Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 221028
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PDT MON SEP 22 2014

.SYNOPSIS...A WEAK FRONT WILL REACH THE COAST TODAY. A STRONGER
FRONTAL SYSTEM WILL IMPACT THE REGION TUESDAY AND WEDNESDAY FOR WET
AND UNSETTLED CONDITIONS OR TYPICAL FALL WEATHER. GRADUAL DRYING
WILL OCCUR LATER IN THE WEEK AS AN UPPER TROUGH OVER THE AREA SHIFTS
INLAND AND IS REPLACED WITH WEAK HIGH PRESSURE ALOFT.

&&

.SHORT TERM...ONSHORE FLOW HAS ALLOWED LOW CLOUD TO FILL IN ACROSS
MOST OF WESTERN WASHINGTON EARLY THIS MORNING. THERE IS EVEN SOME
DRIZZLE OR LIGHT RAIN BEING SQUEEZED OUT OF THE MARINE LAYER AT THE
COAST. IN THE BIGGER PICTURE...AN UPPER TROUGH IS OVER THE NORTHEAST
PACIFIC WITH SOUTHWEST FLOW ALOFT FOR WESTERN WASHINGTON. A
WEAKENING COLD FRONT WILL REACH THE COAST LATER TODAY. THE MODEST
PRECIPITATION THREAT FROM THIS SYSTEM IS EXPECTED TO STAY CONFINED
TO NEAR THE COAST. THERE COULD ALSO BE A FEW SHOWERS OVER THE
CASCADES TODAY IN THE SOMEWHAT UNSTABLE SOUTHERLY FLOW ALOFT.

MODELS SHOW MOISTURE AND PRECIPITATION INCREASING ACROSS THE AREA ON
TUESDAY. IT LOOKS LIKE THE REMNANTS OF THE FRONT ALONG THE COAST
WILL BE PUSHED INLAND AND RE-ENERGIZED BY INCREASING SOUTHWEST FLOW
ALOFT AHEAD OF AN APPROACHING STRONGER FRONT OFFSHORE. THIS SECOND
FRONTAL SYSTEM WILL BRING RAIN...PERHAPS HEAVY AT TIMES...TUESDAY
NIGHT. THE FRONT AND HEAVIER RAINS WILL SHIFT INLAND DURING THE DAY
ON WEDNESDAY. FLOODING IS NOT A CONCERN THIS EARLY IN THE SEASON BUT
IT DOES LOOK LIKE MOST AREAS WILL GET A GOOD SOAKING. SCHNEIDER

.LONG TERM...AN UPPER TROUGH OVER THE NORTHEAST PACIFIC ON THURSDAY
WILL SHIFT ONSHORE AND WEAKEN ON FRIDAY. THERE SHOULD BE A GRADUALLY
DECREASING CHANCE OF SHOWERS DURING THIS PERIOD. FOR THE WEEKEND...A
WEAK UPPER RIDGE WILL MOVE OVER THE AREA FOR DRY AND SUNNIER WEATHER
WITH A SLIGHT WARMING TREND. SCHNEIDER

&&

.AVIATION...SOUTHWESTERLY FLOW ALOFT THROUGH TONIGHT WITH AN UPPER
LEVEL TROUGH OVER THE EASTERN PACIFIC AND A RIDGE OF HIGH PRESSURE
WELL INLAND. AT THE SURFACE...NARROW RIDGE ALONG THE COAST TODAY
DISSIPATING BY LATE AFTERNOON WITH A WEAK FRONT OFFSHORE
DISSIPATING. AIR MASS STABLE WITH LOW LEVEL MOISTURE THIS MORNING
AND MID LEVEL MOISTURE THIS AFTERNOON.

SATELLITE IMAGERY SHOWS STRATUS COVERING MOST OF THE LOWLANDS AT
10Z. CEILINGS IN THE 1500 TO 2500 FOOT RANGE. ONSHORE GRADIENTS
WEAKENING LATER TODAY AS A WEAK FRONT APPROACHES THE AREA. WITH THE
DECREASE IN ONSHORE FLOW EXPECT THE STRATUS DECK TO LIFT LATER THIS
MORNING THEN SCATTER OUT IN THE AFTERNOON. MID LEVEL DECK ASSOCIATED
WITH THE WEAK FRONT OVER THE AREA LATER THIS AFTERNOON INTO THIS
EVENING.

KSEA...CEILINGS NEAR 1500 FEET RISING ABOVE 2000 FEET LATER THIS
MORNING. STRATUS SCATTERING OUT EARLY AFTERNOON WITH JUST A MID
LEVEL DECK OVER THE TERMINAL INTO EARLY TUESDAY MORNING. SOUTHERLY
WINDS 4 TO 8 KNOTS. FELTON

&&

.MARINE...NARROW RIDGE OF HIGH PRESSURE ALONG THE COAST DISSIPATING
TODAY. WEAKENING FRONT MOVING INTO THE COASTAL WATERS THIS AFTERNOON
WITH SMALL CRAFT ADVISORY WINDS EXPECTED WITH THE FRONT. FRONT
DISSIPATING LATE IN THE DAY.

A STRONGER FRONTAL SYSTEM...ASSOCIATED WITH A DEVELOPING SURFACE LOW
WELL OFFSHORE...WILL MOVE INTO THE OFFSHORE WATERS TUESDAY AND INTO
THE COASTAL WATERS ON TUESDAY NIGHT. SOUTH TO SOUTHEAST WINDS AHEAD
OF THE FRONT STILL EXPECTED TO BE IN THE HIGH END OF SMALL
CRAFT...30 KNOTS. SMALL CRAFT ADVISORY SOUTHEAST WINDS ARE LIKELY IN
NW-SE CHANNELED WATERS SUCH AS THE NORTHERN INLAND WATERS AND THE
EAST ENTRANCE TO THE STRAIT AS WELL.

WINDS WILL EASE LATE WEDNESDAY INTO THE END OF THE WEEK AS A 980 MB
LOW NEAR 46N 135W SLOWLY FILLS AND DRIFTS NORTH. FELTON

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY COASTAL WATERS THIS AFTERNOON.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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