Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 190457
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST TUE NOV 18 2014

.SYNOPSIS...A WEAK FRONTAL SYSTEM WILL MOVE THROUGH THE AREA
WEDNESDAY NIGHT BRINGING RAIN TO THE AREA. A WETTER SYSTEM WILL MOVE
THROUGH ON FRIDAY. BOTH WILL BRING RAIN AND LOCALLY WINDY CONDITIONS
TO WESTERN WASHINGTON. WEAK SYSTEMS WILL IMPACT THE AREA THROUGH
EARLY NEXT WEEK.

&&

.SHORT TERM...A HIGH AMPLITUDE RIDGE IS OVER THE PAC NW TONIGHT WITH
DRY AND STABLE WEATHER ACROSS WESTERN WA. LOWS WILL DIP INTO THE 20S
TO 30S OVERNIGHT WITH CIRRUS CLOUDS ALOFT. THE RIDGE AXIS WILL SLIDE
INTO EASTERN WA ON WED AS A WEAK COLD FRONT MOVES IN. THIS FRONT
WILL LIFT N/NE THROUGH THE REGION WED EVENING BRINGING A LITTLE RAIN
TO THE AREA. A WEAK UPPER TROUGH WILL CROSS THE AREA ON THU FOR
ISOLATED TO SCATTERED LIGHT SHOWERS. A STRONGER FRONTAL SYSTEM WILL
ARRIVE ON FRI FOR A WETTER PERIOD OF WEATHER. RAIN ASSOCIATED WITH
THE WARM FRONT WILL REACH THE COAST FRI MORNING THEN SPREAD INLAND
DURING THE AFTERNOON. RAIN WILL CONTINUE FRI EVENING AS THE COLD
FRONT MOVES INLAND. THE MOUNTAINS WILL SEE A FEW INCHES OF SNOW WITH
SNOW POSSIBLE AT STEVENS PASS. 33

&&

LONG TERM...PREVIOUS DISCUSSION...A SERIES OF WEAK SYSTEMS WILL MOVE
THROUGH THE AREA SATURDAY THROUGH MONDAY NIGHT...BRINGING A CHANCE
OF RAIN INTO THE AREA. TUESDAY...THE ECMWF HAS A PLUME OF MOISTURE
CARRIED BY THE JET STREAM HITTING THE NORTHWEST...WHEREAS THE GFS
SHOWS A DEEP SURFACE LOW DEVELOPING OFF THE COAST OF ALASKA AND ITS
ASSOCIATED FRONTAL SYSTEM MOVING INTO THE NORTHWEST. UNCERTAINTY ON
TUESDAY IS HIGH AND WE WILL SEE IF EITHER OF THESE SOLUTIONS PAN
OUT. JSMITH

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED IN THE NEXT 7 DAYS.

&&

.AVIATION...A STRONG UPPER LEVEL RIDGE WILL REMAIN OVER WESTERN
WASHINGTON TONIGHT. A SURFACE RIDGE OVER EASTERN WASHINGTON WILL
MAINTAIN DRY EASTERLY LOW LEVEL OFFSHORE FLOW. THE LOWER AIR MASS
WILL REMAIN DRY AND STABLE WITH UNRESTRICTED VFR CONDITIONS. HIGH
CLOUDS WILL CONTINUE OVER THE AREA THIS EVENING AHEAD OF AN
APPROACHING COLD FRONT. CLOUD LAYERS WILL GRADUALLY LOWER TO AROUND
10000 FEET LATE TONIGHT THROUGH WEDNESDAY. THE COLD FRONT WILL MOVE
ACROSS WESTERN WASHINGTON WEDNESDAY NIGHT WITH CEILINGS LOWERING TO
MVFR TO IFR LEVELS.

KSEA...HIGH CLOUDS WILL CONTINUE OVER THE AREA THOUGH 08Z WITH
UNRESTRICTED VISIBILITY. MID LEVEL CLOUDS AROUND 10000 FEET WILL
INCREASE AFTER 08Z AHEAD OF A DEVELOPING FRONT OFFSHORE. SURFACE
WINDS WILL BE 6 KT OR LESS FAVORING E TO SE. CHB

&&

.MARINE...THE SURFACE RIDGE OVER EASTERN WASHINGTON COMBINED WITH
LOWER PRESSURE FROM A DEVELOPING FRONT OFFSHORE WILL MAINTAIN
EASTERLY FLOW ACROSS WESTERN WASHINGTON THROUGH WEDNESDAY MORNING.

A COLD FRONT WILL APPROACH FROM THE SOUTHWEST ON WEDNESDAY... THEN
MOVE NORTHEAST ACROSS THE AREA WEDNESDAY NIGHT. MODERATE SOUTHEAST
FLOW WILL DEVELOP WITH SMALL CRAFT ADVISORY WINDS OVER THE COASTAL
WATERS AND THE NORTHERN INTERIOR WATERS. A STRONGER FRONTAL SYSTEM
ARRIVING FROM THE WEST ON FRIDAY COULD GENERATE SOUTHERLY GALES OVER
THE COASTAL AND NORTHERN INTERIOR WATERS. CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY WEST ENTRANCE AND ADJACENT COASTAL ZONE.

&&

$$

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