Small Craft Advisory 113, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
235 AM PDT SUN JUN 9 2013

.SYNOPSIS...A VERY WEAK UPPER LEVEL RIDGE WILL KEEP WESTERN
WASHINGTON DRY TODAY AND MONDAY. ONSHORE FLOW WILL KEEP LOW CLOUDS
OVER THE AREA DURING THE LATE NIGHT AND MORNING HOURS WITH AFTERNOON
CLEARING. AN UPPER LEVEL LOW WILL BRING SHOWERS AND COOLER
TEMPERATURES AS IT MOVES SLOWLY CROSS WASHINGTON TUESDAY THROUGH
THURSDAY.

&&

.SHORT TERM...STRONG W FLOW ALOFT WILL CONTINUE OVER W WA TODAY AS A
VERY WEAK UPPER LEVEL SHORTWAVE RIDGE CROSSES THE AREA. WEAK RIDGING
CENTERED OVER E WA WILL CONTINUE ON MONDAY AS THE MIDWEEK UPPER
LEVEL LOW MOVES OFFSHORE OF VANCOUVER ISLAND. THE WEAK RIDGING WILL
KEEP THE AREA DRY TODAY AND MONDAY WITH THE MAIN FACTOR BEING THE
CONTINUING ONSHORE FLOW...WHICH IS KEEPING THE LOWER LEVELS SOMEWHAT
MOIST. SATELLITE IMAGERY AND OBS SHOW CLOUD LAYERS FROM 3500 TO 6000
FEET HAVE EXPANDED IN COVERAGE ACROSS W WA THIS MORNING. LIKE
YESTERDAY...THE CLOUDS WILL DIMINISH ENOUGH IN COVERAGE THIS
AFTERNOON TO CALL IT MOSTLY SUNNY. THE ONSHORE FLOW WILL ALSO KEEP
MAX TEMPS NEAR NORMAL. THIS PATTERN SHOULD REPEAT ON MONDAY.

MODELS REMAIN QUITE CONSISTENT WITH THE UPCOMING CHANGE IN THE
WEATHER PATTERN ON TUESDAY. THE UPPER LEVEL LOW THAT MOVES W OF
VANCOUVER ISLAND ON MONDAY...CONTINUES SLIDING SE TO THE N WA COAST
BY TUESDAY AFTERNOON. IT LOOKS LIKE THERE WILL BE AN ORGANIZED UPPER
LEVEL SHORTWAVE ROTATING AROUND THE LOW CENTER THAT WILL SPREAD
SHOWERS TO THE COAST TUESDAY MORNING...THEN INLAND TUESDAY
AFTERNOON. I HAVE BOOSTED POPS TO LIKELY ALONG THE COAST AND SW
INTERIOR FOR TUESDAY...MATCHING THE LATEST GUIDANCE. POPS OVER
THE REST OF THE INTERIOR WERE ALSO INCREASED...BUT REMAIN IN THE
HIGHER CHANCE RANGE. THE COOLER AIR MASS...CLOUDS...AND SHOWERS WILL
DROP MAX TEMPS TO BELOW NORMAL FOR MOST AREAS. I OPTED TO GO WITH
THE NAM SOLUTION IN MAX TEMP DISTRIBUTION TUESDAY...WHICH HAS COOLER
TEMPS COAST AND SW INTERIOR WHERE THE POPS ARE IN THE LIKELY
RANGE...AND SLIGHTLY WARMER TEMPS AWAY FROM THE GREATER SHOWER
ACTIVITY. KAM

.LONG TERM...THE UPPER LEVEL LOW WILL BE RIGHT OVER W WA ON
WEDNESDAY WHICH SHOULD MAKE THIS THE WETTEST AND COOLEST DAY THIS
WEEK. THE AIR MASS WILL BE UNSTABLE BUT GFS LIFTED INDICES AND MID
LEVEL LAPSE RATES DO NOT INDICATE MUCH OF A THUNDERSTORM THREAT AT
THIS POINT.

GFS/ECMWF REMAIN IN GOOD AGREEMENT TAKING THE LOW SLOWLY E
OVER THE ID PANHANDLE BY THURSDAY AFTERNOON. SCATTERED SHOWERS AND
COOL TEMPERATURES WILL PERSIST OVER W WA THURSDAY. THE 00Z GFS AND
ECMWF SOLUTIONS DIVERGE THURSDAY NIGHT AND FRIDAY DURING THE
TRANSITION PERIOD AFTER THE LOW DEPARTS. BEST GUESS AT THIS POINT IS
TO CONTINUE A DECREASING SHOWER TREND. BOTH MODELS DEVELOP ANOTHER
UPPER LEVEL LOW OFFSHORE SATURDAY AND SUNDAY...BUT THERE HAS BEEN
SOME RUN-TO-RUN INCONSISTENCY THE LAST 2-3 MODEL RUNS WHICH MAKES IT
A LOW CONFIDENCE PERIOD. KAM

&&

.AVIATION...MODERATE WESTERLY FLOW ALOFT WILL CONTINUE TODAY AND
TONIGHT. AT THE SURFACE MODERATE ONSHORE FLOW WILL CONTINUE AS WELL.
AIR MASS IS STABLE AND RELATIVELY MOIST AT THE LOW LEVELS.

AREAS OF LOW CLOUDS WILL BE AROUND THIS MORNING WITH CEILINGS
GENERALLY 4-6K FT. LOCALLY LOWER CEILINGS ARE POSSIBLE THIS
MORNING...PERHAPS AROUND 2K FT. LOW CLOUDS SHOULD MOSTLY BREAK UP
THIS AFTERNOON BUT THEN AT LEAST PARTIALLY FILL BACK IN TONIGHT.

KSEA...NORTHEAST WIND 5-10 KNOTS WILL BECOMING NORTHWEST AROUND
MIDDAY. SCHNEIDER

&&

.MARINE...ONSHORE FLOW WILL CONTINUE THROUGH MONDAY. WEST WINDS OF
AT LEAST SMALL CRAFT ADVISORY STRENGTH ARE EXPECTED THIS EVENING AND
AGAIN MONDAY EVENING IN THE STRAIT OF JUAN DE FUCA. THESE WINDS WILL
SPILL PARTIALLY INTO ADMIRALTY INLET AND INTO THE WESTERN PART OF
THE NORTHERN INLAND WATERS AT TIMES.

MARGINAL GALES ARE NOT OUT OF THE QUESTION THIS EVENING IN THE
STRAIT OF JUAN DE FUCA WITH SLIGHTLY STRONGER ONSHORE FLOW BUT THE
FORECAST IS 20-30 KNOTS FOR NOW. THERE WILL ALSO LIKELY BE SOME
SMALL CRAFT ADVISORY NORTHWEST WINDS OVER THE SOUTHERN HALF OF THE
INNER COASTAL WATERS THIS EVENING.

ONSHORE FLOW WILL EASE A BIT TUESDAY AND WEDNESDAY AS A SURFACE
TROUGH FORMS OVER THE OFFSHORE WATERS AND PUSHES SLOWLY ONSHORE.
SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY MIDDLE AND SOUTHERN INNER COASTAL
     WATERS...CENTRAL STRAIT...EASTERN STRAIT...NORTHERN INLAND
     WATERS...AND ADMIRALTY INLET.

&&

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