Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

000
FXUS66 KSEW 180354
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
854 PM PDT FRI OCT 17 2014

.SYNOPSIS...A COLD FRONT OVER THE CASCADES WILL WEAKEN TONIGHT WHILE
POST-FRONTAL SHOWERS OVER WESTERN WASHINGTON DIMINISH. LEFTOVER
CLOUDS WILL DISSIPATE SLOWLY THROUGH SATURDAY WHILE AN UPPER LEVEL
AND SURFACE RIDGE BUILD OVER THE AREA. THE RIDGE WILL MOVE OVER
EASTERN WASHINGTON SUNDAY WITH INCREASING OFFSHORE FLOW BRINGING
PARTLY SUNNY AND WARMER WEATHER. A FRONT WILL BRING RAIN TO THE
COAST LATE SUNDAY...AND TO THE INTERIOR SUNDAY NIGHT AND MONDAY. A
SERIES OF FRONTAL SYSTEMS WILL MAINTAIN A WET PATTERN THE REST OF
NEXT WEEK

&&

.SHORT TERM...RADAR AT 03Z/8 PM SHOWS THE SURFACE FRONT HAS REACHED
THE CASCADES WHERE IT WILL WEAKEN TONIGHT. THE UPPER LEVEL TROUGH
AXIS IS JUST OFFSHORE AND WILL ALSO WEAKEN AS IT MOVES INLAND
OVERNIGHT. RADAR SHOWS WHAT IS PROBABLY THE FINAL BAND OF ORGANIZED
SHOWERS ALONG THE COAST AT 03Z/8 PM WHICH WILL PROBABLY HOLD
TOGETHER AS IT CROSSES PUGET SOUND LATER THIS EVENING. OTHER THAN
THE FRONT OVER THE CASCADES AND THE SHOWER BAND THERE IS NOT A LOT
OF SHOWER ACTIVITY ELSEWHERE.

MODELS REMAIN ON TRACK KEEPING A RESIDUAL MOIST LOW LEVEL AIR MASS
OVER W WA ON SATURDAY...WHILE AN UPPER LEVEL AND SURFACE RIDGE BUILD
OVER THE REGION. THERE COULD BE SOME SPOTTY LIGHT RAIN OR SHOWERS IN
THE MORNING...AND MAYBE SOME PEEK-A-BOO SUN BREAKS IN THE LATE
AFTERNOON. AT LEAST TEMPERATURES WILL BE WARMER THAN NORMAL.

THE UPPER LEVEL AND SURFACE RIDGE SHIFT OVER THE ID PANHANDLE BY
12Z/5 AM SUNDAY...WHICH ALLOWS LOW LEVEL OFFSHORE FLOW TO DEVELOP.
THIS WILL ACCELERATE THE CLEARING SO THE INTERIOR WILL BE PARTLY TO
MOSTLY SUNNY AND SLIGHTLY WARMER WITH MAX TEMPS IN THE MID TO UPPER
60S.

MODELS HAVE BEEN CONSISTENT IN BRINGING THE NEXT OCCLUDED FRONT TO
THE AREA BY SUNDAY EVENING. THERE IS STILL DISAGREEMENT ON
TIMING...WITH THE FASTER NAM...ECMWF...AND CANADIAN ALL BRINGING
RAIN PARTWAY INLAND FROM THE COAST BY 00Z/5 PM SUNDAY. THE CURRENT
FORECAST FAVORS THIS FASTER SOLUTION. THE SLOWER GFS HAS RAIN JUST
REACHING THE N COAST AT THAT TIME. THIS IS ALREADY A SKINNY WEAK
FRONT OFFSHORE ALONG 140W THIS EVENING AND IT DOES NOT LOOK LIKE IT
WILL GET MUCH STRONGER OVER THE NEXT COUPLE OF DAYS.
REGARDLESS...RAIN WILL SPREAD SLOWLY INLAND SUNDAY NIGHT AND
CONTINUE OVER THE AREA ON MONDAY AS THE FRONT WEAKENS. KAM

.LONG TERM...PREVIOUS DISCUSSION FROM THE 330 PM AFD...MODELS BRING
A SERIES OF SYSTEMS THROUGH THE AREA NEXT WEEK. THE GFS HAS A MORE
PROGRESSIVE SOLUTION WITH THE WET AND WINDY PERIODS TUESDAY NIGHT
AND WEDNESDAY MORNING...WEDNESDAY NIGHT...AND FRIDAY. THE EURO HAS
AN ATMOSPHERIC RIVER SOLUTION WITH HEAVY RAIN TUESDAY NIGHT THROUGH
THURSDAY...MAINLY CONCENTRATED ON THE OLYMPIC PENINSULA. THE
CANADIAN MODEL IS MORE LIKE THE GFS...PROGRESSIVE. FOR NOW HAVE A
LOT OF LIKELY POPS IN THE EXTENDED. THERE COULD BE SOME WINDY
PERIODS AS WELL. BURKE

&&

.HYDROLOGY...330 PM DISCUSSION...NEITHER THE SYSTEM TODAY NOR THE
ONE MONDAY HAVE ANYWHERE NEAR ENOUGH RAIN TO CAUSE CONCERN ON AREA
RIVERS.

THE EURO SOLUTION WITH ITS ATMOSPHERIC RIVER DURING THE MIDDLE OF
NEXT WEEK PROBABLY HAS ENOUGH RAIN TO FLOOD RIVERS ON THE OLYMPIC
PENINSULA. THE OTHER MODELS ARE MORE PROGRESSIVE AND WOULD CAUSE
RISES BUT NOT FLOODING. HURRICANES IN THE PACIFIC OCEAN...THERE ARE
SEVERAL...GENERALLY WREAK HAVOC WITH LONG RANGE MODELS AND THERE IS
SO FAR NO REASON TO FAVOR THE EURO SOLUTION OVER THE OTHERS. THINGS
MAY BECOME CLEARER BY NEXT WEEK. BURKE

&&

.AVIATION...AN UPPER LEVEL TROUGH WILL MAINTAIN SHOWERS ACROSS
WESTERN WASHINGTON TONIGHT. THE AIR MASS IS MOIST AND UNSTABLE. THE
FLOW ALOFT IS SOUTHWESTERLY. GUSTY SOUTH WINDS IN THE INTERIOR WILL
EASE AFTER MIDNIGHT TONIGHT. CEILINGS ARE MAINLY VFR THIS EVENING
BUT CLOUDS WILL LOWER OVERNIGHT WITH MVFR CIGS LIKELY. SHOWERS WILL
TAPER DOWN EARLY SAT MORNING AS THE TROUGH EXITS AND A WEAK RIDGE
MOVES IN.

KSEA...LIGHT SHOWERS WILL REMAIN IN THE VICINITY TONIGHT...WITH MVFR
CIGS LIKELY. SURFACE WINDS WILL REMAIN S/SW. 33

&&

.MARINE...A COLD FRONT IS WEAKENING AS IT PUSHES EAST THROUGH
WESTERN WA THIS EVENING. WINDS ACROSS THE REGION ARE EASING...AND
WILL CONTINUE TO EASE OVERNIGHT. HIGH PRES WILL SHIFT INLAND ON SAT
WITH S/SE FLOW OVER THE WATERS. WINDS WILL INCREASE ON SUN AS
ANOTHER COLD FRONT APPROACHES THEN SHIFTS INLAND. MODELS CONTINUE TO
SHOW GALE FORCE SOUTHERLIES OVER THE COASTAL WATERS. THIS FRONT WILL
WEAKEN AS IT SHIFTS INLAND EARLY MON. ANOTHER COLD FRONT WILL
APPROACH THE REGION ON TUE. 33

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.

PZ...GALE WARNING EAST ENTRANCE AND NORTHERN INLAND WATERS.
     SMALL CRAFT ADVISORY COASTAL WATERS...WEST ENTRANCE...ADMIRALTY
     INLET...PUGET SOUND AND HOOD CANAL.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.

&&

$$

WWW.WEATHER.GOV/SEATTLE

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML








USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.