREAS OF
DRIZZLE...OR IT COULD RAIN IN THE PSCZ AREA IN THE MORNING...FOR NOW
I WORDED THE FCST SCATTERED SHOWERS. A FEW LIGHT SHOWERS OR MAYBE
SOME NIGHT AND MORNING DRIZZLE ARE POSSIBLE FOR THU NITE AND
FRI...THERE IS NOT MUCH OF A RIDGE...REALLY JUST ZONAL FLOW WITH
UPPER HEIGHTS GETTING UP ARND 558DM. A FRONTAL SYSTEM WILL SPREAD
RAIN INTO THE AREA FRIDAY NIGHT. 19

.LONG TERM...PERIODS OF RAIN ARE A PRETTY GOOD BET SAT AND SAT NITE
AS YET ANOTHER COLD UPPER TROF DROPS INTO THE REGION. IT MIGHT BE
COLD ENOUGH ALOFT AND UNSTABLE TO THE POINT THAT IT IS REALLY MORE
CONVECTIVE SHOWERS...BUT THERE IS ENOUGH PRECIP IN THE GFS TO LEAN
TOWARD WET AND PESSIMISTIC. BY SUNDAY NIGHT AND MONDAY THE TROF MAY
BE MOVING INLAND WITH THE SHOWERS BECOMING MORE SCATTERED. 19

&&

.AVIATION...
AN UPPER RIDGE WILL PREVAIL OVER THE REGION THRU WED. NW FLOW ALOFT
WILL BECOME WLY ON WED. CONTINUED LOW LEVEL ONSHORE FLOW. ANTICIPATE
VFR CONDITIONS THRU TONIGHT BUT THERE WILL PROBABLY BE AREAS OF IFR
CIGS OVER MAINLY THE MAJOR WATER BODIES LATE TONIGHT THRU WED
MORNING. OTHERWISE EXPECT PATCHY FOG /REDUCING VSBYS INTO MAINLY THE
MVFR CATEGORY RANGE/ TO DEVELOP IN THE FAVORED RIVER VALLEYS LATE
TONIGHT. THE MTNS WILL BE PARTIALLY OBSCURED THRU TONIGHT.

KSEA...EXPECT VFR CONDITIONS TO PREVAIL OVER THE TERMINAL THRU
TONIGHT...ALTHO THERE IS A POSSIBILITY OF CIGS NEAR 3K FT FOR A
BRIEF PERIOD THIS AFTERNOON. THE PUGET SOUND CONVERGENCE ZONE /PSCZ/
REMAINED ILL-DEFINED THIS AFTERNOON. IT APPEARED TO BE WITHIN THE
VICINITY /N OF/ KBFI AT THIS TIME. EXPECT THE PSCZ TO COMPLETELY
DISSIPATE BY 0300 UTC.

&&

.MARINE...
WINDS WERE FLIRTING WITH GALE FORCE OVER THE CENTRAL STRAIT OF JUAN
DE FUCA AND IT IS STILL POSSIBLE THAT SPEEDS MAY BRIEFLY REACH LOW
END GALE HERE THIS AFTERNOON. THE KUIL TO KBLI PRES GRADIENT WAS
PLUS 2.2 MB AND STILL GOING UP. IT WILL LIKELY PEAK CLOSE TO PLUS 3
MB BEFORE RELAXING THIS EVENING. ESSENTIALLY...THE PRES GRADIENT WAS
WEAKER THAN WHAT THE GFS MODEL PREDICTED BUT STRONGER THAN THE NAM
PREDICTION.

MEANWHILE...ONSHORE FLOW WILL PERSIST THROUGH THU DUE TO GENERALLY
HIGH PRES OFFSHORE AND LOWER PRES INLAND. EXPECT A WEAK SURFACE
TROUGH TO MOVE ACROSS THE COASTAL WATERS ON THU. A COLD FRONT IS
THEN ANTICIPATED TO AFFECT THE AREA LATE FRI.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORIES REMAIN IN EFFECT FOR THE COASTAL WATERS
     AND STRAIT OF JUAN DE FUCA THRU LATE TONIGHT.

     A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR ROUGH GRAYS HARBOR
     BAR CONDITIONS THRU LATE TONIGHT.

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