Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 220446
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
845 PM PST WED JAN 21 2015

.SYNOPSIS...AN APPROACHING FRONT WILL SPREAD LIGHT RAIN INLAND LATE
THIS EVENING. A WET PATTERN WILL CONTINUE THROUGH SATURDAY...WITH
THE HEAVIEST RAIN ON FRIDAY NIGHT AND SATURDAY MORNING. AN UPPER
LEVEL RIDGE WILL BRING SUNSHINE AND MILD WEATHER SUNDAY THROUGH
TUESDAY.

&&

.SHORT TERM...RADAR ECHOES ARE MOVING ONTO THE COAST AND KUIL
REPORTS LIGHT RAIN THIS HOUR. MIGHT BE A FEW SPRINKLES INLAND THIS
EVENING BUT MEASURABLE RAIN WILL PROBABLY NOT GET TO SEATTLE UNTIL
AFTER MIDNIGHT. THIS WILL NOT BE A BIG EVENT WITH A FEW HUNDREDTHS
TO A FEW TENTHS ALL THAT WILL FALL THROUGH THURSDAY AFTERNOON. HIGHS
ON THURSDAY WILL BE A BIT HIGHER THAN TODAY BUT WILL STILL MAINLY BE
IN THE 45 TO 50 RANGE.

THE NEXT IMPULSE ARRIVES THURSDAY NIGHT AND IT WILL BE SLIGHTLY
WETTER BUT STILL NOT A GULLY WASHER BY ANY MEANS. A WETTER WAVE WILL
DEVELOP FRIDAY AFTERNOON AND RAIN WILL CONTINUE THROUGH SATURDAY
MORNING...ESPECIALLY IN THE MOUNTAINS. BY SATURDAY AFTERNOON THE
RAIN WILL SHIFT NORTH. WARM ADVECTION WILL LIFT TEMPERATURES INTO
THE LOW TO MID 50S BOTH FRIDAY AND SATURDAY. A DRY PERIOD WILL
COMMENCE SUNDAY AND LAST INTO NEXT WEEK. BURKE

CONCERNING KING TIDES...WILL NEED TO KEEP AN EYE ON THE TIDES THE
NEXT FEW DAYS. THE KING TIDES HAVE ALREADY BEGUN ON THE COAST AND
WILL BEGIN IN THE PUGET SOUND REGION ON THE 22ND OR 23RD...DEPENDING
ON SITE LOCATION. CANNOT COMPLETELY RULE OUT THE POSSIBILITY OF
MINOR TIDAL OVERFLOW IN THE PUGET SOUND REGION FRI MORNING.
NOTE...KING TIDES HAPPEN WHEN THE EARTH IS CLOSEST TO THE SUN IN ITS
ELLIPTICAL ORBIT AND THE MOON IS FULL. THIS INCREASES THE
GRAVITATIONAL EFFECTS ON THE EARTH...RESULTING IN HIGHER THAN USUAL
TIDES. WHEN UNUSUAL HIGH ASTRONOMICAL TIDES COINCIDE WITH LOW
PRESSURE...THE RESULT IS EVEN HIGHER TIDES. A LINK TO TIDE
PREDICTIONS FOR SITES IN WESTERN WASHINGTON CAN BE FOUND ON OUR
MARINE WEATHER PAGE.

.LONG TERM...PREVIOUS DISCUSSION...SUNDAY THROUGH AT LEAST TUESDAY
LOOK DRY. AN UNSEASONABLY STRONG UPPER HIGH WILL PASS ACROSS NRN
CALIFORNIA ON SUNDAY...WITH A WARM AIR MASS EXTENDING NORTH INTO WRN
WA. THERE WILL BE ENOUGH WIND ALOFT TO AVOID HAVING THE ATMOSPHERE
SIMPLY BECOMING INVERTED. INVERSIONS ARE MORE COMMON IN THE WINTER
WITH WARM AIR ALOFT. DUE TO THE LACK OF INVERSIONS ON SUNDAY...THE
WARM AIR ALOFT WILL MIX TO THE SFC...MOST EASILY ON SUNDAY AFTN. THE
FORECAST HIGH OF 59F AT SEA-TAC ON SUNDAY ALREADY WOULD BREAK THE
OLD RECORD HIGH FOR THE DATE...AND TEMPERATURES COULD EASILY BE
WARMER AND SURPASS 60F.

SHOULD FINALLY HAVE CLEAR SKIES ON SUNDAY NIGHT...WHICH WILL ALLOW
NIGHTTIME TEMPERATURES TO COOL OFF MORE EASILY. WITH A COOLER START
ON MONDAY...THE AFTN DOES NOT LOOK QUITE AS WARM AS SUNDAY.

UPPER HEIGHTS AND TEMPERATURES ALOFT WILL DROP ON TUESDAY...
SUPPORTING THE EASING OF THE WARM WEATHER. ON WEDNESDAY...SOUTHERLY
FLOW ALOFT AND A SHORTWAVE SCOOTING AROUND THE EDGE OF THE UPPER
RIDGE IS ENOUGH TO RE-INTRODUCE LOW POPS TO THE FORECAST NEXT WED.
TEMPS WILL STILL BE ABOVE NORMAL...BUT WILL NOT BE FLIRTING WITH
RECORD TERRITORY BY THAT TIME. HANER

&&

.HYDROLOGY...WILL NEED TO WATCH THE SKOKOMISH RIVER FROM FRIDAY
AFTERNOON THROUGH SATURDAY MORNING...WHERE THERE IS A LOW CHANCE OF
MINOR FLOODING. ELSEWHERE...RISES ON RIVERS ARE EXPECTED FRIDAY
NIGHT AND SATURDAY...BUT FLOODING REMAINS UNLIKELY FOR THE NEXT
SEVEN DAYS. HANER

&&

.AVIATION...UPPER LEVEL RIDGE EAST OF THE AREA WITH SOUTHWESTERLY
FLOW ALOFT. FRONT DISSIPATING AS IT MOVES INTO WESTERN WASHINGTON
THURSDAY MORNING. AMS STABLE WITH INCREASING MOISTURE THROUGH
THURSDAY MORNING.

CEILINGS AOA 7000 FEET SLOWLY LOWERING AFTER 09Z WITH INCREASING
RAIN. ISOLATED VISIBILITIES 3-5SM WITH RAIN 12Z-18Z. CEILINGS IN THE
2000-3000 FOOT RANGE BY 18Z-21Z WITH THE STEADY RAIN COMING TO AN
END. CEILINGS REMAINING IN THE 2000-3000 FOOT RANGE INTO THURSDAY
EVENING.

KSEA...CEILINGS NEAR 8000 FEET LOWERING TO NEAR 5000 FEET BY 12Z AND
TO NEAR 2000 FEET BY 20Z. LIGHT WINDS BECOMING SOUTHEAST 4 TO 8
KNOTS AROUND 12Z. WINDS SHIFTING TO SOUTH SOUTHWEST AFTER 20Z. FELTON

&&

.MARINE...WEAKENING FRONT WILL MOVE THROUGH THE WATERS THURSDAY
MORNING WITH SMALL CRAFT ADVISORY WINDS OVER MOST OF THE COASTAL
WATERS AND THE WEST ENTRANCE TO THE STRAIT. STRONGER FRONT MOVING
THROUGH THE WATERS ON FRIDAY WITH SMALL CRAFT WINDS PROBABLE ALONG
THE COAST AND OVER THE NORTHERN PORTION OF THE AREA. WINDS WILL EASE
ON SATURDAY AS THE FRONT LIFTS NORTH OF THE AREA AND HIGH PRESSURE
BUILDS OVER WESTERN WASHINGTON. LOW LEVEL FLOW TURNING LIGHT
OFFSHORE ON SUNDAY. FELTON

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORIES ARE IN EFFECT FOR MUCH OF THE COASTAL
     WATERS AND THE WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA.

&&

$$

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