FXUS66 KSEW 160426
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
915 PM PDT MON MAR 15 2010
.SYNOPSIS...A COLD FRONT WILL MOVE THROUGH WESTERN WASHINGTON
TUESDAY. A COOL UPPER LEVEL TROUGH WILL BRING SCATTERED SHOWERS TO
THE REGION TUESDAY NIGHT AND WEDNESDAY. HIGH PRESSURE AND AN UPPER
RIDGE WILL GIVE MOSTLY SUNNY WEATHER THURSDAY THROUGH SATURDAY.
&&
.SHORT TERM...INCREASING CLOUDS OVERNIGHT...MAYBE A FEW SPRINKLES ON
THE COAST. THE COLD FRONT JUST OFFSHORE WILL MOVE THRU WRN WA MIDDAY
WED WITH RAIN TO THE COAST BY MID MORNING IN THE MM5NAM AND INTO THE
INTERIOR EARLY AFTERNOON. THAT IS A NOTCH SLOWER THAN THE CURRENT
FCST...HAVE NOT SEEN THE WRFGFS YET. THE SFC LOW PRES WITH THIS
SYSTEM WAS NEAR 42N 135W THIS EVENING WITH A DECENT BENT BACK SFC
TROF...THE MODELS BRING THE TROF TO THE WATERS JUST OFF VANCOUVER
ISLAND TUE AFTERNOON FOR A FAIRLY WIDESPREAD AREA OF FULL GALES
EXTENDING FROM THE COASTAL WATERS WELL OFFSHORE...HOWEVER INLAND THE
WIND AND GRADIENT IS NOT TOO IMPRESSIVE...PDX-BLI SHUD BE ARND +8MB
BY 6PM (MM5NAM) SO IT WILL BE BREEZY TUE AFTERNOON AND NIGHT BUT THE
STRONG WINDS STAY JUST OFF THE COAST. MAYBE A CHC FOR A PSCZ TUE
NITE OR WED...ALTHOUGH I DO NOT SEE MUCH OF ONE IN THE MM5NAM. H850
TEMPS DROP TO -2C TUE NITE AND -5C BY DAYBREAK WED...AIR MASS IS
COOL AND DRYING WED NITE AND THU.
.LONG TERM...DRY THU THRU SAT AS UPPER RIDGE BUILDS OFFSHORE AND
DRIFTS EAST OVER THE NW THROUGH THE PD. MOSTLY CLEAR WITH COOL
NIGHTS AND SEASONABLY WARM DAYS. OFFSHORE FLOW WILL PROBABLY PEAK
FRI OR SAT...THEN 18Z GFS HAD ONSHORE FLOW DVLPG SUN...BUT NO PRECIP
TIL SUN NITE THEN A COLD UPPER TROF MOVES INTO THE PACNW MON. WILL
SEE IF THE 00Z GFS FOLLOWS SUIT...BUT IF THE 18Z RUN IS CORRECT THE
FIRST PART OF NEXT WEEK WILL BE CHILLY AND SHOWERY. 19
&&
.HYDROLOGY...COLD FRONT TUE WILL NOT HAVE ENUF PRECIP TO MOVE THE
RIVERS MUCH. THEN HIGH PRES THU-SAT WILL BRING DRY WEATHER. THE
UPPER TROF EARLY NEXT WEEK IN THE LATEST GFS LOOKS RATHER COOL...IF
THE 00Z RUN FOLLOWS SUIT OUR FCST OF 4500FT SNOW LEVEL NEXT MON
WOULD BE TOO HIGH AND SNOW SHOWERS IN THE MOUNTAINS WITH A SNOW
LEVEL OF 2000 FEET WOULD BE A BETTER FCST...AND THAT LIMITS RUNOFF
AND MAYBE PUTS SOME MORE SNOWPACK INTO THE MTNS. THERE RISK FOR ANY
RIVER FLOODING WILL CONTINUE TO BE VERY LOW...THRU NEXT WEEK. 19
&&
.AVIATION...AN UPPER TROUGH AND ASSOCIATED SURFACE LOW WILL DEEPEN
OFF THE CA COAST TONIGHT AND TRACK NE INTO QUEEN CHARLOTTES BY TUE
EVENING. MODERATE SLY FLOW ALOFT TONIGHT WILL BECOME VERY STRONG ON
TUE...THEN BECOME MODERATE WLY FLOW TUE NIGHT. MAINLY STABLE
CONDITIONS EXPECTED WITH MAINLY MID AND HIGH LEVEL MOISTURE TONIGHT.
THE LOWER LEVELS WILL BECOME MOIST ON TUE AS RAIN INCREASES AHEAD OF
A FRONT WHICH WILL SWING THROUGH WRN WA BY LATE TUE AFTERNOON. LLWS
WILL BE POSSIBLE ON TUE AHEAD OF THE FRONT WHERE SURFACE WINDS
REMAIN RELATIVELY LIGHT AS THE FLOW ALOFT INCREASES.
MEANWHILE...VFR CONDITIONS WILL PREVAIL OVERNIGHT. CIGS WILL LOWER
INTO THE 2-4K FT RANGE DURING THE DAY TUE WITH RAIN INCREASING.
KSEA...VFR CONDITIONS WILL PERSIST. LIGHT NLY WINDS WILL INCREASE TO
ABOUT 10 KNOTS FROM THE E OVERNIGHT. INCREASING SLY WINDS ABOVE THE
SFC TUE MORNING WILL RESULT IN LLWS AT THE TERMINAL.
&&
.MARINE...A 1008 MB LOW WELL OFF THE CA COAST TONIGHT WILL
DEVELOP INTO A 988 MB LOW ON TUE AN HEAD TOWARD THE QUEEN CHARLOTTES
TUE AFTERNOON. THE ASSOCIATED COLD FRONT WILL SWEEP ACROSS THE
COASTAL WATERS LATE TUE MORNING...AND THE INLAND WATERS TUE
AFTERNOON. STRONG GALES WILL DEVELOP OVER THE COASTAL WATERS AND W
ENTRANCE TUE.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...A GALE WARNING IS IN EFFECT FOR THE COASTAL WATERS AND WEST
ENTRANCE TO THE STRAIT OF JUAN DE FUCA.
.A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE REMAINING
WATERS.
.SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR CONDITIONS
REMAINS IN EFFECT THROUGH TUE NIGHT.
$$
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