FXUS66 KSEW 290427
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
830 PM PST SAT NOV 28 2009
.SYNOPSIS...A WARM FRONT OVER THE REGION WILL CONTINUE TO BRING A
THREAT OF LIGHT PRECIPITATION TO THE AREA INTO SUNDAY MORNING AS IT
SLOWLY LIFTS NORTHWARD. A WEAK COLD FRONT WILL BRUSH THROUGH THE
REGION LATE MONDAY THEN AN UPPER LEVEL RIDGE OF HIGH PRESSURE WILL
BE IN CONTROL OF OUR WEATHER DURING THE MIDDLE OF THE WEEK.
&&
.SHORT TERM...THE LATEST RADAR LOOP SHOWS LIGHT RAIN HAS FILLED IN A
BIT OVER THE LAST COUPLE HOURS NORTH AND WEST OF SEATTLE. MODELS
SHOW THE WARM FRONT STALLED OVER THE AREA TONIGHT WITH LIGHT RAIN
BRUSHING WRN WA AT TIMES THROUGH SUNDAY MORNING. THE HIGHER POPS
NORTH AND COAST WITH CHANCE POPS FURTHER INLAND AND S LOOK GOOD FOR
TONIGHT.
MODELS LIFT THE WARM FRONT NWD ON SUNDAY WITH LIGHT SPOTTY RAIN
DECREASING FROM S TO N. MOST THE AREA SHOULD BE DRY BY SUNDAY
EVENING AS A TEMPORARY RIDGE BUILDS NWD OVER THE AREA. EXPECT FOG TO
DEVELOP AGAIN SUNDAY NIGHT WITH LIGHT SURFACE GRADIENTS AND SOME
RESIDUAL MOISTURE IN THE LOWER LEVELS WITH HIGHER PRES ALOFT.
THE COLD FRONT FINALLY PUSHES ACROSS THE AREA ON MONDAY BUT THE BULK
OF ENERGY MOVES ACROSS SRN B.C. JUST CLIPPING WRN WA. EXPECT A BAND
OF LIGHT RAIN TO PUSH ACROSS...MAINLY IN THE AFTERNOON BUT AMOUNTS
WILL BE VERY LOW AS THE TAIL END OF THE FRONT WEAKENS. DRIER AND
SOMEWHAT COOLER AIR WILL FILTER IN BEHIND THE FRONT MONDAY NIGHT.
DRY OFFSHORE FLOW DEVELOPS ON TUESDAY WITH A SURFACE HIGH CENTERED
OVER SRN B.C. MERCER
.LONG TERM...PREVIOUS DISCUSSION FOLLOWS...AT LEAST THROUGH
WEDNESDAY WE WILL BE UNDER THE INFLUENCE OF THE UPPER RIDGE AND SO
WILL REMAIN DRY AND PARTLY CLOUDY. BEYOND THAT...THINGS GET REAL
FUZZY IN THE MODEL WORLD AND CONFIDENCE IS RATHER LOW IN THE DETAILS
OF THE FORECAST. NONE OF THE SOLUTIONS ARE VERY WET...BUT NOT DRY
EVERY DAY EITHER. THE VARIANCE IN THE MODELS IS RATHER STRIKING OUT
OVER THE PACIFIC WHICH OF COURSE AFFECT OUR WEATHER. AT THIS POINT
WE...ALL THE OFFICES IN THE NORTHWEST...DECIDED TO INTRODUCE A
SLIGHT CHANCE OF PRECIPITATION...STILL WELL BELOW CLIMATOLOGY...INTO
THE FORECAST WITH A BIT OF ADDITIONAL CLOUDS FOR THE THURSDAY ONWARD
TIME FRAME. WE WILL HAVE TO SEE HOW THIS PLAYS OUT. CERNIGLIA
&&
.HYDROLOGY...THE WARM FRONT TONIGHT WILL BRING VERY LIGHT RAIN TO
WRN WA...MAINLY ALONG THE N COAST/OLYMPICS AND BRUSHING THE N
INTERIOR AT TIMES. RAINFALL AMOUNTS WILL NOT BE SIGNIFICANT ENOUGH
TO CAUSE RIVER RISES OR FLOODING CONCERNS. THE WARM FRONT LIFTS
NORTH LATER ON SUNDAY WITH DRYING CONDITIONS...THEN THE COLD FRONT
SWEEPS THROUGH ON MONDAY WITH ANOTHER ROUND OF VERY LIGHT RAINFALL.
AGAIN...AMOUNTS WILL BE LIGHT AND NOT CAUSE FLOODING.
EVEN THOUGH THERE IS SIGNIFICANT VARIANCE IN THE LONG RANGE MODELS
FOR LATE NEXT WEEK AND NEXT WEEKEND...NONE OF THE SOLUTIONS ARE GOOD
FOR HEAVY PRECIPITATION. THEREFORE NO FLOODING PROBLEMS ANTICIPATED
THROUGH NEXT WEEKEND.
NO FLOODING IS EXPECTED ON THE GREEN RIVER THROUGH NEXT WEEK.
CERNIGLIA/MERCER
&&
.AVIATION...A WEAK WARM FRONT IN THE COASTAL WATERS WILL MOVE BY TO
THE NORTH OF THE AREA THROUGH EARLY SUNDAY MORNING WHILE A
PROGRESSIVE WEAK RIDGE OF HIGH PRES AT THE SURFACE AND ALOFT MOVES
BY TO THE SOUTH OF THE AREA LATE TONIGHT THROUGH SUN. CEILINGS ARE
MAINLY MVFR. LOCAL IFR CIGS AND VISIBILITIES ARE BEING REPORTED ON
THE COAST WHERE LIGHT RAIN AND DRIZZLE ARE OCCURRING.
SOUTHERLY PRES GRADIENTS WILL GRADUALLY WEAKEN LATE TONIGHT AND
EARLY SUN. THE COMBINATION OF THE LIGHTER FLOW AND THE MOIST LOWER
LEVELS IN THE WARM ADVECTION PATTERN WILL RESULT IN CEILINGS COMING
DOWN TO NEAR 010 AROUND 10Z AND POSSIBLY GOING INTO THE IFR CATEGORY
THROUGH THE MORNING HOURS. SOME DRYING ALOFT AND WEAK INSOLATION MAY
BE SUFFICIENT TO LIFT CIGS A FEW HUNDRED FEET SUN AFTERNOON AND
PROVIDE A FEW BREAKS.
WITH ANY CLEARING AT ALL SUN EVENING...LIGHT OFFSHORE FLOW AND SOME
RADIATIONAL COOLING EARLY SUN EVENING COMBINED WITH INCREASING
DEWPOINTS ALOFT THROUGH THE BOUNDARY LAYER SPELL ABUNDANT FOG AND
LOW STRATUS FORMATION EARLY SUN EVENING THAT WILL PERSIST INTO
MIDDAY MON.
KSEA...SOUTHERLY WIND WILL GRADUALLY DECREASE OVERNIGHT. EXPECT
CEILINGS...AROUND 015 AT 04Z...TO GRADUALLY LOWER TO AROUND 010 BY
10Z AND REMAIN THERE THROUGH ABOUT 20Z SUN. A WEAK WARM FRONT RIDING
BY TO THE NORTH OF THE AREA IS BRINGING CIGS DOWN TO 007 AT KSHN
WITH VIS 5SM BR. THERE IS A CHANCE THAT THESE LOWER CONDITIONS
SPREAD INTO THE TERMINAL 10Z-18Z TIME FRAME. SOME PARTIAL CLEARING
IS LIKELY LATE SUN AFTERNOON...WHICH IS LIKELY TO RESULT IN FOG AND
LOW STRATUS DEVELOPING EARLY SUN EVENING AND CONTINUING THROUGH
MIDDAY MON. ALBRECHT
&&
.MARINE...A WEAK WARM FRONT MOVING THROUGH THE COASTAL WATERS
TONIGHT WILL MOVE INTO SW BRITISH COLUMBIA EARLY SUN MORNING. SMALL
CRAFT ADVISORY CONDITIONS WILL GENERALLY SUBSIDE FROM SOUTH TO NORTH
06Z-12Z TONIGHT.
LIGHT OFFSHORE FLOW WILL GIVE AREAS OF RESTRICTED VISIBILITY SUN
NIGHT. A DECAYING SWELL TRAIN MOVING ONTO THE COAST WILL LIKELY KEEP
SMALL CRAFT ADVISORY CONDITIONS FOR HAZARDOUS SEAS AND ROUGH BAR
CONDITIONS CONTINUING THROUGH SUN AFTERNOON OR SUN NIGHT.
A WEAK TO MODERATE COLD FRONT WILL SWEEP SE THROUGH THE WATERS LATE
MON...LIKELY GIVING SMALL CRAFT ADVISORY CONDITIONS TO THE COAST AND
STRAIT.
HIGH PRESSURE WILL BUILD OVER BRITISH COLUMBIA MON NIGHT AND
CONTINUE THROUGH WED...GIVING LIGHT TO MODERATE OFFSHORE FLOW TO THE
WATERS. ALBRECHT
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS GRAYS HARBOR.
.SMALL CRAFT ADVISORY COASTAL WATERS...ENTRANCES TO THE
STRAIT...ADMIRALTY INLET...AND PUGET SOUND AND HOOD CANAL
UNTIL 10 PM THIS EVENING.
.SMALL CRAFT ADVISORY NORTH INLAND WATERS UNTIL 3 AM EARLY SUN.
.SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS COASTAL WATERS AND WEST
ENTRANCE TO THE STRAIT LATE THIS EVENING THROUGH SUNDAY
AFTERNOON.
$$
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