Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 150401
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
800 PM PST SUN DEC 14 2014

.SYNOPSIS...AN UPPER RIDGE OVER WESTERN WASHINGTON TODAY WILL SHIFT
EAST TONIGHT. A SERIES OF WEAK SPLITTING SYSTEMS WILL MOVE ACROSS
THE AREA FOR MOST OF THE WORK WEEK.

&&

.SHORT TERM...SKIES REMAIN MOSTLY CLEAR THIS EVENING WITH AN UPPER
RIDGE SHIFTING INLAND AND LOW LEVEL OFFSHORE FLOW OVER WRN WA. THE
CROSS CASCADE GRADIENT IS -8 MB FOR SOME WINDY CONDITIONS IN THE
TYPICAL AREAS LEADING UP TO THE PASSES. A WEAK SPLITTING FRONT WILL
BRING LIGHT RAIN MAINLY TO THE COAST ON MONDAY. A TROUGH WILL LIFT
NORTH THROUGH WESTERN WA MONDAY NIGHT AND TUESDAY WITH SOME AREAS OF
LIGHT RAIN. A CHANCE OF RAIN PERSISTS INTO THE MIDDLE OF THE WEEK
WITH AN UPPER LEVEL TROUGH OVER THE PAC NW...PRECIP STILL LOOKS
LIGHT AND SPOTTY. TEMPS CLOSE TO NORMAL.

.LONG TERM...THE GFS IS TRYING TO BUILD A WEAK UPPER LEVEL RIDGE
OVER THE PAC NW ON THURSDAY FOR A DRY PERIOD OF WEATHER. HOWEVER
LEFT LOW-END CHANCE POPS IN THE FORECAST AS THE ECMWF STILL BRUSHES
WESTERN WA WITH A LITTLE MOISTURE. A COLD FRONT WILL THEN MOVE
INLAND ON FRIDAY FOR SOME RAIN. THE GFS IS THE WEAKER SOLUTION AS IT
SHOWS THIS FRONT SPLITTING AS IT MOVES INLAND. THE ECMWF IS WETTER
AND A BLEND OF THE ECMWF AND GFS WAS USED FOR THIS PERIOD. A COOL
UPPER TROUGH WILL CROSS THE AREA FRIDAY NIGHT INTO SATURDAY FOR A
FEW SHOWERS. A WETTER PAC SYSTEM WILL MOVE INTO SOUTHERN B.C. ON
SUNDAY...POSSIBLY CLIPPING WESTERN WA SUN NIGHT OR MON AS IT SHIFTS
SOUTH. 33

&&

.HYDROLOGY...FLOODING IS NOT EXPECTED DURING THE NEXT 7 DAYS.

&&

.AVIATION...UPPER LEVEL RIDGING IS CENTERED OVER SOUTHERN BRITISH
COLUMBIA THIS EVENING WITH EAST TO SOUTHEAST FLOW ALOFT OVER WESTERN
WASHINGTON. THE AIR MASS IS DRY AND STABLE. THE FLOW ALOFT WILL
BECOME SOUTHERLY ON MONDAY AS A WEAK UPPER LEVEL TROUGH APPROACHES
THE REGION. MID AND HIGH LEVEL MOISTURE WILL INCREASE DURING THE DAY
MONDAY. LOW LEVEL OFFSHORE FLOW CONTINUES.

VFR CONDITIONS EXPECTED OVERNIGHT WITH DRIER LOW LEVELS AND EASTERLY
FLOW. THE ONLY EXCEPTION IS LIKELY TO BE PROTECTED FOG PRONE SPOTS
LIKE OLYMPIA AND MUCH OF THE SOUTHWEST INTERIOR WHERE PATCHY FOG
COULD DEVELOP 05Z TO 14Z.

KSEA...VFR. EAST WIND 7-13 KNOTS...WITH GUSTS NEAR 20 KNOTS POSSIBLE.

&&

.MARINE...MODERATELY STRONG EASTERLY FLOW WILL CONTINUE THROUGH
MONDAY. THE EASTERLY FLOW WILL WEAKEN MONDAY NIGHT AND TUE. LIGHT
OFFSHORE FLOW WILL PREVAIL ON WED. A COLD FRONT IS EXPECTED TO
APPROACH THE AREA THURSDAY NIGHT AND THEN MOVE ACROSS THE REGION ON
FRIDAY. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING IN EFFECT TIL 6 AM MON FOR THE NEARSHORE WATERS
     FROM CAPE FLATTERY TO JAMES ISLAND AND THE WEST ENTRANCE TO
     STRAIT OF JUAN DE FUCA.

     SMALL CRAFT ADVISORIES ARE IN EFFECT FOR MUCH OF THE COASTAL
     WATERS AND THE CENTRAL/EASTERN STRAIT OF JUAN DE FUCA.

&&

$$

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